Abstract•Stability derivatives are calculated by using DATACOM

•Transfer function θ/δe is found by using longitudinal stability derivatives i.e.

-1.6 s^2 - 0.96 s - 0.01--------------------------------------------------

s^4 + 0.9 s^3 + 3.3 s^2 + 0.02 s - 0.003

•Three displacement autopilots are designed;1) Blackelock displacement autopilot2) Modified blackelock autopilot3) Self designed autopilot with PID

compensator

Methodology Results

Design Parameters

• Jan Roskam, Airplane Flight Dynamics And Automatic Flight Control, Part 1.

• John H. Blake Lock, Automatic Control of Aircraft and Missiles, Second Edition.

• http://gangmadhu.blogspot.com/2010/09/history-of-autopilot.html

• Stone, R. H., “Aerodynamic Modeling of the Wing-Propeller Interaction for a Tail-Sitter Unmanned Air Vehicle", Journal of Aircraft, Vol. 45, No. 1, pp. 198 – 209, 2008

• WANG Xiao-Yan, WANG Xin-min, XIAO, Ya-hui,YU Xiang, “Design of robust H_∞ controller for UAVs three-dimensional formation flight”, Control and Decision, 2012

.

3D view of A-3:

Implementation1) Blackelock Displacement Autopilot:

2) Modified Blackelock Displacement Autopilot:

3) Self designed autopilot with PID compensator:

Inside PID block:

Longitudinal stability derivatives:

Step Responses of 1) Blackelock displacement autopilot 2) Modified blackelock autopilot and 3) Self designed autopilot with PID compensator

1)

2)

3)

Conclusion

References

Stability and Control is the most important factor to be taken into account, during all phases of design of an aircraft specifically during preliminary design. Converse relation exists between stability and control. Stability requirements are greater in transport airliners, because transport plane does not require fast maneuvers.This paper discusses the comparison between different displacement autopilots of self-designed transport airliner A-3. Results of all three autopilots are analyzed on the basis of root locus and best suited displacement autopilot for A-3 is described.

Displacement Autopilots

Damping Ratio

Settling Time(sec) Remarks

Blackelock’s Autopilot 1.0 150 Poor

Modified Blackelock’s Autopilot

0.54 6 Good

Self-designed Autopilot 0.65 0.1 Excellent

Cruise Mach 0.8Mach Max 0.92Number of Passengers 350Number of Crew 16Cargo 60 tonsTotal Weight 446125 lbRange 4414.7 milesEndurance 17 hoursTake off distance 7236.88 ftLanding distance 7058.6 ftAbsolute Ceiling 38000ftPrice Per Aircraft 191.48 million $