FLYING QUALITIES OF PILOTED AIRCRAFT - CAFE Foundation

MIL–STD–1797AAPPENDIX AA critical design review of the departure and spin characteristic should be performed using pilots whorepresent the contractor and the procuring agency in a manned simulation program. Prior to CDR, thecontractor should submit an evaluation plan, to be approved by the procuring activity, that:a. Indicates the range of aircraft gross weights/center–of–gravity positions, and aircraft normal and failurestates associated with each flight phase.b. Specifies maneuvers and control inputs to be evaluated for each flight phase. The control inputs evaluatedshould be broadly classed into four techniques:(1) Ordinary control inputs(2) Misapplied control inputs(3) Consecutive misapplied control inputs(4) Pro–spin control inputs (optional)It shall be tailored to the Class and structural design criteria of the aircraft. MIL–S–83691 gives guidance.Aerodynamic data should be of sufficient quality and quantity to recognize at least the initial characteristics ofdivergence and spin. The piloted simulation shall address the maneuvers associated with each flight phase,with some extra simulation time allotted to the pilots to allow them to evaluate entry maneuvers not covered bythe plan.Prior to flight–test evaluation of departure and spin characteristics, installation of a recovery system on theflight test aircraft is recommended. In particular the recovery system should be installed such that it does notsnag on the control surfaces, regardless of control surface deflection during or after deployment jettison.A flight test plan similar to the one used for simulation will be submitted before initiation of flight test.Throughout flight test, frequent procuring–activity/contractor coordination meetings should be held to reviewresults to date and determine the safest course to achieve program objectives. The initial flight test evaluationshould include a careful buildup to the maneuvers of Technique (1) (ordinary control inputs) in addition tothose maneuvers necessary to define stability derivatives and calibration of the air data sensors. Afterevaluation of Technique (1), a careful buildup test to positive and negative angles of attack and sideslip inexcess of planned production limit settings is needed to verify and define stability derivatives. The simulatoraerodynamic data, sensor effects, and subsystem effects (e.g., hydraulic/electrical power) should beupdated. Continued piloted simulations should be performed to evaluate departure characteristics forTechnique (2) control inputs (misapplied control inputs) and for Technique (3) control inputs (the effects ofconsecutively misapplied control inputs). The effects of Technique (2) control inputs should then be test flown.The results of flight–test and updated simulation results should be utilized for system refinement and pilothandbook information. After completion of the departure phase of the F–15 program, a spin recovery programwas initiated using Technique (4) maneuvers.VERIFICATION LESSONS LEARNEDOn the F–15 and some other aircraft for which vortices off the nose are prime contributors to the high–αcharacteristics, the flight test nose boom had a marked effect on departure. External stores and store orinternal fuel asymmetries have also been found to influence some aircrafts’ high–α characteristicssignificantly.615