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  #1  
Old 03-09-2020, 07:31 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,138
Default Braided line inspections/failure

We all trust those SS braided lines and other flex hoses on our aircraft will seldom fail, and and give them all the standard inspections relevant to the yearly health check or when we have access. I, as an RV builder, A&P, and IA, got the wake-up scare this weekend that sheds some different light on the "normal" inspection. Here is the scenario.. I went to Fla to pick up and fly a recently purchased RV-4 home for a friend who is not yet checked out to fly it. The aircraft was recently condition inspected, regularly flown and didn't seemingly pose any threat to a 3 hour flight back to NC. After the more than normal walk-around pre-flight, I mounted up to depart, with the new owner and a friend standing to the side observing. Boost pump on, 3-4 blades and I get signal from them we have something coming out the cowling. Turns out it was fuel..alot of it, right on the exhaust. De-cowl and find the SS flex line from the carb to the fuel pressure indicator is nearly porous, and weeping out all over. It certainly is undetectable without pressure. This could have been a fireball ! I will add too my inspection criteria, all fuel lines will be checked with pressure applied, and periodic pre-flights will get the same with me not in the cockpit. It would never be seen by someone just going out to fly with no bystander...lessons learned every day. We did get it fixed, and the rest of the adventure home was uneventful...check/replace those flex lines!!
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  #2  
Old 03-09-2020, 07:49 AM
WingsOnWheels WingsOnWheels is online now
 
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Do you know what the failure was? Was it cracking of the liner? heat marks?
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  #3  
Old 03-09-2020, 08:47 AM
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rocketbob rocketbob is offline
 
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Location: 8I3
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I once annualed a Champ that had a braided fuel line made out of washing machine hose. Needless to say it got replaced with the right stuff.
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  #4  
Old 03-09-2020, 08:55 AM
fixnflyguy fixnflyguy is offline
 
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Location: Winston-Salem, N.C.
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No heat marks or close proximity to the exhaust. I haven't done forensics on it yet, as its still in the plane. It is possible it was not compatible with fuel or the liner just deteriorated. Since the aircraft has a fuel flow transmitter installed, I capped the port and flew home without this line being pressurized. Its looks to be a well made line, with no obvious damage or deterioration.
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  #5  
Old 03-09-2020, 08:59 AM
zmatt zmatt is offline
 
Join Date: Jul 2007
Location: OK
Posts: 69
Default

Had a very similar thing happen to a buddy. When he was shutting down there was someone watching and noticed there was something leaking from the cowl. It was a braided line and I think just about the same location.

It very well could have been a fire.

Fly Safe.
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  #6  
Old 03-09-2020, 09:03 AM
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rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
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Beware of using hoses which don't have a conductive lining in applications where there are high fuel flow rates. Static charge can build up and eventually cause perforations in the liner.

See Tom at TS Flightlines if you want the proper stuff.
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  #7  
Old 03-09-2020, 11:57 AM
TS Flightlines TS Flightlines is offline
 
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Location: Ridgeland, SC
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I'd guess it was a "rubber" liner with a stainless braid. WE know that today's fuels, whether Avgas or Mogas have additives that attack the 'rubber" liner. Whether its neoprene, nitril, EPDM, whatever is in the fuels attacks it. Looks like heat cracks. So when the hose flexes, it leaks through the liner and out of the braid. NOT FUN.
For our purposes, teflon is the best answer---impervious to all the chemicals we see---in most anything. Hot grease, bio-chemicals, aerospace, automotive, etc.
Good catch Bill----
Definitely would have been a bad day.

Tom
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  #8  
Old 03-09-2020, 12:41 PM
Canadian_JOY Canadian_JOY is offline
 
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 2,217
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Importantly, what type of hose (brand etc) and fittings were involved?

We embark on building and maintaining these aircraft; while in many ways they are stone-simple, often it's the simple things that can really bite us.

Thanks for offering up this learning opportunity.
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  #9  
Old 03-09-2020, 12:44 PM
74-07 74-07 is online now
 
Join Date: Dec 2016
Location: Greenville, SC
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I just replaced every fuel line from the fuel valve to the cylinders and all other fluid lines with the new molded internal fire-sleeved hoses from Tom at TS. The braided lines I took off were apparently original (2004). Finally got around today to looking at the old ones. From the open ends you can see cracking and general deterioration. Glad they are out of my 8!
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  #10  
Old 03-09-2020, 01:48 PM
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RV7A Flyer RV7A Flyer is offline
 
Join Date: Jul 2013
Location: US
Posts: 2,159
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Quote:
Originally Posted by 74-07 View Post
The braided lines I took off were apparently original (2004). Finally got around today to looking at the old ones. From the open ends you can see cracking and general deterioration.
Thing is, though, this isn't any help to anyone without knowing WHAT TYPE of hoses they were, which manufacturer, date of *manufacture* (did they sit on a shelf for 10 years?), etc.

It'd be much more useful for people to post more info on the *parts themselves* when they find a failure or potential failure, so we can be better informed.
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