JPI Data Question

I'm studying the JPI data from my recent trip to Key West and back to
Wisconsin. One thing stands out.

A sudden drop of 60 degrees EGT and rise of 30 degrees CHT on one cylinder
while all other cylinders remain rock solid stable.

After an extended period of idling at KEYW waiting for a clearance and then
an amended clearance and then a second amended clearance (20+ min) while
aggressively leaned, we performed a second run up to check for fouled plugs
and everything was normal.

Looking at the JPI data for this leg of the flight shows the #1 cylinder on
the left engine reading the lowest EGT and lowest CHT for that engine during
runup, but during takeoff it jumped to the hottest EGT while remaining the
lowest EGT. It remained the hottest EGT for approximately 1 hour and 30
minutes of flight at which point it dropped 60 degrees EGT and gained 30
degrees CHT. This brought the EGT for #1 back into it's "normal" position
as 2nd coolest between #3 and #6, where it had been on most previous and
subsequent flights.

Since this "event" I flew 6+ more hours back to Wisconsin and another 2
hours yesterday shooting approaches. No abnormalities noted.

I can understand a sticky intake valve causing a high EGT then a drop to
normal levels if the valve returns to normal operation, but what's with the
rise in CHT?

Curious.
Jim

"Jim Burns" wrote in message
...
I'm studying the JPI data from my recent trip to Key West and back to
Wisconsin. One thing stands out.

A sudden drop of 60 degrees EGT and rise of 30 degrees CHT on one cylinder
while all other cylinders remain rock solid stable.

After an extended period of idling at KEYW waiting for a clearance and
then an amended clearance and then a second amended clearance (20+ min)
while aggressively leaned, we performed a second run up to check for
fouled plugs and everything was normal.

Looking at the JPI data for this leg of the flight shows the #1 cylinder
on the left engine reading the lowest EGT and lowest CHT for that engine
during runup, but during takeoff it jumped to the hottest EGT while
remaining the lowest EGT. It remained the hottest EGT for approximately 1
hour and 30 minutes of flight at which point it dropped 60 degrees EGT and
gained 30 degrees CHT. This brought the EGT for #1 back into it's
"normal" position as 2nd coolest between #3 and #6, where it had been on
most previous and subsequent flights.

Since this "event" I flew 6+ more hours back to Wisconsin and another 2
hours yesterday shooting approaches. No abnormalities noted.

I can understand a sticky intake valve causing a high EGT then a drop to
normal levels if the valve returns to normal operation, but what's with
the rise in CHT?

Curious.
Jim

How about an intermittent leak on the induction tube on that cylinder? I
could see a slightly lean mixture resulting in the behavior you noted.

"Kyle Boatright" wrote in message
...
How about an intermittent leak on the induction tube on that cylinder? I
could see a slightly lean mixture resulting in the behavior you noted.

That seems to make sense and something I'll check.
Thanks
Jim

I don't know about you, but all this data from recip engines
reminds me that I really want a turbine powered airplane, with
the simple and smooth operation they provide.

Too bad they are soooo danged expensive.

Ronnie


"Jim B" wrote in message
...

"Kyle Boatright" wrote in message
...
How about an intermittent leak on the induction tube on that cylinder? I
could see a slightly lean mixture resulting in the behavior you noted.

That seems to make sense and something I'll check.
Thanks
Jim

After seeing dozens of turbine twins and singles during the last week, they
had my mouth watering also. My aerial applicator is currently converting a
Air Tractor 301 to a 401-B w/ PT6, this will be his 3rd PT6 AirTractor and
he loves them, even though when maintenance is finally required, it is more
costly, the bills come much less frequently.
Jim

"Ronnie" wrote in message
et...
I don't know about you, but all this data from recip engines
reminds me that I really want a turbine powered airplane, with
the simple and smooth operation they provide.

Too bad they are soooo danged expensive.

Ronnie


"Jim B" wrote in message
...

"Kyle Boatright" wrote in message
...
How about an intermittent leak on the induction tube on that cylinder?
I
could see a slightly lean mixture resulting in the behavior you noted.

That seems to make sense and something I'll check.
Thanks
Jim