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RoXIy C0w. IAO T pOF~ CHS ArmE(%n EDfatva nlBo. OTRC R RNTNMBR
2I. CONRCLN OFFICE IAMN NO, ADREIIETRESSLO UME
USAF School oftAropce eiie(N)ýe 7
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-P.ROCEDURALTEONSTATEME .NT IGXOETV DEVCf 1h O.prl
I ---. SUPLM NTR NOTES R RNTN MB R
Accelerati on I Cormnto sytmE-etrfg Perfomanc ofA
Paucl Er omeer ECGR recording-C-
zO.~STRACT (oI, gcr A N ADDRES I0. neaPr aridT TASKtb lokn~tb
Suan CAntrnifuge Thease studie inovd7teC 93P une1rns th1ta
recrdA g SchoolotArol-acenter aadistiuion;B coed-opcenturifgecotrlAndosthe Mediclg recorder. (AS)162%MMe
DD ~ 173'~(UNCLASSIFIED ISEC~~RITY 4 CLASSIFI F1CATION O HSP 'DOWiN GRDI NGeed
¾ ~ iŽ SCHED9LE
CONTENTS
Section /PaeNo.
l. ANTi-C VALVE (ACV) FAILURES............................. 9
1.1 Historical Data ............. ............. .............................. 9
1.1.1 Limitations of the Data ............ ..... ....................... 91.1.2 Explanation of the Data Used ................. ................... 3.01.1.3 Pertinent Notes ............ ... ........................... .... 10
1.2 Analysis of the Historical Failure Data ........... .................. ... 11
1.2.1 Description of Illustrations ............. .................... ... 111.2.2 Suggestions for Future Data Collection on ACV Failures .. ....... .. 33
1.3 Induced ACV Failure Analysis .......... ... ........................ .... 33
1.3.1 Failure Analysis of Bendix ACV FR139A2 ....... ............... ... 341.3.2 Failure Analysis of ALAR ACV 8400A ......... ................. ... 36
"1.4 Standardized ACV Test Protocol (SVTP) Testing of Failures ..... ......... 37
1.4.1 Test of Bendix ACV Failure #1 .......... .... ................ ... 371.4.2 Test of Bendix ACV Failure #2 ............ .................... ... 441.4.3 Testing of ALAR ACV Failure ................ ..................... 641.4.4 Failure Testing Conclusions ................ ..................... 19
2. SPECIFIC EQUIPMENT EVALUATIONS ........... ........... .......................... 110
2.1 CWU-9/P Undergarment C-Effects Tests .I. . ........... ..................... 110
2.1.1 Test Instrumentation and Calibration 110................1"2,1.2 Test Methods ............. ........... ............................ 1102.1.3 Data Presentation .......... ... .......................... 111
2.1.4 Discusslon and Conclusions ............. ..................... 111
2.2 G-Sensitivity Evaluation of the Statham PMI31TC Pressure Transducer .... 123
2.2.1 Test Configuration ............. ... ......................... ... 1232.2.2 Test Protocol ............................ 1232.2.3 Data-handling Techniques for Performance Evalution .......... 1232.2.4 Performanct Evaluation ......... ..... ....................... ... 142
2.3 Ready Pressure AC o Ma~nequin Test ............. ..................... ... 142
2.3.1 Test Protocol .............. ... ............................ ... 1422.3.2 Description of the Test Data .................... .......... ..... 1432.3.3 Data Analysis ............ ..... ............................ ... 1442.3.4 Data Presentation ............ ... .......................... ... 1452.3.5 Test Conclusions ......... ... .......................... 156
2.4 ALAR "High Flow" and "Special" Examinations ......... ................ ... 156
2.4.1 Design Modifications ........... ..... ........................ ... 1562.4.2 Open-flow Capacity of "High Flow" ................... 1572.4.3 First-stage Regulator Shim Effect .......... .................. ... 157
2.5 Accelerometer Calibration ............. ... ......................... .... 57
2.5.1 Gondola Acceleration Environment ........... .................. ... 1572.5.2 Dynamic Calibration ............ ... ......................... ... 170
A.A
' : - ; .i , " ' .: .,- .-; ,, .*,i ,
aeP~ I~'t~* 1.'
cONTENTS (cont'd.)
Section PageNo.
2.6 Continuous ECC Recordings in Primates . .................. 171
2.6.1 Objective . .. ......................... 1712.6.2 ECG from Chronically implanted Electrodes .1.7..........1712.6.3 Animal Instrumentation .............. ........................ 1752.6.4 Conclusions ...................... ............................. 1762.6.5 References .............. ..... .............................. .. 176
2.7 Control Center Data Distribution System Study .... ............. .. . 177
2.7.1 Undesirable Characteristics ...... ..................... 1772.7.2 Recomumendations ..................................... 178
2.8 Closed*-'.oop Centrifuge Control Study ....... ............. ...... . 179
2.8.1 Objective .... .............................. 1792.8.2 Normal Centrifuge Operation. ..................... 1822.8.3 Closed-loop Control System Developed by the Air Force ............ .. 1832.8.4 Design Modifications ................ ......................... .. 183
2.9 Medilog Recorder G-sensitivity Test .... .................... 189
2.9.1 Introduction ... ..... ..... .. .. ......... , 1892.9.2 Test Protocol and Configurations ............ . , 1892.9.3 Test Results ................................... 1922.S.4 Conclusions ............... ..... ............................. .. 196
ABBREVIATIONS, ACRONYMS, AND SYMBOLS ............. . ...... ............... 198
FIGURES
FigureNo.
1 Number of failures for Bendix and ALAR anti-G valves for July 1974 to June 1977 122 Number of OTH/MAL's for Bendix and ALAR anti-G valves for July 1974 to June 1977 . . 13
3 Total number of failures and OTH/MAL's for Bendix and ALAR anti-G valves forJuly 1974 to June 1977 ..... .. .. .. .. .. .. .. .. .. .. .. .. 14
" 4 Rate of occurience of failures ............................................... 15
5 Rate of occurrence of OTH/AL's ............. ............... . 16
6 Rate of occurrence of failures and OTH/MAL's ... . ..... ....... 17
Distribution of:
7 F-ill-A failures per 1000 flight hrs ........•...................... 18
8 F-ill-A oTH/MAL'as per 000 flight hr. ........... 20
9 F-111-A total failures and OTH//AL's per 1000 flight bra ...... . ..... . ... 20
10 F-11-D failures per 1000 flight hrs .................. 21
11 F-111-D OTH/MAL's per 1000 flight hrs ....... . .................. . 22
2
rnwyxTs ("Distribution of." cont'd.)
T, Figture PageNi o.
12 F-l1-D total failures and OTH/MAL's per 1000 flight hr . .......... ..... 23
13 F-III-E failures per 1000 flight hre ....... .......... . .... . 24
14 F-111-E OTH/MAL's per 1000 flight hr. ....... .......... . ... 25
15 F-111-E total failures and OTH/MAL's per 1000 flight hrs. ............. 26
16 F-111-F failures per 1000 flight hrs ............... .......... . ....... 27
17 F-111-F OTH/MAL's per 1000 flight hr. ...... ......... ............ ... 28
18 F-11-F total failures and OTH/MAL's per 1000 flight hrs. .................. 29
19 T-38 failures per 10,000 flight hrs ............. ...... . .... 30
20 T-38 OTH/MAL's per 10,000 flight hrs ........... ................ ...... 31
21 T-38 total failures and OTH/MAL's per 10,000 flight hr. .... ........ ..... 32
22 Exploded view of the FRO39A2 anti-G valve ...... ................. ....... 35
23 Exploded x oZ the ALAR 8400A anti-G valve ............... . . 38
Bendix Failure #1:
24 flow as a function of source pressure ...... ..................... .. 42
25 variation (three sigma) in flow as a function of source pressure . , . , 43
F 26 0.1 G/sec suit pressure profile as a function of source pressure ........ 45
27 0.1 G/sec suit-pressure variation as a function of source pressure ... ....... 46
2L 0.1 G/sec decreasing suit pressure profile as a function of source pressure 47
29 0.1 G/sec suit pressure hysteresis as a function of source pressure ........ ... 48
30 suit pressure profile coparison as a function of onset rate ................ 49
31 suit pressure profile as a function of G-onset rate . ....... .. .... 50
32 dP/dG as a function of G-onset rate. ........ .............. 51
33 1.5 G/sec suit pressure profile as a function of source pressure ......... .... 52
34 1.5 G/sec suit pressure variation as a iunction of source pressure , . , . . . 53
35 -1.5 G/sec decreasing suit pressure profile as a function of source pressure 54
36 1.5 G/sec suit pressure hysteresis as a functiQn of source pressure . . . . 55
37 SACM suit pressure profile comparison with minimum source pressure andmaximum suit volume ...... . ...... ............... . .. . 56
38 suit pressure deviation and dG/dt for the minimum source pressure, maximum
suit volume SACM ................... I.......... 57
39 SACM suit pressure profile comparison with maximum source pressure andminimum suit volume ........... ,...., 58
-..iý' ..3
* . .jI"ý
F~~~ ........... J .~.
CONTENTS ("Bendix Failure #l"cn'.
Figure PaleNo.
40 suit pressure deviation and dG/dt for the maximum source pressure,minimum suit volume SACM .. .............. ..................................59
41 SACK suit pressure profile comparison with median source pressure andsuit volume .. .................................. ..........................60
42 suit pressure deviation and dG/dt for the median source pressure andsuit volume SACM. .. .................... ......... ........................ 61
43 SA(CM suilt pressure profile comparison with C vector misalinement .. ............ 62
44 eiuit pressure deviation and dC/dt for the C vector misalinement SACN.......63
Bendix Failure #/2:
45 flow as a function of source pressure .. .............. ........................66
46 variation (three sigma) in flow as a function of source pressure .. ............ 67
47 0.1 G/sec stilt pressure profile uts a function of source pressure .. ............ 68
48 0.1 C/sec suilt pressure vnriation as a function of source pressure .. .......... 69
49 0.1 C/soc decreasing stilt pressure profile as n function of source pressure 70
50 0.1 C/sec suilt pressure hysteresis as a function of source pressure. .. ........ 71
51 suit pressure profile comparison as a function of onset rate. .. ............. 72
52 ,uit pressure profile as a functiou of C-onset rate. .. ........................ 73
53 dP/dC as a function of C-onset rate .. ............ ............................ 74I
r54 1.5 C/sec suilt pressure profile. as at function of source pressure .. ............ 75
55 1. 5 C/sec suit pressure variation as a func tion of source pressurc .. .. ........ 76
56 -1.5 C/sec decreasing suilt pressure profile as a function of source pressure .77
51, 1.5 C/sec suilt pressure hysteresis as a function of source pressure. .. ........ 78
58 SACM suit pressure profile comparison with minimum source pressure and
maximum suilt volume........ ........................................ 79
659 suilt pressure deviation anid dC0/dt for the minimum source pressure.maximum suit volume SACM .. .............. .................................. 80
60 SACM suit pressure profile comparison with maximum source pressure andminimum suilt volume .. .................................. ..................81
61 suit pressure deviation and dC/dt for the maximum source pressure,minimum suilt volume SACM .. .................................. ............. 82
62 SACM suit pressure profile comparison with median source pressure andsuilt volume .. ................................ .............. 83
63 -;ulit pressure deviation soil dC/dt for the median source pressure and
auit volume SAC . .. .............................. ........................ 84
64 SACM suit pressure profile comparis.on with C vector misalinement .. ............85
65 suit pressure deviation and dC/dt for tho G vec tor misaliorment SACH.......86
4
______ __~~'i
CONTENTS (cont'd..)
FigureNo.
ALAR Failure !Ili
66 flow as a function of source pressure . ................. 88
67 variation (three sigma) In flow as a function of Fource pressure . 89
68 0.1 C/sec suit pressure profile as a function of source pressure. . ... 90
69 0.1 C/sec suit pressure variation a.% a functicen of source pressure. .. ......... 91
70 0.1 C/sgec decreasing suit pressure profile as a funct imi of source pressure . 92
71 0.1 C/sec suilt pressure hysteresis as a function of scurce pressure.... .. ... 9...3
72 suit pressure profile comparison as a funotion of onset rate......... 94
73 suilt pressure profile as a function of C-onset rate...............9
74 dP/dG as a function of C-onset rate. .. ... . ...................... ............. 96
75 1.5 G/sec suit pressure profile as a function of source pressure. .. .... ....... 97
76 1.5 C/sec stilt pressure variation as-a function of source pressure........98
77 -1.5 C/sec. decreasing suit pressur? profilte as a function of source pressure . 99
78 1.5 G/s.~c suit pressur'g hysteresais as a function of source prvsaure. .. ........ 100
79 SAGN Suit pressure profile comparison with mintisus source pressure andmaximum Stitt volume .. ...... . ............................... 101
80 suit pressure devitition and dC/dt for rhe minimum souirce pressure,maximum .uit volume SACM. .. ... . .............................. 102
81 SACt. suit pressure profile comparison with maximum Source presst'reand minimum suit volume.. ..... ... .. .................. .................. 103
82 suit pressure deviation and dG/dt for the maximum source. pressure,minimum suit volume SAC . .. ....... . .... ............ .................... 10483 SACM suilt pressure profile comparisoo with median s4ource pressiurv aid
suit volume .. ....... . .................. ..................... . ........... 105
84 suiit pressure deviation and dC/Jt for OL- msedian source prossui-e and
Suitt volume SACM. .. ..... . ......................................... ...... 106
85 SACM suit pressure profile comparison with C vector misalinement.........107
86 suit pressure deviation and dG/dr for the gvector misalinement SAcN.......108
Nomainnned~ ",wosure Suit:.abdomen force. .. ......... . ................ .................. .... . ......... 118
88 right thigh f-rce.. ......... . .................... ............. ... . . .. .. .f 19
89 left thigh force .. ....... . ....................................... ........ 120
s0 right calf force .. ......... . .................... ..................... . ..... 121
91 left calf forcc ..... . ..... .. .. .. .. .. .. .. .. .. ... 122
C; '1
CNIT-(cont d.)
Figure PageSNo.
Acceleration influence on the:
92 +Z axis of the PM131TC-3644 transducer with 0-psig stimulus ..... .. . 124
t..93 -Z axis of the PM131TC-3644 trat~sducer with 0-pusg stimulua .s ..... 125"
94 +Y axis of the PM131TC-3644 transducer with O-psig stimuluw ...... .. , 126
95 -Y axis of the PM131TC-3644 transducer with 0-psi8 stimulus . . .. . . 127
96 +X axis of the PM131TC-3644 transducer with O-psig stimulus ....... ..... 128
97 -X axis of the PM131TC-3644 transducer with O-psig stimulus . ; . . . 129
98 +Z axis of the PM131TC-3644 transdUcer with 10-psig stimulus .. . ..... ... . 130
99 -Z axis of the PM131'C-3644. transducer with 10-peig stimulus ..... 131
100 +Y axis of the PM131TC-3644 transducer with 10-psig stimulus ..... " . 132
101 -Y axis of the PM131TC-3644 transducer with 10-psig stimulus . . . . . . .
102 +X axis of the PM131IC-3644 transducer with 10-psug stimuluj ..... 134
103 -X axis of the PM131TC-3644 transducer with 10-psag stimuluw ... ......... .. 135
104 +Z axis of the PMI31TC-3644 transducer with 18-paig stimulus .... .......... .16
105 -Z axis of the PM131TC-3644 transducer with 18-psig stimulus ...... 137
106 +Y axis of the PM131TC-3644 transducer with 18-psig stimulus .......... 138
107 -Y axis of the PM131TC-3604 transducer with 18-psig stimulus ..... ......... 139
108 +X uxis of the PM131TC-3644 transdecee with 18-pasig stimulus . .. .... 140
109 -X axis of the PM131TC-3644 transducer with 18-paig stimulus ... ......... .. 141
RPV Mannequin Test:
V...•. 110 suit pressure response for four test cases ................ . 47
111 abdominal force rasponsb for four test cases ...... ..... ..... ..... ..... 149
1:,, 112 left thigh force response for four test cases ...... ................. ... 151
S113 left calf force response for four test cases. . ................ 153
114 right thigh force response for four test cases ..... ................ ... 155
U15 suit pressure residuals.. . . ...................... ............... 159
116 abdominal force residuals ............. ............................ 161
117 left thigh force residuals . .. ................ ...... ..... ... 163
118 left- calf force residuals ........ ........................... ... 165
119 right thigh force residuals ......... .......................... ... 167
120 Recommended arrangement of new patchcord programming system .... ............ .. 180
6
S-k
J•g k .. . . . • . • :. :., • . • :•. :.> .-
CONTENT6 (cont'd.)
NO.
121 Now patchcord programmsing systen . ..... . ..181 ...... e
121 Electrical rotor arm drive subsystem (Part 1) .* 184
123 Electrical rotor arm drive subsystem (Part 11) . ................. 185
124 Hydraulic rotor ariadrive subsystem (Part 1) ................ 186
125 Hydraulic rotor arm drive subsystem (Part IT) .. ..... ............. ............187
126 Air Force closed-loop control circuit. .. ....... ... .... ... . .. ... .. 8
127 Time base expansion test configuration. .. ... . .... ...... ............ ........190
128 Recorder axis orientation .. ...... .......... ......... . .... ..... . ..........191
129 Hedilog recorder test configuration .. ...... .......... .... ..... . .... ........ 191.
130 oxford reproduce and re-record test configuration .. ..... . .... ...... .... ......193
TABLES
Table
No.4
1 Bendix AGV failure #1 performance evaluation table .. .. ........ ......... . ....
2 Key to symbols in figures 24 to 86. .. ... . .... .................. .... ....... 41
3 Bendix AGV failure #2 performance evaluation table .. .. .. ........ .............65
* 4 ALAR AGV failure #1 performance evaluation table. .. ...... .......... ..........109
5 First set of runs without exposure suit. .. ......... ..... ..... . .... .......... 112
6 Second set of runs without exposure suit .. .. .. ..... . ............ ............113
8 Thirst set of runs withou exposure suit. ..... ..... ........ .......... ..........114
F Tirdt set of runs withou exposure suit ..... .. .. ... ...... ......... .......... 115
9 Second as-! of runs with exposure suit .. ...... .... ..... . .... ..... . .... ......116
10 Third set of runs with exposure suit. .. ... ...... .... .................. 117
RPV Mannequin Test:
11 ~~suit pressure response (psig). .. ... ............. .... ...... .... ........ 146
12 abdom1.ial force response (psi). ...... .............................. ....... 148
13 left thigh force response (psi) .. .... ................................ ..... 150
14 left calf force r~aponse (psi). ...... ................................ ..... 152
15 right thigh force rtsponse (psi).......... ..... . . .. . .. .. .. .. .. .. .... 14
16 suit pressure residuals (paig). ...... .............................. ....... 158
7
CONTENTS ("RFV Manneguln Thst."co0tcIt'd-.)
Table UNo.
1?abdominal force reesidual4 'psi) . ....................... 160
i8 left thigh force residuals (psi) . . 1 b2
19 left calf fqlrce residuals (psi). .. ................. ............ .. .. ........164
20 right thigh force residuals (psi). .. ............... . ............ .. ........166
21 ALAR. "high-flow;1 1 ,ind "special" design modifications... .......... ............. 168
it22 ALAR "high-flow:" and "special" open-.flow capacities i. . . . . . . . . 169
23 ALAR 8400A fiiat-atage regulator shim effect......... ................... 169
24 Accelerometer calibration values for location 13 ft. 9 in. t 0.1 in. from thecent, of; rotation. .. .......... ......................... . ....................172
25 order of nx~.s testing nnd test signals. .. ...... ........ ................... .....192
26 Oxford repfodmce test setup .. ............... . .... .............. ................ 193
27 Time base expansion accuraccy. .. ........... . ...................... ............... 194
28 Reproduced frequency (mean).... ................ . .... ...................194
29 Percent error in frequency reproducwtion at 1-f, start of run. .. ............ ........195
*30 Percent error channel 1.reproduce normnlized to I-C start of run .. .. ..............195
2,1;;
x
itI
PROCEDURAL TESTS FOR ANTI-G PROTECTIVE DEVICES
VOLUME II:
G-SENSITIVITY TESTS
1. ANTI-G VALVE FAILURES
Two lines of investigation were taken to develop an anti-gravity valve(AGV) failure analysis for predicting lifetime expectations and reasons forfailure of respective valves. In the first of these investigations, histori-cal anti-G valve failure data were obtained for analysis. In the second,failures were induced in functional AGV's; and these "failed" valves weretest3d. Test results then were analyzed using the GVALVPGM (described inAppendix A).
1.1 Historical Data
Data on AGV failure were sought. Because the most frequentlyused valve (i.e., the ALAR 8000 series--which includes the 8400A, 8000A, and
ar 8000BQ is considered to be a low-cost (or throw-away) item, only two reposi-tories of AGV failure data were found: The Naval Aviation Integrated LogisticsSupport Center (NAILSC), Naval Air Station, Patuxent River, Maryland 20670; andThe Department of the Air Force Headquarters, Air Force Logistics Command,Wright-Patterson AFB, Ohio 45433.
1.1.1 Limitations of the Data
The data available through NhILSC were most pertinent tothis study. Because a major overhaul of the computer programs used to accessthis data repository was in process, however, the data were inaccessible forthe period of thiL contract. Any followup work should consider this NAILSC
For this report, the data were provided by the Wright-Patteraon LogisticsCommand, and were more limited than the NAILSC data. The limitations of theWright-Patterson AFB data are as follows:
(a) Data were available on only two valves, the ALAR and the Bendix.
(b) Each of these valves was used in only one type of aircraft--theALAR AGV in the T-38, and the Bendix AGV in four models of the F-lll,
EDITOR'S NOTE: Appendix A applies to, and supplements, Volumes I and II.(Information on how to order this Appendix appears at the close ofeach volume.)
.... ,~m~-- - - --.-- --. :X- .
r .............
"•(c) Both the T.38 and the F-ill are low-G aircraft. No data are Aail- .able on AGV failures in high-G aircraft.
' () At the time of the study, the repoestory, contained only, three yearsof monthly data (Y uly 1974 - 4une 1977).
. () .The failures -were classified in such. a manner that neither the reason.s-for failure nor the time of failure (ihether preflight or inflight) could bedetermined.
1.1.2 Explanation of the DAta Used
rnThe original data used in the following analysis were
.recorded in colums headed.- (1) month; (2) op-time-(or flight hrs); and(3)'occurrences, both fail (failures) and OTH/MAL, (other malfunctions).D"NOTE: These raw data are not included in this report.] The classificationsunder occurrences, .failures, other malfunctions, and total can be interpretedas follows:
.1) Failures means any Type 1 HOW MALFUNCTION. CODE--which indicatesithat the item can no longer meet the minimum specified perform-
ance requirements due to its own internal failure pattern.
2) Other Malfunctions (OTH/MAL) means any Type 2 HOW MALFUNCTION CODE--which indicates that the item can no longer meet the minimumspecified performance requirements due to some induced conditionand not due to its own internal failure pattern.
3) Total included, inexplicitly in the total for this column along withFailures au.d OTH/MAL's are Type 6 HOW MALFUNCTION CODES--whichindicate that maintenance resources were extended due to policy,modification, location, or cannibalization, and no defect existedat the time of maintenance. Because Type 6 HOW MALFUNCTION CODESI. .were not considered pertinent to this investigation, they wer!.not included in the report. All figures of Totals, therefore,refer to the sum of the failures and OTH/MAL columns only. Fora more detailed explanation on these three classifications, thereader is referred to:
AFLC Regulation 66-1523 August 1974Equipment Maintenance/Product PerformanceCh 5 and 13
1.1.3 Pertinent Notes
A. In general, operating time (or flight hrs) for the T-38is approximately 1.8 times that for the F-1ll.
B. Moisture accumulation on the internal surface of avalve can affect the way it functions. Therefore, climate conditions of thegeographic region in which the valve is used may be of importance.
EDITOR'S NOTE: Available, on pp. 198-199, is a selective list (plus defi-nitions) of the "Abbreviations, Acronyms, and Symbols" usedthroughout this volume.
10
I bit.;0
- .. - .'-A" 4.*4•. •,.•. .,•• T, ,. • •• ! ... ,
12-sf ..p
1.2 Analysis of the Historical Failure Data
Due to the limited nature of the data obtained, the followinganalysis is strictly desrriptive of the data, Sufficient data are not yetavailable for a predictive study.
1.2.1 Description of Illustrations
Two types of descriptive figures are presented in thefollowing pages. In the first sets (Figs. 1 - 6)Y, sctematics are used toreflect the distributions of the five data sets, their means, medians, ranges,extremes, etc. [NOTE: This form of analysis was developed by J. W. Tukey inExploratory Data Analysis, Addison-Wesley, Reading, Mass., July 1977.] Ini each of these figures, the five sets are plotted side by side, so that com-
r parisons can be readily made. In Figures I - 3, raw counts, or the numbers offailures, OTH/MAL's, or totals are presented. The mean flight hours, shownbelowv each of the box-and-whisker plots, are an important part of these figures.It is immediately apparent that the MAR valve porformed comparably with theBendix, even though the ALAR sustained approximately 18 times uore flightI hours per month.
In Figures 4 - 6, the failures, OTH/MAL's, and totals per 1,000 flighthours arE presented, also in side-by-side box-and-whisker plots. Again, theALAR performance was much more reliable than the Bendix. On the right side ofFigures 4 - 6 are expansions of the ALAR failures, OTH/MAL's, or totals over10,000 flight hours (i.e., a 10-to-l expansion), to give the reader a clearerindication of the numbers involved.
The conclusions that can be drawn from these figures are:
a) Over the same number of flight hours, Bendix malfunctions andfailures are relatively consistent in the four F-lll models.
b) The ALAR valve is approximately 10 times more reliable than theBendix in terms of flight hours sustained before malfunction oz failure.
>> In the second set of figures (Figs. 7 - 21), data set means and mediansare used to indicate monthly variation and yearly trend. These figures areonly descriptive, for too few years of data are available to draw conclusionsabout monthly or yearly patterns. Several important facts should be notedabout these figures.
a) For trend, the years 1974 and 1977 are biased toward the last sixkonths aud the first six months, respectively.
b) The bias in a) may carry over to monthly variation if the years1974 and 1977 are significantly different.
c) The Bendix failures, other malfunctions, and totals are over1,030C flight hours, while the MAR figures are over 10,000 flight hours.
Again, stress is placed on the fact that these figures are strictlydescriptive of the data. No conclusion can be drawn about the monthly oryearly patterns.
11
7 -: . .; .:.., .;.
Fill T- 38
40A B C D
30-
~20
10
0BENDIX ALAR
MEANOP TIME
(FlghtHrs 15 1308 1640 1868 2,7-PerLNonth
Figure 1. Number of failures f or Bendix and ALARanti-G valves for July 1974 tu June 1977.
Key: a - Arithmetic meanMiddle bar - MedianUpper & Lower Bar - Upper & Lower Quartilex -Extremes of Data SetOP -operating
12
.7`777-
. FillT-38
40A B C D
40
LIP)
~20~LL
00
10
0 J -!3>1BENDIX ALAR
(FlghtHr .115 130'8 1640 1868 2,7
Figure 2. Number of OTH/MAL's for Bendix and ALARanti-G valves for July 1974 to June i977.
Key: * Arithmetic meanMiddle bar - Median
x Exreme ofDataSet(excluding separate
4 13
F11l T-38
30 -
LL.
10
I
BENDIX ALAR
NEANOP TIME
(Flight Hrs) 1415 1308 1640 1868 28.373-V Per Month
I,':Figure 3. Total numnber of failures and 0TH/HAL'5 f or Bendixand ALAR anti-C valves for July 1974 to June 1977..
Key: 0 - Arithmetic meanMiddle bar -MedianUpper & Lower bars = Upper & Lower Quartilesx -Extremes of Data Sets
4 14
I:,
F111 T-38 T-38 EXPANSION
A' V j F .40.
0I
F~ii ures Failures~per 1000 30per 10,000
F'IlghtHrs. Flight Hrs.
X ~20,
10.
I -41 LI
BENDIX ALAR ALAR
Figure 4. Rate of occurrence of failures.
[IKey: 9 Ar~ithetc meanMidde br -MedianUppe & Lwerbar - Upper & Lower Quartileso -epaatevalues
x - Extremes of Data (excluding separate values)
15
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A 0 E F 40-
0TH/M~tSOTH/MALSper 1000 per 10,000Flight Hrs. 30. Flight Hrs.
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02
x V0 op
BENDIX ALAR ALAR
Figure 5, Pq- of occurrence of OTH/MAL's.
IKeyt * - ArithMetiC Mean
Middle bar - MedianUpper & Lower bar Upper & Lower Quartiles0 - Separata. valuesx -Extremes of Data (excluding separate
values)
16
1~M
F1ll T-38 T-38 EXPANSION
- - - F 40
_ __0STotal Failures 0 Total! and OTH/MALS Failures
per 1000 and OTH/MALSFlight Hrs. 30- per 10,000
Flight Hrs.
20-
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*0 0
BENDIX ALAR ALAR
Figure 6. Rate of occurrence of failures and OTH/MAL's.
Key: - Arithmetic meanMiddle bar - MedianUpper & Lower bar - Upper and Lower Quartileo - Separate valuesx - L-tremes of Data (excluding separate
values)
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1.2.2 Sunestions for Future Data Collection on ACV Failures
Even over the limted three-year period, the followingtypes of data collected on the anti-G valves could have-generatad moremeaningful information:
a) The name and model of the valve
b) Type of aircraft
c) ClimAte conditions and G-stress the valve sustained
d) Length of time valve was in service (both full-time and actualflight hours)
a) Reason for failure (as specifically as possible)
f) Indication of a preflight or inflight failure
g) Data from all (especially,. high-performance) aircraft.
1.3 Induced AGV Failure Analysis
One of the primary objectives of the PTAP program was to obtaininformation on AGV failures. To supplement"the limited data available, anengineering evaluation of potential failure modes on selected AGV's was xmder- -1taken. This study, which was limited to failures existing in the valve-before preflight testing, concentrated on insidious failures which might not
be noted on preflight tests.
For this study, the selected AGV was completely divassembled and ar ngoed -
sequentially on a work table. Starting at the inlet port, each part and sub-assembly was examined for possible failure modes. As each potential failurewas identified, it was listed, along with the expected results of such a failure.During this phase of the evaluation, potential failures were listed withoutregard to probability of occurrence, or to the fact that such a failure wouldbe readily apparent on preflight examination, or to the fact that such a failurewould have little effect on AGV performance. No double failures were considered,except in cases where one failure precipitated another. After each part andsubassembly of the valve had been examined and all failure cases listed, eachcase was analyzed to determine the relative likelihood or practicality of sucha failure, and its effect on function. Failure cases which were deemedimprobable, or which had slight effect on valve performance, were deleted fromthe list. The remaining candidate failure cases were then examined to determine
which ones would be immediately apparent to the pilot during the preflight checkof the ACV, and which failures were insidious in nature and would probably passthe preflight test, but would result in degraded performance during flight. The
33
i ' S - -.... . ,.., .,' .-..- . -. ' -• ,. -, .- • • _ ..... .... .
rr
failure cases which would be detected on the preflight test were removed fromthe list. Finally, the remaining cases were examined to determine if a waycould be devised to simulate this failure in an AGV in a reversible manner.
The final list, of AGV failures which were to be candidates for testing,included only those failures which were believaA to be probably degrading toAGV performance, not readily apparent on preflight test, and producible in theAGV in a reversible manner.
The test portion of this study was accomplished in two phases. The firstphase was a static test of the AGV which was accomplished by inducing theselected failure in the valve and testing by use of the presstoo-test button.During this phase, data were recorded only on oscillograph charts and wereanalyzed by inspection. Several of the candidate failure cases yielded resultsother than those predicted during the initial study of the valve. This finding
* was anticipated; for the AGV are reasonably complex, and all of the inter-active effects are difficult to anticipate. This uncertainty was thereforeone of the primary reasons for the static testing.
The second phase of testing was the performance of a full SVTP on thosefailure cases not deleted during the first phase.
The results of the study and the first phase of testing are listed onthe following pages. The results of the final (SVTP) phase of testing aregiven in section 1.4.
1.3.1 Failure Anelysis of Bendix ACV FR139A2
A Bendix AGV FR139A2 was completely disassembled andminutely examined. The function of each individual element and subsystem was
cataloged, and possible failure modes were listed. A total of 28 failuremodes were postulated and reviewed. Where any doubt existed concerning the
r i: . ;effect of a postulated failure, the failure was simulatpd and otaticallytested. Only two failures were judged worthy of furthet OSVTP) investigation.[In the following description, the item numbers in brackets refer to thepart-identification Key to Fig. 22.]
1.3.1.1 FR139A2 (Bendix ACV) Failure Case 1
Failure. Mass valve seat [Item 40] l~eaking
Rbsult: Reduced ACV function
Simulations Scratch valve seat
Discussion: Reeeartch on the Bendix valve failurehistory revealed that one comon failure was caused by the mass valve seat[Item 401 falling out of the valve cover body. This failure makes the valve
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S7. Compression Spring 20. Retainer Ring 2. netFittingSppigBern ahe 1 ltinghr 3 Pac ilte
9. elcoFlatrt22 Pack ean lte 3. inge ileConical Spring 35. Screw (four)
I0 as osng2.Valve & Lever 36. Relief Valve Cover
ii akgAssembly 37. PackingiS1.Screw (four) 25. Diaphragm Outlet 38. Relief Valve RingS1.Valve Housing Lever 39. Relief ValveS1,Packing 26. Plug (two) Diaphragm
S40. Mass Valve Seat
35
1' " . screw w " " F " S (
entirely inoperative, and is therefore easily discovered. However, since aleaking valve seat may be a cause of failure, the valve seat should be tested.
In order to simulate this failure, a leak rate had to be establishedwhich was large enough to degrade AGV performance, but would not render thevalve Inoperative. Since the Bendix CV design is such that a constant,though very small, flow is present through the valve when the system Is atconstant pressure, the initial baseline flow rate had to be measured. Thismeasuri.ng was accomplished by fabricating a set of weights to simulate Gforces, and by measuring the flow through the valve at various 0 loads andsource pressures. Once the baseline flow was established, the valve seatwas "nicked" with a fine file, and flows were again measured. A final flowof approzimately 700 cc/min. or about twice the unmodified flow at 70-psigsource pressure, was established.
The valve was then subjected to the SVTP, and results are listed insection 1.4.1.
1.3.1.2 71139A2 (Sendix AGV) Failure Case 2
Failure: Orifice or screen (Fig. 22: Item 15)contaminated
r
Result: Increased AGV response time
Simulation: Partially block orifice
Discussion: This case is the most likely andmost common failure in this AGV. It was decided that this failure should beI thoroughly tested using the SVTP; therefore, static tests were not consideredto be useful. The failure was simulated by Inserting a number 46 AVG (AmericanWire Gage) wire, of 0.0018 in. diam., through the orifice and screen. Thiswire blocked 51.82 of the area of the orifice. Results of SVTP testing of thisfailure are listed in section 1.4.2.
1.3.2 Failure Analysis of ALAR AGV 8400A
The failure analysis of the ALAR AGV 8400A was approachedin the same manner as that of the Bendix AGV. In the ALAR ACV case, 24 failureswere postulated; and only one was judged worthy of SVTP investigation.
1.3.2.1 8400A (ALAR AGV) Failure Case 1
Failure: Leaking bellows (Fig. 23: Item 18)
Result: Exhaust valve control of suit pressure
Simulation: Bellows plugs (Fig. 23: Items 13,14, and 15) were replaced by screw with small hole drilled through the center.Failure simulator was manufactured with the same physical dimensions as Item 15.
36
/ .!
' " .. " ' '/ .' , i' ,•X.2 w,- . .. "
The position of Item 15 was then carefully measured when the bellows spring[Item 16] was properly adjusted, and the failure simulator was positioned
i ilDiscussion: Under normal operating conditions,
a hole in the top of the bellows aintains the Interior bellows pressureidentical to the suit pressure. With a leaking bellows, the interior bellowspressure more closely resembled the first-stage regulation pressure. Two con-ditions result: First, the air from the first-stage regulator bleeds throughthe bellows directly into the suit without control. Control ti establishedby the exhaust valve. Second, the mass [Item 3] must overcome a greater forceto open the normal second-stage regulator control 'port sealed by Item 19 (an"0" ring).
Under normal operating conditions, the force generated by the action ofacceleration on the mass must overcome the force of two springs t(tems 5 and16] and the natural stiffness of the bellows. In this failure case, it mustadditionally overcome the force generated by the difference in pressure betweenfirst-stage regulated pressure and suit pressure acting across an area equal tothe top of the bellows. The result is a late pressurization start on thepressure-G profile. The results of SVTP testing of this failure mode are dis-cussed In aection 1.4.3.
1,4 Standardized AGV Test Protocol (SVTP) iTesting of Failures
Those induced failures judged worthy of serious consideration were
subjected to SVTP testing and GVALVPGM analysis. In the absence of adequatedata on failures in the field, the failures tested were derived from engineer-ing evaluation. They were, by design, "soft failures" (those which did notrender the valve inoperative). Emphasis was placed on those failures which,in addition, might not be detected during normal preflight checkout.
1.4.1 SVTP Test of Bendix AGV Failure #1
Bendix Failure #1 is especially insidious because it willpass all normally prescribed static tests, including that performed afteroverhaul. The nature of the failure is described, in detail, in section 1.3.1.1.For specific comparisons of the effect of this failure, all graphs and tablesin this section may be compared directly to those in section 5.2 of PTAPVolume I. Comparison of the total performance scores, shown on line 33 ofthe two PET's (i.e., 200.3 for the failure #1, compared with a normal 111.2),gives a quick indication of the effect (PET, Vol. I, Table 3; and PET, Vol. II,Table 1). The reader is reminded that the lower score indicates more desirableoperating characteristics, and that the Ready Pressure Valve's (RPV) performancescore of 25.4 sets the standard for this report.
1.4.1.1 Bendix AGV Failure #1 Flow Characteristics (Figs. 24and 25)
Very little difference exists between the normalflow characteristics and the failure flow characteristics. The differnce
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TABLE 1.: BEN1l1X AGV FA'L.jRE #1 PERFOR~MAN4CE EVALUATION TABLE
TEST STANDARDS:
r1. SPMIN a .,,40. PSIG2. SPMID - 70. PSIG
SPMAX = 20. PSIG4. THETA p 20./ DEGREES5. 'SVMIN r 6.' LITERS6. SVM4ID -10.. LITFRS7. SVMAX =14. LITRa
CHARACTERISTIC NUMBERS:8. XSPtIX = 2;50009. XSPMN = 1,. 3333;
W0. XTHTA = 1'0000-N1 TO(1L:A 833_
12. XFLBR2 3X/113. XDELF= 2..'13 614.. XDDV = 2'.156,15. XSIGf =0.234
16. FLOW TOTAL: 8.297.17. XCC!01 = 26.238p .....18. XICDP1 = 36.98619. XSGP1 = 1.45320. XLJPP1 = 1.464
21. LOW-ONSET TOTAL: 6.422. XCCP2 = 10.81723.. ýXDP2 = 37.91024. XDGP2 = 5.44425. XDPP2 = 5.294
2> .26. XTDP2 = 13.242K27. HIGH-ONSET TOTAL: 72.706
28. XIDPA =9.54829. XIDPB = 15.98330. XIDPC = 5.11931. XIDPD = 17.J8632. SACM TOTAL: 48.33733. VALVE: BENIX FALR 1TTA:2033
40
TABLE 2. KEY TO SYMBOLS IN FIGURES 24 TO 86
[Symbols are shown-as data pointot on the curves. See footnote.]
1 - 0.1 G/SEC G-ONSET RATE
2 - 0.5 G/SEC G-ONSET RATE
3 = 1.0 G/SEC G-ONSET RAIE
4 - 1.5 G/SEC G-ONSET RATE
A - MAXIMUM DESIGN ANGLE
D - MEDIUM SOURCE PRESSURE, OR DECREASING(WITH RESPECT TO G)
I - INCREASING (WITH RESPECT TO G) OR P-IDEAL(ACMS)
N •. MINIMUM SOURCE PRESSURE
R -- P-REAL (ACMs ONLY)
X - MAXIMUM SOURCE PRESSURE
7* - -REAL LESS P-IDEAL OR G-ONSET
EDITOR'S NOTE-: Due to the limitations of thetechnique initially used, these symbols arenot always discernible on the respectivecurves. In such cases, however, the symbolsI. are insignificant as compared with the closerelationship obvious between the curves ineach figure.
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between a normal 7.147 (Vol. 1, Table 3, line 16) and 8.297 CVol. 1, Table 1,line 16) is primarily reflected in the source pressure influence scored onlines 13 and 14. The same effect is apparent in Pigure 26 (Vol. 1) of thenormal case and Figure 24 (VoL II) of the failed case, with the saturatingmedian-source-prassure open-flow curve.
1.4.1.2 Bendix AGV Failure #1: Low-Onset-Rate Charac-teristies (Figs. 26 - 29)
Approximately 602 of the PIT performance scoredifference occurred in the low-onset-rate test, and the majority of this changeoccurred on line 17 (indicating poor linearity) and line 18 (indicating alarge source pressure influence). The cause of these high (undesirable) scoresmay be readily seen in a comparison of Figure 28 (Vol. 1) and Figure 26 (Vol. II).The inability of the low and median source pressures to outrun the mass valveleak rate (i.e., drive the output pressure above 3 psig and 6 psig, respectively)degraded both linearity and source pressure response. Lines 19 and 20 of thePET actually improved over the normal valve score. The saturrted pressuresactually reduced the 3 sigma of the data (in Fig. 27 of Vol. 1I compared tothat in Fig. 29 of Vol. I), and the hysteresis (in Fig. 29 of Vol. II, comparedto that inlig. 31 of Vol. 1).
1.4.1.3 Bendix AGV Failure #1: High-Onset-Rate Charac-teristics (Figs. 30 - 36)
Approximately 20% of the performance degradation,reflected in the PET (Table 1), occurs in lines 22 through 27. The failure
case scores actually improved in the tests for 3 sigma (line 24), hysteresis(line 25), and profile lag due to onset rate (line 26). In each case, saturated
.T . .output at'high-onset rates was essentially identical to the low-onset-rateoutput. However, the poorer performance shows dramatically on lines 22 (doubled1* linearity score) and 23 (tripled source-pressure influence score). Figures 30-36
graphically represent these results.
1.4.1.4 Bendix AGV Failure #1 SACM Characteristics(Figs. 37 - 44)
The Simulated Aerial Combat Maneuver (SACM) testis almost entirely self-comparative. Since the standard for comparison isgenerated in the earlier tests, even very poor performance may score reasonablywell if it is consistent. As a result, only 17% of the PET score degradationappears in this section. Figures 37 - 44 support these results.
1.4.2 SVTP Test of Bendix AGV Failure #2
Bendix Failure #2 is an extremely probable failure.Probably, the weakest link in the Bendix AGV system design is the minute ori-fice which supplies pilot pressure to the regulator. Even though multiplefilters were used during SVTP testing, this orifice had to be cleaned frequentlyby the PTAP crew. The exact nature of the induced failure is described indetail in section 1.3.1.2. For specific comparisons of the effect of this
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failure, all grarh# and .,•les my bA directly compared with those of eution 5.2In Volume T. A comparison of the total performance scores sbown on line 33of the two PET'& (i.e., 144.9 for failure #2, Table 3 compared to a normal 111.2,Fig. 3, Vol. I) Sivee a quick indication of the effect. The reader isreminded that the lower store indicates the more desirable operating charac-
teristics, and that the RPV's performance score of 25.4 sets the standerd forthis report.
1.4.2.1 Bendix AGV FAilure #2 Flow Characteristics(Fists. 45 - 46)
Very little effect of the failure is apparent inthe •Jo. chkracteristics, as evidenced by lines 12 through 16 of Table 3 (cor-respoiding to Table 3, Vol. I), and the open-flow curves in Figures 45 and 46.
1.4.2.2 Bendix AGV Failure #2 Low-Onset-Rate CharacteristicsI!~i (Fg.47_-_50)
Examination of lines 17 through 21 of Table 3indicates Bendix Failure #2 exhibited an only slightly better performance thana normally operating valve. It is doubtful this improvement is real. Thereader is reminded that the nature of this failure has absolutely no affectin static situations. The pilot "pressure" is not restricted, only the flowinto the chamber containing that pressure. As a result, the 52% occlusiondid not prevent pilot pressure from reaching required levels on the 0.1 G/secprofiles. Figures 47-50 graphically represent these results.
1.4.2.3 Bendix AGV Failure #3 High-Onset-Rate Characteristics(Figs. 51 - 57)
The majority of the performance decrement (71%according to the PET, Table 3), resulting from Bendix Failure #2, occurs inthe high G-onset tests. The reduced rate of flow into the pilot pressurechamber is apparent in increasing delays as the onset rate increases (Fig. 52).These increasing delays naturally affect linearity (line 22 of the PET) andsource pressure influence (line 23 of the PET, and Fig. 54).
1.4.2.4 Bendix AGV Failure #2 SACK Characteristics:•; :(Figs. 58 - 65)
:;' The late precsure rise characteristic of this
failure is very apparent in the SACM tests. Approx:Lnately 32% of the PETscore decrement occurs in these tests. The self-comparison did not mask thisfailure, since its effect was not apparent at low C-onset rates.
1.4.3 SVTP Testing of ALAR AGV Failure
The exact nature of ALAR Failure is described in detail insection 1.3.2. For specific comparisons of the effect of this failurc, allgraphs and tables in this section may be compared directly to those in section 5.1of Volume 1. A comparison of the total performance scores on line 33 of the
64
TABLE 3. BENDIX AGV FAILURE #2 PERFORMANCE EVALUATION TABLE
TEST STANDARDS:
1. SPMIN = 40. PSIG2. SPMID = 70. PSIG3. SPMAX = 120. PSIG4. THETA = 20. DEGREES5. SVMIN - 6. LITERS6. SVMID = 10. LITERS7. SVMAX - 14. LITERS
CHARACTERISTIC NUMBERS:
8. XSPMX = 2.50009. XSPMN = 1.333310. XTHTA = 1.000011. DESIGN TOTAL: 4.83312. XFLBR = 3.66813. XDELF = 2.18614. XDDLF - 2.17515. XSIGF = 0.216S16. FLOW TOTAL: 8.24517. XCCP1 = 2.52018. XDDPI = 2.59419. XSGP1 - 1,77120. XDPPI = 2.43121. LOW-ONSET TOTAL: 9.31622. XCCP2 a 9.83723. XDDP2 = 30.25024. XSGP2 9.273"25. XDPP2 8.79026. XTDP2 20.415I 27. HIGH-ONSET TOTAL: 78.56628. XIDPA % 5.46029. XIDPB 9.032
S30. XIDPC 6.33831. XIDPD 23.10832. 5CM TOTAL: 43.93833. VALME: BENDIX FAILURE #2 TOTAL: 144.898
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1.4.3.1 ALAR AGV Failure #1 Flow Characteristics(Fiss. 66 - 67)
The decrement in open-flow performance accountsfor 102 of the PET score reduction. The leakage flow through the bellows andthe very late initiation of pressurization are apparent in Figure 66. Thelatter characteristic is primarily responsible for the higher (less desirable)total score on line 12 of the PET (Table 4).
1.4.3.2 ALAR AGV Failure #1 Low G-Onset-Rate Characteris-tics (Figs. 68 - 71)
ALAR failure #1 resulted in a very slight, butrecognizable improvement in low G-onset performance. Apparently, the leakageinduced through the bellows was enough to fill the median-sized anti-G suit(AGS), used during the 0.1 G/sec onset-rate tests. During normal operation,the mass (Item 3, Fig. 23, section 1.3) seals the exhaust valve (Item 10,Fig. 23) at 1.4 to 1.5 G. Normally, pressurization begins considerably later,as the acceleration force on the mass opens the inflation valve (Item 19,Fig. 23). In this failure case, the leakage flow fills the suit much earlier,forcing exhaust-valve control cf the suit pressure at all times (i.e., duringboth escending and descending G profiles). The result is some improvement inlinearity and a significant improvement in hysteresis (Vol. I1: Fig. 71; andVol. I: Fig. 10).
1.4.3.3 ALAR AGV Failure #1 High G-Onset-Rate Characteris-tics (Figs. 72 - 78)
The high G-onset-rate performance of ALAR failure#1 suffers a slight overall decrement from normal operation. The late turn-on•i ~is very apparent in Figurc 73, result:U-g in a degraded linearity (line 22) and..onset-rate influence (line 26) scores op. the PET (Table 4). The source-pressureinfluence (line 23) and 3 sigma (line 24) scores in Table 4 were improvedbecause of the concentration of acti\-'.ty (and error) around the 6-G level.
1.4.3.4 ALAR ALý Failure #1 SACM Characteristics(Figs. ,79 - 86) :
Most of the PET score degradation oacurs on theSACM tests. Since the ideal pressures are derived from the 0.1 Gisec tests,the large response deadband induced by this failure resulted 'A a ve-, poorcomparison. Examination of Figures 79, 81, 83, and 85 discloses the verygood descending-G response of this failure and the very poor ascending-Cresponse.
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TABLE 4. ALAR AGV FAILURE #1 PERFORMANCE EVALUATION TABLE
TEST STAN4DARDS:
I. SPMIN = 30. PSIG2. SPMID = 125. PSIG3. SPMAX = 300. PSIG4. THETA = 20. DEGREES5. SVMIN = 6. LITERS6. SVMI0 = 10. LITERS7. SVMAX = 14. LITERS
CHARACTERISTIC NUMBERS:8. XIPMX = 1.0C009. XSPMN = 1.0000
10. XTHTA = 1.000011. DESIGN TOTAL: 3.00012. XFLBR = 3.91913. XDELF = 2.02914. XDDLF = 2.23115. XSIGF = 0.39F16. FLOW TOTAL: 8.57517. XCCP1 = 0.01218. XDDP1 = 0.89619. XSGPI = 0.90920. XDPP1 = 0.65121. LOW-OISET TOTAL: 2.46822. XCCP2 = 6.09523. XDDP2 = 2.12824. XSGP2 = 1.68725. XDPP2 = 4.44926. XTDP2 = 16.32827. HIGH-ONSET TOTAL: 30.68728. XIDPA29. XIDPB = 6.67030. XIDPC = 5.19231. XIDPD r 6.36132. SACM TOTAL: 21.94633. VALVE: ALAR FAILURE #1 TOTAL: 66.676
I1.4.4 SVTP Failure Testing Conclusions
All three of the AGV failures tested were clearly indicatedon the PETs (Tables 2, 3, and 4) and supported by GVALVPGM graphic documentation.The authors agree that te system is somewhat subjective, and could probably beimproved with extended study (i.e., by analyzing the results from a much largernumber of valves).
109
2. SPECIFIC EQUIPMENT EVALUATIONS
2.1 The CWU-9/P Undergarment G-Effects Tests
The item under test was a two-piece, quilted, anti-exposureundergarment designed to be worn under a flight suit. The jacket, designatedthe "Liners, Flyers, CWU-9/P Jacket," was manufactured by Gibralter Industries,Inc. The trousers, designated the "Liners, Flyers, CWU-9/P Trousers," weremanufactured by Lankford Manufacturing Company, Inc. Both garments were of"medium" size and were labeled in accordance with MIL-L-27546C (Naval Publi-cations and Forms Center, 5801 Tabor Ave., Philadelphia, Pa. 19120).
The purpose of these tests was to establish the relative anti-G suit toskin interface force difference (if any), with and without the exposure suit,over a spi i of suit pressures.
2.1.1 Test Instrumentation and Calibration
For these tests, a 0 to 30 psia transducer (Gianninimodel 431212-4) was used to monitor anti-G suit pressure. This transducerwas calibrated from 0 ti 10 psig, prior to each work shift, using the pressurecalibration system installed in the USAFSAM/VNB centrifuge facility.
The transducers used to monitor anti-G suit to mannequin interface force,ere Houston Scientific Model 1200-15C force gages especially calibrated forthis purpose [Houston Scientific (the HSI Corporation), 4202 Directors Row,Houston, Tex. 770181. These forie buttons were calibrated prior to each workshift, for a 0- to 10-lb span, using a lead weight.
All data from these tests were recorded on the USAFSAM/VNB Control-RoomBrush-Chart system. Data were recorded on six channels: suit pressure, rightthigh force, left thigh force, right calf force, left calf force, and abdominalforce.
f e Anti-G suit volumes were determined using the "known volume-pressure dropsystem" developed by Technology Incorporated for this purpose.
All tests were conducted under static (1 G.) conditions; for, as previouslydetermined, a Gz field would have no significant influence on the test data orvalidity. Prior to each test series (with, or without, exposure suit), thesuit was so fitted to. the mannequin that the suit volume was ±7.7 liters, toprovide uniformity of the suit fit on the mannequin.
2.1.2 Test Methods
The test subject for these tests was a Fiberglas mannequinwith strain-gage-type force buttons mounted in the abdomen, left and rightthighs, and left and right calves. The mannequin was fitted with a CSU 13A/P"medium" anti-G suit, and the suit volume adjusted to 7.7 liters. The mannequinwas mounted in a seat and the suit was evacuated with a mild vacuum. Suitpressure was then slowly increased, in 1-psig steps, from 0 to 10 psig, and
110
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corresponding force-gage readings were recorded. Two more sets of data, takenin this configuration, were recorded with measurements at 0, 5, and 10 psig.
The anti-G suit was removed from the mannequir' and the exposure suitinstalled. The anti-G suit was installed aver the exposure suit and readjustedto a 7.7 liter fit. A set of data identical to the first test (without expo-sure suit) were recorded. Three separate iterations of this test sequencewere made to establish an adequate statistical data base.
2.1.3 Dcta Presentation
The data from the foregoing tests were taken from the Brushcharts at each test point and were recorded in tabular form. These data arepresented in Tables 5 - 10.
The minimum, mean, and maximum data points for each test pressure pointwere calculated and normalized f or each force-button location (Figs. 87 - 91).
2.1.4 Discussion and Conclusions
The data in Figures 87 - 91 show graphically the resultsof these tests. Previous testing by this contrictor has shown that the forcebuttons, used to measure interface force, exhibit good linearity and fairrepeatability from one run to the next--as long as the suit is not moved onthe mannequin. If, however, as in these tests, the suit is removed and rein-stalled, a significant change results in the pressure-force data. For thisreason, several runs were made and mean values used. The maximum and min~imumdata points for each test pressure are also shown to indicate the amount ofvariation in data. We suspect that this variation is caused by slight dif-ferences in the location and orientation of the suit bladders to the forcebuttons. Slightly more variation appears in readings when the exposure suitis installed than when it is not. This variation is probably due to the tend-ency of the suit bladders to slip more on the surface presented by the expu suresuit.
Also, the force buttons seem to have a tendency to exhibit a slightlyhigher force when the exposure suit is installed. In the opinion of theinvestigating team, this innrease is a product of the measurement techniqueand does not predict a real increase in force on a human subject. We suspectthat this effect is caused by the exposure suit forming a small "~tent"I overthe force button, which protrudes above the surface of the mannequin skin,presenting a slightly larger contact area to the suit bladder. This judge-ment is empirically based on results of previous testing with these forcebuttons. Also, the mannequin is a comparatively rigid body, and only approxi-mates the condition of the anti-C suit to human interface--facts which shouldbe considered when applying the results of these tests to results with ahuman subject.
Lacking clear correlation between the CWU-9/P and the changes in suitto mannequin interface force in these thest results, we concluded that the iexposure suit had no significant effect on anti-G suit performance.
TABLE 5. FIRST SET OF RUNS WITHOUT EXPOSURE SUIT
RUN Ps ABDOMEN Th-hLEFT CafTihRIGHT Cl
10 0 0.18 0.3 0.2 0.2
1 0.7 .0.8 1.3 1.0 0.6
2 1.4 1.55 2.1 1.8 1.1
3 2.1 2.3 3.0 2.6 1.65
4 2.6 2.95 2.85 3.3 2.1
5 3.2 3.6 4.7 4.0 2.6
6 3.8 4.3 5.6 4.8 3.1
7 4.4 5.0 6.45 5.5 3.6
8 5.0 5.8 7.4 6.2 4.1
9 5.5 6.4 8.2 6.8 4.6
10 6.1 7.1 9.1 7.5 5.0
2 0 0 0.1 0.25 0.15 0.2
5 3.2 3.6 4.6 4.15 2.7
10 6.05 7.05 9.0 7.65 5.1
3 0 0 0.05 0.25 0.15 0.15
5 3.2 3.7 4.9 4.2 2.8
10 5.95 6.85 9.1 7.55 5.45
Ps =source pressure
TABLE 6. SECOND SET OF RUNS WITHOUT EXPOSURE SUIT
RUN P.ABDOMEN LEFT RIGHTThigh Calf Thigh Calf
10 -0.05 0 0.15 0.35 1.1
1 0.6 1.0 1.1 1.3 1.8
2 1.3 1.8 1.95 2.0 2.45
3 1.9 2.6 2.9 2.85 3.2
4 2.5 3.3 3.7 3.6 3.9
5 3.1 4.0 4.6 4.3 4.6
6 3.6 4.8 5.5 5.0 5.3
7 4.2 5.4 6.35 5.7 5.95
8 4.8 6.1 7.2 6.4 6.6
9 5.35 6.8 8.0 7.0 7.3
10 5.95 7.5 8.85 7.7 7.95
2 0 -0.05 0 0.2 0.35 1.1
5 3.1 3.95 4.7 4.2 4.7
10 5.95 7.45 8.95 7.6 8.0
t3 0 -0.05 -0.05 0.15 0.35 1.15
5 3.1 4.0 4.8 4.3 4.65
10 5.95 7.45 9.05 7.6 8.0
Ps source pressure
113
TABLE 7. THIRD SET OF RUNS WITHOUT EXPOSURE SUIT
RUN Ps ABDOMEN LEFT RIGHTThioh Calf Thlh Calf
1 0 0.05 0.05 0.15 0.45 0.45
1 0.8 105 1.2 1.55 1.15
2 1.55 1.9 2.2 2.5 1.75
3 2.15 2.7 3.15 3.2 2.3
4 2.8 3.5 4.1 4.1 3.0
5 3.4 4.2 5.0 4.95 3.6
6 4.0 5.0 6.0 5.7 4.3
7 4.65 5.75 7.0 6.6 4.95
8 5.2 6.5 7.8 7.25 5.5
9 5.8 7.15 8.75 8.0 6.2
10 6.35 7.8 9.6 8.7 6.7
2 0 0 0.05 0.2 0.5 0.5
5 3.3 4.25 5.1 5.0 3.7
10 6.3 7.85 9.55 8.8 6.7
3 0 0 0.05 0.25 0.5 0.5
5 3.2 4.2 5.15 5.05 3.65
10 6.2 7.8 9.6 8.8 7.75
Ps = source pressure
114
TABLE 8. FIRST SET OF RUNS WITH EXPOSURE SUIT
RUN P_5 ABDOMEN LEFT RIGHTThigh Calf Thigh _Calf
1 0 0 0 0.15 0.4 0.9
1 0.7 0.8 1.2 1.3 1.4
2 1.3 1.6 2.3 2.2 2.0
3 2.0 2.4 3.3 3.0 2.6
4 2.6 3.2 4.4 3.8 3.2
5 3.2 3.9 5.3 4.6 3.8
6 3.8 4.7 6.35 5.4 4.4
7 4.3 5.35 7.25 6.1 4.95
8 4.9 6.2 8.3 6.9 5.5
9 5.5 6.8 9.2 7.6 6.2
10 6.0 7.55 10.1 8.3 6.6
2 0 0 0 0.25 0.4 0.9
5 3.0 3.85 5.3 4.6 3.7
10 5.9 7.55 10.1 8.3 6.5
3 0 0 0 0.25 0.35 0.95
5 3.1 3.95 5.4 4.66 3.810 5.9 7.5 10.1 8.25 6.35
Ps= -,'urce prpssure
:15
.e .* 'q . ** *-~~* *..
TABLE 9. SECOND SET OF RUNS WITH EXPOSURE SUIT
RUN P. ABDOMEN LEFT RIGHTLhigh Calf Thih Calf
0 0 0 0.2 0.35 1.2
1 0.5 1.0 1.15 1.4 1.9
2 1.15 1.85 2.15 2.4 2.55
3 1.7 2.6 3.05 3.25 3.2
4 2.3 3.6 4.0 4.15 3.85
5 2.85 4.1 4.9 4.9 4.5
6 3.4 4.85 5.7 5.7 5.1
3.95 5.6 6.7 6.5 5.7
8 4.6 6.3 7.45 7.25 6.3
9 5.0 7.0 8.35 8.0 6.85
10 5.6 7.7 9.2 8.75 /.4
2 0 0 0 0.3 0.4 1.3
5 2.75 4.0 4.9 5.0 4.45
10 5.5 7.6 9.25 8.8 7.1
3 0 0 0 0.35 0.4 1.3
5 2.8 4.1 5.0 5.05 4.3
10 5.5 7.7 9.25 8.85 6.9
Ps= source pressure
116
ALI, v
r'I
TABLE 10. THIRD SET OF RUNS WITH EXPOSURE SUIT
RUN P ABDOMEN LEFT RIGHT-Ahigh~ Calf Thigh Calf
0 0 0.05 0.25 0.45 0.95
1 0.85 1.2 1.2 1.6 1.3
2 1.6 2.2 2.0 2.6 1.65
3 2.4 3.2 3.0 3.6 2.0
4 3.1 4.1 4.0 4.6 2.3
5 3.9 5.0 4.85 5.6 2.6
6 4.5 5.8 5.75 6.5 2.85
7 5.3 6.7 6.5 7.4 3.15
8 6.0 7.5 7.4 8.3 3.4
9 6.5 8.4 8.3 9.3 3.65
10 7.35 9.15 9.15 10.05 3.8
2 0 0.1 0.05 0.35 0.50 1.15
5 3.75 5.1 4.8 5.7 2.55
10 7.2 9.2 9.5 10.0 3.7
3 0 0.05 0.05 0.4 0.5 1.0
5 3.8 5.0 4.9 5.4 2.55
10 7.35 9.2 9.2 10.1 3.7
Ps source pressure
117
S- . . .. o,
10
9 6
8
MAX W
7/
MAX W/0MEAN WMEAN WWO
6 0, MIN 16/0
S~MIN W
z5
4
3
.... ..........Data with exposure suit
--- --------- Data without exposure suit
0 1 2 3 4 5 6 7 8 9 10
SUIT PRESSURE (psig)
I-
Figure 87. Normalized exposure suit abdomen force.[Key: W = with suit; W/O without suit.!
118
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MAX W
MEAN W)AX W/O
P MIN W
oMEAN W/O
/ •MIN W/O
--7J
/ , -A/, ,
,
Data wit exosr sui
/ /
6 2 3 -8 9 1
/ S
S. S
Figure 88. Norh exposure suit
- .S
[e W Data without exposure suit
1
VJ
1 2 3 SUIT P•ESWURE (ps)g8
t ~-1'
• .• Figure 88. Normalized exposure suit right thigh force.S[K•) W -with suit; 4/0- without suit.]
.,&2*> '
V _t
10
l•MX W
9
8 EAN W.MAX W/o
- IN W-/,/ NEAN W/O
4_- -4
7 4,- ,,,.NIN U/O
4- "
3f
2~ Data with exposure suit
----Data without exposure suit
I 2 3 4 54 74 8,I
SUIT PRESSURE (psig)
-I-
Figure 89. Normalized exposure suit left thigh force.[Key: W with suit; W/o = -.ithout suit.]
120"
/ .7r• o-i••i! r - 4. . -,. . . .. /...•
10
9
8
-.MAX W/O
7
MAX W6 -,MEAN W/O
5 'OfMIN W/O
3
MTN W
2
Data with exposure suit
----------------------------------------Data without exposure suit
S1 2 a 4 5 6 7 8 9 10
SUIT PRESSURE (psig)
[Key: W -with suit; W/O without suit.]
.5 121
10 MAX W
MEAN W9
MIN W
8 MAX W/O
" MEAN W/O
7 --- -/ - MIN /O
- . ,# .
4#
3-
/ -- 4
/ / /
3 /4/ /.4/ -/
5Data with exposure suit
2 ~~-----Data without exposure suit
g ,4,
1 2 3
//
SUIT PRESSURE (psig)
Figure 91. Normalized exposure suit left calf force.
[ey: W with suit; W/O without suit.]
122
~4 5: 6 .1
2.2 G-Sensitivity Evaluation of the Statham PM131TC Pressure Transducer
The purpose of this test was to quantify the acceleration sensi-tivity of the Statham model PMI31TC pressure transducer (Gould, Inc., Measure-ment Systems Div., Oxnard, Calif.). Linearity and sensitivity were alsoevaluated.
2.2.1 Test Configuration for the PMI•3IT. ressure Transducer
All tests were conducted with the transducer installed inthe gondola of the USAFSAM human centrifuge. Pressure stimulus was providedby the Datametrics pressure calibration system, installed in the gondola[Datametrics (a subsidiary of ITE Imperial Corp.), 340 Fordham Rd., Wilmington,Mass. 01887]. All stimulus pressures were maintained at the stated value,±0.02 psig. Excitation for the transducer was applied through the centrifugeslip-rings from a laboratory power supply located in the control room andmaintained at +5.0 ± 0.02 VDC. For purposes of acceleration testing, theaxes of the transducer were defined as: +Z with the pressure port verticaland on top of the transducer, +X parallel to a line from pin 4 to pin 2, and+Y parallel to a line from pin 3 to pin 4. The PMl31TC was so mounted in thegondola as to experience the same acceleration forces as the gondola accelerom-eter.
2.2.2 Test Protocol of the PM131TC Pressure Transducer
The linearity and sensitivity of the PM131TC were deter-mined by manually recording the transducer's response to stimulus (in 1.0-psigsteps) from 0 to 20 psig, both ascending and descending. The accelerationsensitivity was determined by subjecting the transducer to three ascendingand three descending 0.1 G/sec acceleration profiles from 1 to 11 G along eachaxis, in each direction, with 0-, 10-, and 18-psig stimulus applied. Thisprotocol resulted in 108 recorded acceleration data runs.
2.2.3 Data-handling Techniques for the Performance Evaluationof the PM131TC Pressure Transducer
The data from the linearity and sensitivity tests wereanalyzed using a T159 hand calculator. First, the mear and hysteresis werecalculated, in 1-psig steps, for each ascending and descending pressure pair.The maximum hysteresis in all six sets of data was determined in 1-psig steps.Finally, a 62-point (the 63rd point was lost) linear regression was run of theascending and descending means first calculated.
Data from the G-sensitivity tests were recorded on analog magnetic tape,converted to digital data in the USAFSAM/BRP analog laboratory. The digitizeddata was then processed through the BRP digital facilities. All data in eachset (for three ascending and three descending runs, testing a particular axissensitivity at a particular pressure stimulus) were normalized to the mean of"all 1-G data. The mean and the ±3a points for all higher G levels in that setwere then calculated and plotted (Figs. 92 - 109). In each case, the abscissarepresents the acceleration level, while the ordinate represents the deviationin equivalent psig from the 1-G output of the transducer.
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The PM131TC (serial no. 3644), using 5.00 VDC excitation.responds as:
E - 0.9415 P + 0.6458,
where E is the output voltage in millivolts, and P is the pressure stimulus inpounds per square inch. The maximum hysteresis was 0.04 mV at 6 psig, consti-tuting 0.13% of full scale. The maximum deviation from the least squaresstraight line through the data was found at the same point and was 0.06% offull scale.
The only axis indicating any significant acceleration sensitivity wasthe Z axis, with up to 1% of fL i-scale (i.e., up to 0.2 psig) error occurring(i.e., a maximum of 0.1%/G, or 0.02 psig/G). The -X axis and +Y axis showinconsistent tendencies to respond to acceleration but at lower levels. Sincethese errors, at 10 G, are on the order of ten times the apparent accuracy ofthe transducer, the investigator is cautioned to consider their effect on hisdata.
2.3 Ready Pressure AGV Mannequin Test
The performance of the ready pressure valve (RPV) has been testedand analyzed by SVTP and GVALVPGM (refer to Vol I, section 5.4). The obviousextension of that analysis is to investigate the application of the protectivepressure at the equipment-subject interface.
That interface was simulated using a CSU-13A/P anti-G suit on a Fiberglasmannequin. The transfer of protective pressure was monitored, using four forcegages located on the abdomen, left thigh, right thigh, and right calf.
2.3.1 RPV Mannequin Test Protocol
The RPV mannequin (RPM) test was conducted in four phaseson the USAPSAM human centrifuge. During each phase, a CSU-13A/P AGS wasmounted on a Fiberglas dummy which was equipped with surface force gages.These force gages were on the abdomen, left thigh, right thigh, and rightcalf. The mannequin was mounted in an upright seat in the centrifuge gon-dola. (The instrumentation configurations and calibration are essentiallydescribed in Vol. I, section 3; and in Vol. II, section 2.1.)
Phase I generated the ideal (I) or control case which served as a base-line for detecting change in performance. In this phase, the valve-suit-mannequin system was subjected to three trapezoidal 0 1 s/sec G profiles. Thesource pressure to the AGV during this phase was 125 psig.
Phase II generates the median (D) data set, using a valve source pressureof 125 psig, and a set of three 1.5 G/sec (High G) trapezoidal G profiles (i.e.,a linear increasing G profile followed by a linear decreasing C profile).
Phase II generates the maximum (X) data set, using 300 psig for valvesource pressure and a High G profile set.
142
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Phase IV generates the minimum (N) data set, using 30-.psig source pres-sure with the High G profiles.
2.3.2 Description of the RPV Nanneqxln Test Data
Analog data recorded at the USAFSAM./VNB centrifuge facilityis converted to digital data, using the USAFSAM/BRP analog-to-digital supportfacility. The digitized data, recorded on magnetic tape, serves as a database for the RPM program. The 0.1 G/sec onset data (group I) is digitized at20 samples/sec, thus giving approximately 2,000 samples for one increasing ordecreasing low-G-onset data set. The 1.5 G/sec onset data (groups D, X, andN) are digitized at 80 samples/sec, which gives approximately 500 samples forone increasing or decreasing high-G-onset data set.
The six channels of data digitized and processed by the RPM program are:
a) acceleration;
b) suit pressure;
c) abdomen force;
d) left thigh force;
e) left calf force; and
f) right thigh force.
The data sets collected consisted of:
a) five sets of data, collected as calibration (CAL) runs; thoseCAL runs pertinent to this study are:
Run 1--acceleration at 1 G, suit pressure at 0 psig, andthe four force-gage channels at C psi;
Run 2--acceleration at 10 G and suit pressure at 10 psig;and
Run 5--the four force-gage channels at 9 psi;
b) a total of six data sets, collected on each of the four testcases listed in section 2.3.1--three on the increasing slope of the trapezoidalprofile, interspaced with three sets collected on the decreasing slopes. Priorto digitizing the test data set, the CAL runs were digitized at the samplingrate required by the G-onset rate used in the particular test case. In all
* test cases, data were collected at G-intervals of: 1 - 11 G (increasing), and11 - 1 G (decreasing). The G intervals used in the RPM program are: 1 - 10 G(increasing), and 10 - 1 G (decreasing).
143
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2.3.3 Data Analysis
The computer progrm designed to analyze these data isdesignated the "RPM Program." It assumes the first sets will be the CAL runs,and reduces them j an arithmetic mean and a standard deviation. The standarddeviation is checked for excessive variance (a value of greater than 2.5333).If excessive variance is found in the CAL runs, the following data are con-sidered invalid and new data are required for further processing. Otherwise,RPM begins data procest rg.
Then, each test data set is calibrated using the means reduced from theCAL runs, and is assigned :he values nf the standards stimulating that channelon that run. The formulnqs utilized in data calibration are:
Gl - (RH-RL)/(CI-CL)
G2 - RAI - (01) x (CH).
Then, the calibrated value Gi x (digitized value) + G2,
where RH- real high,
RL - real low,
CH - actua.- calibrated high, and
CL = actual calibrated low.
Values used for normalizing the force gage channels to the suit pressurechannel are then calculated. These values are taken directly from the call-brated data sets, according to the following formulas on each test data set:
sum of first val of 3 incr G runsNOM - NL Low norm value 3
NORM2 - N High normval sum of first val of 3 decr G runsNOM H =ignomalf 3
The remainder of the RPM Program works with data points selected fromthe calibrated data sets. Prom each channel, of each run, for each whole Gvalue (i.e., 1, 2,..., 10), a mean is calculated for digitized data within thespan G ± 0.05. These mean values are then entered into an array designatedthe "H" array.
Each column pair (i.e., the ascending and descending partners in a trape-zoidal profile) of the H array is normalized according to the formula:
Ci - (Fi - Fl) kN - NL)/(FN - F1) - NL9
In which
Ci - corrected array element value,
Fi - original array element value,
144
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F = the first array element in the ascending column (corresponds intime to NL),
FN - tha last array element in the descendiig column (corresponds intime to N H),
N - iow normalization value (as already explained), and
NH - high normalization value (as already explained).
At this point, one full (calibrated and noimalized) test case bas beenstored in the holding array (H) in such a manner that the number of valuesaround each G-level is known. An arithmetic mean is calculated for each ofsix runs at each C-level and stored in the "A" array. This A array Is dimen-sioned A(10,5,8) or A(G-level, data channel, table), where data channels I to5 are: 1--suit pressure; 2--abdomen force; 3--left thigh force; 4--ft calfforce;and 5--right thigh force. [NOTE: Information from the original channel I(acceleration) is contained in the gravity-level dimension of this array.]
The eight tables of the A array are filled so that:
a) Test Case I yields Tables 1 and 2,
b) Test Case D yields Tables 3 and 4,
c) Test Case X yields Tables 5 and 6, and
d) Test Case N yields Tables 7 and 8.
The odd-numbered tables will contain increasing run data, and the even-numberedtables will contain decreasinS run data. Each table of the A array containsthe sum of the C averages about each G level (1 - 10, and 10 - 1) for threeruns. [NOTE: each test case is made up of three runs increasing, and threeruns decreasing.] The cells of the A array are now divided by three to givethe average pressure for the three runs they (the cells) represent.
Since the first test case is considered to be the optimal case, the com-parison of the suit pressure and the four bladders, in test cases D, X, and Nto test case I, is of special interest. Therefore, an R array is set up suchthat the various týables (6 in all) hold the residuals from the optimal case(or test ca.- I).
2.3.4 Data Presentation
1 sThe output of the RPM Program consists of 10 tables and
S 10 graphs. Tables 11 - 15 contain the reduced data (from the program's A array)for the suit pressure and the four force gages. The columns represent thetest conditions, while the rows represent the discrete G-levels at which the
data were averaged. Figures 110 - 114 (graphic representations of Tables 8 -
12, respec*ively) permit easier visual interpretation of what is really happen-ing across the four test cases.
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Tables 16 - 20 contain coLmns showing the residuals (from the program'sR array), from the optimal test case I, for each of the less than optimal testcases (D, X, and N); and Figures 116 - 119 are, again, plots of the correspond-ing tables. The residual plots, which permit easier v'isual interpretation,are actually expansions of the response differences in Tables 11 - 15 andFigures 110 - 114.
2.3.5 RPV Mannequin Test Conclusions
Reviewing Figures 110 - 114 yields an excellent overviewof the RPV performance. The tables are presented for examination, in whichmore subtle characteristics may be found.
The residual plots probably overstate their case. In no case does apressurization lag exceed 0.75 psig. That maximum occurs in the abdominalbladder and corresponds to a 0.5 psig lag in suit pressure. The apparenttendency of the AGS to maintain pressure on the mannequin is obvious whenFigures 116 - 119 are compared with Figure 115. This "mechanical" responsewas noted and discussed in detail on the preceding contract (refer to SAM-TR-78-12: TEHG, Vol. III: Anti-G Suits).
2.4 ALAR "High Flow" and "Special" Examinations
Two design modifications to the ALAR 8400A AGV were tentativelytested by the staff of USAFSAM/VNB. These modificationq have been designatedthe "High Flow" and the "Special." The PTAP examination of these valves hadthree phases: First, the mechanical differences between the two modifiedvalves and a standard 8400A were cataloged. Second, the open-flow capacityof the two modified valves was measured. Third, the effect of spring shimthickness on first-stage regulator output pressure was examined.
2.4.1 Desiga Modifications
The design modifications associated with the "High Flow"and the "Special" are summarized in Table 21. The "item numbers" referencesin that table may be correlated with those in Figure 23, section 1-3.
The modification to the bellows assembly [Item 181 increases the flowcapacity between the first- and second-stage regulators. The modification tothe bellows seat [Item 21] increases the flow capacity out of the second stageto the suit. The additional holes in the second-stage body [Item 23] increasethe flow capacity to the suit. The shims [Item 28] increase the first-stageregulator output pressure, thus increasing flow capacity of the second stage.The enlarged spool assembly [Item 29] and spool seats Tltem 34] increase theflow capacity of the first stage and increase the first-stage regulatingsurface. The additional holes in the main body lItem 46) increase the flowcapacity between the first- and second-stage regulators. The ventilatedspaces increase the exhaust flow capacity of the valve.
156
2.4,2 Open-flow Capacity of "High Flow"
The open-flow capacity of each of the valves was statically
tested using the pr.•ss-to-test button. In each case, the button was manuallydepressed to the mechanicaL limit of its travel. The results are shown inTable 22. The "Special" provides 11%, 44%, and 44% flow increases nver the"High Flow" for sourca pressures (Ps) of 30, 125, and 300 psig, respectively.
Recalling that the major differences between the "Special" and "High
Flow" are the shims [Item 281 and bellows seat [Item 2J], the effects of thesemodifications were examined. In the 30-psig tests, ao significant changes
were detected. In the 125-psig and 300-psig tests, the first-stage regulatorshim [Item 28] produced slightly more than half the increased flow capacity.
2.4.3 First-stage Regulator Shim Effect
In order to optimize the first-stage regulator performance,an ALAR 8400A was modified to allow measurement of the first stage regulation
pressure. The effects of various shim thicknesses were measured under staticconditions (Table 23). All tests were run using 125-psig source pressure.Spot checks were made using 30 psig and 300 psig, with no noticeable changes.
2.5 Accelerometer Calibration
The primary objective of this effort was to define a procedure
for calibration of the accelerometers used on the USAFSAM/VNB human centrifuge.The initial approach was to define the acceleration environment experiencedby the gondola accelerometer, allowing its calibration in place. This approachbecame prohibitively complicated. An alternate approach is presented herewhich removes the accelerometer to a location for which the accelerationenvironment is easily defined.
2.5.1 Gondola Acceleration Environment
trThe resultant acceleration through any specified point is
the vector sum of all acceleration vectors through that point. In the caseof the USAFSAM human centrifuge, an adequate assumption is that (for most pur-poses) the acceleration vectors in the gondola are limited to the accelerationof gravity (g) and the centrifugal acceleration (a) generated by the rotationof the system. These two vectors may be considered perpendicular, withnegligible error, and the resultant through any point defined by a vector of
magnitude
JAI /2 + g2
located in a plane, defined by the vectors a and g, at an angle
6 = tan- g/a
from t. Using this definition, 0 also approximates the roll angle of thegondola.
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The magnitude of the centrifugal acceleration vector is coummonlydefined as
a w 2 R
where w equals the angular velocity of the system in rad/sec, and R equalsthe radius of rotation (in some convenient dimension) of the specified point.The determination of R makes prohibitively c.omplex the expression describingthe acceleration environment of the accelerometer in the gondola.
The accelerometer is normally located on the forward wall of the gondola,at a position which approximates the elevation of a subject's heart from thegondola floor. This position places the accelerometer approximately 10-47/64±1/64 in. (27.265 ± 0.040 cm) above the center of rotation of the gondola. Theaccelerometer is approximately 20 ft 2-17/64 in. ± 3/64 in. (6.15355 m ± 0.0012 m)from the centrifuge center of -otation when the system is at rest. The obviouschange (shortening) in radius as the gondola rotates would, if not accounted for,introduce an error of unacceptable magnitude. Therefore, the rotation of thegondola must be predicted; and, at this point, the theoretical expressionbecame unmanageable.
Obviously, a significant acceleration gradient exists in the gondola dueto the differences in radii of rotation of the various locations. A subject'sfeet may experience at least 10% more acceleration than his head! The physicalstructure, equipment, and instrumentation experience an even larger gradientdue to their wider distribution.
At this point, the difference between the center of mass and the centerof gravity must be considered. These two points only coincide in a uniformacceleration field. In the case of the gondola, this field occurs only whenthe gondola is at rest. When an acceleration gradient is applied to the sys-tem,, the gondola will rotate to aline the center of gravity and the axis ofrotation. The center of gravity can (and in the case of the gondola, does)move a considerable 4istance from thQ center of mass. Furthermore, thismovement is not perpendicular to the gondola floor and through the centerlineof gondola rotation. Empirical data indicate errors in excess of 4 0 betweenactual and theoretical roll angles. These errors can result in as much as 20%error in acceleration reading (although usually the resulting errors a3.e muchsmaller) for low-G levels. At this point, attempts to calibrate an accelerometer,theoretically or empirically, in the gondola vere abandoned.
2.5.2 Dynamic Calibration
Two means of transducer calibration are available. Bothtechniques involve rotating the transducer so that the sensitive axis is per-pendicular to the natural G irector, and adjusting the variable resistor marked"Z" for a zero output from the transducer.
Coarse adjustment of the "S" (span) control on the transducer may beaccomplished by alining the sensitive axis of the transducer with the G fieldand adjusting "S" for the proper response. The acceleration of gravity forthe USAFSAM human centrifuge was cal-culated, using Helmert's equation, anassumaed altitude of 594 ft, and a latitude of 29020'30", (longitude is
170
2I
approximately 98*26'30"). This estimated value is 979,214 cm/sec (32.126 ft/ isec2 , or 0.9985 G) compared to a standard of 980.665 cm/sec 2 (.32.174 ft/sec2 ,or 1.0 G).
Greater resolution may be obtained by installing the accelerometer in aspecial bracket, manufactured by the PTAP crew, which locates the aensitiveaxis of the accelerometer 13 ft 9 in. ± 0.1 in. (419.10 ± 0.25 cm) from thecenter of rotation (CR). In this case, the "S" and "Z" controls may beadjusted to respond according to Table 24, using the rotational speed of thesystem as a standard. Estimated error of this approach is 0.149%.
2.6 Continuous ECG Recordings in Primates
2.6.1 Objective
The purpose of this investigative effort was to examinesome of the problems VNB has experienced while performing long-term (6 months)ECG monitoring in animals. This portion of the report covers two areas: first,a discussion of various types of percutaneous lead devices; and second, adiscussion of silver and silver-silver chloride electrodes. Recommendationsare made and methods are suggested in h,'ith areas.
2.6.2 ECG From Chronically Implanted Electrodes
Using chronically implanted electrodes for ECG eliminatesmany of the problems associated with conventional surface electrodes; namely,daily skin preparation, electrode attachment, impedance variations, and elec-trode impedance measurements. Most importantly, consistent repeatable ECOmeasurements can be obtained. With implanted electrodes, the most difficultproblem, of course, is the data recovery method--which is limited to telemetryor -'-rd wire. TelemeJzry has several distinct disadvantages for long-term(6 .onths) monitoring. The first disadvantage is that the power consumptionfor trans-•itting the data over long periods necessitates using rechargeablebatteries and a convenient method of recharging. A power loop transmitterplaced over the skin yqd an inductive coil placed beneath the skin, withassociated circu -for charging the device (6,9), adds immensely to thevolume and complexity of the circuit to be implanted. The second disadvantage
is the surgical implantation of the telemetry/power-supply device, which iscertainly more extensive and traumatic than the implantation of subcutaneouselectrodes. Since the ECG is the only anticipated parameter to be measured inthe near future, it i1 advisable to keep the surgical procedures at a minimumand to continue using a hard-wire system.
A. Percutaneous Leads: Using a hard-wire system, theproblem now becomes one of finding a biologically inert feed-through, and
EDITOR'S NOTE: For the convenience of the reader, the author has included"References," No. 1-18 (.section 2.6.5), which pertain specificallyto the material in section 2.6.
p 171
tin.
TABLE 24. ACCELEROMETER CALIBRATION VALUES FOR LOCATION13 FT 9 IN. ± 0.1 IN. (419.10 ± 0.25 Q4) FROMTHE CENTER OF ROTATION
Centrifugal AngularAcceleration Velocity
(ft/sec2) -Sraesc) _ýKpm
0 0 0 0
1 32.174 1.530 14.607
2 64.348 2.163 20.658
3 96.522 2.649 25.301
4 128.696 3.059 29.215
5 160.870 3.420 32.663
6 193.044 3.747 35.781
7 225.218 4.047 38.648
8 257.392 4.327 41.316
9 289.566 4.589 43.822
10 321.740 4.837 46.193
11 353.914 5.073 48.447
12 386.088 5.299 50.601
13 418.262 5.515 52.668
14 450A436 5.724 54.656
15 482.610 5.924 56.574
16 514.784 6.119 58.430
17 546.958 6.307 60.228
18 579.132 6.490 61.974
19 611.306 6.668 63.672
20 643.480 6.841 65.326
172
maintaining the percutaneous lead system. Given that one has a biologicallyinert material, the development of infection due to rejection has been mini-mized; but disruption of the skin outlet interface may occur, due to mechani-cal stress applied to the leads, thus causing drainage. Chronic infectiousdrainage can cause the infection process to follow the leads deep into theanimal, causing death or local necrosis, and disrupting the percutaneousleads (13).
In the development of a biologically inert percutareoua lead system,various types of materials have been used, includiag Teflon, silicone, velour,epoxies, titanium, and pure carbon (1-3, 13-18). Of these materials, pure car-bon and velour seem to be best suited for a natural ingrowth of subcutaneoustissue and the formation of a bacteria-proof barrier.
The velour technique, which is presently being used by VNB, is usuallya matter of securing the velour fabric around the lead system with a medicalgrade of silicone adhesive, Dow Corning Type A (Dow Corning, Inc., Midland,Mich.). The literature indicates that adherence of the tissue tc the fabricis good, producing a bacteria-proof seal; however, the silicone adhesive tendsto fail, causing drainage and subsequent infection. The tissue-velour inter-face tends to be delicate and is subject to disruption by mechanical trauma(13). Nevertheless, this method appears to be fai~ly successful and simplefor obtaining a percutaneous lead system.
During the past decade, several types of high purity (90-99%) carbon havebeen developed in the interest of biomedical applications (2,4). This highpurity carbon, having extremely low chemical reactivity, is presently beingused in human subjects for prosthesis, cardiac assist devices, dental implants,and percutaneous lead devices. The fact that high purity carbon is biologicallyinert is well documented (2-4,8,10), and apparently seems to be "number one"candidate for many of the percutaneous lead problems. In work done at RanchoLos Amigos Hospital, Downey, California, carbon devices have been implaated inhuman subjects for over 3 years. These patients have been exposed to fulldaily activities, including sporting activities.
The mechanical stability of these devices is very good, and consequentlythey do not need additional support. The devices are not perfect, however,and are subject to disruption due to mechanical stress; but apparently theydo not cause a drainage problem when disrupted (5,11).
One property of vitreous carbon is very low resistivity--lO ohm-cm (2,8).Consequently, to use this :.aterial for a percutaneous lead system, an electri-cal connector must be used in conjunction with the carbon device for electricalinsulation. Earlier pure carbon devices were molded and then fired (vitreouscarbon) to their final form. The problem with vitreous carbon is that about40% shrinkage occurs during the firing process; and consequently, maintainingaccurate dimensions for an electrical connector feed-through is difficult.Also, in its final form, vitreous carbon is very hard, and thus difficult toS~ machine.
Another process has been developed whereby high-purity carbon is deposited
(pyrolite carbon) on a substrate base, and subsequently the dimensions of thedevice are precisely controlled. A pyrolytic caribon device can be depusitedon a substrate base having a feed-through for a miniature multi--pin connector
173
L .4'.
(female end). These pyrolite carbon devices are custom-made for a selectedconnector by General Atomic Co. (Medical Products Div., 11388 Sorrento ValleyRd., San Diego, Calif. 92121) for approximately $30.00 each. General Atomichas already produced this type of device, using miniature electrical connec-tors wSth as many as 200 pins. These percutaneous devices are presently beingused in subjects for chronic nerve impla,.ts for external visual stimulus (5).The connector, a Cannon NJS series (9-, 24-, or 72-pin), can be obtained--unterminated, or terminated with individual wires, or as a one-piece multicon-ductor cable--for approximately $30.00 each (ITT Cannon Electric, 666 E. DyerRd., Santa Ana, Calif. 92702). The contractor recommends ordering the con-nactor terminated with individual 30-gage insulated wires of a specified length(long enough to reach from exit site to electrode site). In thi3 way, the feed-through connector device can be obtained as a sealed, moisture-proof unit.Ordering the connector in the 9-pin configuration is also advisable, to allow& sufficient number of electrodes for measuring the ECG or VCG, if desired.(However, consideration should be given to future experiments, in which casethe 9-pin configuration would be insufficient.)
B. Silver and Silver-Silver Chloride Electrodes: Whenelectrodes come in contact with an electrolyte, a voltaic cell is created atthe electrode-electrolyte interface. This effect, known as polarization, isa function of temperature, of the concentration of the electrolyte, and ofthe manner in which the metal reacts with the electrolyte. Because the tem-perature ane concentration of the electrolyte are fixed for this particularapplication, only the type of metal and its reaction to the electrolyte (NaC1)will be co-,•sdered.
The effects of polarization are usually minimized by the fact that thispotential occurs at each electrode, and the net difference between electrooesshould be zero--assuming electrodes are identical in materipl, size, and shape,and are immersed in the same electrolyte. In practice, however, an unstableresidual potential difference will exist. This residual is probably due toslight differences in surface contamination and irregularities in the metalelectrode (7). If these potential differences were stable, they could simplybe removed by ac coupling the ECG signal at the preamplifier. Actually, thesepotentials are not stable, vary constantly in a random fashion, and cannot becompletely filtered out by the high-pass filter, which is usually set at 0.05 Hzfor the ECG.
When silver is used as the electrode, metallic silver combines with achloride ion of the electrolyte, releasing an electron and eroding silver awayfrom the electrode. The polarizing potential, developed at the silver surface,is approximately 0.8 V, with residual potential differences of 95 mV (18).
The conventional method of eliminating the polarization potential in silverelectrodes is to remove the electrode-electrolyte interface by plating thesilver with sil'er chloride, thus providing a non-polarizable electrode. TheAgCI maintains a high concentration if ionized Ag and Cl at the Ag-AgCl inter-face, and current flow at the AgCl-electrolyte interface is maintained by dif-fusion of the chloeide ions (12). Unlike the Ag electrodes, current flow inthe Ag-AgC! electrodes does noc result in an irreversible electrochemical reac-tion. Silver chloriding silver electrodes reduces the residual potential dif-ference to approximately 2.5 mV.
174
Another advantage of chloriding silver electrodes i that ever thoughthe process raises the overall electrode impedance, the caipa¢,tive bfects aredecreined for the lower frequencies, thus decreasing impedance nonlinearities.There is an optimum amount of chloride plating tn obtain the lowest possibleimpedance while reducing electrode capacitance, as will be explained later.
Ag-AgC1 electrode pellets are produced commercially by tombtning As andAgCl (about 60/40), thus eliminating the plating process. Howevo*-, because ofthe number of experimental animals involved and because thE electrodes will bechronically implanted, the contractor suggests that VNB continues to use thesilver electrodes, but that they be plated with AgCl as follows:
The electrode lead must be soldered to the silver electrode. All of the wire not used in making the connec:ion shouidbe covered with polyvinylchloride (PVC) insulation. A medfcalgrade adhesive, Dow Corning Type A (Dow Corning, "nc., Midland,lich.), is used to seal the solder connection and the insulatc..This adhesive will protect the solder connection and the elec-trode lead from electrolyte infiltration and subsequent erodingpotentials.
The electrode surface is then polished with an emory cloth and washedto free the surface of contaminants. The electrode is then placed in a clean,nonmetallic container of fresh 0.9% NaCl solution and connected to the posi-tive terminal of a constant current source. A larger bare silver electrode(approximately 1.0 in. 2 ), also cleaned as just described, is placed at theopposite end of the container. The lead of this electrode is connected tothe negative end of the constant current source. A milliammeter is placed inseries with the electrode to be plated for determination of applied current.
The literature indicates (7) that the optimum electrode impedance canbe achieved by using a current density in the range of 500 - 2000 mA-sec/cm2 ,and should be applied at a rate greater than 5 mA/cm2 . Using a 6-mm-diam.electrode (A . 0.28 cm2 ) and an arb.ttrary current density of ]000 mA-sec/cm2
at a rate of 7.5 mA/cm, 2.1 mA of current should ba applied between the elec-trodes for 133 sec. Each electrode should be plated in this vanner, andfresh NaCl should be used for each plating process. After plating, the elec-trodes should be handled with some degree of care, since the AgCl surface canbe removed by abrasion. A small electrode (3-mm-diam., for example) could beused without degrading the amplitude or fidelity of the ECG. For a 3-mm elec-trode, with all other factors remaining constant, 0.53 mA should be appliedfor 133 sec.
2.6.3 Animal Instrumentation
Given the chlorided electrodes with leads fnd the percu-taneous device with connector and leads, the animal can be instrumented forECO by introducing the percutaneous leads subcutaneously at the exit site andbringing them out at the electrode site. The excess lead from each lead is then
trimmed off and dressed for soldering, and all but approximately 2 in. trimmedoff the electrode lead. A small p:'ece (approximately 1/2 in.) of polyolefinheat-shrinkage tubing, Alpha FIT-300-1/8 (Alpha Wire, 711 Liderwood Ave.,Elizabeth, N.J. 07207), is placed over one of the lead wires, The wires are
175
then soldered together, leaving only a small length (approximately 1/8 - 3/16in.) of exposed wire. This shrinkable tubing is then slid over the exposedwire, and heat is applied at approximately 275"F at the splice. Care shouldbe exercised so that the excessive heat is not applied to the PVC insulationof the leads. The polyolefin tubing has different characteristics from normalPVC heat-shrinkable tubing in that when heat is applied to polyolefin, theouter wall shrinks, but the inner wall melts, thus providing a moisture-proof,encapsulating Jacket.
After the connectors have been positioned and sutures applied, a protec-tive cap should be placed over the electrical connector to protect the pins.This protective cover should be kept in place when measurements are not beingmade.
2.6.4 Conclusions
In conclusion, we recommend using pyrolytic carbon percu-taneous devices designed specifically for use with the miniature connectordiscuscea in this report. We feel this device .s a biologically compatiblefeedrhrough which will facilitate physiologic measurements. Adequate pro-tr on for the connector, especially with the anim, l unrestrained, shouldr •It in a maintenance-free percutaneous lead sy..em. We also recommend
F ver chloriding the silver electrodes, as VNB hav done in the past (referto section 2.6.2, B). The use of polyolefin tubing to obtain a waterproofseal will decrease the time required i, instrumenting the animal, and willallow repeated use of the electrodes, percutaneous connector, and leads.
2.6.5 References
I. Al-Nakeeb, S., P. T. Pearson, and N. R. Cholvin. A thoracic percutaneouslead system: development and evaluation. J Biomed Mater Res 6:245-265 (1971.
2. Benson, J. Elemental carbon as a biomaterial. J Jiomed Mater Res Sym-posium (Aug. 3-7, 1970, New England College, Henniker, N.H.). No. 2(part 1), 41-47, 1971.
3. Bokros, J. C., et al. Prosthesis made of carbon. Chemtech 7:40-49 (1977).
4, Bokros, J. C., L. D. LaGrange, and F. J. Schoen. Control of structureof carbon for use in bioengineering. In Q. L. Walker (ed.). Chemistryand physics of carbon, vol. 9. N.Y.: Dekker, 1972.
5. Bokros, J. C. General Atomic Corporation, Division of Medical Products,San Diego, Calif. 92138. Personal communication, 1978.
6. Fryer, T. B., et al. Multichannel implantable telemetry system. NASATech Brief ARC-11079, Dec 1977.
7. Geddes, L. A. Electrodes and the measurement of bioelectric events.N.Y..: Wiley-Interscience, 1972.
176
8. Kadefors, R., and J. B. Reswick. A percutaneQus electrode for long-term monitoring of bioelectric signals in humans. Med Biol Eng 8:129-135 (1970). [Now: Med Biol Eng Comput]
9. Kojima, G. K. Latteryless implanted echosonometer. NASA Tech BriefARC-11035, Dec 1977.
10. Laenger, C. J., et al. A :aew communication method for deaf-blind people.Southwest Research Institute Technical Report 13-9134, 1974.
11. Laenger, C. J. Southwest Research Institute, San Antonio, Tex. Personalcommunication, 1978.
12. Miller, H. A., and D. C. Harrison. Biomedical electrode technology.N.Y.: Academic Press, Inc., 1974.
13. Miller, J., and C. E. Brooks. Problems related to the maintenance ofchronic percutaneous electronic leads. J Biomed Mater Res Symposium(Aug. 3-7, 1970, New England College, Henniker, N.H.), No. 2 (part 1),41-47, 1971.
14. Mooney, V., et al. Percutaneous implant devices. Ann Biomed Exig 5:34-46 (1977).
15. Mooney, V., et al. The use of pure carbon for permanent percutaneouselectrical connector systems. Arch Surg 108:148-153 (1974).
16. Owen, L. J. Skin implant multiwire connector. NASA Tech Brief KSC-11030, Spring 1977.
17. Rogers, A., and L. B. Morris. Percutaneous leads for power and controlof artificial hearts. Trans Am Soc Artif Intern Organs 13:146-150(1967).
18. Vasco, K. A., and R. 0. Rawson. A chronic non-reactive per'lutaneouslead system. Trans Am Soc Artif Intern Organs 13:143-145 (1967).
2.7 Control Center Data Distribution System Study
The patch panel system, presently installed at the USAFSAM human,centrifuge control console, has several undesirable physical and electricalqualities. Technology Incorporated was assigned the task of locating, evalu-ating, and recommending a suitable replacement for the patchcord programmingsystem. in addition to the resulting recommendation, this report includes adrawing of a suggested physical arrangement and a generalized block diagramof the recommended electrical arrangement.
2.7.1 Undesirable Characteristics
The more annoying of the electrichl inadequacies of thepresent system is the problem of poor electrical contact between the patchpanel receptacles and the patchcord tips. Poor contact causes erratic changes
I;? I
in the signal levels whenever the console is bumped or the patchcords are moved.Perturbations of the signals during several tests have been painstakinglytraced to the patch panel.
The physical contruction of the present patch panel system createsseveral recurring problems--one is the force required to insert or removepatchcord tips; and another, the poor arrangement of the signal processinginputs and outputs. The force required to patch or unpatch the tips frequentlyresults in broken patchcords; and the poor arrangement almost always resultsin a maze of tangled patchcords.
2.7.2 Recommendations
Specification sheets and other literature pertaining topatchcord programming systems were sol ,:itei from 43 manufacturers of suchsystems. The manufacturers were select., those listed in the 20th edi-tion of the Electronic Engineer's Master Technical Publications, Inc.,645 Stewart Ave., Carden City, N.Y. 11530).
Initially, much consideration was given to obtaining a shielded systemidentical to the one presently installed at the data collection center. Thispurchase would have been an advantage because spare patchboards are either onhand or available. However, according to the manufacturer, Amp Inc. (Box 3608,Harrisburg, Pa. 17105), the data center system was obsolete. The productiondepartment of Amp Inc. advised that a system (identical to the one presentlyinstalled at the data collection center) could be fabricated; but it wouldrequire "intensive labor," and so would tend to be cost prohibitive.
The better patchcord programming systems available are of the shieldedtyp" with all contact surfaces gold plated; and such systems yield a goodsignal-to-noise ratio with little crosstalk. These are the qualities requiredfor best results in signal processing at the centrifuge console.
After the available literature on several systems from various manufac-turers had beex, studied, the patchcord programming system recommended was the960 system manufactured by Amp Inc. The 960 system is of the preprogrammable,removable type, and has the format of 3C holes vertical by 32 holes horizontal.The external dimensions of the patchcord (including the frame) are 16-13/64 in.ligh by 14-47/64 in. wide (41.2 cm high X 37.4 cm wide). The front of the 960system patchboard extends 2-1/4 in. (5.7 cm) forward from the panel on whichit is mounted. Dividing the patch panel into its various system inputs andoutputs sections, by contrasting color patterns, tends to increase the speed
and ease of reprogramming for various tasks. Amp Inc. can silk-screen thepatchboard according to any convenient pattern furnished by the buyer of thesystem at additional cost. Technology Inc. recommends that several patchboardsbe purchased so that they can be preprogrammed for each test protocol. Thenrepatching between tests and experimonts wo-Id consist of simply removing onepatchboard and replacing it with the proper one. This approach would insurestandardization of the patching procedures and also save time.
A suitable enclosure for mounting the system Is manufactured by thePremier Metal Products Company $Div. of Sunshine Mining Co., 381 Canal Place,
178
Bronx, N.Y. 10451). The stock number is TIC 21-19-13; and the dimensions are21 in. high by 19 in. wide by 13 in. panel-to-panel depth (53.3 cm X 48.3 cmX 3.3 cm).
The new patch-panel system should be lo.ated in approximately the sameposition as the presently installed patch panel. The rear frame of the patchpanel should be physically located in the enclosure, such that easy access fortroubleshooting and/or wiring is afforded.
The physical arrangement of the inputs and outputs of the various datasystems (Fig. 120) is the composite of the better features of several arrange--ments studied for this report. rigure 121 is a block diagram of the proposedcentrifuge data distribution system. Special consideration was given toarranging the inputs and outputs of the various systems to be programmed bythe patch panel. The inputs and outputs that are more frequently patched intoeach other are placed either adjacent to each other, or as close as physicallyfeasible.
The 16 BNC connectors, that in the present system provide access to sys-tems external to the patch panel, are very useful; and this arrangement shouldbe retained in the new system. An additional recommendation is that severalMS-type connectors be placed at the convenient locations, either on the consoleor the patchboard system enclosure, and wired to the available patch panel con-
tacts. This arrangement would allow flexibility in patching external systems,such as tracking tasks to the centrifuge. Several nonpolarized capacitorsshould be wired between ground and convenient patchboard contacts to provideac bypass to ground and/or glitch filtering, as required.
An arrangement for monitoring the outputs of the sigial conditionersshould be provided. It should be able to switch select all 16 preamplifiers.instead of just 12, as in the current system.
Patchable access to permanently installed digital multimeters (DM4's)would be very useful for monitoring signal levels, determining resistances, orchecking the continuity of signal pairs.
The signals from the accelerometers are usually patched into channel 1 ofthe data recording systems, and this arrangement should also be kept in the newsystem. Hard wiring into channel 1 is not recommended. Because the patchboardsare pre-programmable and quickly changeable, the selector switch (presently usedto select either the gondola accelerometer or the animal end accelerometer) isnot necessary.
One final consideration that may be of some future value is the utilization
of a few spare, or seldom used, signal pairs for an instrumentation ground.These signal pairs wculd be useful for patching through a ground to the signalpatch panels on the centrifuge to provide an instrumentation ground separatefrom the power ground.
2.8 Closed-Loop Centrifuge Control Study
2.8.1 Objective
The purpose of this study was to perform circuit analysis,circuit design. and troubleshooting on an Air Force developed electronic methodfor closed-loop control of the human centrifuge.
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2.8.2 Normal Centrifuge Operation (Figs. 122 - 125)
Pressurized hydraulic fluid for the drive system is suppliedby 5 variable volume pumps which are driven by 4 electric motors. The pressur-ized hydraulic fluid turns the 8 fluid motors, which, in turn, drives the rotorarm through gear trains. The motor speed, which is proportional to fluid flowthrough the motors, is adjusted by means of a servo control, which varies theoutput volume of the pumps. ThE motor inlet pressure is controlled by theonset pressure control, A207 (Fig. 122), which determines the nressure (between0 psi and 5000 psi) at which the onset relief valves (RV-3 through RV-7, inFig. 125), vent the pump output to the main reservoir. As shown in Figure 125,when the 4-way valves (DCV- 1 through DCV-5) are in the spring offset position(solenoids L-7, L-8, L-403, L-404, L-405, not energizeA), this pressure isreservoir pressure. When these solenoids are energized by the pressure com-mand, the pilot pressure to the onset relief valves is determined by thesetting of the electrically operated relief valve, B-402 (Fig. 125). B-402 isadjustable between 0 psi and 5000 psi by the onset pressure control, A-207.
Deceleration of the rotor arm is accomplished by depressurizing thehydraulic motor inlets and restricting the motor outlets so that the motors,as they are driven by the moving rotor arm, pump the fluid against a backpressure, thus resulting in a braking torque. This mocor outlet pressure iscontrolled by brake pressure control signals, which determine the pressureat which the brake relief valves will vent hydraulic fluid to the mainreservior.
Specifically, the hydraulic fluid flows frum the outlet ports of fluidmotors MF-l through MF-8 (Fig. 124) through the return manifold, through thethree braking relief valves (RV-8, RV-9, and RV-10), which are designed torelieve at their spring setting (5000 psi) or at their pilot pressure (0 to5000 psi), whichever is lower. When 4-way valve DCV-7 is in its spring-offsetposition, it blocks the flow of oilot fluid through the three braking reliefvalves. When DCV-7 is activated (first ready status) by L-401, pilot pressureflows from the three braking relief valves, through the three chteck valves(CV-22, CV-23, and CV-24), through DCV-7 itself, to electrically adjustablerelief valve B-401. B-401 is adjustable between 0 psi and 5000 psi by deceler-ation pressure control A-206 (Fig. 122) on the console. The closure ofK-3 22 (first ready) contacts energizes relays K-308, K-226, K-309, and onsetpressure control A-207. Relay K-226 is energized through K-4 contacts (whichremain closed until final ready status), thereby energizing deceleration pres-sure control A-206 and preventing pressurization of the main hydraulic pumps.
The momentary closure of pressure switch S-212 (Fig. 123) energizes andlocks K-323, the contacts of which energize the solenoids (L-7, L-8, L-403,L-404, and L-405) of the pump vent valves DCV-l thcough DCV-5. These valvesallow onset pressure control A207 to control relief valves RV-3 throug RV-7which, in turn, control pump outlet.
Momentary closure of hydraulic brake switch S-208 energizes K-226 andopens the normally closed contacts K-226 which, in turn, causes K-323 to bedeenergized and depressurizes the system. During the time of S-208 closure,the deceleration pressure control A-206 is energized and hydraulic brakingis available.
182
2.8.3 Closed-Loop Control System Developed by the Air Force
The closed-loop control system, developed by the Air Force,n~tilizes a control stick command voltage and feedback voltage from an acceler-ometer (Fig. 126). The design intent was that, when these two signals were inequilibrium, the gondola would reach a G-level proportional to the controlstick position.
The closed-loop control circuit, which takes the place of the onset pres-sure control A-207 and .e deceleration pressure control A-206, has two outputs.When the control stick voltage (Vr) is greater than the accelerometer feedbackvoltage (Va), voltage is applied to the onset relief valve B-402. When Vr isless than Va, voltage is applied to .he brake pressure valve B-401. Also,when the closed-loop control system was tested, hydraulic brake switch S-208 3(console) and the pressurize switch S-212 (console) were each shorted to theclosed position at all times, and the normally closed contacts of K-226 wereexternally shorted. These are the contacts that open and break the pressuriza-tion circuit when the hydraulic brake switch is momentarily closed. In otherwords, with the control circuit wired in this configuration, the hydraulicsystem cannot be depressurized when the hydraulic brake is applied (Vr < Va).
The centrifuge has many electrical and hydraulic interlocks, many ofwhich were designed for subject safety, and several of which were designedto prevent damage to the hydraulic system itself. For example, the contactsof K-4, which energize the deceleration pressure control for hydraulic brakingand prevent the system from being pressurized, are normally closed until firstready status Under the test configuration just discussed, the interlockingsafety features of K-4, S-208, and K-226 are circumvented. The contractor feelsthat these interlocks should not be bypassed and that the hydraulic systemshould be depressurized before applying the hydraulic brake. Operation of thecentrifuge without these designed safety interlocks could cause catastZophicdamage to the hydraulic system.
2.8.4 Design Modifications
The cortractor feels that the electronic circuit of thecontrol system developed by the Air Force is a workable design that, with cer-tain modifications, can be used in the closed-loop control :ystem. These modi-fications must provide three modes of operation--pressurization and onsetpressure control, depressurization, and hydraulic brake control--which possiblycould be accomplished by comparing the control voltage (Vr) with the accelerom-eter voltage (Va). When Vr > Va, the pressure switch S-212 would close and thegondola would accelerate until Vr - Va. The pýsition of the control stick wouldrepresent a certain 0 level. When Vr < Va, by some small fixed difference,S-211 would be opened and the system depressurized. This small voltage differencewould allow for minor adjustments in C level by pressurizing and depressurizingthe system, without applying hydraulic braking. When Vr << Va by some larger butfixed difference, the system would be depressurized and hydraulic braking appliedin proportion to the difference between Vr and Va. The contractor feels that allthree modes (pressurization, depressurization, and hydraulic brakiag) are neces-sary for operating the gondola on an SACM profile.
In addition to having control over the gondola via the emergency kill, thepilot controls (already described) should also be designed for manual over-rideat the console.
183
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Additional design modifications in the Air Force developed system shouldAlso include hysteresis and temperature compensation of the electrolytic valves(B-401 and B-402) employed in the A-206 and A-207 control circuitry. Thesechanges are not essential in the initial design stages, and could easily beincorporated after the design concept han been proven.
In conclusion, we recommend making the following design changes on theclosed-loop control system developed by the Air Force:
(1) pressurization and onset pressure control with control stick volt-age 7r greatar than accelerometer voltage Va;
(2) depressurization and subsequent deceleration with control stickvoltage Vr slightly less than accelerometer voltage Va;
(3) hydraulic braking proportional to the difference between Vr and Vafor large jVr - Val; and
(4) hysteresis and temperature compensation for control valves B-401and B-402.
2.9 Medilog Recorder G-sensitivity Tests
2.9.1 Introduction
'ne Medilog recorder is a miniature 4-channel tape recorderdesigned specifically for monitoring of ambulatory subjects. Data is recordedon a 2-hr or 24-hr recorder, and is recovered from the Ocford reproduce unit ata rate of 60 times real-time of the recorded tape.
The purpose of these tests was to determine the sensitivity of the Medi-log 4-24 tape recorder to various levels of G forces orn the three orthogonalaxes. The recorder selected for these tests was a 24-hr recorder (S/N 06481)with the following preamplifier configuration: channel l--EG2 (ECG); channel 2--AM3 (acceleration); chann(l 3--AM3 (G-suit pressure). and channel 4--AT2 (tem-perature).
2.9.2 Test Protocol and Configurations
A. Time base expansion tes..: Since the recorded datacannot be recovered from the recorder on a real-time basis, and the fact thatthe record unit has an upper frequency respons3e limitation (100 Hz on the EG2,and 4 Hz on the AM3) precluded the use of tijAe code recording and the corre-lation of real-time events with recorded tesrt data--all events during thecentrifuge runs were correlated to recorded G levels (channel 3). Also, the60 times real-time reproduction speed neccssitated using a second instrumenta-tion recorder to obtain a 32:1 expansion of all test data.
The test configuration for the time base expansion is shown in Figure 127.Signal amplitudes and frequencies were selected to be compatible with actualrecorded data for channels 1 and 2 (ECC and pressure respectively). Aplitudes
18Q 1.i
Ampex FR1300
HP 204-B
OSCI LLA rOR 3_2_BRUSHUj MARK 200
1.0 V P-P, 6.0 Hz I CSine wave U
4 • 3WVETEK 114
| FUNCTION5SGENERATOR_ 5
1.0 V P-P, 6.0 HzTrian~gular wave
Figure 127. Ti7"e base expansion test configuration.
and frequencies for channels 3 and 4 were selected as a matter of convenience.Test signals were recorded at a speed of 60 ips and were reproduced at 1-7/6ips for a time base expansion of 32:1. All test signal frequencies and ampli-tudes were monitored with a Systron Donner 6152 A counter and a Tektronix 564oscilloscope during both record and reproduce modes.
B. Mediog recorder and reproducer tests: This experimentwas designed to test the Medilog for fidelity of record and reproduction of sig-nals while being exposed to various levers of G forces.
The recorder axis orientation is shown in Figure 128, and the test con-figuration in Figure 129. The 10 Hz sine wave was selected for channel 1;for this sine wa'$e was well within the bandpass of the EG2 amplifier, and thereproduced signal (10 X 60/32 - 18.75) was fast enough to be counted on thefrequency counter but slow enough to copy on the Brush recorder. The 0.1 Hztriangular signal was selected because it was within the bandpass of the AM3recorder and would allow an easy method for testing amplitude variation in theMedilog recorder. The signals for channels 1 and 3 were differential inputs,with the tape recorder common used as the reference ground. These signalswere sent through the instrumentation slip rings, but were monitored in thegondola at the recorder input--before and after tbe centrifuge runs--with aTektronix 564 scope. The input signal frequency for channel 1 was Tuonitoredat the console with a Systron Donner 6152A counter.
190
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FEMLECONFECTOR
4Z
Figure 128. Recorder axis orientation.
HP 204 8 1OSCILLATOR
,, z EOtLOG4-24
ACCELER014ETER 4 EP
FUNC.I.ON' GENERATOR
THI4 | STORCL IBRATOR
Figure 129. Medilcg recorder test configuration.
191
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TABLE 25. ORDMER OF AXIS TESTING AND TEST SIGNALS
AXIS CHANNEL I CHANNEL 2 CHANNEL 3 CHANNEL 4(10 Rz) (0.1 Hz)
+Z 1 mV p-.p 1-10 G 8 miV p-p 37 0 C
-Z " 40*C
+X "1 " "330C
-X " " 34*C
+Y " ""270C
_y " , 30 0 C
The Medilog recorder was exposed to 1 min of acceleration, from 2 to 10 Gand back to 2 G, in 2-G increments (Table 25). The recorded test tape wasthen reproduced from the Oxford reproduce unit at 60 times real time and re-recorded on the Ampex FR1300 at 60 ips. This test setup is shown in Figure 130,
and the test conditions are described in Table 26. The 6152A counter timebase was set on 10-sec count to provide at least 3 frequency counts at eachG level. The digital multimeter was used to Jndicate different G levels andto insure that frequency counts were not taken between different P, levels.
2.9.3 Test Results
A. TUme base expansion: Test results from the time baseexpansion test (Fig. 127) are shown in Table 27. The actual measurement ofthe 600 Hz signal, reduced by 32, should be 18.75 Hz; however, the resolutionof the counter is only provided for 0.1 Hz, so percent error is not shown forthis frequency. The 6 Hz signal for channels 2 and 3 should be 0.1875 Hz.This frequency was determined by strip-chart measurement and chart speed.The amplitude of all signals was approximately 1.05 V peak-to-peak, and didnot vary significantly throughout the test. The absolute amplitude of eachsignal was tiot considered important for this test, and only the variations inthe frequency during the test were considered. This test indicates chat noappreciable frequency or amplitude error would be introduced into the Hedilogrecorder test by using a 32:1 time base expansion.
B. Medilog recorder-reproducer: The recorded data tapewas reproduced and re-recorded using the test configuration of Figure 130.The mean frequency count for the G level in each axis is shcwn in Table 28.The standard deviation of frequency for any G level was less than 0.1 Hz, andwas usually less than 0.06 Hz.
192
'.u. -
Ampex FR1300OXOD 1 2 1 1
OXOR U, BRUSHREPRODUCE2 3 AIRK 200
UNIT 3 4 L • 3RECORDER" ! j4!5 5
SYSTRON DONNER DATA PRECISION
6152A 245
COUNTER NULTIMETER
Figure 130. Oxford reproduce and re-record test configuration.
TABLE 26. OXFORD REPRODUCE TEST SETUP
CHANNEL AMPL•ET GAtN 7LTER
1 PD-2 "a MTN (botht lters.)
2 PN-3 MAX 5 MAX)
3 pK-3 MAX 0 (tMN)
4 P14-3 "MX 5($)
- .. 1193
TABLE 27. TIME BASE EXPANSION ACCURA~CY
CHANNEL FREQUEhNCY (4 PER~CENTTnput Output ERROR
1 600 18.7 --
2 6 0.18E 0.27
3 6 0.188 0.27
4 600 18.7 --
TABLE 28. REPRODUCED FREQUENCY (MEAN)
G +Z-Z+ -x +Y -YI1 16.93 16.60 16.60 16.60 16.64 16.602 17.04 16.68 16.54 16.60 16.70 16.63
4 18.19 16.73 16.64 16.75 16.80 16.80
6 18.43 16.80 16.75 16.83 16.90 17.03
8 18.48 16.95 16.85 16.90 17.02 18.50
10 18.52 17.05 16.92 17.00 17.08 18.53
8 18.50 16.95 16.82 16.88 16.93 18.47
6 18.48 16.87 16.70 16.80 16.85 18.43
4 18.45 16.78 16.60 16.73 16.87 18.45
2 18.45 16.65 16.56 16.63 16.63 18.47
1 13.47 16.57 16.57 16.68 16.56 18.43
194
TABLE 29. PERCENT ERROR IN FREQUENCY REPRODUCTIONdr I-G START OF RUN
AXIS PERCENT ERROR
+Z -9.71-Z -11.47+X -11.47-x -11.47+y -11.25
-Y -11.47
TABLE 30. PERCENT ERROR CHANNEL 1 REPRODUCE NORMALIZED TO1-G START OF RUN
G +Z -Z +X -x +Y -y
1 0 0 0 0 0 0
2 0.65 0.45 -0.36 0 0.36 0.18
4 7.35 0.75 0.24 0.90 0.96 1.20
8.83 1.20 0.90 1.36 1.56 2.59
8 9.13 2.11 1.51 1.81 2.28 11.45
10 9.39 2.71 1.93 2.41 2.64 11.60
8 9.27 2.11 1.33 1.69 1.74 11.27
6 9.13 1.66 0.60 1.20 1.26 11.02
4 8.98 1.06 0 0.75 0.84 11.14
2 8.98 0.30 -0.24 0.18 -0.06 11.27
1 9.07 -0.18 -0.18 0.45 -0.48 11.02
195
The l-G level (start of the run) shows that the reproduced frequencywas lower than the expected 18.75 Hz. This systematic error indicates thatthe recorder-reproducer combination of speed is different from the specifiedvalue. Specifically, the record speed is too fast and/or the reproduce speedis too slow. This error in reproduction (shown in Table 29) is normalized to18.75 Hz, and indicates an error in irequency reproduction of approximately-11%. Consequently, if the recorded ECG is used to derive heart-rate infor-mation, the same -11% error can be expected.
To separate this sytematic tape recorder error from the G-induced error,each axis run was normalized to the l-G frequency output at the start of therun. This error (shown in Table 30) indicates that an error in frequencyreproduction for all axes reaches a maximum at the 10-C level. The error for-Z, X, -X, and Y is only slight (a maximum of 2.7% for -Z with little hysteresis)compared to that for Z and -Y. The Z and -Y axes show considerable error(939% and 11.6%, respectively) and a considerable amount of hysteresis. Fromthe axis orientation (Fig. 128), nothing indicates a Z, -Y G relationship whichwould affect record speed. It should be pointed out that the Z-axis run wasconducted on one day, and the remainder of the axes were tested on consecutiveruns of the next day.
Interestingly, the G-induced error is the opposite direction of thesystematic system error. Since we have no reason to suspect a change inreproduce speeds due to G levels (other than possible random changes), thisfinding indicates the record speed in all axes is reduced as a result of Gforces. This conclusion accounts for the almost linear change (minus a smallhysteresis) in tape speed with respect to G for the -Z, X, -X, and Y axes,but does not explain the large error and hysteresis observed in the Z and -Yaxes. The only explaistion for these deviations is the possibility of randomvariations in tape recorder speed. Since the tape recorder has a phase-locked loop speed control, speed variations should not occur in the recorder.We should also point out that, before the test, the record head and guideswere cleaned and a fresh set of batteries were installed in the recorder.
Test signal amplitudes were also observed for variations due to G forces.The contractor feels that the amplitude variations in the test signalh, due toG, were inconsequential. In fact, amplitude variations in the AM3 (channel 3)were virtually nonexistent, and only minor variations were observed in the EG2(channel 1). One problem did occur in the initial tests with regard to ampli-tude variations--which appeared large (30% - 40%), with occasional dropout atI G. Although a bad cassette proved to be the cause, the possible problemarea is one of which VNB should be aware. The contractor suggests that eachcassette be tested briefly before being used in the field. This test couldbemmnde by simply recording and reproducing the calibration signals beforeeach subject is instrumented.
2.9.4 Conclusions
The large systematic errors observed in the system canprobably be isolated to the recorder or reproduce units. Since VNB has two24-hr recorders and one 2-hr recorder, a common signal should be recorded
196i ~,
Ijon a single channel of each recorder simultaneously. The signal should be moni-
tored with a frequency counter during recording and reproducing. Using the three
recorded tapes, and the two reproduce speeds, a process of elimination could
indicate recorder, reproducer, or a combinational error of the two. ?or example,
if the two 24-hr tapes are reproduced at the same but lower than expected fre-
quency, the reproduce speed should be adjusted for the desired frequency output.
If, however, the two 24-hr tapes are different In response, with only one
reproducing as expected, we would suspect that the record speed of the second
recorder needed adjustment. This suspicion should be confirmed by checking
the accuracy of the 2-hr recorder before any adjustments are made. By using
this process, a logic table could be used in isolating the recorder(3) and/or
the reproduce unit, which are operating at the incorrect speed. Continued
investigation into the speed (frequency) error of the Medilog recorder system
is beyond the scope of this effort.
1197
J•1
ABBREVIATIONS, ACRONYMS, AND SYMBOLS
ac alternatin!S current
ACM Aerial Combat Maneuver
Ag silver
Ag-AgCl silver-silver chloride
AgC1 silver chloride
AGS ant .-G suit
AGV anti-G valve
AWG American Wire Gage
BUP Data Processing Branch, Data Sciences Division, USAFSAM
BNC Bayonet "N" Type Connector
CAL calibration
CR center of rotation
dc direct current
dG/dt rate of change of acceleration with respect to time
DMM digital multimeter
dP/e.G rate of change of pressure with respect to acceleration
EC6G electrocardiogram
FAIlL failures
'•,VALVPGM a specialized FORTRAN IV and IBM Assembly computer program for theanalysis of anti-G valve data recorded in accordance with the SVTP
GVALPROC an IBM procedure, written in IBM JCL, which utilizes analog-to-digital tapes
Cz acceleration along the Z axis (head to foot) [also: G(Z)]
Hz Hertz (cycles per second)
ips inches per second
m meter
mA milliampere
198
MS Military Standard (when used as a prefix for an electrical connector)
mV millivolt
NAILSC Naval Aviation Integrated Logistics Support Center
OP TIME operating time (flight hours)
OTH/MAL other malfunctions
PET Performance Evaluation Table
p - p peak-to-peak
Ps source pressure
psig pounds per square inch gage
PTAP Procedural Tests for Anti-G Protective Devices
PVC polyvinylchloride
RPM ready pressure anti-G valve mannequin
RPV ready pressure valve
SACM Simulated Aerial Combat Maneuver
SAM School of Aerospace Medicine (Brooks AFE, Tex.)
SVTP Standardized Anti-C Valve Test Protocol
V volt
Va accelerometer voltage
VCG vector cardiogram
VDC volts (direct current)
VNB Biodynamics Branch, Crew Technology Division, USAFSAM
Vr control voltage
WRT with respect to
199
[How to order Appendix A
'I
RE: The USAF School of Aerospace Medicine's Technical Report Serieson Procedural Tests for Anti-G Protective Devices--
Volume I (SAM-TR-79-30), and Volume I1 (SAM-TR-79-31).
APPENDIX A:
In order for comprehensive information on this researchto be readily accessible, microfiche have been made ofthis Appendix. The microfiche are available through:
The Strughold Aeromedical LibraryDocumentation Section (USAFSAM/TSK)USAF School of Aerospace MedicineBrooks AFB, Texas 78235
200 Ii
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