Cessna 120-140 Association

My 140 with O200 has a 69-48 prop (climb). I need a recommendation for a cruise pitch. Engine will overspeed in cruise if I am not careful.

hughrawls wrote: ↑Tue Nov 12, 2019 1:17 pm My 140 with O200 has a 69-48 prop (climb). I need a recommendation for a cruise pitch. Engine will overspeed in cruise if I am not careful.

I was under the impression that over speeding in cruise at full throttle was normal for climb props - it’s one of the trade offs that comes with being able to make more RPM and thus power at climb airspeeds.

Climb props will overspeed if you don't reduce throttle setting at level off. If you're in a hurry and want a few knots more in cruise, a cruise prop is your choice. If you want better performance on takeoff and climb, keep the prop you have.

Check your tach. Is it accurate.

A 69/48 should just nicely make rated RPM, straight and level with full throttle at 1000 feet.

I would expect a 69-48 to easily exceed redline in level flight. Remember, it's on an O-200, not a C-85. -50 or -52 is probably what you want if you want to cruise at high throttle settings.

Can a 6948 be legally installed on a Cessna 140/120/140A with the 0-200 conversion? At one time the only approved propeller was the 6950. Paperwork in my 0-200 installation specifically calls for only the 6950. Personally I wouldn't kick a 6948 out of the house. On more than one occasion I would have liked to had a 6948 installed especially during 100+ degree weather while doing patrol work. Can someone shed some light on this subject and tell us if a 6948 is legal on an 0-200 powered 140/120/140A?

Ask Randy. I thought he was working on having a static range approved rather than a specific pitch, although I may be thinking of my own problem, having a 6948 as the only approved prop for an Ercoupe/O-200.

If you have the current version of my STC, it allows pitches from 48 to 54. I fly a McCauley 69-48, 1A101. Maximum static RPM is 2600. I seldom exceed the red line of 2750 RPM. I think the prop on Hughs is a Sensenich. The static rpm limitations are narrower than the McCauley, on them. The McCauley 1A100 pitch range is 50-54.