Stefan writes:

The most simple solution would be the possibility to trim all
three axis.

Hmm ... is trim in all three axes uncommon? The Baron has aileron,
elevator, and rudder trim.

On the more expensive level (much more expensive, I would guess), you
can overcome the P-factor effects by using two contra-rotating coaxial
propellors. This would not only overcome the effects of the P-factor,
but also those caused by torque. Kamov helicopters are an example of
such a design.

With a single powerplant turning in one direction, there would still
be some residual torque from the engine itself.

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