Reduced power Take Offs?

[jrs14855]

The industry standard for light aircraft, normally aspirated, with constant speed prop, is a power reduction to something around 24" /2400 rpm, at a safe altitude after takeoff. Turbocharged aircraft are similar but the power reduction would be from perhaps 38" mp to 32" mp, numbers vary depending on the engine.
Many have no limitation to prevent a full power climb, but it does use a lot of fuel, especially with turbocharging.

[Arie]

Originally Posted by jrs14855

The industry standard for light aircraft, normally aspirated, with constant speed prop, is a power reduction to something around 24" /2400 rpm, at a safe altitude after takeoff. Turbocharged aircraft are similar but the power reduction would be from perhaps 38" mp to 32" mp, numbers vary depending on the engine.
Many have no limitation to prevent a full power climb, but it does use a lot of fuel, especially with turbocharging.

Once again what you describe is NOT a reduced thrust take off

[jdearborn]

There are a lot of angles from which to view this. Here is mine.
Years ago, as a 727 Captain I was a Max Power guy. That was until I read that over 96% of all engine failures that occur on takeoff, occur when utilizing maximum power. The engines failed because they were being operated under maximum strain, at their limits. Seldom do engines fail when they are simply 'loping' along. And for those that do, they may well have been abused on a max power takeoff flights before. That realization gave me a way to reduce my chances of having an engine failure on takeoff to less than 4%. I liked those odds and it served me well thru the 757, MD11 and my C-180. I'll use it on my RV-8 too. Extended engine life and fuel savings are just side benefits from not abusing your engine with max power takeoffs (when not needed). Minimizing engine failure on takeoff is the prize.

[jrs14855]

I did not say that it was, just pointing out that reduced power in the CLIMB is not likely to cause engine damage on small recips.
I absolutely believe that reduced power from start of takeoff run WILL cause damage on some small recips. The takeoff from standing start to climb airspeed is a very critical time, especially in high ambient temperatures, and reduced power causes additional prolonged stresses on the engine.
Small piston engines should be operated at full power for all takeoffs unless there are red line considerations such as on the turbocharged engines.

[jimgreen]

Arie, I beg to differ. At 2500rpm, you cannot develop full thrust.
The point I wanted to make is that many of us accept less than full thrust routinely for reduced noise.

The airline stuff is interesting but irrelevant. Good for another forum.
BTW in countless assumed temp takeoffs I rarely saw as low as 300fpm.
Plus there was always the option of a throttle push if you lost a fan.

[Arie]

@jdearborn, I was also a 727 captain, and now 777 captain, but I was never a max power guy. Reason is ,the planes we flew was so thoroughly tested and certified regarding the power available ,to what is needed to get the job done. Therefore a reduced thrust take off in a airliner is standard operating procedure. That is the reason the plane I fly now cost close to $300 000 000 a piece , but you could most properly build it for 10% of that if you take the cost of testing and certifying out of the price tag. To bring you back to your C-180 ,you would have a pilot operating manual ,with graphs showing you what your performance is going to be regarding weight, temperature, and altutude. But they all asume that you are going to push the throttle all the way into the instument panel on take off. How do you decide that today I am only going to use what ever manifold pressure on this take off instead of going with that the manual says.

[Arie]

Jim you are correct, it is not RV related. I apologize for the thread onto airline opperations. Sorry about that, now lets get back to the topic. The OP asked a question regarding using reduced thrust on take off. For me the take off phase start at the beginning of the runway up to the point where the wheels leave the ground. Once the wheels are of the ground you are in the climb phase. What ever you decide to do in the climb phase regarding your thrust setting has got nothing to do with the take off.
Regards
Arie

[TomVal]

My 2 cents:

Airlines began using reduced power or flex power takeoffs for two reasons: Extending the time between engine overhauls and for good neighbor noise abatement departure procedures.

Of the many engine operating parameters that are monitored, the "hot section" of the engine takes the most abuse. By taking off at a reduced power setting the turbine section is exposed to lower peak operating temperatures, thus the turbine blades, metallurgically speaking, are subject to less stress (fatigue cracks and turbine blade creep). From an economic standpoint, the airline will gain about 20% more operating cycles out of that engine before that hot section would require overhaul.

Wrt my single engine airfliver...always full power takeoffs.

[terrye]

Hmmm...
The current Cessna 172R uses a Lycoming IO-360 engine rated at 160 hp. The engine has been derated from its usual 180 hp rating. Does this mean that EVERY Cessna 172R is doing a reduced power take off? Or that the Robinson helicopters that derate their engines are doing the same?

[jdearborn]

Hi Arie. When I started airline flying the 727 was still in production, Reduced Power takeoffs were just being developed and the old timers weren't really buying in to it. We had to be convinced it was a good thing and I was convinced. I liked going from the 96+% to the 4-% probability of an engine failure on takeoff.
Judging from the fact you are still flying the 777 you entered the airlines at a time when Reduced Power takeoffs were the norm. Regardless, I think we are both on the same side of the issue and I'm not sure why you are taking exception to my supporting Reduced Power takeoffs.
The C-180A POH does not address required takeoff power settings. It does address limitations and performance parameters. Density altitude, weight and runway length allowing, I use climb power as my takeoff power. It is supposed to: "work good and last a long time" . . . and keeps me in the less than 4% area.
For those who want to claim I'm 'just an airline pilot'. . . I learned to fly in a J-3 over fifty years ago and I have over 20,000 hours. I have flown most of the Piper and Cessna singles and the Beech twins. I've flown round engine ag stuff and T-28s. I flown military fighters and I have a Vietnam combat tour in the OV-10A and the YOV-10D. I'm not glider or seaplane qualified. That doesn't make me 'know it all' or right, but it does give me a considered and qualified opinion.
Cheers!