IO-470 Fuel Distribution Line Failure

[Rob58]

A friend running an IO-470 discovered a break on one of the fuel distribution lines, directly above the attachment to the injector nozzle. It was a clean fracture about 1/8" above the point where the line is welded to the end fitting. Looks like a stress fracture and there is no visible indication that some external force hit the line. Had this break not been identified before going airborne a bad fire would have undoubtedly resulted. My question is: has anyone heard of a similar failure? It's a scary situation.

 

[Norman]

Likely work-hardening from vibration. They don't last forever.

 

[Joshuajayg]

Shock cooling of the fuel line

Really, Norman said it. They get old. Maybe wiggled from time to time while removing and installing spark plugs. Vibrations from the engine running. Slightly more stress applied during manufacturing.... plenty of options that add up to it being old.

 

[Stewartb]

Primer lines do it, too. And like FI lines, if you never inspect with the lines pressurized you won't know that you're sprayinf fuel onto your engine.

 

[SoCal RV Flyer]

Were the lines properly secured with Adel clamps? They really help damp out the vibration.

Some of the Subaru flat-4 engines had this type of failure with the oil pick-up tube in the sump...a cause for concern with the RV guys who do the Eggenfelter Subie conversion.

 

[Checkout_my_Six]

So....how do we know it failed while it wasn't running? Did someone see it fracture?

btw....they do break from time to time....as evident by the blue staining and they don't usually go up into a fire ball.

 

[BigBadLou]

Shock cooling of the fuel line

Or from spraying water into the cowling to cool the engine after a lesson??

Agreed, glad it was found before a fireball gave it away.
My injector lines have clamps from a very old AD. I guess they found issues with the lines shortly after fuel injection came to life on aviation engines.

 

[Let'sgoflying!]

Im not convinced a fire is a sure outcome of a failed injector line. Or even likely. Someone spray fuel onto their hot engine so we can know, please.

 

[Dan Thomas]

Lycoming has an AD on all of their injected engines that forces inspection of the injector lines and their clamps every 110 hours or annually. They've been known to break due to vibration or chafing or fatigue caused by mechanics aggressively bending them out of the way and work hardening them. The AD refers to the Lyc service bulletin that preceded it, and the SB has diagrams for every injected engine's line and clamp installation. They take it seriously.

http://rgl.faa.gov/Regulatory_and_G...B39E0B81ACB0F30786257ECF005D80C7?OpenDocument

No doubt Continental will come up with something similar.

 

[Omalley1537]

Shock cooling of the fuel line

Really, Norman said it. They get old. Maybe wiggled from time to time while removing and installing spark plugs. Vibrations from the engine running. Slightly more stress applied during manufacturing.... plenty of options that add up to it being old.

Haha, was going to ask if that "Horse" guy took a lesson in it...

 

[pmanton]

Im not convinced a fire is a sure outcome of a failed injector line. Or even likely. Someone spray fuel onto their hot engine so we can know, please.

A few years back I was called to repair the fuel pump in an Ercoupe that had failed. The C-85 Continental fuel pump is mounted in front of the cylinders on the right side of the engine. When I got to the plane I found the cylinder dyed blue from the fuel that had leaked. The top cap on the pump had worked loose and fuel had been spilling for a considerable time. I was called when it finally sucked too much air to pump.