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Appendix 2. Air Turbulence Vibration

Version 1.4d+ of the Shaker software adds Air Turbulence vibration output. This is a Beta feature and is available for FSX/P3D (and now X-Plane from V1.4e).

The air turbulence vibration effects provide bursts of vibration at a specified base frequency in response to turbulence in the air stream.

The turbulence acting on the aircraft is determined using Angle of Attack (AoA) fluctuations which become more energetic the stronger the turbulence becomes.

By isolating these fluctuations a vibration feed is developed which triggers the vibration output

An option to use aircraft acceleration fluctuations is also provided as an experimental feature - it is recommended however that AoA is used as the turbulence feed. The acceleration feed tends to false triggers due to normal flight manoeuvre variations.

The air turbulence output uses the same vibration channel as stall, flaps and gear buffeting effects and uses the same wave mix parameters. A separate buffeting frequency can however be set for the air turbulence effect.

The settings are shown in the image.

Each setting has a pop-up tool tip which gives details - hold the cursor over the setting for a few moments to activate the tool tip.

The Air Turbulence output is blocked when the aircraft is on the ground.

The amplitude of the vibration output is derived from the turbulence feed. The turbulence feed is obtained from a trace of the Alpha AoA fluctuations due to weather effects, which is filtered to isolate only the high frequency components, range set, then smoothed. The processed feed is displayed in the "Output" progress bar, but can also be viewed in detail using the Scope button.

Amplitudes below the specified ON threshold are blocked, and the final vibration can be further scaled using the Output Gain setting. The base frequency of the wave mix used for the vibration is set by the Turb Buff Hz setting.

It is best to tune the settings by first disabling all other vibration outputs. Use the Advance Weather settings in FSX to set up flights with different levels of wind turbulence and tune the output accordingly.

The default settings work for me in a GA aircraft - however they will be bass shaker and general setup dependent.

X-Plane:

The AoA turbulence characteristics in X-Plane are a bit different from those in FSX and so the settings are a bit different also. Check the "Light GA -X-Plane" config file in the zip for suggested X-Plane settings (the default settings in the software are those suggested for FSX).

Just copy them across into any of the other config files to use as a start point in your tuning. NotePad or any other text editor can be used for this.

X-Plane does not provide the same turbulence level indicator as FSX and for the time being the higher of the two control movement rate attenuation triggers (In Turb) is inactive in the software when X-Plane is the active sim.

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