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5052-O Fuel Tube Age Hardening?

DavePlaneGrips

Well Known Member
I was working on my 4th attempt at a fuel line and found a cutoff that was the perfect length. When I went to bend I noticed it was very difficult, like it had already been hardened, but it was straight stock.

The piece has a lighter look to it compared to other sections of fuel tube I have. The mfg date of the offending line is '17, and my other lines are '18. Could this tube have age hardened somehow?

I opted to use different stock for that section, I don't want to chance over bending pre-hardened line. 4th time was the charm too.
 
call Tom at T.S flightlines and ditch the alum tubing, the stainless lines he makes fit perfect and should be much safer than Aluminum.
 
The tubing that Vans supplies is 3003-O and is very soft (not very strong either) and usually supplied in a coil. 5052-O from Aircraft Spruce is supplied in straight lengths and is much harder and stronger. It should be marked as 5052-O on the outside. Aircraft Spruce also stocks 6061-T6 tubing, which is much harder and stronger again. So check the tubing you are using and make sure it really is 5052-O.

Regarding age hardening from -O temper, I have never heard of this happening.

Regarding hose, I use it in appropriate places, where flexibility is required. I use in down the gear legs and from the brake reservoir to master cylinder to the firewall. All other fuel and brake lines in the fuselage are 5052-0.
 
Right, as far as I know 5052 doesn't age harden. So how the heck did these? It's for sure stamped 5052-O.

I'm no expert, but I have plenty of experience trying to bend already-bent 5052 so I know how it feels after it hardens, and what unbent tube should feel like.

The section is done so I've moved on, but a CRES braided PTFE hose wouldn't be suitable here anyway. They are also not safer.
 
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"The section is done so I've moved on, but a CRES braided PTFE hose wouldn't be suitable here anyway. They are also not safer."


Ok I'll bite---where is the tube located that you are having issues with? 5052-O doesnt harden when stored. WE bend 5052-O and 6061T6 alot. Different spring back dimensions for the same sized tube. Granted 90% of what we bend is on the CNC, but I still bend concept prototypes by hand. YEP---6061T6 takes some effort.

Why arent stainless braid hoses safer?

Tom
 
I had an aluminum fuel line fatigue crack forward of the firewall in my RV-4. When it fractured, the engine driven fuel line started sucking air and the engine quit. The electric pump pressurized the line, the engine started running again, and I headed home. Good call... what wasn't apparent was that I was pumping one gallon per minute overboard between the two exhaust stacks.

My opinion on aluminum fuel lines... two guesses.
 
I had an aluminum fuel line fatigue crack forward of the firewall in my RV-4. When it fractured, the engine driven fuel line started sucking air and the engine quit. The electric pump pressurized the line, the engine started running again, and I headed home. Good call... what wasn't apparent was that I was pumping one gallon per minute overboard between the two exhaust stacks.

My opinion on aluminum fuel lines... two guesses.

Thru the firewall I only use steel AN fittings. Forward of the firewall and only between firewall mounted equipment I only use stainless steel tubing. Between the firewall and the engine I only use firesleeved hose.

Aft of the firewall where tubing is attached to the structure I only use 5052-O aluminum tubing.

Ed, where was the aluminum tubing on your RV-4 forward of the firewall?
 
No idea what kind of aluminum it was as I bought the plane already flying.

The fuel line went from the gascolator on a slightly flexible mount to somewhere else. It cracked at the gascolator fitting.

Sorry I can't be more precise, but that was 30+ years ago...
 
No idea what kind of aluminum it was as I bought the plane already flying.

The fuel line went from the gascolator on a slightly flexible mount to somewhere else. It cracked at the gascolator fitting.

Sorry I can't be more precise, but that was 30+ years ago...

5052-O will work harden from vibration or bending multiple times. Typically aluminum lines shouldn’t be used anywhere where it can be flexed enough through vibration or other movement to work harden, like engine vibrations may do. This can happen if the resonate frequency of the line happens to be near the engine frequencies. If they work harden they can experience low cycle fatigue and fracture.
 
Ok I'll bite---where is the tube located that you are having issues with?

Hey David--
Where are the tubes located you are having issues with?

"CRES braided PTFE hose wouldn't be suitable here anyway. They are also not safer." Inquiring minds want to know, especially the "not safer" thing.
Tom
 
The tube is finished, so I no longer have issues.

A CRES braided PTFE hose is no safer than a properly made rigid hose, where applicable.
 
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