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  #21  
Old 02-26-2015, 05:31 AM
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AircraftWraps AircraftWraps is offline
 
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In a Single screw, altitude and airspeed is my safety net. Reducing power while coming off the ground will neither provide airspeed or altitude as quickly as full power (for me at least to 800' AGL). Reduced power takeoffs in single engine extend the time flying within that "no-return" window. Its well worth it to me to allow the engine to provide it's fully rated power and get me out of the "danger zone" as quickly as possible. These things are tractor engines, not porcelain doll

On the inverse... coming in and recovery to the runway: I hate being slow and low! If I am ever able to take a break over the runway into a circling approach... I do it or ask for it. I always try to play nice with others (C152/C172 trainers). SA is the key, you can "time it" with traffic normally. 1000' traffic pattern I can be slow, breaking that I better be glide distance to rwy or smoking fast with all kinds of energy to zoom climb above my personal 800' agl number.
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  #22  
Old 02-26-2015, 05:49 AM
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Weasel Weasel is offline
 
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Quote:
Originally Posted by N546RV View Post
Boy, you're missing out on a lot of fun!

I know. I remember when I was driving my parents vehicles. .......
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  #23  
Old 02-26-2015, 06:02 AM
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sprucemoose sprucemoose is offline
 
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Quote:
Originally Posted by claycookiemonster View Post
As to how airlines would do things if they flew single engine aircraft; I bet they'd take really good care of that engine! If you were flying in a single engine airliner, would you be concerned to learn that they'd been using full power for every take off because of the thrill they got from the acceleration?

For the moment, count me as skeptical that somehow in horizontally opposed aircraft engines, using less than the full power available is actually bad for the engine. Seems to me that for every other mechanical object and engine I can think of, going a bit easier and staying a bit further from the redline is usually wise, but I'm willing to learn.
It does seem intuitive that engines wear faster at higher power, but what is intuitive is not always true. Based on all I've ever read and heard, I believe that this is not the case for piston aircraft engines, which are designed to run at or near full power for their entire life. A car or other ground based engine may not perform the same way.

My point about the airlines (meant to stimulate discussion) was that they can afford to operate at less than full power (meaning reduced climb and more time closer to the ground) because they have the luxury of multiple engines. If the whole scheme was based on one engine, I suspect the risk/ reward math would have them going full power all the time to climb as quickly as possible to get away from the hard ground sooner.

I'm looking at this purely from a safety of flight viewpoint. Noise, high altitude practice etc. are issues but less important than safe operations.

Good discussion.
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  #24  
Old 02-26-2015, 06:08 AM
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N941WR N941WR is offline
 
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A warbird friend of mine said they used to use reduced power on takeoff until they realized they were eating up cylinders. Now they use full power and full rich until they are about 1000' AGL. Then they set up cruise climb to their cruising altitude.

I wonder if Doug R. can confirm this.
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  #25  
Old 02-26-2015, 06:51 AM
N733JJ N733JJ is offline
 
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Default Lycoming says...

Full power should be used for all takeoffs.
The issue is that the increased fuel flow helps cool the cylinders when there is little airflow over them. Take offs with partial power will shorten the life of a ;piston engine.

Full burner in the T-38 and B-1 was too much fun, especially on a cold day!

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  #26  
Old 02-26-2015, 07:10 AM
912ry 912ry is offline
 
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The airlines use an assumed outside air temperature. By pretending that it is as hot as the charts allow for a safe takeoff, they find a thrust setting that will still meet the balanced field requirements. They did this even in the piston days. I'm convinced that it does reduce wear. However the safety of altitude in a single engine airplane seems pretty important too. I will admit to doing reduced power take offs in RY from time to time. I still remember my CFI's words of wisdom "slow is smooth, smooth is fast, less is more...." he was a real zen kinda guy.
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  #27  
Old 02-26-2015, 07:51 AM
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claycookiemonster claycookiemonster is offline
 
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Default Maybe just generally?

The airline and engine manufacturers have spent uncountable engineering hours calculating the procedures and economics and confirming the safety of using reduced power on take off - we're unlikely to have that time or expertise or maybe even the data.

Trying to come up with even a simple reduced power plan for RV's is both simpler and more complicated than it would be for the airlines.

1. The airline version needs to address the possibility of continuing a take off after an engine failure; the classic V1 cut. In an RV, if the motor quits, we're just going to stop.
2. A 737 could, at best, get airborne in about 3000 ft. If we operate from a 10,000' runway, we're using 1/3 of the concrete. An RV can be airborne in 500', if it's on a 5000' runway, it's only using 1/10th of the runway! Given our lack of computing power and data, it's comforting that we can do a simpler job and be confident that margins are still in place.
3. Our complication is that no two RV's are the same, however during Phase I there is time to do many take off rolls and note time/distance to take off and "safe" altitude and arm ourselves with our own data.

Perhaps the engine guys could chime in here with information on operation at reduced RPM/MP?
I'd assume "blow by" would be a factor of combustion chamber pressure, is that pressure significantly reduced when operating at lessened RPM?
I'd also like some information on how much engine cooling is accomplished by full throttle/ full rich operation. I'm not much of a piston guy, is this a known and proven thing or urban legend?
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  #28  
Old 02-26-2015, 07:53 AM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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I'm not sure I understand what the attraction of a low powered takeoff is.

Is it to save some money somewhere down the line?

If so, let's think about this. We invest tens of thousands of dollars into these planes, we prime them in the unlikely event they'll turn to dust around us, we invest the kids college fund in an instrument panel when, really, all we need is an airspeed indicator.

And we're going to be cheap on the first thing of actually flying that might kill us?

If that's not the point, I need to hear more.

Because the only thing I care about is getting to an altitude that I can turn back with an engine failure just as quickly as I possibly can.
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  #29  
Old 02-26-2015, 08:21 AM
ShortSnorter ShortSnorter is offline
 
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Quote:
Originally Posted by LettersFromFlyoverCountry View Post

...We invest tens of thousands of dollars into these planes, we prime them in the unlikely event they'll turn to dust around us, we invest the kids college fund in an instrument panel when, really, all we need is an airspeed indicator.

And we're going to be cheap on the first thing of actually flying that might kill us?

If that's not the point, I need to hear more.

Because the only thing I care about is getting to an altitude that I can turn back with an engine failure just as quickly as I possibly can.
I couldn't have said it better
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  #30  
Old 02-26-2015, 08:22 AM
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wirejock wirejock is offline
 
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Default Engine failure

I'm no expert but I did drive race cars for a few years. Granted, they were very different from our Lycomings and driven very hard usually at redline as long as possible. Every failure I saw or experienced seemed happen coming off a high speed straight. Boom, oil all over the place. Never once saw a failure on hard a acceleration.
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