The LAHOS study indicated that an excessive time delay could lead to a PIO.[1] Rate limits as a possible PIO trigger during combined pitch and roll maneuvers were also taken into account.[1] The stick must be able to be moved sinusoidally in pitch and roll at a 1Hz frequency and 50% travel amplitude without exceeding actuator rate limits.[1] If the rate limits were hit during an unstable flight condition, the aircraft would depart controlled flight in under 1 second.[1] Large hinge moment margins were needed to prevent an actuator stall.[1] No PIO tendencies were detected although faulty components could cause low damping.[1] The F-117 satisfied Gibson’s criteria at typical flight conditions, although it did not satisfy all parts of the criteria.[1] The equivalent time delay in the pitch and roll axes were between 0.07s and 0.11s.[1]
LAHOS Study – studied PIO on a T-33
[[F-117 Actuators]] – had large rate limit margins
Sources
- [1] R. Loschke, “Development of the F-117 Flight Control System,” in AIAA Guidance, Navigation, and Control Conference and Exhibit, Austin, Texas: American Institute of Aeronautics and Astronautics, Aug. 2003. doi: 10.2514/6.2003-5762.
Backlinks
[[Control Surface Rate Limits]]
[[Disadvantages of Elevons]]
[[Equivalent System Time Delay]]
[[F-117 Control Stick]]
[[F-117 Flight Control System]]
[[F-117 Nighthawk]]
[[Gibson Criteria]]
Pilot-Induced Oscillations