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carb ice de-rated engines

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carb ice de-rated engines

Old 14th Nov 2017, 02:38
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carb ice de-rated engines

According to the CAA....

"Engines at reduced power settings are more prone to icing because engine induction temperatures are lower. Also, the partially closed butterfly can more
easily be restricted by the ice build-up. This is a particular problem if the engine is de-rated as in many piston-engined helicopters and some aeroplanes."

Looking for information/examples of de-rated engines in piston airplanes.

Thanks

Last edited by JammedStab; 14th Nov 2017 at 20:55.
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Old 14th Nov 2017, 07:39
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The Robinson R22 has a derated engine. I believe certain Cirrus aircraft are also derated.

http://www.planeandpilotmag.com/arti...thout-the-stc/

The basic Continental TSIO-550 engine is rated for 350 hp, whereas the 550K version is derated to only 315 hp. This means that max cruise can be established at 85% without violating the traditional 75% rule. Seventy five percent of 350 hp equals 262 hp, but expressed as a percentage of the 550K’s derated 315 hp, the number works out to about 85%. For pilots more interested in economy cruise to stretch nmpg to its limits, 55% at 25,000 feet reduces fuel burn to 12.7 gph while maintaining 175 knots cruise.
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Old 14th Nov 2017, 18:47
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Helicopter engines are usually derated because of the gearbox limits. Let's say you want 200 horsepower. If you put in a 200 horsepower engine, as soon as you climb to altitude you will lose performance as the manifold pressure drops. To get your 200 horsepower back you could turbocharge it which would be expensive, or you could start with a bigger engine and derate it. The Derate is simply a red line on the manifold pressure gauge equating to 200 hp. You only have atmospheric pressure pushing air into the engine and all engines will reduce in power as you climb - so essentially you start off with a bigger engine. Having a derate means you can never use full throttle at sea level hence icing becomes an issue.
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Old 15th Nov 2017, 15:15
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The O540 in our Maule (derated from 300hp to 235) was very prone to icing.

But propensity to carb icing depend on many other factors including cowling and airflow through the engine bay.
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Old 16th Nov 2017, 05:46
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For the last couple of years, Ive been flying a 182 that has a carburetor-temperature gauge. It takes all the guess work out of avoiding carb icing. Just keep the needle out of the yellow arc, by judicious use of carb heat.

It has also been a very valuable learning experience. There have been many lovely summer days where carb icing was the last thing on my mind, but the needle told me otherwise!
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Old 16th Nov 2017, 21:16
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The basic Continental TSIO-550 engine is rated for 350 hp, whereas the 550K version is derated to only 315 hp. This means that max cruise can be established at 85% without violating the traditional 75% rule. Seventy five percent of 350 hp equals 262 hp, but expressed as a percentage of the 550Ks derated 315 hp, the number works out to about 85%. For pilots more interested in economy cruise to stretch nmpg to its limits, 55% at 25,000 feet reduces fuel burn to 12.7 gph while maintaining 175 knots cruise.
Of course the TSIO-550 is fuel-injected, which probably reduces its susceptibility to carb icing somewhat.
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Old 6th Dec 2017, 10:11
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Originally Posted by rudestuff View Post
Helicopter engines are usually derated because of the gearbox limits. Let's say you want 200 horsepower. If you put in a 200 horsepower engine, as soon as you climb to altitude you will lose performance as the manifold pressure drops. To get your 200 horsepower back you could turbocharge it which would be expensive, or you could start with a bigger engine and derate it. The Derate is simply a red line on the manifold pressure gauge equating to 200 hp. You only have atmospheric pressure pushing air into the engine and all engines will reduce in power as you climb - so essentially you start off with a bigger engine. Having a derate means you can never use full throttle at sea level hence icing becomes an issue.
Originally Posted by Flyin'Dutch' View Post
The O540 in our Maule (derated from 300hp to 235) was very prone to icing.

But propensity to carb icing depend on many other factors including cowling and airflow through the engine bay.
Hi Flyin' Dutch. Is the operation on your Maule similar to the post above yours with only partial throttle opening available at lower altitude airports?

Thanks
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