Mounting the flight controller away from the centre of gravity

Hello, I am preparing to mount a Cube flight controller on my quadplane (which was redesigned after a previous crash in the following post).

I notice from the following documentation that the flight controller should ideally be mounted within a few centimetres from the centre of gravity. However, due to mechanical limitations, there is a possibility that we might have to mount the Cube away from the plane’s centre of gravity.

I have three questions:

  1. Does mounting the flight controller away from the CG have an effect on the aircraft’s flight behaviour? And if it does, how is the behaviour affected?
  2. Is there any rule of thumb on how far the flight controller can be mounted away from the CG?
  3. Are there any parameters in ArduPlane that allow us to specify the linear offset of the flight controller from the CG (if needed)? I have previously tried to search but could not find such parameters

Thanks (:

yes, If you think of the extreme case where the flight controller is mounted right on the nose, as the aircraft pitched up or down it would also see a up and down acceleration, likewise for yawing the controller would see a lateral acceleration rather than just a rotation.

Yep there are some params for this, see

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Many thanks for the reply.

Based on my interpretation, in order to mount the flight controller away from the CG, the key parameters to set are the offsets for all 3 IMUs as mentioned in the link. Please correct me if I am not getting it correct.

Also, based on the documentation:

“In practice the distance to the sensor can be measured from the center of the flight controller unless the flight controller itself is placed a significant distance from the vehicle’s center of gravity in which case the IMU position offsets can be specified and then the other sensor’s position offsets can be specified from the vehicle’s center of gravity.”

Hence, if the flight controller and other sensors (e.g. rangefinder) are not at the CG, then the offsets for the affected sensors (e.g. RNGFNDR_POS) should be taken with respect to the vehicle’s CG, instead of the IMUs?