I have used a 1.kk flight controller along with an Arduino Nano and an ultrasonic sensor to add the feature of altitude hold.

This project describes of a low-cost GPS data logger for RC planes. In a previous project I described how to build a GPS data logger.

I wanted an additional analog control in FlightGear - nice, cheap and compact.

To add the feature of Direction Control using the initial direction as a reference and applying a proportional controller.