If you are not sure how an in-flight adjustable propeller works, well that’s OK – here’s a simple explanation:
Having an in-flight adjustable propeller instead of a fixed-pitch (or Ground Adjustable) propeller is like going from a car that only has a single gear, to a car with 1st, 2nd, 3rd and 4th. In our imaginary car, you would need to decide before leaving home if you wanted to set your car up for hill-starts (STOL) or for the highway (cruise efficiency). If you set your gear up for the highway then it will take a long time to get off the mark and up to speed, likewise, if you set your gear up for hill-starts, it will get off the mark really well and then red-line below your best cruise performance.
The in-flight adjustable propeller can twist the blade angle AS YOU FLY so that you have the best angle at take off, and again as you speed up for the cruise.
That’s all it is!
In-flight adjustable propellers give you more value when they are used on faster aircraft. As you move faster through the air, the angle of the relative airflow increases against the fixed-pitch blades until they are past their optimum design pitch. In other words – fixed pitch propellers only work perfectly at one air speed and at one RPM setting. Everything outside of that they are not at their optimum. An in-flight adjustable propeller can always working at the optimum efficiency.
What sort of performance gains? It depends. Less % gain on slower aircraft. STOL series – think maybe an extra 7 or 8 knots and 10% less fuel burn. Faster stuff (Cruzer or 650 – and certainly the Velocity) these numbers will improve from there.
I have the VIP on my CH750 STOL and I am still impressed by what a significant difference this option has made to my performance and enjoyment of the aircraft. Adding an in-flight adjustable propeller is not essential on any aircraft that is designed to cruise below about 100 knots, but if you can afford it – I promise that you will not regret it. They really are that good.
I hope this helps!