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19. Touch-down bump and Engine start/stop shudder generation

V2.80 of the FS9/X version of the BFF 3 DOF motion driver adds a feature for generating touchdown bumps and engine start/stop shudders.

The features are enabled using manual settings in the .bff configuration file.

NOTE some experimentation with the settings will likely be required to obtain the best results for individual platform drives. The default settings described below are for guidance only.

Touch-down Bumps:

Touch down can often be felt in the motion cue when it causes a big enough spike in the vertical acceleration of the aircraft. If you make good landings however the acceleration spike might be small and no bump will make through into the cue naturally.

In V2.80 of the driver artificial TD bumps can be produced using the following settings in the .bff confg file....

;Touchdown bump effects

;Touchdown bump sine wave frequency (Hz)
TD_Freq=2.5
;Touchdown bump amplitude (as a proportion of VaMAX above - ie as a proportion of the max heave cue range). Set = 0 to disable effect.
TD_Scaler=1.0
;Touchdown bump time to decay to zero - in seconds
TD_Decay_Time=2.0
;Heave acceleration inhibit during touchdown bump, =1 to inhibit normal heave accel on TD, =0 to allow as normal ?
TD_Acc_Disable=0
;Duration in seconds for which the on-ground indicator is held at 0 (in-air) when aircraft first lifts-off. To prevent TD bump if OG indicator toggles on lift off
TD_HIA_Duration=1.0

The bump effect is a decaying sine wave initiated by the TD event in the flight sim which is added to the heave cue output. The frequency, amplitude and duration of the wave can be set using the above parameters to allow tuning of the effect to suit your platform drive.

Parameter TD_Acc_Disable adds the option to block the "real" heave acceleration input to the motion cue whilst the generated wave is active. This can produce unrealistically uniform TD bumps however which are independent of the quality of the actual landing.

Parameter TD_HIA_Duration provides an option to hold the FSX TD indicator in the "in-air" position on lift off. This is to prevent false TD bumps from being generated if the lift off isn't clean and the indicator "toggles" momentarily before the aircraft fully leaves the ground.

Engine Start/Stop Shudders:

The start/stop shudders are generated by a decaying sine wave added to the Roll axis of the motion cue which is initiated by start/stop of engine No. 1

The amplitude, frequency and duration of the decaying sine wave can be adjusted to suit using the parameters described below....

:Engine start/stop shudder effects

;Shudder sine wave frequency (Hz)
ES_Freq=4.0
;Shudder amplitude (as a proportion of LaMAX above - ie as a proportion of the max roll cue range). Set = 0 to disable effect.
ES_Scaler=0.2
;Shudder time to decay to zero - in seconds
ES_Decay_Time=1.5

Some experimentation will be needed to obtain the best results for your platform.

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