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pjvr99

Power increases with engine anti-icing ON

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For several weeks flight and ground crews have been pecking away at a problem where engine torque, fuel flow 

and TIT increase when engine anti-icing is turned on. We're not talking 100"lbs of torque here, its over 4000"lb

and/or 300 to 500 pph of fuel. Every conceivable component from FCU, speed valve, anti-icing side valves, and

the whole TD system has been replaced at least once with no change.

 

Last week the engine was finally removed and sent to test cell. Engine was started, runs great, makes good power,

but when anti-icing is turned on there is a massive surge of torq and fuel which the TD barely contains. I had the 

to see what happens in NULL - instant soil-the-underwear moment as torq jumps from 12500"lb to almost 18000"lb,

fuel goes 1600pph to 2000pph, and TIT from 900°C to 1040° ......

 

I have a small flapper installed over the inlet duct anti-icing vent so we can see when the anti-icing valve opens. This

device was working as intended, meaning a/icing on flapper flaps, but ...... massive torq, TIT and FF increases.

 

We eventually shut down the engine without any real idea of how to proceed with troubleshooting. Then I started

thinking: what if, somehow, a/icing air is getting into the FCU CIT or CIP lines .... Some examination of diagrams

led me to the CIP inlet in the compressor inlet housing. A/icing air is pumped into the same strut  as the CIP

fitting. If the fitting is corrode, cracked or loose, you'd be dumping 100psi air onto the CIP bellows.

 

Long story short, a really skinny guy was sent up the 'S'-duct and CIP fitting was replaced. VOILA! A/icing no

longer causes massive increases in torq, ff, and TIT

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Pleased to read this topic... Very interesting fect u explained.... Thanx dear..... It really increased the knowledge of many....

REGARDS. 

 

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we found a crimped plenum in the same area of a recently changed # 3 eng. took us 3 failed test flights and about  a week of hunting to find it. frank t.

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