On one of the Metro's I flew, I
had a problem when starting it once - It just refused to finish spooling
up, and so I aborted to start. A friend came rushing up the steps and
said that, "Some red-hot bits of metal just came out the exhaust
pipe!" I figured that this couldn't be good, so parked the plane
for the day. To cut a long story short, what the problem was is that
some of the other pilots hadn't been cooling the engine down properly
before shutdown, and so the fuel injector nozzles were coking up with
unburned fuel. So, five of them (You can count five burn-throughs in the
above pic of the second stage stator) started to 'torch', and thus
inject fuel in a stream instead of a spray, causing dangerous hot-spots
in the turbine section. These Garrett TPE-331's are a very tough engine,
but what was happening was rather bizarre - The 12 Turbine Temp
Indicator sensors are located around this stator section, and they were
also being melted along with the turbine blades and stators themselves,
so, as fate would have it as the turbine burned away so did the temp
sensors, which caused both a loss in temperature indication AND a loss
in torque - Just as is you'd pulled the throttle back - So it was quite
normal to simply push the throttle back up to get the right amount of
torque back, which amazingly corresponded to the right temp reading! The
problem was, that instead of a temp of 870°C, the engine was
actually running at around 1,100°C!!!! So, to no-one's
surprise it shat itself big time. The problem was that it decided to do
it when I started it ... Boy, did I get in trouble! That is,
until the engineers convinced my bosses that it wasn't me. (I'm as
gentle as a kitten on engines) So, anyway, about $100,000 later the
problem was fixed, and a stern warning to all the pilots to COOL THE
BLOODY ENGINES DOWN PROPERLY!!!
Yeah, I knew that ... |
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