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Fuel line fracture in flight

dozewase

I'm New Here
My RV10 has 1470 hrs on a IO 540. It is maintained by my A&P who has built two RVs and is familiar with the 100 hr AD to inspect the fuel lines. So less than fifty hrs after annual I experienced a ruff running engine suddenly with power change an a immediate landing was made and fracture of fuel line to # 2 cylinder and small crack #1 fuel line was discovered. My question is has anyone else experienced this or found cracks in their fuel lines? You can imagine I am quite freaked out by the potential for fire from this so any additional info I can collect will be welcomed

Dozewase
 
Support?

Wasn’t there a Service Letter or AD note about supporting the stainless steel injector nozzle lines? If’n I remember rightly, something about needing two Adel clamps per line or something like that.
 
Ah,Here It Is

https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/b39e0b81acb0f30786257ecf005d80c7/$FILE/2015-19-07.pdf

If the link doesn’t work, Google AD 2015-19-07.
 
Yup, been there done that. Happened to me about 9 years ago. I was in moderate turbulence at 2500. Was smelling a bit of fuel. I thought it was coming out of the vents since I had just refueled. Decided to climb to 8500 to get out of the turbulence. Faced a 40 kt headwind but got a smooth ride. The serenity lasted about a minute when all heck broke loose. Felt like a jug departed the airplane. The shaking and roughness was horrible. Brought the throttle to idle and roughness was mostly gone. Traded airspeed for altitude, got to best glide speed. The nearest field was 8 miles ahead, but impossible to make in that headwind. Turned to a field 12 miles behind me and easily made it to Low Key.

Landed, and closed out my emergency with Atlanta Approach. It was a Friday afternoon and I knew my friends at the Falcon RV Squadron were getting ready to brief a formation flight. I called one of them to let them know I might need some help. And finally called my wife and let her know that I was alright and I might be late for dinner.

Removed the cowl and the problem was immediately obvious. The #4 injector line was severed about a 1/4” past the braised joint. There were blue stains everywhere. Hard to believe nothing caught fire. Called my friends and let them know. They called me back and told me Avparts only needed my credit card no. One of them flew to Newnan to get the replacement line. They briefed up an alternate mission and came to my rescue 80 miles east of Atlanta. It was very touching to see a 4 ship pitch out overhead for me! One of them brought enough tools to do an engine change and another handed me a Coke and told me to have a seat. I was home before sunset.

I checked my injector lines per the MSB referenced above. Everything was perfect. To this day I’m dumbfounded as to the cause. My only guess is that the line was twisted when installed by engine shop. I’ve put another 1000 hours on it since then and everything is fine.
 
Top of the engine photos . . . .

Lycoming MSB 342G.
Pics or description of your failure would be helpful.

Tom

Pics of the whole top of the engine to see where the lines are secured is the objective here. Those lines can/will vibrate and stainless is not good for fatigue. There is a 45 deg slice where they are brazed at the ends to reduce stress concentration, and fatigue issues.
 
Hi Bill---certainly, but I was more interested in the ops pics, to see if his lines were properly secured. Pretty sure his A&P is a great guy, but it wouldnt be the first time something got overlooked.

Tom
 
Injection lines

Was the IA at a busy shop for years and occasionally found cracks in the solder joint where the SS line goes into the end fitting. Usually it would be a hairline crack and the line would get replaced before a real problem developed. This area needs a close look for cracks and how good the clamping hardware is working at inspection time. I would look at mine every time the top cowl came off. In the E/AB arena I’ve seen various deviations from how Lycoming wants these lines secured.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
It happens.

Why do we still use hard lines here? Tom, is there an equivalent ID flex line?
-
 

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Yep. I've broken one in flight as well. Called Don and replaced all the lines on both my airplanes after that.
 
Dan---we've used -3 teflon for injector lines, mainly on SDS systems. These are on a IO390 with SDS and a baffle mounted fuel block. Similar idea for a flow divider.

Tom
 

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Dan---we've used -3 teflon for injector lines, mainly on SDS systems. These are on a IO390 with SDS and a baffle mounted fuel block. Similar idea for a flow divider.

Tom

I have ben looking at those on our neighbor’s project - man, are they slick...and beautiful!!
 
Dan---we've used -3 teflon for injector lines, mainly on SDS systems. These are on a IO390 with SDS and a baffle mounted fuel block. Similar idea for a flow divider.

Well 'ole buddy, it sounds like a product idea. However, I think we would want -2 lines to minimize the fuel quantity boiling out the open nozzle into the intake port after shutdown. Not a problem with the SDS application, as the injectors park with the pintle closed.
 
-2 teflon is hard to find, and pricey. When we need a -2 hose, such as for primer or older oil pressure/fuel pressure installs, we convert our -3 straight hose ends to -2. Same -3 hose, same stems, we turn the bodies and the flareheads down on the lathe so the -2 nuts will clear. The 471-2D stem ID is .060, our -3 stem after crimp is .079.
Works well.

Tom
 
-2 teflon is hard to find, and pricey. When we need a -2 hose, such as for primer or older oil pressure/fuel pressure installs, we convert our -3 straight hose ends to -2. Same -3 hose, same stems, we turn the bodies and the flareheads down on the lathe so the -2 nuts will clear. The 471-2D stem ID is .060, our -3 stem after crimp is .079.
Works well.

Tom

DanH's idea is to reduce the internal volume as much as possible. Just changing the ends doesn't do it. Even if the -2 line is pricey, a bunch of us might happily pay it to avoid this cloud hanging over.

I look mine over every time the cowl is off. I have seen one break on a Maule.
 
time between replacement?

Assuming the failure at 1470 hours was with well secured lines... perhaps replacing the injector lines every 1000 hours would be advised?
 
Steve--I think Earls might be the only other source for -2 hose ends, and they are reusable. $50.00 EACH for 1 straight. 45* is like $75.00, and 90* is $87.00. Each. These are block style, heavy.
That takes care of the flow divider side, where you can substitute a AN816 nipple (usually AN816-2 is aluminum). Doesnt fix the injector side.
On another note, I do have some prototype -2 ball seat primer/flow divider fittings in straight and 90* that I messed with several years ago. Big issue is the nut, and making the stem small enough for the nut to pass over, without changing the nut alot.

Can be done though

Tom
 
Happily pay !

Heh Tom ...I wholeheartedly agree with Steve ...would happily pay for -2 lines fir this application!
 
Flex Replacement Lines

Tom,
I would certainly be interested!
Could you work up some estimates assuming various sales levels using -2 and -3?
Sounds like a potential improvement in safety and maybe a greater margin before air bubbles in the lines!
Cheers
db
 
Well, we broke out the drawings and made a few minor tweeks. Lookiing at feasiblilty. The injector side is the hardest, because it needs the -2 ball seat ends, like AN800. Not that big a deal other than you need a 90* and that gets alittle tricky. The flow divider side could be AN800, OR AN flare, and change the nipples to AN816-2 Steel. Just as easy to keep it the way it is, and use AN800 on both sides of the hose.

Only big issue I see is the variations of hose end angles to connect at the flow divider. Because this is experimental, flow divider configurations are all over the place. BUT---can it be done? Yep.

I sent Steve a sample of what I wanted so he could machine 1 or 2 on the HAAS. Stay tuned.

Tom
 
Probably a long shot and might make the assembly too tall, but what about creating an AN800 male seat to AN2 male flare adapter for the nozzle? Then standard AN-2 hose ends could be used.
 
HI Lars----needs to be a 90*, and in all proablity something brazed like the pic below. Problem is capturing the nut, and its a brass 5/16-32 nut, and it would be hard to do, and defeat the purpose of a strong, billet, unbrazed fitting.

But, I may look into it to see.
Tom
 

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OH---the fitting in the post above is NOT brazed, it has a pinned(wired) on nut, and there just isnt room on a primer nut. AND expensive to do.

Tom
 
I was actually thinking a straight adapter with a 90 on the hose, but that is probably too tall.

Regardless, I was eyeing my own injector lines suspiciously a couple of days ago. Add my name to the customer list if you come up with a solution, Tom.
 
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