MOC VTOL.2245 Aeroelasticity

• n/a found in: Small Category VCA (Revision 0) SC-VTOL (Oct 2024)

MOC VTOL.2245 Aeroelasticity n/a (a) General. The aeroelastic stability evaluations referred to in this MOC include flutter, divergence, control reversal and any undue loss of stability and control as a result of structural deformation. The aeroelastic evaluation should include whirl modes associated with any lift/thrust unit or other rotating devices that contribute to significant dynamic forces. Compliance with this paragraph should be shown by analyses and tests. (b) Aeroelastic stability envelopes. The aircraft should be designed to be free from aeroelastic instability for all configurations and design conditions, including transition phases, within the aeroelastic stability envelopes as follows: (1) For normal conditions without failures, malfunctions, or adverse conditions, all combinations of altitudes and speeds encompassed by the VD versus altitude envelope, enlarged at all points by an increase of 20 percent in equivalent airspeed at constant altitude, should be considered. In addition, a proper margin of stability should exist at all speeds up to VD and there should be no large and rapid reduction in stability as VD is approached. (2) For the conditions described in (c) below, for all approved altitudes, any airspeed up to VD should be considered. (3) Failure conditions of certain systems should be treated in accordance with [VTOL.2205](#_DxCrossRefBm1877490425). For these failure conditions, the speed clearances defined in [MOC VTOL.2205](#_DxCrossRefBm1877490426) Figure 3 apply. (c) Failures, malfunctions, and adverse conditions. The failures, malfunctions, and adverse conditions which should be considered are: (1) For aircraft with disposable fuel: critical fuel loading conditions not shown to be extremely improbable which may result from mismanagement of fuel (2) Single failures, malfunctions, or disconnections, and any combination of these that is not extremely improbable, of elements in the primary flight control system, tab control system, or flutter damper (3) Failure of any single element of the structure supporting any engine, lift/thrust unit, shaft, or large externally mounted aerodynamic body (4) Failures of any single element of the lift/thrust unit structure that would affect the aeroelastic characteristics of the aircraft (5) Any lift/thrust unit or rotating device capable of significant dynamic forces rotating at the highest likely overspeed (6) Any damage or failure conditions, required or selected for investigation by [VTOL.2240](#_DxCrossRefBm1877490436) (a) and (b) (7) Any other combination of failures, malfunctions, or adverse conditions not shown to be extremely improbable. (d) Flight flutter tests should be made to show that the aircraft is free from flutter, control reversal and divergence and to show by these tests that: (1) Proper and adequate attempts to induce flutter have been made within the speed range up to VD; (2) The vibratory response of the structure during the test indicates freedom from flutter; (3) A proper margin of damping exists at VD; and (4) There is no large and rapid reduction in damping as VD is approached. (e) For modifications of the type design which could affect the flutter characteristics, compliance with (a) should be shown, except that analysis alone, which is based on previously approved data, may be used to show freedom from flutter, control reversal and divergence for all speeds up to the speed specified for the selected method.