Loose Fuel Line Fittings, a very close call !!!

[Walt]

This guy was extremely lucky, he asked me to do a prop balance and check for what he thought may be a vaccum leak because the engine was running "a little rough" (the aircraft had recently made a long cross country trip into our airport).

Well when I taxed the aircraft over to do the balance I could barely keep the thing running unless I kept working the throttle. No way I could balance this thing without fixing whatever was going on first. After about a 2 minute taxi over to my hanger, I shut it down and proceed to do a preliminary inspection.

It didn't take me to long to spot the rather large fuel puddle that had already accumulated on top of the airbox and fuel dripping everywhere. Further investigation revealed that the 'B' nut on the fuel manifold was loose and fuel was spraying on the engine block and running down the fuel line inside the fire sleeve

Keep in mind the fuel pressure in this line at idle speeds is just a few PSI, at high power settings the pressure goes much higher. I had a really good leak going at idle, at full power, fuel would have been spraying everywhere.

This is why I always say: put a wrench on all critical bolts and fittings everytime you do an oil change or at least every condition inspection. Merely looking at things is not good enough!!!

Somebody was watching over this guy....



Here's the 'B' nut that was loose, you can see behind it all the blue on the bracket and engine case. Fuel was also running down inside the fire sleeve. The top of the fire sleeve "had" red silicone sealing it, I peeled it away to inspect the hose fittings (it was loose and coming off anyway at this point from being soaked in fuel).



Needless to say I checked the rest of the fuel lines FWF and found a few others that were under torqued.

The prop balance came out good: from a very high 0.523 to nice 0.022 IPS

Be safe out there folks, and take care of your machine.

[Omega232Devils]

Walt,
Thanks for the pictures and explanation. I am sure someone will learn from this and take heed of your warning.
The A&P that did the pre-purchase inspection on my 6A told me to never say "I HAVE to take the cowling off", but rather "I GET to take the cowling off" and to use every opportunity to look over the FWF.
This prevented something very bad from happening to me recently when I caught a bent push rod during an oil change! (Engine had ran great without any issues!)

Dan

[mkbreezy]

First of all, I want to give Walt a HUGE THANK YOU for finding this.

The issue was on my airplane and here is the backstory. This airplane has just a tad under 100 hrs total time, and has been a perfect runner the entire time I have owned it. I took the airplane to Walt's field to get the airplane painted at Glo-Custom in the middle of Feb. On the last leg of three from the Farm, I noticed that the fuel flow was very slowly creeping up. The engine was running fine, and the EGT's were stable at 30 deg LOP. The only indication of an issue was the .75 to 1 GPH higher fuel flow, and a sub normal #3 CHT. There was NO smell of fuel at all, and the heat was on. On landing at 52F I could barely keep the engine running for the short taxi to Grady's, and now had some real concerns about the return trip in six weeks. I had already set up with Walt to do the prop balance, and to fix a tank leak. I also asked him to investigate what I thought was an induction system leak (no fuel smell at all) , as that was what I thought might be the problem. I was obviously not going to fly the airplane again until these issues were resolved. Walt emailed me last night with the prop balance results and what he found with the fuel line. That was an OMG moment if there ever was one.

It seems obvious that the B nut was under tourqued and that over time it had been vibrating loose. It finally got loose enough to spray fuel on that last leg. Now as Walt said, someone was looking out for me, because the fitting was spraying fuel at some rate for the better part of an hour. Only providence could have kept that airplane from catching on fire.

So folks, take Walt's advice to heart and check stuff every time the cowl is off or other things are open on the airplane. I KNOW I certainly will.

I will end this missive by saying again that Walt has jumped to the very top of my good guy list. He is a wonderful resource for all of us in the Van's world, especially us RV newbies.

[TS Flightlines]

Mike---you are a very lucky guy. Looks like the builder used 701 hose, and a NYLON tie wrap to secure the firesleeve? suggestion---fix it right. Walt can do that.
Tom

[aerhed]

A guy brought me a 210A one time that had a leaking diaphragm on the flow divider. Old style divider with pinhole instead of drain line. It had been leaking so long that it and the top of the case were encapsulated in blue putty. When I scraped off the putty, I found a chunk of crankcase and one bolt torn out and epoxied back into place. Someone had tried to lift the plane by the engine hoist loop after a gear-up and tore a chunk out of the case. A skysmasher I worked on had 3 injector lines chafed through on the rear engine that were shooting fuel everywhere. No way all 3 lines chafed through at once. I guess you take your luck where you find it.

[Walt]

Originally Posted by TS Flightlines

Mike---you are a very lucky guy. Looks like the builder used 701 hose, and a NYLON tie wrap to secure the firesleeve? suggestion---fix it right. Tom

I agree with Tom, when you get back to your home base I would recommend, as soon as practical, you pull all the fuel/oil hoses and send them to Tom for duplication with properly fire sleeved Teflon hoses with swaged fittings.

[GregM]

Torque seal is another great low cost product to help in visual verification of torque.

[Walt]

Originally Posted by GregM

Torque seal is another great low cost product to help in visual verification of torque.

Torque seal will only show if relative motion has occured between the painted surfaces, it does not show "torque". In the case of a sheared bolt head for example (which I have seen) "torque seal" will still look good but obviously will not be representitive of torque. Broken bolts can only be found using a wrench (although sometimes you will find the head laying somewhere and now you must search for the origin).

I learned "inspection" from an old geezer that told me you must inspect with all your senses, especially feel, not just by looking. This motto has served me well over the years.

When I inspect an airplane torque seal don't mean didly to me, for all I know you marked it "by accident". Nobody leaves fuel lines loose on purpose, so don't tell me it can't happen.

[GregM]

Originally Posted by GregM

Torque seal is another great low cost product to help in visual verification of torque.

Walt, thanks for shooting me down. You will note in the above quote that it will "help" in the verification. I did not say it was the end all to all problems. Your original post stated that the B-nuts had backed off their torque. In that situation, torque seal, if it was applied properly would have easily indicated that condition. I work on and fly OH-58 and UH-1 helicopters. With the extreme vibratory conditions, our lines are marked with torque seal. During pre-flight, it provides a quick visual condition indicator along with physically checking the lines. I have personally located a perfectly torqued, torqued striped, B-nut that when I tugged on the line, the line came out in my hand. The stainless tubing had failed at the base of the flare. Torque seal did its job, but that wasn't the problem area. The problem was the failure of the tubing. I have also found nuts that have backed off their torque and was quickly noticed by the broken torque striped line. This was similar to what you described. I was merely adding a low-cost additional safety step that people can use in determining if their aircraft is safe to fly. It is imperitive to understand what torque seal does, and it's limitations. If you don't fully grasp it's function, don't use it. I have over 25 years experience in maintenance with a foundation started in army helicopters. In the army, everyone of the un-safetied nuts on my helicopter was torqued striped. This has continued into my current law-enforcement job and into the construction of my own RV. The proper application requires one to torque the part and immediately apply the torque stripe. The practice of merrily painting away of the fittings isn't even considered. And no, Walt, I have never just painted a nut without first torquing it. If you did do that, then I could see what you said could happen. The discipline of the Army and hopefully for any A&P would dictate that they not do that. Many peoples (A&P's) standards vary, but for the above stated reasons, I insist on using torque seal as another tool in the chain of safety of flight. I truely hope some of the other RV'ers would consider the same and not be discouraged by the berating of the subject in your previous post.

[PCHunt]

Greg: Interesting, I didn't take Walt's post as berating at all, merely adding information which you subsequently agreed with. I think you two are on the same sheet of music.

All good info.