Engineers & Technicians In this day and age of increased CRM and safety awareness, a forum for the guys and girls who keep our a/c serviceable.


Old 23rd Nov 2016, 10:30
  #1 (permalink)  
Thread Starter
Join Date: Nov 2016
Location: Tisdale
Posts: 1

Looking for anyone who has had trouble with their PCM from factory new. Specifically failure of the return shuttle valve when hooked up to the service cart such that the service cart fills the tank and overflows the system through the overboard drain (Overpressure) valve. We have a 28% failure rate in fleet.
Only one was caught durring the warranty period and they have denied the MMIR's for the others. Looking for instances of similar failures to help plead the case.
AC built in Italy. S/N in the 10-60 range.
Just wondering if we have three anomoulous PCM's or if Gary on the assembly line was sleeping for a bunch of them...
ProdigalSon is offline  
Old 24th Nov 2016, 09:37
  #2 (permalink)  
Join Date: Nov 2013
Location: Singapore
Age: 53
Posts: 69
I've only got one Italiano - but haven't had PCM issues at all. Are you sure the hyd rig is okay?
CAR42ZE is offline  
Old 24th Nov 2016, 13:29
  #3 (permalink)  
Join Date: Oct 2007
Location: England
Posts: 62
The rig will be fine this is a common fault on the 139.
They recommend and I believe it is also in the maintenance manual that you increase pressure rapidly and in some way this "assists" the valve.
Had to clean up the mess under the aircraft more than once. If that doesn't work then it's a pcm change. I have seen at least three of these.
dieseldo is offline  
Old 25th Nov 2016, 02:44
  #4 (permalink)  
Join Date: Nov 2013
Location: Singapore
Age: 53
Posts: 69
I must be lucky... So far. But I'll keep that procedure in mind. Thanks Dieseldo.
CAR42ZE is offline  
Old 25th Nov 2016, 14:07
  #5 (permalink)  
Join Date: Oct 2006
Location: USA
Posts: 411

Following diese's line of thought...

I don't speak Italian, so not sure this will help...but:

Since the 139 was originally a Bell/Agusta project to supposedly replace the 412, this problem sounds very familiar.

The 212/412 had a similar feature in their hydraulic systems whereas if you were a little weak in dialing in the test pressure it would overfill the reservoirs and puke everywhere.

There was a big caution in the M&O to reduce pressure to zero below a certain level. 600psi comes to mind. And if I recall, we used to listen for the "clunk" of the shuttle valve when applying pressure.

wrench1 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.