Re:Belgian startup Magnax has found a way to mass-produce th...
by AdrianB1 on Tuesday October 01, 2019 @01:25PM
(#21128042)
Yes, for some light airplanes a constant speed propeller is not required, but if it is simple enough and you get sizable benefits (even 10% more range), then why not?
There are many planes in Europe that have the cruise speed much higher than the best climb speed. The best climb speed is around 100-120 km/h for light planes, while several plane models have the cruise speed over 200 km/h, up to 250 km/h. I am not aware of any plane with cruise speed below 200 km/h to use constant speed propellers, they have fixed pitch propellers, but the faster ones have in-flight adjustable pitch. I personally flew 7-8 different models of planes, only one with adjustable pitch, but they were all in the LSA class and const-speed is not used there.
Normal operation of a constant-speed propeller involves setting the desired rpm via the pitch control, and then adjusting the power, via the throttle, according to your purpose (such as level cruise at a specific IAS, or climb at maximum sustainable power), with the propeller govenor maintaining the chosen rpm via pitch changes, and I do not see how electric power changes this relationship. I understand that electric power might simplify making a sort of FADEC for electric airplanes (so that there is only one power control), and that constant-speed propellers could eke out more duration from the batteries, but now you are adding the cost and complexity of a constant-speed prop. I am not sure that it would be justified in a light airplane having a cruise speed not much higher than its best climb speed.