Reduced power setting on take off

tgrayson said:
And yet you duplicated their technique exactly, with no evidence in favor of it, so I suspect this "25 squared" mantra has indeed influenced you. The only thing unambiguously true is that lower RPM will result in lower noise.
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I use 25 squared because its easy to pull to - I don't have time to be selecting some complicated book power setting that's corrected for DA on my first power reduction after takeoff, and its pretty close to the climb power setting in the book, and because the engine seems to run a little smoother there.
 
tgrayson said:
almost all of them advocate a power reduction immediately after takeoff in aircraft with a constant speed prop, and the only source of this technique is from flight instructors. Once someone gets it into his mind he should do this, the lack of a specific recommendation for the technique in the POH is not sufficient to eliminate the habit, at least for most people.

My own view is that a great many pilots would benefit from throwing away what they were taught about flying a particular airplane and start from scratch using the POH.
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The Seminole POH actually suggests a power reduction to 75% for cruise climb. Sorry for the bad cell phone pic, but I didn't have a scanner available.

28518_437305777931_783337931_5870421_8164436_n.jpg


Deakin says this is bad, but it is recommended procedure for this airplane. I haven't actually seen the "power enrichment valve" he refers to, but I will ask the mechanic tomorrow. I did do a search on the Lycoming O-360 and they mention it is in the carb. I guess 75% power is enough to activate the valve.
 
mojo6911 said:
The Seminole POH actually suggests a power reduction to 75% for cruise climb. Sorry for the bad cell phone pic, but I didn't have a scanner available.

28518_437305777931_783337931_5870421_8164436_n.jpg


Deakin says this is bad, but it is recommended procedure for this airplane. I haven't actually seen the "power enrichment valve" he refers to, but I will ask the mechanic tomorrow. I did do a search on the Lycoming O-360 and they mention it is in the carb. I guess 75% power is enough to activate the valve.
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Yup. The power enrichment valve is there in the carb. I even have a diagram of the HA-6 carb (the one that I think is in the Semi, I know it's in the Duchess) somewhere in physical form.
 
mojo6911 said:
Deakin says this is bad, but it is recommended procedure for this airplane.
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I doubt Deakin would object to cruise climb settings; you increase airspeed enough to counter the loss of the power enrichment system. What I presume he DOES object to is pulling back the throttle while keeping the same relatively low airspeed, which likely results in a net increase in engine temperature.

What I suspect that Piper doesn't have, though, is data that shows the procedure increases the life of the engine, particularly when you don't see the same recommendation in other of their products, using very similar engines. The Seneca, for instance, says nothing about it. I suspect what you have is the test pilot's own personal preferences, since you see a wide range of technique in different models. For instance, in some Pipers, the POH says you have to control airspeed with the yoke, but others require that you use power. They should have just built them one way. :)

Still, I agree that it's prudent to follow the POH recommendations, unless you have a compelling reason not to. For safety reasons, I wouldn't dream of reducing my climb rate until I'd achieved an altitude that would allow safe maneuvering in an emergency and that's considerably above any obstacle clearance altitude.
 
Leave the throttles up and pull the props back.

Bingo.

Power reduction.

Or do the "big pull" and get on the lean side.

Power reduction.

Roadhouse.

-mini
 
Here is some one else who recommends pushing the levers/knobs full fwd and leaving them there until cruise altitude

http://www.mooneypilots.com/mapalog/powersettings.html

With that said, here is my general list of guidelines for climbing a normally aspirated Mooney the most efficiently to altitude:
Full throttle. Keep the power tip. The induction system is tuned for full throttle settings--the cylinders get a more even distribution of induction air with the throttle full open. Unless specifically required by the manufacturer in the POH (and the Mooneys we fly are not), forget that old practice of reducing the throttle after take-oil to "save the engine". Forget the old "25 squared" idea. There is no reason on a normally aspirated engine to reduce the throttle for climbs. Why sacrifice climb performance for nothing?
Maximum rated RPM. Static thrust (the thrust the propeller produces with the airplane standing still) increases with RPM. Static thrust is also stronger at climb airspeeds with higher RPM. The engines we fly are rated for continuous operation at max RPM (redline). So why not climb there? Your thrust will be better and your climb to altitude will be quicker. The only area where reducing RPM for climb might be a consideration is over noise sensitive areas in the departure path of the airport. But Mooneys don't put out a horrible exterior noise profile like a Cessna 185 cranking away at 2800 rpm. And the idea of reducing the RPM in climb to "make the engine last longer" is simply wrong. You can reach TBO operating at 2700 rpm while climbing just as easily as climbing at 2500 rpm.
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