FLYING QUALITIES OF PILOTED AIRCRAFT - CAFE Foundation

MIL–STD–1797AAPPENDIX A4.6.7.8 Yaw axis control force limits for asymmetric thrust during takeoff. The following requirementsshall be met:Takeoff run: During the takeoff run, to stay within the allowable path deviation of 4.6.5.1,yaw–control forces shall not exceed _____ lb.Airborne:For the continued takeoff, to achieve straight flight following sudden asymmetricloss of thrust and then maintain straight flightthroughout the climb–out, as in4.6.5.1, shall not require a yaw control pedal force greater than _____ lb.REQUIREMENT RATIONALE (4.6.7.8)Safe operation in the event of a propulsive failure is a critical consideration for multi–engine aircraft. Yawcontrol force is one important aspect.REQUIREMENT GUIDANCEThe related MIL–F–8785C requirements are paragraphs 3.3.9.1 and 3.3.9.2.Recommended values:Maximum yaw pedal forces:180 lb for both takeoff run and airborneThis requirement is a companion to 4.6.5.1. The object is to insure that, following loss of thrust during thetakeoff run, the pilot can either safely abort or safely continue the takeoff and climbout without losingdirectional control.Again, 120 lb may be a more satisfactory, safer upper limit considering the capabilities of the entire pilotpopulation. Pending further data, that limit (as in FAR Part 23 for prolonged operation) might be used here.REQUIREMENT LESSONS LEARNED5.6.7.8 Yaw axis control force limits for asymmetric thrust during takeoff—verification. Verificationshall be by analysis, simulation and flight test.VERIFICATION RATIONALE (5.6.7.8)Verification should be accomplished during demonstration of compliance with 4.6.5.1.VERIFICATION GUIDANCESee 5.6.5.1 guidance. With the aircraft configured at its lightest weight, simulated engine failures duringtakeoff must be performed in the conditions specified. Simulation is not recommended for ultimate verificationof compliance with the ground roll portion of this requirement because of the known problems with developingan accurate landing gear model.VERIFICATION LESSONS LEARNED595