carb ice de-rated engines
Thread Starter
Joined: Apr 2008
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From: nowhere
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
"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 November 2017 at 19:55.
Joined: May 2009
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From: Hotels
The Robinson R22 has a derated engine. I believe certain Cirrus aircraft are also derated.
http://www.planeandpilotmag.com/arti...thout-the-stc/
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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.
Joined: Dec 2005
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From: Hong Kong
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.
Joined: Jun 2002
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From: Nanaimo (CAC8)
For the last couple of years, I’ve 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!
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!
Joined: Dec 2000
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From: London, UK
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.
Thread Starter
Joined: Apr 2008
Posts: 1
Likes: 2
From: nowhere
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.
Thanks
Joined: Nov 2018
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From: UK
Well what does "derate" mean on a Lycoming piston engine? It is usually just an RPM restriction, for example, limiting it to 2500RPM instead of the 2700 that is the redline of most Lycoming engines. Outright manifold pressure limitations are unlikely on a naturally aspirated engine.
Some installations rarely get carb ice, such as the airbox on the Vans RV homebuilt line.
Some installations rarely get carb ice, such as the airbox on the Vans RV homebuilt line.
Joined: Nov 2018
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From: UK
Yes, the Maule with its constant speed prop will have had the governor max RPM set to something below 2700rpm - probably 2500. A standard 8.5:1 compression parallel valve O540 will be good for 260hp at the full 2700rpm redline. Only paperwork stopping you adjusting the governor of your Maule to get the extra 200rpm and extra horsepower - prop limitations aside.
Joined: Aug 2001
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From: Europe
Yes, the Maule with its constant speed prop will have had the governor max RPM set to something below 2700rpm - probably 2500. A standard 8.5:1 compression parallel valve O540 will be good for 260hp at the full 2700rpm redline. Only paperwork stopping you adjusting the governor of your Maule to get the extra 200rpm and extra horsepower - prop limitations aside.
