FLYING QUALITIES OF PILOTED AIRCRAFT - CAFE Foundation

MIL–STD–1797AAPPENDIX AOn the F–18, the pitch control–deflection range of 20 deg. moved with pitch trim position, but could neverexceed 24 deg. trailing–edge–up (–) stabilizer. It was possible to mis–set trim for takeoff as that –24 deg.deflection could not be obtained when needed during takeoff. The pilot should always have full deflectionavailable.The requirement is especially important for turbojet aircraft for which relatively large pitch attitudes arerequired for lift–off.5.2.7.3 Pitch axis control power in takeoff—verification. Verification shall be by analysis, simulation andflight test.VERIFICATION RATIONALE (5.2.7.3)Normally the critical test will be to start the rotation, i.e., to at least balance the aircraft with the nosewheel ortailwheel just touching the runway but bearing no load. The main gear extension at this condition, whichdetermines the attitude there, can be found from the lift and load–stroke equations. Control to maintain thetakeoff attitude should also be checked, for compliance with the limitation of 4.2.9.1 on control travel duringtakeoff. In flight test, takeoff performance tests are monitored for flying qualities.VERIFICATION GUIDANCEThe ability to comply with this requirement should be obvious during operational flight test. Special emphasisshould be placed on short–field takeoffs at the maximum forward and aft center–of–gravity limits for lift–offand overrotation, respectively.From the equationqScC + Tz – (W m T – qSC L – Tsin ) χ(x + y) µ = 0the lift–off speed is given by1W 1ρ V q2 L O –L O __ – T _ sin + z T /c2W( ξ X/c + µ Y/c )S CmX/c + µ Y/c where ξ = i T + α; C m and CLare the aerodynamic pitching moment and lift coefficients, in ground effect, ofthe entire aircraft with takeoff thrust and fully deflected pitch controller, X and Y are the horizontal and verticaldistances between the c.g. and the main–gear axle; and is the main–gear coefficient of rolling friction.VERIFICATION LESSONS LEARNEDA balance must be struck between adequate control and overrotation tendency, e.g. the DC–9–80 takeoffperformance tests. The test pilot should be alert to avoid tail–strike.294