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Old December 11th 07, 04:06 PM posted to rec.aviation.owning
Jay Honeck
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Posts: 3,573
Default JPI Engine Data Analysis Questions

A regular, one minute cycle of about 50 to 100 degrees (I think that
was the number) of EGT for one cylinder is an indication of a burned
(not sticky) exhaust valve that will fail, typically 100 hours after
first indications. The mechanisim seems to be that the valve rotates
as it goes up and down, about one rpm. Every time the nick in the
valve meets the nick in the valve seat extra gas escapes. Once you've
seen the plot of this, it shows up like a neon light.


Interesting stuff!

If you've ever seen the flight engineer's station of a Lockheed
Constellation, it's amazing to see the engine monitors they had 60
years ago. It's basically an oscilloscope that they could switch from
one engine to the next, and they had a huge book with pictures of
readouts that they constantly referred to for engine diagnosis. (I
was fortunate enough to log a little right-seat time in the MATS
Connie, before they mounted it on a stick in South Korea.)

If the screen looked like *that*, it was *this* problem. If it looked
like *this*, it was *that* problem. It was amazing how they discerned
what was going on from a squiggly line on a cathode ray tube.

THAT is the kind of book I wish JPI would publish. If the graph looks
like THIS, you've got a valve going bad. It it looks like THAT,
you've got morning sickness. The articles on AvWeb get close to that
-- but why isn't JPI doing it?

Don't tell me, let me guess: "liability"...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"