Justbored201
Topic Author
Posts: 1
Joined: Mon Jul 01, 2019 5:28 pm

Apu overheat protective shutdown in flight

Mon Jul 01, 2019 5:37 pm

Any idea why Boeing 737 apu Honeywell 131-9 experienced auto shutdown due to overheat in cruise fl 350, no moisture upon landing started normally
 
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Horstroad
Posts: 490
Joined: Thu Apr 08, 2010 8:19 pm

Re: Apu overheat protective shutdown in flight

Mon Jul 01, 2019 6:39 pm

You should ask the FIM, not an online forum :D

An APU shuts down due to overheat, when the EGT reaches its limits. Maybe it's a faulty EGT thermocouple or a fault in the wiring.
 
unimproved
Posts: 90
Joined: Sun Jun 22, 2014 7:14 pm

Re: Apu overheat protective shutdown in flight

Mon Jul 01, 2019 7:10 pm

Too much power asked for the FL? IIRC the max altitude for packs is around 15,000ft and elec at 37,000.
 
Redbellyguppy
Posts: 201
Joined: Sat Apr 01, 2017 3:57 am

Re: Apu overheat protective shutdown in flight

Mon Jul 08, 2019 2:11 pm

Why were you running it at 350? Overwater? And more importantly, why did you attempt a restart on the ground?
 
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HAWK21M
Posts: 30042
Joined: Fri Jan 05, 2001 10:05 pm

Re: Apu overheat protective shutdown in flight

Mon Jul 08, 2019 6:28 pm

Check your APU module BITE, you will get the reason for the shutdown & suspect component.
Since it started normally on landing, it could have been a signal error too.
Best is to troubleshoot it.
I may not win often, but I damn well never lose!!! ;)

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