JPI Engine Data Analysis Questions

The information I received in the Savvy Aviator seminar is:

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.

- Steve Mills
N2679V 'Vicky" @ PDK
Cardinal RG '75



On Mon, 10 Dec 2007 06:18:02 -0800 (PST), Jay Honeck
wrote:

What I have started doing is looking at average, peak-to-peak variation, and
standard deviation on each channel, over a half-hour or so of stable cruise.
I am watching for any trend or sudden change in variability of data on a
channel. Doesn't tell all, but I hope it will alert me to something going
awry, whether it is engine or sensor. And it was easy to do in Excel.

In another forum a guy mentioned that you want to look for
fluctuations up and down in EGT, as it is an early indicator of a
sticky valve.

The question, of course, is what's a "normal" fluctuation, and what's
"abnormal"... Looking at my data most cylinders go up and down 10 to
15 degrees pretty regularly...

I'm assuming that's "normal" because they're all doing it -- but it
would be good to see some hard data on what these lines actually mean.

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"

Jay Honeck wrote:
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?

Jay, you can download the manual for the Insight "GEM" series at:
http://www.insightavionics.com/
It has the pictures you want.

Rip

Jay, you can download the manual for the Insight "GEM" series at:http://www.insightavionics.com/
It has the pictures you want.

Thanks! The actual link is:

http://www.insightavionics.com/pdf%2...EM%20GUIDE.pdf

Pages 67 through 77 have pictures of the instrument when different
things are going wrong in flight. It's specifically for the Insight
GEM, but that instrument is virtually identical to the EDM-700. Very
useful information, indeed.

Now, what we need are pictures of the corresponding graphs (from the
downloaded data) that match up to the specific problems depicted.
THAT would be very useful indeed, to be able to recognize the problem
signs just from the graphs -- in case you missed the indications in-
flight.

Any ideas?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"