Fuel Burn for a PA 24 250

[Randy Johnson]

Would like some practical experience advice from other owners of non fuel injected 250 0wners regarding cruise fuel burn.

Ive read the engine performance graph and agree with the 15 gph at 24 squared. Not so sure about the 12 gph at 22 squared in straight and level flight.

Am very interested in others experience in flying a little slower to save gas. Also Ive heard from some "old schoolers" that I am lugging the engine at 22 squared cruise. Would also appreciate any thoughts on that issue.

Am very interested in what other owners do to save gas and extend engine life. My aircraft has an engine with 2100 hours on it with strong compression all around. Want to keep it that way as long as I can! Any thoughts on this issue would be much appreciated.

[David Pyle]

There is a school of thought that says squaring the MP/RPM is uncreative.

Lindbergh's practice during WWII to extend (P-38) range was to reduce RPM to lowest book value and maintain max MP for altitude. Reference to your 250 chart will show those values and fuel consumption. While I didn't know Lindbergh personally I once lived down the street from his wife in CT.

[Tom Veatch]

Yesterday, Jun 2, N7032P, a 1960 PA24-250, 2.2 hours round trip from K32 to KIXD and return @ 5500/4500 MSL, 22"/2200, leaned to ~25 ROP with JPI700 Lean Find, CHT's ~340-360, ~12.5 GPH.

I've found the "Power Setting Table" page 48 of my POH to be pretty close to what I see in flight.

[Mark Anderson]

Randy,

I usually cruise between 8k-12k feet and run the engine at wide open throttle. I try to stay 125 degrees ROP. At 12k feet I get about 12 GPH; at 8k feet 15 GPH. I bought a plane to save time and go fast. At these altitudes I'm only getting about 18-20 inches of MP. If you are low 24 suared is probably a good idea.

Just my thoughts,

Thanks Mark

[Jay]

It's harder to fine tune fuel burn in a carbureted engine than on a fuel injected one, but you can still be pretty efficient. And 2200 is not "lugging". Any MP/RPM combination that your power charts show is OK.

For efficiency I would run wide open throttle at 7,500 feet or higher and reduce RPM to whatever level feels comfortable. Nothing wrong at all with 22 hundred or even less. Lean to roughness, enrich till smooth and see how it goes. Different airplanes seem to to have different "sweet spots" for RPM, find whatever works best for yours.

Jay

[Randy Johnson]

Thanks to all for the good advice and experience. Its most appreciated!

[Paul Klouda]

Greetings All,

Haven't been on the site for a long time but saw this and had to reply. I've been charged with a '64-250 normally aspirated and see 10.5 - 11.5/GPH running between 6 - 10K altitude in the 2300rpm and 19 - 21"mp range. I usually indicate 140 - 145Kts. About 50 - 75 ROP with ~300 CHT. This is on a factory reman with about 350 - 400 hours on it, 3 blade Mac prop.

[Randy Johnson]

Thats pretty darned good! Those are some terrific numbers. Thanks for the input. Im jealous!