©1998 Scott E. Lanis ELTs: Everything You Wanted to know- and MORE BASIC GROUND ELT LOCATION COURSE (CLASSROOM)

©1998 Scott E. Lanis

ELTs: Everything You Wanted to know-

and MOREBASIC GROUND ELT LOCATION COURSE

(CLASSROOM)


OBJECTIVESBy the end of this course, you should:

Know what an ELT is, and how it can be activated Understand why an ELT signal is an emergency Describe how CAP is called out on an electronic search Be familiar with these fundamentals:

• Plotting a SARSAT hit on a map (latitude/longitude)

• Direction finding - Little L-Per™ Operation

• Triangulation

• Body shielding

• Aircraft coordination/LORAN/GPS operations

• Ground Vehicle Operations


Is An Aircraft Missing?

How would we know?Radio distress callMonitored aircraft drops from RADAR

Overdue Flight PlanReport from friends/relativesELT Signal (maybe!)


How does CAP Search for Missing Aircraft?

Purely Visual SearchesVery Difficult: often few clues

Air - most effective to cover ground Ground

Electronic Searches - “Quick” (24 hrs) Air - best reception and range Ground - autonomous search is slower and more difficult

Advanced TechnologyFew of these resources available directly to CAP

Synthetic Aperture Radar (SAR), Thermal/Infrared Imagery, Other Remote Sensing (satellites/reconnaissance aircraft)


What Will A Crashed Airplane Look Like?


Air To Ground CoordinationThe most effective way to searchThe only way CAP stays in the SAR businessThe plan:

CAP aircraft locates crash (visual / electronic)Coordinates to bring ground team on scene

• Radio (transmit the Lat-Longs from LORAN/GPS!)

• Radio Out

• Lat-Long (LORAN/GPS)

Ground Team effects rescue


Aircraft LimitationsWeatherCan’t pinpoint signal

Row of hangers


Ground Search Types for Missing Aircraft

Ramp SearchEnsure the missing aircraft has not landed safelyCan be conducted by both air and ground crews

Bastard SearchEnsure the missing person isn’t in a favorite hangout“You bastard!”


How does a search start?There is the possibility of a missing aircraft

Radio distress call, aircraft drops from RADAR, overdue flight plan, report from friends/relatives, ELT Signal

AFRCC performs a telephone search Airport managers, towers, etc.

Missing Aircraft Confirmed! AFRCC activates the appropriate CAP wing


What if only an ELT signal is Received?

AFRCC Telephone SearchAirports: “Do you hear it too?”

Likely false alarm at this point; signal silenced by crews on airport

CAP called sooner if “after hours” No one else answers the phone!

Is there another indicator of a missing aircraft?If not, AFRCC will wait to see if the signal terminates

Tests Inadvertent actuations terminated


Huh? What is an ELT anyway?Emergency Locator Transmitter

It’s an automatic radio beacon!

3 Frequencies of Operation121.5 MHz (VHF)AND 243 MHz (UHF)

(Military Guard)406.025 MHz (new)

Most aircraft have ELTsinstalled

Wave Sound


General Types of ELTsAircraft (General Aviation)Military (“beepers” or “beacons”)Personal (PELTs or PLBs)Marine EPIRBsAdvanced (406/GPS)


Typical Aircraft ELT Operation3 Switch positions--on, arm/standby, and off G-switch activated (Generally 9G)Activates ELT upon impact when armedMay be manually operated by placing the switch in

in the ‘ON’ position


Can you test an ELT?Yes, with restrictions:

First 5 minutes of the hour, no more than 3 sweeps

Battery must be replaced after:One cumulative hour of use or50% of useful life has expiredFAR §91.207(c)

Does not apply to our Practice BeaconsCall nearest FSS in advance: 1 (800) WX-BRIEF

Give a contact phone-interference happens on 121.775!


Inadvertent Activation of an ELT

May Occur From:Excessively hard landingInadvertent change of switch positionRemoval of the unit

activating the switch or G-switch

Malfunction switch short battery leakage


Who is listening?SARSAT/COSPASFAA Facilities

FSS, Centers, Towers

Airliners Only if pilot chooses

Military Aircraft 243 MHz Required

General Aviation Aircraft That’s us! Help the system work: monitor 121.5 MHz

Signal report is relayed to AFRCC


SARSAT/COSPAS


How SARSAT WorksReceive 121.5, 243, 406 MHz SignalsOrbiting and Geostationary Satellites

Orbiting: SARSAT/COSPAS High Inclination (polar) orbits

Geostationary: GOES Weather Satellites SAR payloads for 406 only

Operated by Canada, France, Russia, USAThey give us digital lat-long coordinates

CAP Mission Coordinator plots these and assigns assetsGround teams must interpret for land navigation


System Operation Details

SARSAT/COSPAS in polar orbit

Calculates location of signal by measuring Doppler shift

This yields a latitude and a distance


Narrowing The Search (SARSAT/COSPAS Only)

First pass Ambiguity


Where Is It?Second Pass

average 30-45 minute wait Ambiguity resolved 5-12 Nautical Mile Average Error


How Do Different ELTs Stack Up?121.5 MHz ELT

12 NM Radius, 452 Sq Mi Ave. 6 Hour Notification 60 Milliwatt Transmitter

406 MHz ELT 2 NM Radius, 12.5 Sq Mi Ave. 1 Hour Notification 25 Milliwatt 121.5 Beacon

406 ELT with GPS .05 NM Radius, .008 Sq Mi Ave. 5 minute Notification 25 Milliwatt 121.5 Beacon


System ReviewELT, PLB, EPIRB Signal ReceivedAFRCC gets coordinates from SARSATAppropriate CAP Wing is activated


False Alarms97% of received ELTs are false alarms

121.5 MHz: 1 in 1000 is an actual emergency (0.1%)406 MHz: 1 in 8 is an actual emergency (12.5%)

Why is a False Alarm a big deal?SARSAT can only monitor 10 ELTs at once (within

footprint) bent-pipe repeater

VERY easy to overload the systemBlocks emergency communications

Blocks the real emergency!


How Should We Treat An ELT?As an EMERGENCY!

You can’t know which ones are Distress ELTs

And even the false ones are good training!


Transportation to Target

Ground Teams generally will use vehicles for transportation to and from mission base

Aircraft Coordination will get the Ground Team to the target the fastest

If no aircraft is available:Vehicles provide enough speed and range to triangulateClose range may be required for signal acquisition


Direction FindingDF unit Measures equal strengths of signal

• not wholly accurate, but good enough!

Therefore, when needle is centered, ELT could be either direction

Needle always POINTS to the ELT (DF=Direct to the Flipping target)

Use a TURN to TELL if the ELT is in front or behind you


DFing with theLittle L-Per™

6 Steps: use the full procedure every time! Turn the unit to Receive, check proper frequency and volume Turn the Sensitivity Knob to HALF SCALE

• This will prevent oversense and a good starting point

Turn the unit to DF (Direct to the Flipping target) Turn at least one FULL circle, stopping and calling,

“Center!” Check: Use Turn to Tell: the needle will point Direct to the

Flipping target Use your compass, shoot an azimuth to get a bearing to the

ELT


Direct to the Flipping, Turn to Tell


REC1/2DFCenterTurnShoot


Little L-Per™ Receive ModeMeasures Signal Strength only

From a direction of the arrows on the antenna (to your left)

Use it with multiple centers (more than 2) to verify strongest path Due Reflections That’s most likely the

true direction to the ELT


ReflectionsCaused by flat surfaces

Hangars are notoriousRock wall, cliff, or mountains

To beat reflectionsCheck sensitivity half scale oftenUse RECeive modeRubber ducky antennaOff-frequency tuningUsually strongest DF center is not a reflection


TriangulationBest method for ground troops to get an accurate fix

when search aircraft support is unavailableYou must be able to receive the signal

Center up DF unit on the signal Take the magnetic bearing (shoot an azimuth) Correct for magnetic variation

• East is least, West is best

Plot your bearings (draw a line) on map

The ELT should be where the lines cross!


Let’s See That


Body Shielding The BEST method of beating

reflections at close rangeCan use L-Per™Radio Shack JETSTREAM radio is better and CHEAP!At extremely close range, a 2m VHF radio unsquelched

may work• This works ok when trying to figure out a

particular aircraft on a flight line, it willprobably not identify a particular hangar

Body blocks out the signal Called a NULL Null should be at your BACK


Off-Frequency TuningDecrease sensitivity when:

Sensitivity (L-Per™) is at the minimum and signal is still too strong (full scale on receive)

You don’t get a null during body shielding You don’t have a sensitivity knob (Jetstream) Shortening (Jetstream) or removing (Little L-Per™) the

antenna will also decrease sensitivity

Off-Frequency tuning may be used any time you have too much signal, but this technique is especially effective during body shielding


Hey, I Can’t Hear the Signal!ELTs are limited to Line of Sight propagationYou don’t always need to hear the ELT

Carrier wave may be broadcasting with no audible sweep

Especially true in low batteries, or odd transmissionsYou can tell by DEFLECTIONGood needle deflection generally indicates a signal that

is strong enough to DF


What Else Can Affect An ELT Signal?

Power lines EM RadiationIf you get an actual ELT during a practice search, shut down

all practice beacons. The signal on 121.5 may be frequency shifted from your practice beacon! (often due to powerlines)

Fence Line (signal can follow)Coffee Can/Stovepipe effectHangarsMoving Target


How Does An Aircraft Perform An Electronic Search?

Aircraft use the same type of methods as used on the ground

DF mode (most common) Wing Null Method (body shielding with the wing!) Signal Strength Aural Search (rare)


Before Going Home, Silence The Signal!Sometimes that’s the only goal!Methods of disabling an ELT:

Switch off (not always effective!)Foil tentGrounding wireRemove batteryRemove antennaThe Sheriff is required for forcible entry

Most folks will be very cooperative

Ensure the aircraft operator is notified you disabled the ELT!


SummaryYou Should Now:

Know what an ELT is and how it can be activated Understand why an ELT signal is an emergency Describe how CAP is called out on an electronic search Be familiar with these fundamentals:

• Plotting a SARSAT hit on a map (latitude/longitude)

• Direction finding - Little L-Per™ Operation

• Triangulation

• Body shielding

• Aircraft coordination/LORAN/GPS operations

• Ground Vehicle Operations


QUESTIONS?

Documents

©1998 Scott E. Lanis ELTs: Everything You Wanted to know- and MORE BASIC GROUND ELT LOCATION COURSE (CLASSROOM)