Last August I posted a blog "New offer of help with tuning PID loops" putting forward the idea of applying control doublets to a fixed wing aircraft in flight and using the responses to capture stability derivatives and decide autopilot gains. At that time I only had simulation results and was seeking flight test data. I have since got hold of some flightt test data  and analysis confiorms that my processing concept does work.

The first step is to fit a model of the aircraft response to the real data. Once this is done (the software only takes seconds) I've got an airframe transfer function from which I can directly calculate autopilot gains and stability derivatives which I can plug into an aircraft simulation.

Since autopilot gains need to be matched to vehicle aerodynamics, with further development, this scheme could end the era of triasl-and-error autopilot tuning. In the near term, if anyonre is interested, I could act as consultant on individual projects. Over the longer term, I could work with someone to package up the algorithms into existing autopilot software or perhaps and App with a view to bringing something to market.

I suspect my first method for tuning PID loops was not a great hit because it required 3-view drawings or photos of the aircraft plus inertia data all of which is a bit fiddly. I've now got a new method based on flying the aircraft and logging accelerometer and gyro outputs in response to elevator, rudder and aileron doublets. This method works well with simulated data and I'd like to try it on real data. If you are interested in this experiment, let me know your email address and I'll send you more information and a short test specification.

Sorry, but I should have made clear that my autopilot design experience relates to fixed wing aircraft so I won't be able to help with rotary airframes.

I should also emphasise that the databse I have relates to PID control only. After a lot of hard work, I have established which stability derivatives the PID gains depend on so that the job for the user becomes one of estimating certain stability derivatives (for which formulae are also available). The PID gains then drop out as functions of speed. Robustness is assessed by perturbing the values of the stability derivatives.

Finally, could I caution people using textbook PID tuning merthods to do so with care. They concentrate on obtaining a good response to the desired input. In a flight control context, it is just as important to be able to reject unwanted disturbances and this modifies tuning objectives.