The DIGITAC system for the A-7D has 3 augmentation modes: the standard augmentation for the A-7D, the “Flight Path” mode, and the “Precision Attitude” Mode. The maximum phase distortion is 5 degrees and up to 2 Hz.[1] The flight path mode and precision altitude mode provides directional stability at high AOA.[1] This is due to high yaw-rate gains at low frequencies instead of standard washouts.[1]
The program identified several control techniques that may be effective improvements:
- parabolic stick shaping that re-centers the nonlinearity around the trim
- Amplitude-Sensitive performance
- Robust directional control
- Tolerance to servo saturation
- Direction cosines are useful in flight controls for gravity projection on the aircraft body
[[A-7 Flight Path Mode]]
[[A-7 Precision Attitude Mode]]
[[DIGITAC Yaw Controller]]
Sources
- [1] R. C. Hendrick, “DIGITAC Multimode Control Laws,” SAE Transactions, vol. 94, pp. 556–565.
Backlinks
[[A-7A Flight Control Systems]]
[[Direction Cosine Matrix]]
[[High AOA Flight Dynamics]]
Pilot-Induced Oscillations
[[Transfer Function of an Integrator]]
[[Washout Filter]]