The legacy Hornet suffered losses due to out-of-controlled flight accidents caused by the “Falling Leaf” mode. This was one of the two sustained departures from controlled flight modes. The two-seat variant was more susceptible to a falling leaf mode. The control system of the two-seat hornet had more sprung mass than the original. During departure from controlled flight, the high forces interacted with the increased mass and the flight computer commanded uncontrolled control surface actuations that may have prevented proper recovery. These displacements were up to 0.79 in. In the presence of high lateral forces as in a spin, it was impossible for the pilot to hold the stick neutral. Early flight control software falsely displayed spin recovery control arrows to the pilots who were in the falling leaf mode. This would delay recovery or aggravate the departure oscillations. The F-18 was statically unstable in most flight conditions with typical fuel and ordinance loads and longitudinally stable at any AOA over 35 degrees. The F-18 was susceptible to departures at low speed and close to zero AOA.
[[OFP V10.7]] – FCS upgrade to improve high AOA and reduce upsets
[[Falling Leaf Mode]]
[[Legacy Hornet Control Stick Overshoots]]
Sources
- C. S. Buttrill, P. D. Arbuckle, and K. D. Hoffler, “Simulation model of a twin-tail, high performance airplane,” NASA-TM-107601, Jul. 1992. Accessed: Feb. 24, 2024. [Online]. Available: https://ntrs.nasa.gov/citations/19920024293
Backlinks
[[F-18 Legacy Hornet]]
F-18 OFP v10.5.1
[[Falling Leaf Mode]]
[[Relaxed Static Stability