Prop pitch

hughrawls · Post by **hughrawls** » 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.

8451 · Post by **8451** » Tue Nov 12, 2019 5:07 pm

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.

6277 · Post by **6277** » Wed Nov 13, 2019 6:53 am

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.

Post by **V529** » Wed Nov 13, 2019 3:32 pm

Check your tach. Is it accurate.

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

Post by **6643** » Wed Nov 13, 2019 3:58 pm

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.

Post by **6183** » Wed Nov 13, 2019 4:27 pm

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?

Post by **6643** » Wed Nov 13, 2019 4:36 pm

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.

6298 · Post by **6298** » Wed Nov 13, 2019 5:04 pm

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.

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