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

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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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.

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.

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!

Of course the TSIO-550 is fuel-injected, which probably reduces its susceptibility to carb icing somewhat.

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

Long time ago and old thread.

But to answer the question, I don't know how the derating was achieved. Clearly by limiting revs but how, I am not sure.

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.

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.

It's know too long for me to reliably know but think it was 2400 rpm max. The prop was big, so think tip velocity might have been a consideration in the total set up. Miss the aeroplane, miss the strip and the fun it afforded us.