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Cockpit fuel lines and fire prevention

Like many others, I'm not putting a single hard line anywhere in my airplane.

Not because they aren't really capable of living a long and useful life, but because I know I'm not really capable of building a line I'd be proud of putting in my airplane. The margin for creating the perfect line is thin and it's something you can waste many weeks of evenings tweaking and rebuilding.

Even after building the perfect line, I'd still be paranoid. Been there and done that with the brake lines originally.

For me the machined fit of a teflon/braided/sleeved (on fuel) hose is idiot proof. That means it's perfect for someone like me. :)

Phil
 
Regarding flex lines, be advised that the hard lines tend to pinch shut when torn apart in a wreck; not so with rubber hose.

It's worth noting that much of the "re-engineering" that is being suggested has already been tried over the last 100 years and was found to be inferior to modern standard aircraft methods. We really should look to what has worked historically and stop trying to reinvent the wheel. Having said that, putting fuel lines and a sparky little motor in the same small box is an I.E.D. just waiting to explode.
 
TSwezey said:
...our boost pumps were after the valve running at 60 PSI.
Click to expand...

"Pumps", plural, more than one? Self regulated, or were there also full flow return lines from separate pressure regulators at the engine fuel rails?

Perhaps we should document the failed system before further speculation about the stock RV-10 fuel system.

Todd, can you post a system diagram please? And perhaps build log photos of your completed tunnel package?
 
Does anyone know which stainless tubing from Spruce would be suitable for fabbing fuel lines. Even though I am happy with my 3003 aluminum, I might change the line from the pump to the gascolator. Mostly because my son (co-pilot) has really long legs and I can see him pushing on the line.
 
Phil said:
Like many others, I'm not putting a single hard line anywhere in my airplane.

Not because they aren't really capable of living a long and useful life,

snipped
Click to expand...

One advantage of a hard line ...........is the life of the part. I'd say that many hard lines could easily last the life span of the airframe.

Yet, flexible lines have shelf life, as well as a service life. You'll just have to keep inspecting, or replace at 5-8 years. And firesleeve makes the inspection even tougher.

L.Adamson --- RV6A
 
Be Careful About Knee Jerk Reactions

Todd's incident has scared a lot of people, and rightfully so. However, as others have already pointed out, we really need to think and proceed cautiously before we start redesigning entire fuel systems because of this incident. If we simply start replacing every aluminum part on our planes that makes us nervous with steel parts, our aircraft will be too heavy to get off the ground. Hey, there's been it least one in-flight break up of an RV due to spar failure (N58RV)...why not replace our spars with something stronger like steel? Our machines will be too heavy to fly, but at least they'll be safe!

OK, in all seriousness certified aircraft have been using aluminum components for the fuel system throughout the aircraft and fuselage for years without too many issues...and most issues are the result of poor maintenance. In the last couple of weeks I've looked closely at both an older Cessna 310 and a 60's era Piper Aztec-Geronimo that were undergoing annuals. Both of these planes have aluminum fuel plumbing throughout (including lines running to the nose mounted gas heater) and have been flying for many years without fires or explosions. These aircraft even have aluminum fuel fittings fire-wall forward.

My own personal construction choice that I made 4 or 5 years ago on my RV-8 was to throw away the Van's supplied "soft" tubing and to use 5052-0 for all fuel and hydraulic plumbing aft of the firewall. I used 5052-0 not so much because of its increased strength, but because it has vastly superior fatigue resistance over the soft tube. Secondly, I have paid careful attention to fabricating and installing all of these lines properly to avoid unnecessary stresses and chafing. Finally, I pressurized every leg of pluming in my aircraft with shop air using a gauged leak test device and performed decay checks on everything as well as bubble checking all fittings and joints while they were under pressure.

In addition, I believe that minimizing high-pressure plumbing inside the cockpit/cabin is probably more realistic and useful than trying eliminate all fuel plumbing inside of our aircraft. A small fuel leak in the low pressure plumbing will be more likely to result in air drawn into to the line rather than large amounts of fuel leaking out of the line in our aircraft.

I think we would all be better served to pay close attention to using standard practices and materials in the correct fashion in our aircraft, instead of starting to redesign whole systems and use non-standard materials (for light aircraft). Of course, if any one does figure out a way to improve fuel system safety without increasing airframe weight, drag, or complexity, I'm all for it!

Skylor
RV-8 QB, Final Assembly
 
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When did it start raining flaming RV's all over the world? I must have missed that...


Lee...
 
Phil said:
Like many others, I'm not putting a single hard line anywhere in my airplane.

Not because they aren't really capable of living a long and useful life, but because I know I'm not really capable of building a line I'd be proud of putting in my airplane. The margin for creating the perfect line is thin and it's something you can waste many weeks of evenings tweaking and rebuilding.

Even after building the perfect line, I'd still be paranoid. Been there and done that with the brake lines originally.

For me the machined fit of a teflon/braided/sleeved (on fuel) hose is idiot proof. That means it's perfect for someone like me. :)

Phil
Click to expand...


OK, couple of comments, not the least of which is the fact that you are afraid of properly bending and flaring hard line, yet you are constructing a four passenger aircraft... Do you see the irony here?

To more practical comments:

If you do "all braided hose" you are signing up to:

1. About a 10-12 pound decrease in useful load;
2. Significant unnecessary expense;
3. A complete fuel line replacement schedule every few years;
4. A packaging nightmare;
5. Decreased reliability (hose does fail, degrade, chafe, cause damage and LEAK!.)

I wholeheartedly echo those here who call to not "reinvent the wheel". Flex hose has its application in standard aviation practices, (but it's usually a LAST resort), as does other material. We're building aircraft here, so it's best to follow "aircraft standards" don't you think? The standards for proper fluid systems are readily available to all of us and are fairly easy to understand. Most "standard practices" can be found in AC43-13, and the T.O.s 1-1A-1 and 1-1A-8.

The purpose for building amateur built airplanes is to learn... Don't sell yourself short on the experience of learning how to fabricate a few hard lines.
 
apkp777 said:
Mike,

The 304 seamless? I don't remember the stainless I used in the past being .035 wall thickness. Maybe it was, just seems awfully thick.
Click to expand...

I've used the .035 because that is what is readily available. Given the choice I would go a lot thinner on the wall thickness, but the .035 still is fairly easy to work with. The thicker wall does give you a bunch of margin for damage and working out the flare tool bite marks.
 
Mike S said:
Would you just not run a fuel valve, or do you intend to install the valve outside the fuse also, and remote the control handle inside somehow??
Click to expand...


I'm still reading htis excellent thread so please forgive me if someone else has already addressed this.

Andair used to advertise a remote fuel valve. I know that the canard world was very excited about it at the time. I'm just not sure if it was ever produced, etc..

Bob
 
bhassel said:
I'm still reading htis excellent thread so please forgive me if someone else has already addressed this.

Andair used to advertise a remote fuel valve. I know that the canard world was very excited about it at the time. I'm just not sure if it was ever produced, etc..

Bob
Click to expand...

Andair does make a fuel selector with long remote extension. If you really want to move things outside the cabin, electric fuel solenoid valves are available.
 
Comments are added in-line and in red.

Phil



Toobuilder said:
OK, couple of comments, not the least of which is the fact that you are afraid of properly bending and flaring hard line, yet you are constructing a four passenger aircraft... Do you see the irony here?

Nope, I don't see it.... There are far less qualified or less modest folks who are building airplanes today. A good builder is one who recognizes a limitation and addresses it adequately. A bad one is the one who pushes on and says it's okay.

Airplane construction is a terrible time to play hero, pound your chest, and claim you can do more than you can really do. I've yet to meet anyone who knew everything and had mastered all the skills. If they think they do, I try to stay away.

I'm level headed enough to know 1) I don't know it all and 2) I make mistakes. I'm human. A good airplane builder (and pilot for that matter) starts with that understanding and manages against it.

To more practical comments:

If you do "all braided hose" you are signing up to:

1. About a 10-12 pound decrease in useful load;
Not a problem for the mission of my airplane.

2. Significant unnecessary expense;
It's mice nuts in the cost of the RV-10. It's about 0.25% (1/4 of 1%) of the total project cost. There are better places to worry about cutting cost in this airframe. The fuel system is a bad place to start getting cheap anyway.

3. A complete fuel line replacement schedule every few years;
Maybe... Teflon hoses in the tunnel have a different lifespan than those who operate in the harsh environment under the cowling. I agree they should be inspected regularly and replaced upon a condition inspection - but so should a hard line. Everything FWF will be replaced every 5 years; though there are some Teflon pundits that claim you don't need to replace them until they fail a conditional inspection. (I don't share that opinion.)

4. A packaging nightmare;
Been down this path already. It's really no big deal to properly support the lines in the RV-10 tunnel at least every 24 inches per 43-13. The factory supplied supports in the RV-10 tunnel are already 12" to begin with.

5. Decreased reliability (hose does fail, degrade, chafe, cause damage and LEAK!.)
And hard lines don't?
In the past two weeks we've heard of two major failures of hard lines in RV's. One RV-10 in IMC and then this one. (I agree verdict isn't in.)

I wholeheartedly echo those here who call to not "reinvent the wheel". Flex hose has its application in standard aviation practices, (but it's usually a LAST resort), as does other material. We're building aircraft here, so it's best to follow "aircraft standards" don't you think? The standards for proper fluid systems are readily available to all of us and are fairly easy to understand. Most "standard practices" can be found in AC43-13, and the T.O.s 1-1A-1 and 1-1A-8.

43-13 addresses the use of Teflon hoses and in fact reference their use for "superior qualities" relative to other lines (hard & rubber). Their only caution against using them is to avoid bending them too much, twisting them, or attempting to re-shape them after they've been installed and set-up into a specific shape.

The purpose for building amateur built airplanes is to learn... Don't sell yourself short on the experience of learning how to fabricate a few hard lines.

I agree completely. In fact I already built hard lines once and even took them to a couple of A&P's for inspection. They looked great and the skill was gained. But I still don't trust them because I know of too many hard lines that have snapped over the years. I can't say that for a flexible line. I have heard of slow drip leaks and other not-so-catastrophic failures, but nothing as catastrophic or as common as a severed hard line.
Click to expand...
 
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In the past two weeks we've heard of two major failures of hard lines in RV's. One RV-10 in IMC and then this one. (I agree verdict isn't in.)
Click to expand...

I haven't seen the report of a RV-10 in IMC with a fuel line failure. Only the two accidents you provided links for in a previous reply, as well as a 10 with door problems, and Dan Lloyds. Are there others?

L.Adamson --- RV6A
 
Phil,

Your lack of concern about 10 extra pounds would get you fired as an engineer at my company, but it's your airplane, so I won't comment further on that. Nor will I comment on your individual responses because it would just take too long. But let me leave you with some thoughts: If flex hose is so superior, why is it in such limited use in the "real" aviation world? Why do military fighters and civilian transport aircraft still use miles of "inferior" hard line?

Running all flex hose may make you sleep better, but as hard as you try to justify it, there's no good engineering reason to do so. I'd encourage you to stick with common aerospace practice.
 
I don't get it..

There is nothing at all very challenging or significant in fabricating a solid fuel line. The comments in this thread and others has raised this pretty simple task to some level of artisanship it simply does not deserve.

Riveting solid -4's is harder and requires more skills. Certainly the layup of the windscreen fairing or the alignment of the landing gear is harder..even bending the elevator leading edge is more problematic (IMHO).

The fuel system is no more or less critical than the control system, the landing gear system, the spar, the canopy, blah, blah, blah... they all have to be built correctly and to a standard which matches their function.

The reason most hardlines fail is not because of tiny little tool marks left by the tools having been used for decades but rather the lack of support at the correct points in the line. If the line nor connection pointst move the stress is very low. If you use alum lines, support them very well with adel clamps and don't use them to connect between two points with relative motion and they will last longer than your flex lines. You don't have to polish them to a mirror finish either. That is simply paranoia, akin to worrying about the carbon content in black magic markers causing corrosion..cmon!
 
FWF hardline

Engine failure in IMC had a hard line break in the FW forward area.
No one in their right mind would install a hard line where that one failed.

As to Todd's explosion. We don't actualy know that a hardline broke.
 
Those cautioning calm and thought before doing anything have a point and are heard, at least by this builder. I've been looking over the -10 fuel system drawings and I don't see a need for a wild redesign. I like hard lines and I think the potential problems can be addressed with careful building - though I don't think it hurts to explore some possible improvements, like tunnel venting. I've also been very happy with the -6A fuel system, except for the transverse lines behind my heels. Unlike the -7/9 setup, where these lines are behind kick panels and have additional ribs to support them, I find the -6A lines to be rather exposed and vulnerable. One way to address this might be to use -7/9-style structure. Another might be flex lines to the wings; they are so exposed that inspection and maintenance would not be difficult. I have not made up my mind and I'm not rushing to a decision. I'm just saying, let's not turn this into a 'pr---r wars' type of issue.
 
More easily addressable ones. We just see things differently.

Toobuilder said:
Phil,

Your lack of concern about 10 extra pounds would get you fired as an engineer at my company, but it's your airplane, so I won't comment further on that.


That's the beauty of building your own plane. It's your airplane customized the way you want it. The RV-10's are fast, but most -10 builders are not building them for performance. They're building them for comfort, cruising, and spacious cross country travel. That's where the -10 separates into its own branch from the RV family tree. If you'd check the weight of most RV-10's, you'd find they're a portly group. Nicely finished interiors, air conditioners, and entertainment systems are not uncommon. The typical mission for the RV-10 is completely different from it's cousins.

Nor will I comment on your individual responses because it would just take too long. But let me leave you with some thoughts:

If flex hose is so superior, why is it in such limited use in the "real" aviation world? Why do military fighters and civilian transport aircraft still use miles of "inferior" hard line?

AC43-13 says they're "real aviation" materials. I'm not sure what the problem is?

Remember I never said they were inferior and I said they would have a long and useful life for many years if they're installed properly. They're accepted in 43-13 (just like teflon), they've been accepted for years, and they are just fine in our application. There are plenty of airplanes who have been flying for decades on the same aluminum lines.

My problem with them is the margin for error. It's very thin and any mistake in craftsmanship results in a catastrophic failure. It's that simple.

To further answer your question about their use, it's a slam dunk. Because they're much cheaper and much lighter.

Cheaper is important to any spam can manufacturer who is trying to squeeze every penny of margin they can out of the airplane. When was the last time you saw the big manufacturers take the more expensive route when there is a cheaper way? Especially one that's a magnitude of 900-1100% more expensive than the cheaper 43-13 accepted alternatives.

Lighter is important in any performance airplane who's mission is to be fast, agile, and tasked with getting even the most minimal performance advantage over the other airplane.

Running all flex hose may make you sleep better, but as hard as you try to justify it, there's no good engineering reason to do so. I'd encourage you to stick with common aerospace practice.
Click to expand...
 
NP... Yeah, that was a bad decision.

I'm not sure how that one got by any inspection. You'd think the entire fuel system would be one that would be checked from tank to injector.
 
Todd,
What type of fuel did you have? High-octane auto-gas is my guess for the LS1 engine.

Group,
Is there a difference in flamability between 100LL and auto-gas?

I ask because I recently saw someone try to ignite cardboard soaked in 100LL by arcing jumper cables from a 12v battery--didn't work.

-Jim
 
yep!

well said Ken!
Tom
RV8R999 said:
I don't get it..

There is nothing at all very challenging or significant in fabricating a solid fuel line. The comments in this thread and others has raised this pretty simple task to some level of artisanship it simply does not deserve.

Riveting solid -4's is harder and requires more skills. Certainly the layup of the windscreen fairing or the alignment of the landing gear is harder..even bending the elevator leading edge is more problematic (IMHO).

The fuel system is no more or less critical than the control system, the landing gear system, the spar, the canopy, blah, blah, blah... they all have to be built correctly and to a standard which matches their function.

The reason most hardlines fail is not because of tiny little tool marks left by the tools having been used for decades but rather the lack of support at the correct points in the line. If the line nor connection pointst move the stress is very low. If you use alum lines, support them very well with adel clamps and don't use them to connect between two points with relative motion and they will last longer than your flex lines. You don't have to polish them to a mirror finish either. That is simply paranoia, akin to worrying about the carbon content in black magic markers causing corrosion..cmon!
Click to expand...
 
was this guy dressed in Nomex?






fehdxl said:
Todd,
What type of fuel did you have? High-octane auto-gas is my guess for the LS1 engine.

Group,
Is there a difference in flamability between 100LL and auto-gas?

I ask because I recently saw someone try to ignite cardboard soaked in 100LL by arcing jumper cables from a 12v battery--didn't work.

-Jim
Click to expand...
 
I've been reading this thread on my Iphone while I've been traveling the past 24 hours, and it's not a very good way to post things - but now that I am back on the computer, I have to agree with those who suggest that folks slow down on modifications to their fuel systems as a quick reaction to Todd's incident - or any others. There a thousands of RV's flying - and there have been for over twenty years - with the standard van's fuel system. That is a LOT of hours of test time. the two recent RV-10 mishaps cited had NON-STANDARD systems in one way or another. Deciding to build yet another non-standard system - with significantly less (or no) field experience makes you that much more of a test pilot. Frankly, it's one thing to be a test pilot in a two-place. But in a four-place, you're probably intending to carry more people. Will all the passengers know of the "more experimental" nature of the airplane?

Hard lines have a known service life (pretty much indefinite when properly built and secured. I have recently researched Teflon-coated lines to find the recommended service life. The manufacturers say that "service life is to be determined by the designer for their specific application" - giving no other guidance. So....how is the homebuilder going to determine it? It's hard to do the right kind of testing to come up with that number.

Folks - fuel systems are critical safety items. Testing history is important. How about building the configuration that has been proven time and time again? It's less "experimental" - but much more determinate. As a builder, engineer, and Tech Counselor, I am pretty conservative - because it is generally safer.

Just my opinion of course - based on a little engineering knowledge and close to 40 years of working on airplanes.

Paul
 
Hey Paul,

I was hoping you were watching and would chime in because I know this is a subject that's near and dear to your heart, and rightfully so.

Unfortunately the thread has taken the tone of primer. It's not about discussion, but about hardline (no pun intended) positions. You can't have a healthy discussion if you can't understand any perspective other than your own, which is why I continue to acknowledge that properly fabricated aluminum fuel lines have been proven throughout the decades and are very acceptable for our application. My position in the debate is pretty straight forward; an "amateur built" airplane that uses flexible hoses and AN-fittings provides a wider error for margin and less catastrophic failures to the fuel system.

But I guess I need to be more specific about a piece of logic I'm struggling with. It's bizarre how we demand flexible fuel lines to transport fuel through the harshest environments, where temperatures can reach extreme highs, extreme lows, and where vibration is extreme. In the most extreme circumstances we depend upon flexible fuel lines to move the gas to our engine.

So here's the hangup. Once we get to the task of transporting fuel through the relatively peaceful environment between the tanks and firewall, it's suddenly inadequate? That's the logic that just doesn't make any sense to me. (Assuming you're using TSO'd teflon hoses - btw. Otherwise all bets are off.)

I understand exactly where you're coming from. If it ain't broke, don't fix it; and that's the most known (and predictable) position of them all. From an application perspective, it's spot-on.

What I'm hoping to hear is someone who can provide a clear reason not to run it and I haven't heard that yet. Every objection is pretty easily defended.
Cost? Money isn't a safety item.
Weight? Weight, isn't a safety item.
Inspections? Every fuel line needs inspected.
Not Airworthy? 43-13 says they are and they're TSO'd too.​

It seems like there's no silver bullet. I'm hoping someone can shoot it down with more relevant and scientific data. "Because" isn't a good enough explanation and that's really all that we've heard.

For those following the thread, don't take my words as advice. God knows I've given and been give bad advice before. My words are words of devils advocate for the purposes of the debate.

Phil
 
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Phil, you're not going to hear...

...that braided teflon is inferior.

Most certified aircraft builders take bids on much of their materials....a reason to go cheapest.

In my mind, what you're proposing is actually, and in reality, a step up in quality.

Best,
 
Ditto,

TSwezey I feel for your loss :(

I reserve judgment until I see the modified fuel system diagram; AND
until someone runs a Flap DC motor in a fuel vapor rich environment as an experiment and manage to ignite it.

This sounds like something "Myth Busters" the TV series must tackle :p

Regards
Rudi
 
I have worked on aircraft for many years and have seen many flared lines break at the flare bend radius on the lines, mostly due to people overtorqueing them and thinning the metal on the flare, also most of the ones I've seen break are the 3/16 and 1/4 brake lines and there is alot of vibration at the brake caliper so that is where they mostly break. I havn't seen hard fuel lines of #6 or #8 size break(yet). What do most people do when they find a leak in a flared line at the fitting? Crank it a little tighter. Not the correct fix but easier than dissasembly and inspection or line replacement. This can lead to thinning of the flare. It is also easy to use a hand flaring tool to over tighten and excessively thin the metal while flaring the tubing.
The advantage of flex hoses to me seems to be that the end fittings on the hoses were made to exacting specifications and will fit the nipple perfectly. They also don't work harden and are much less likely to crack because of vibration or work hardening. I've seen the metal on some flared aluminum lines smashed to the thickness of notebook paper by either improper use af a hand flaring tool or overtorque, just a short time from breaking off, but they didn't leak.
If you use hard lines be sure the flare is inspected and investigate leaks properly.
Factory aircraft usually have factory made hard lines and they are built with a precision machine and go through a thorough inspection process before use on an aircraft.
I only have a couple of hard lines in my plane and I'm going to change them to flex lines as a little insurance I think.
 
logansc said:
When did it start raining flaming RV's all over the world? I must have missed that...


Lee...
Click to expand...
Sorry Lee it was my fault!I just said I was going to do it different next time. Our fuel system was not a standard Van's system. I don't like the all that stuff crammed into a little area either. People can do it how ever they want and I won't criticize them one bit. Many people have been doing it Van's way for many years and have not had any problems. I just want everybody to check their fittings and make sure they don't have any leaks. I/we had too much stuff in the tunnel and I don't think that is where the leak was though but I could be wrong. I wish we would have been able to put the fire out early so we could have found the problem or the culprit.
 
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Phil said:
Cost? Money isn't a safety item.
Weight? Weight, isn't a safety item.
Inspections? Every fuel line needs inspected.
Not Airworthy? 43-13 says they are and they're TSO'd too.​
Click to expand...

It's true! I've been making flares for years and years in the HVAC business, and I'm not scared of them............

Therfor, I wouldn't use all flex fittings if they were given to me. I wouldn't do it with free life time replacement either. IMO, they're inferior for the application. Heavy, ugly, need better suspension, won't last near as long, and I'd be worried about making total inspections much more often.

There, I feel better now... :)

L.Adamson --- RV6A
 
Speculation

Todd acknowledged that he does not know the source of the fuel or vapor leak.
Before you change all your fuel lines consider this.
Maybe a hose busted in the engine compartement and sprayed fuel all over
a hot exhaust. Vapour entered thru heating valve into the tunnel and found an ignition source. Just speculation like many of the posts in this thread.

Todd, were all your hoses in the engine compartement steel braided and fire sleeved?
Automotive engines have barbed fittings on their fuel rails and use rubber hoses with clips to attach high pressure fuel hoses.
 
N427EF said:
Todd acknowledged that he does not know the source of the fuel or vapor leak.
Before you change all your fuel lines consider this.
Maybe a hose busted in the engine compartement and sprayed fuel all over
a hot exhaust. Vapour entered thru heating valve into the tunnel and found an ignition source. Just speculation like many of the posts in this thread.

Todd, were all your hoses in the engine compartement steel braided and fire sleeved?
Automotive engines have barbed fittings on their fuel rails and use rubber hoses with clips to attach high pressure fuel hoses.
Click to expand...

I can tell you with 100% certainty there was no engine compartment fire.
 
Source of vapor?

Todd, glad your feeling better.
I am not saying you had an engine fire.
I am trying to find out the source of fuel vapor.
Was it at all conceivable that a hose busted in the FW area and vapors
(not fire) enterded the tunnel?
I really am curious about the kind of hose set up you had in the FW forward area.
It would be a shame if people started to spend time and money to improve something that did not need improving.
I realize it will be hard to pinpoint the origin of the fuel leak, but it is important not to ignore sources other than tunnel aluminum tubing.
 
I did not have a "hot" tunnel. We did not have the heating vents like most RV's. The whole firewall is completely sealed. Our fuel line from the firewall to the engine is still connected.
 
I think it would be a good idea to put a weap hole in the floor near the fuel lines to at least have somewhere for the fuel to go if there is a leak. Kind of like what we do for the air box for built up fuel. Maybe even design in some kind of fresh air to blow into the fuel line area for normal operation, just thinking outloud.

Something I did with my fuel lines that run on the floor is to put a spot of silicon between the line and floor to stabilize the line and to help with vibration.
 
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Multiple changes?

Folks, I would encourage all of us to slow down here and take a deep breath. In both my aviation life and my professional technology life I am very much an advocate of understanding what, if anything, was changed when there is a failure BEFORE taking any other action or making any other changes. First, we should really understand from Todd if he changed any of the fuel system inside the tunnel. I may have missed that, but I haven't seen his response to requests for that or the fuel system diagram he used. Todd, I understand you might not be able to type so well given your injuries, but I have seen you post here in this thread, so a simple yes/no would probably suffice. :)
For those who favor alternative engines, please read this gently..... the real change here to what has been a rock solid fuel system could have been the alternative engine and it's fuel plumbing requirements, or even just a bad flare or failed component. So, given that, I would submit that perhaps we shouldn't jump to the conclusion that changes are needed for the fuel system when applied to the standard engine configuration. And, again no slight intended, but it could have been as simple as a bad flare. Who hasn't had a flare that they have had to remake during the building process? And there are those flares that don't show up as leaks and/or failures until fluids are actually in place for a while. I will admit that I have seen that.

I will also share with you that I did use the Bonaco fuel lines on my new 10 from the wings to the selector valve. Not because I didn't trust the metal lines, but because I just didn't want to fight with making them again. And guess what? One of the Bonaco lines leaked from a bad crimp right at the selctor valve. I had LOTS of fuel in the tunnel and it flowed back and ran out along the drain holes I had put in the bottom of the fuselage, and our towards the wings and out of the plane from underneath the upper gear intersection fairings. Bonaco quickly replaced the line without any questions, but the point is that we can have a failure of any manufactured part. That doesn't mean we should redesign the whole subsystem.
By the way, I didn't think to NOT use the flaps when landing, so I at least found out by luck that the flap motor will not cause 100LL to ignite in this scenario. I did exit the ariplane before I turned the electrical system off.
So, my thoughts if I were to build again..... the metal lines or the flexible lines both work fine. Workmanship can cause a failure or a problem, or there could be a manufacturing defect that causes a failure, but we shouldn't over react to it. Step back, analyze what changed, and perhaps address that first.
Vic
 
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Hmmm

TSwezey said:
........Our fuel system was not a standard Van's system.......... I/we had too much stuff in the tunnel and I don't think that is where the leak was though but I could be wrong.........
Click to expand...

TSwezey said:
.........The whole firewall is completely sealed. Our fuel line from the firewall to the engine is still connected.
Click to expand...

I have been following this discussion along with many others. Todd, you obviously know your airplane the best, and while I understand there cannot be any certainty, your view on the source of the vapours would be helpful.

Let me add that above all, it is a wonderful miracle that this event occurred on the ground and not in the air. When you allow yourselves to think about it, you and your daughter must feel like you've been given a second life!
 
Some thoughts

Several have made very compelling statements. I agree with Dan that most leaks are as a result of the builder. In Todd's case we have no way of knowing but I'd suspect a cracked line or loose fitting.

I also agree with many that the 10 does not require a redesign of the fuel system, only due diligence while building. Same with the other designs. There have been few, if any similar accidents and no reason to panic.

I did not enjoy doing fuel lines. It took a long time to learn how to get the radius in the right place and learn flaring. I went through enough fuel line to get a homeless guy a new pint at the recycle center. Each flare was inspected with a magnifying glass. Flaring was easy, bending was my nemesis. 4.5 years, 525 hours, no failures.

For some unknown reason, the use of braided shielded hoses has become vogue for all purposes. I have seen no conclusive evidence that these hoses are safer. They are easier but safer? As has been noted, aluminum fuel lines have been used for decades with success. Someone shoot me some evidence. Later I'll demonstrate the opposite!!!!!

My hoses are the standard aluminum lines to the Firewall. FWF is all professional made hoses from Precision Hose Technologies. This is no place to shortcut. The only two lines that are not PHT are the fuel pressure transducer line and the oil pressure transducer line.

Interestingly, the only line I have ever had fail was the fuel pressure transducer line. It was a braided line made at a race car place. The failure was in the center of the line and appeared the internal hose split. The hose was rated at 1000 psi. Poor material? Who knows, it failed. This failed in flight. My fuel flow went from 8.2 gallons per hour to 20 gallons per hour in the blink of an eye. This line was replaced with a specially made, fire sleeved hose. My next door neighbor had a braided line fail. Another RV buddy had a braided line fail.

My thoughts. Learn how to do aluminum lines properly and follow the plans. Do not get a false sense of security because you are using "braided" lines. To me, an aluminum fuel line done properly look great. FWF, SPEND THE MONEY AND LET AIRCRAFT PROFESSIONALS MAKE PROFESSIONAL AIRCRAFT LINES. For my RV with IO360 it ran about $500 for the fuel and oil lines. Money well spent.

My main word of caution here is the use of the braided lines. Do not think these are superior. I've experienced a braided failure and have seen two others. Lets build safe, lets build smart.
 
thanks Vic for your response. Right on the money there. I would like to ask, since he did have a v8 engine, what kind of fuel was used?
 
I did not build the fuel system my partner did. I think he is taking it much harder than me and my daughter. He has shown the design to the FAA along with pictures of it. I will wait until the NTSB report comes out before fully discussing anything. I don't thing anybody should be changing any of their/Van's design but should be checking for bad flares, loose connections and loose nuts. Smell and look for fuel.
 
Vic and Darwin have excellent posts which should be read by everybody.

Darwin I had a great helicopter ride!
 
Let's Back the bus up a second...

Ok there are a lot of unsubstantiated opinions floating around in this thread. If you are going to offer an opinion, state it as such. If you are going to state a fact, back it up.

Fact: Scratches, nicks die marks, and burrs will be removed from all hard lines because they cause significant stress risers. For tube systems less than 500PSI, the scratch limits in the straight section of tube is 15% of wall thickness. In other words, less than 15% deep damage will be blended out, more than 15% is cause for rejection of the assembly. Ref. older versions of T.O.1-1A-8 and now the T.O 42E1-1-1 (among others). And BTW, the damage limits are even less if found in the bend of the tube. That should just about cover the issue of whether tool marks are "OK" to leave in your tube.

Fact: "Paper thin", deformed, split, or over/undersized flares are unserviceable. Inspection criteria to determine serviceability can be found in a number publications (including the older versions of 1-1A-8 and now the T.O 42E1-1-1). We should not point to unserviceable examples of ANY system as justification for why they are good or bad. Hardlines, properly fabricated, installed and maintained, will generally last the life of the airframe - Even properly installed hose can't claim that distinction.

Fact: Flexible hose is a "specialized" product, generally used by exception. Because of it's expense, weight, bulk and yes, relative unreliability and fragility, it is used only when hardline can't be used. Examples include high relative movement between connections, or in some cases, to facilitate periodic maintenance (like engine removal). Aircraft designers go to long lengths to avoid flex line because except for a few specialized uses, hardline outperforms hose in every way. I doubt there is an aero engineer alive that dreams of someday building an aircraft plumbed exclusively with hose (..."if only it wasn't for the darn bean counters, I could finally do this aircraft right"...) :rolleyes: This information is simply common aerospace practice.

There are a few good reasons to use hose assemblies - but replacing hardline in a misguided attempt to increase system reliability is not one of them. Yes, that part is my opinion, but I doubt you will find an aero engineer who will disagree.

Bottom line: It?s your airplane and you are free to do what you want, but it is the responsibility of those of us who know better to point it out. If you want to ignore standard practice and blaze your own trail, at least be honest with yourself and the rest of us on the board. The danger here is that when it comes to design, most of the time there is ?right? and there is ?wrong?, and this is not decided by popular or personal opinion, politics, or a vote. It?s found in long standing, well documented engineering standards.

We all have a lot to learn? Let?s make sure we learn the ?right? things.
 
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Darwin brings up some good points. However, at least to me, he is tarring ALL braided hose with his experience. However, all braided hose is NOT equal. So much of what is sold for aircraft is just "racer hose" and is not useful for aircraft for several reasons that have been discussed here and in other posts. There is a lot of research out there showing this to be true.
I started out last year using "racer hose" and my A&P friend was somewhat horrified. Kind of put me out so I spent quite a bit of time investigating the various hoses, rigid as well as flexible.
Some issues like conductive vs. nonconductive hose was investigated at least 50 years ago.
I have personally had several flares break and leak fuel. These were all on certified aircraft with "suposedly" professionally made flares.
As with most things in life, there is a place appropriate for rigid tubing and also for braided. Do the research and then make the choice that YOU will be comfortable flying behind. That is what I'm doing.
 
For a moment let's take Todd's fire out of the discussion.

1. The -10 fuel system/tunnel is not typical of the thousands of RV's out there.

2. Fuel lines can leak despite our best efforts.

3. The flap motor has brushes and is not sealed.

I'm not bashing Van's, but this seems like an engineering oversight. The very best engineers can overlook things that in hindsight seem obvious. The fix should simply be to keep leaking fuel from collecting and get a safe motor. Whether or not Todd's plane had this type of failure has zero to do with it. We all see the potential here and it would be irresponsible to ignore it.

On the subject of hard lines vs. hoses, when I built my -4 I made all the lines and hoses myself from standard aircraft grade materials and I can say without reservation that the hoses were just as difficult to get right as the hard lines. It is certainly possible to bugger a flare or bend, but it is just as easy to create a flap of rubber inside the hose (Van's sold a bunch) or have the end push off the hose a bit as the end is tightened. It's just not true that hoses enjoy some sort of idiot-proof quality.

If I go down this path again, I will use hard lines wherever appropriate and have the firewall forward hoses made with the integral firesleeve. They are expensive, but doing them yourself saves very little money and the integral sleeved type look so much nicer.
 
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