Prop pitch

Ask Questions and Offer Advice Related to the Cessna 120 & 140 Type

Moderators: 6643, 6183, V529

Forum rules
You must be a member of the Cessna 120-140 Association in order to post new topics, reply to existing topics, or search for information on this forum. Use the "Join" link in the red menu bar.
Post Reply
hughrawls
Posts: 2
Joined: Fri Oct 25, 2019 2:24 pm
Location: Florida
Name: Hugh Rawls
Aircraft Type: C-140
Occupation-Interests: Pilot and cfiime, a&p
Contact:

Prop pitch

Post by hughrawls »

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
Posts: 83
Joined: Wed Apr 24, 2019 1:20 am
Name: Daniel
Aircraft Type: Formerly a 120
Occupation-Interests:
Contact:

Re: Prop pitch

Post by 8451 »

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
Posts: 230
Joined: Tue May 01, 2018 7:00 am
Location: Ann Arbor, MI
Name: Ray Hunter
Aircraft Type: C-140
Occupation-Interests: Retired AF, B-17, UH-1, pilot for Yankee Air Museum
Contact:

Re: Prop pitch

Post by 6277 »

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.
V529
Posts: 552
Joined: Tue May 01, 2018 7:00 am
Location: Michigan
Name: Victor G
Aircraft Type: C-120
Occupation-Interests: Work on airplanes till the cows come home..........they're still out.
Contact:

Re: Prop pitch

Post by V529 »

Check your tach. Is it accurate.

A 69/48 should just nicely make rated RPM, straight and level with full throttle at 1000 feet.
User avatar
6643
Posts: 2326
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: Prop pitch

Post by 6643 »

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.
6183
Posts: 303
Joined: Tue May 01, 2018 7:00 am
Location: Florida
Name: Mike Smith
Aircraft Type: 140A (2) 1949 & 1950
Occupation-Interests: Retired aerial power line patrol pilot for Gulf Power Co
120-140 Assoc. Florida Rep. N9633A & N9688A
Contact:

Re: Prop pitch

Post by 6183 »

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?
User avatar
6643
Posts: 2326
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: Prop pitch

Post by 6643 »

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
Posts: 242
Joined: Tue May 01, 2018 7:00 am
Location: California
Name: Randy Thompson
Aircraft Type: Cessna 140
Occupation-Interests: Work on airplanes and engines
Contact:

Re: Prop pitch

Post by 6298 »

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.
Randy Thompson A&P IA Pilot
Hold STC SA547EA for installation of O-200 engine in Cessna 120/140 and 140A"s
Overhaul small Continentals
Post Reply

Who is online

Users browsing this forum: Google [Bot] and 8 guests