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So long as we are on temp probes and in the same
thread "jet-hot" appears, let me just recite my experience that got me very
interested in this subject.
After about 60 hours of flying, I was looking
around the engine compartment and noticed that the hose cover that leads to the
gascolator looked frayed. I thought "Huh. you would think
those would last longer than 60 hours just sitting there". Looking
around further I found that there were actually indications of melting on the
cover. I traced it down to exhaust escaping the slip joint on the transfer
tube.
I had just received the exhaust system back from
jet-hot at zero hours so now I was curious. Did the soap bubble test
on the exhaust system and found that EVERY slip joint was leaking. Not a
good situation so I had the entire exhaust system removed and sent to AWI to
have them fix the slip joints. They got into it and discovered
that the wall thickness (remember this was a new tcm exhaust system) was below
spec on all components. Long story short, I had to have a complete new
exhaust system built.
How did this happen? It happened because I
decided (flame suit on) to coat the interior of my pipes. Jet hot used
normal automotive techniques and bead blasted the heck out of the pipes so there
wasn't enough material left. I called them and they reminded me that I had
signed a waiver of damage. I'm not sure you are immune to this problem if
you only have them coat the outside, by the way.
Learnings:
1) Olympic coatings is better for this kind of
thing (they do all of PE's work)
1A) do the soap test on re-installation of any
exhaust component.
2) exhaust leaks can cause a lot of local damage
before they actually light anything on fire.
3) open cowl inspections are a great
idea.
4) serious fire sleeve is a great
idea.
5) in this case heat happened and fire
didn't. Therefore for early warning, a heat sensor would be
better.
6) calibrate all your emergency sensors before the
test pilot gets in the airplane. Mine wasn't so the information was
probably there but the test pilot wasn't looking at it.
7) consider what is in the path of a joint failure
leak when you lay out your engine compartment.
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