Supremely stupid question ...

[pilot602]

[ QUOTE ]
Also in a lot of airplanes (but not all), the RPM (with the last two zeros knocked off) should be higher than manifold pressure- i.e. 22/23 (22 in. MP/2300 RPM).

[/ QUOTE ]

Not necessarily ...

It all comes down to the power chart. On our O-320's to get 65% power at any given altitude it generally requires that the MP is set higher than the RPMS (if you want to run with LOW rpm settings, which in many cases you do). So on a standard day at 7 or 8,000 feet we might set 2100 RPM and 22.8 or FT on the MP.

Higher MP actually helps seal the pistons thus increasing efficeincy. Low RPMs saves fuel and wear and tear on the engines. Using the low RPM high MP settings we routinely beat the book's fuel burn figures on 20-year old (actually 40-year old engines but they were overhauled 20 years ago), 1,000hr engines.

 

[DE727UPS]

Eagle, in this case it was heavy tanks, being it was one and three greater than two. Two is not supposed to be less than one and three by more than two thousand pounds. (I'll look that one up again before my recurrent limitations test). There was no procedure for it becuase it's not supposed to happen. Normally, though, you could feed out of a heavy wing tank to keep 1 and 3 within 1000 pounds, which is the inflight limit.

 

[EatSleepFly]

[ QUOTE ]
It all comes down to the power chart.

[/ QUOTE ]

No, actually, for me it comes down to: "This is my airplane, and this is how you will fly it." The boss signs the paycheck, I'll do whatever floats his boat. Thats why I edited my post to remove that paragraph.

 

[MDPilot]

Actually Doug, on overwater routes, you will see those "even" numbered flight levels used right now, and as Eagle correctly identified, once we go to RVSM in North America, you will see them here too.

 

[pilot602]

[ QUOTE ]
No, actually, for me it comes down to: "This is my airplane, and this is how you will fly it."

[/ QUOTE ]

Boss/owner (right or wrong) does trump the power chart.

 

[EatSleepFly]

That, and the fact that when I was a student I always used the good 'ol "rental power setting" anyways...so I very seldom actually had the props behind the MP.

 

[cointyro]

Eagle, I didn't mean RPMs versus M.P... I meant physical location of the throttle lever versus prop lever. Unless that is what you meant.

Thanks for the great post, it filled it me in well.

 

[davetheflyer]

[ QUOTE ]
What is the official phraseology, as well as pilot slang, for the blue knob, the prop control?

Also isn't there a rule of thumb, keep your prop control forward / ahead of the throttles (forward being lower prop blade AoA / "flatter" prop disk)? Or have I got this confused?



[/ QUOTE ]

Officially: Propeller RPM Control
Slang: Props

It's an old wives (of pilots?) tale. Lindbergh (yes, that Lindbergh) disproved that during WWII. US pilots were having problems flying extended ranges in the Pacific. Lindbergh showed them that they could extend their range by burning less gas. This was done by flying with a higher manifold pressure and a lower RPM.

The final authority on operating your engine is the manufacturer. When all else fails, read the instructions.

 

[cointyro]

Rausda said "Another is
"Climb to the left, Descend to the right", meaning if you are adding power (climbing) then go from left to right, prop first throttle second. If you are reducing power (descend) then throttle first, prop control second. "

Specifically, you said "if you are adding power (climbing) then go from left to right, prop first throttle second..."

How is going left to right mean prop first throttle second? I thought prop was right of the throttle, not left? CTPM... Carb heat (if no fuel injection), Throttle, Prop, Mixture... right? Throttle black, prop blue, mixture red...

 

[fr8dog]

BE58...for ex

 

[Alchemy]

So I'm hearing that running High MP's and comparatively low RPM's isn't a huge crime?

I'm a novice when it comes to high-perf aircraft but I remember my CFI jumping on my case for leaving the MP at takeoff power for more than 500 AGL. He acted like the engine was about to come apart if I didn't the throttle back from 24" to 23". Beyond overheating, what's the big concern here?

 

[Eagle]

[ QUOTE ]
if I didn't the throttle back from 24" to 23". Beyond overheating, what's the big concern here?

[/ QUOTE ]

in the real world, there is little problem.

Some old wives tales, but that is about it.

 

[EatSleepFly]

That depends on the airplane. Many airplanes should be throttled back at 500'. The T210 has a 5 min. limitation on takeoff power, so we throttle back quite a bit upon reaching 500 ft. Other high performance airplanes you just bring the MP back to "top of the green" or whatever the POH specifies.

The old wives tale that Eagle was referring to was in cruise. The instructor who gave me my H.P. signoff way back whenever said the same thing: "Can't have the MP higher than the RPM!" But if you look in most POH's, there are power settings where the MP is higher.