FLYING QUALITIES OF PILOTED AIRCRAFT - CAFE Foundation

MIL–STD–1797AAPPENDIX A4.8.4.3.2 Recovery from post–stall gyrations and spins. The post–stall characteristics shall bedetermined. For all aircraft:a. The proper recovery technique(s) must be readily ascertainable by the pilot, and simple and easyto apply under the motions encountered.b. A single technique shall provide prompt recovery from all post–stall gyrations and incipient spins.The same technique, or a compatible one, is required for spin recovery. For all modes of spin that can occur,these recoveries shall be attainable within ____________. Avoidance of a spin reversal or an adverse modechange shall not depend upon precise pilot control timing or deflection.c. Operation of automatic stall/departure/spin prevention devices and flight control modes shall notinterfere with or prevent successful recovery of the aircraft by the pilot.d. Safe and consistent recovery and pullouts shall be accomplished without exceeding the followingforces: ____________, and without exceeding structural limitations.REQUIREMENT RATIONALE (4.8.4.3.2)Recovery from post–stall gyrations and spins must be possible and prompt, with simple control application.Even for aircraft in which flight demonstration is not feasible, the post–stall characteristics need to be known inorder to give guidance for inadvertent encounters.REQUIREMENT GUIDANCEThe related MIL–F–8785C requirement is paragraph 3.4.2.2.2.Recommended values: Recovery should be specified in terms of allowable altitude loss or number of turns,measured from the initiation of recovery action:TURNS FOR ALTITUDECLASS FLIGHT PHASE RECOVERY LOSS*I Category A, B 1–1/2 1000 ftI PA 1 800 ftOther classes PA 1 1000 ftOther classes Category A, B 2 5000 ft* –Not including dive pullout.For conditions that require control actions in more than one axis it is recommended that the forces specified by4.8.3 be applied.AFWAL–TR–81–3109 described the evolution of the MIL–F–8785 requirements:Prior to Amendment 1 to MIL–F–8785B there had been no general requirements onpost–stall gyrations, as distinguished from spins. MIL–F–8785B had only a reference to thethen–current spin demonstration requirements of the Air Force (MIL–S–25015) and theNavy (MIL–D–8708). For aircraft to be spun, MIL–S–25015 required ready recovery fromincipient and fully developed (5–turn) spins—1–turn spins for landing, 2 turns inverted.MIL–F–8785B Amendment 1 kept the MIL–S–25015 numbers of turns for spin recovery andadded more bounds on altitude loss during recovery. The Class I requirements are similar to643