Light Aircraft Association

Hi!
What sort of Static RPM can I expect from an A75 and what Prop is being used. I cannot get the 2600rpm Max even with fairly Fine Prop. Aircraft performs OK but never goes beyond 2300rpm. Electric Tacho used to double check. I don't want to strip it down as it starts and runs beautifully other than max rpm never reached.
Regards
Gerry
Corben Junior G-BSDI

You should only get max rpm on a fixed pich prop in a dive. If it goes to max rpm in level flight it will be ineficient in cruise.
I test flew this plane several years ago and was suprised by its performance and lovely handling.
If it still has the same prop as it had then I would leave it alone!

Gerry,
I have an A75 in my Aeronca. Having had the aircraft 6 months I’ve been looking extensively at how the engine performs.
The book figure for an A75 are 2600 redline with 2300 (ish) static.

I have a Lodge 72x44 wooden prop on it and get 2200rpm static and 2400 flatout whist flying.

Talking with pop manufactures, a rough ‘rule of thumb’ every inch off the prop diameter will give 100 extra rpm.

Also spoken to many other A75 owners, internet searched, & prop manufactures & 'experts'. The ideal wooden prop for an A75 are;

70 x 40 climb prop
70 x 42 standard prop
70 x 44 cruise prop

My current 72 x 44 pop is for an A65 and thus giving A65 performance figures.

A metal prop will obviously give you better performance, but my wooden prop looks very nice on my aircraft so I’m living with it.

Send me a pm/email if you like to see all the info I’ve gathered.

Jon

Jon and John.
Thanks for your input.
I will continue 'as is'. The Aircraft flies well.
Regards
Gerry