Installing firesleeve

[LettersFromFlyoverCountry]

I've watched the very excellent EAA video on installing firesleeve, but I still have one question that was unanswered. I've installed a couple of right-ange Aeroquip fittings on an Aeroquip 701 hose used for a fuel line. It's clear to me on a straight fitting, the firesleeve should go right to the nut, but I have a hose with a couple of right angle fittings. Should the firesleeve end at the hose-to-fitting connection? Or should it go onto the much smaller tubing that forms the right angle?

 

[cfiidon]

My thoughts

I'm no expert but here's my opinion:

I used steel fittings on all fuel and oil lines firewall forward. With that approach, all you need to worry about is that the firesleeve covers the hose.

Yours appear to be aluminum. I'd cover it.... or change to steel.

Don

 

[foka4]

For what it's worth

I wondered the same thing, and researched what others have done. Here are the most popular solutions I found in my non-scientific study:

1) terminate the fire sleeve before the elbow and leave the aluminum elbow exposed. Not the greatest solution in the world, but keep in mind you're attaching the hose to an aluminum gascolator, an aluminum fuel pump, or an aluminum carburetor in most cases. The fire sleeve still protects the rubber.

2) order a steel 90 degree fitting from Aircraft Spruce. Part number 04-05800. This option eliminates the aluminum elbow and the hefty price tag that goes with it. This fitting does add another threaded connection in the system, though.

3) use some other series of flex hose for the fuel lines. I'm not aware of steel end fittings for Aeroquip 701 hose.

I went with option 2. Let us know what you decide to do!

M

 

[TS Flightlines]

for whats its worth-

Put your firesleeve up to the nut that screws into the collar over the hose. You want to protect the liner of the hose. You can seal the firesleeve end with red RTV, or end dip (expensive-look on here for alternatives). No point in firesleeving if a flame could get to the hose liner. Also, for whats its worth, that's why I use stainless hose ends.
Tom

 

[LettersFromFlyoverCountry]

that's why I use stainless hose ends.
Tom

Sigh. I'm beginning to wonder if I should even bother finishing this project. At this stage it seems like I'm spending hundreds of dollars for stuff only to find out I need to spend hundreds more for something better.

It'd be a lot easier if I had hundreds of dollars.

 

[Brantel]

Bob,

Good enough is good enough....

Put the sleeve up to where the elbow screws into the hose. That is how all the factory ones are made.

Thousands of these in use today on certified birds. Move on....don't spend more!

 

[LettersFromFlyoverCountry]

This is one of those areas where it's impossible to get actual data. Is there a significant safety difference between steel and aluminum fittings? Or is it more "this could happen or that could happen" fear that's driving the issue? If there is a definitive safety margin, what is it? Is it greater than, say, not properly securing a line? Is it a difference along the lines of the difference in safety between putting one of those (overpriced) stainless steel heat deflectors on an exhaust pipe under a fuel line and not putting one on.

Very, very difficult to make educated decisions based on actual calculations and testing. At least for me.

 

[Ironflight]

Here's a suggestion that might help Bob. Next nice day at the airport, go wandering around to open hangars to see if anyone has their cowl off of their certified airplane. Poke around - see what the industry does, what has been CERTIFIED by the FAA. It will make you feel alot better.

You're right - many builders without a lot of aircraft maintenance (or design) background simply don't know the difference between "good", "good enough", and "perfect". Don't be a non-finisher because you're afraid to say it is "good enough".

Paul

 

[foka4]

Experimental is experimental

Bob,

Many of us share your frustration. Although I know we are building experimental aircraft, I'd expect with so many RVs flying, a number of these details would be well sorted by now. Unfortunately, much is still left to the individual builder, and as importantly, the DAR who will sign off your project.

Opinions vary widely on many seemingly trivial details, but such is the nature of any pursuit of this complexity.

The forum has been a tremendously valuable resource, but at times it's almost a curse, since there is so much information and so many opinions on any topic. Often, it's best to do a quick search to see your options, choose one that you think will work, and ask your A&P/DAR if it's okay. Beyond that, it's pretty easy to get endlessly bogged down in weighing uncertain options with incomplete information.

With regard to fuel hoses and such, certified aircraft are often a good guide. A trip to the local airport for a peek under the hood of a 172 or Cherokee can work wonders.

If you think fuel hoses are a vague, varied, and contentious topic, just wait until you start figuring out what to do about running the primer lines. Oh, and speaking of primer...

Good luck, and best wishes. Hope your frustration is short lived. In the end, having a flying RV will make you quickly forget the bumps in the road.

M

 

[FredMagare]

This is one of those areas where it's impossible to get actual data. Is there a significant safety difference between steel and aluminum fittings? Or is it more "this could happen or that could happen" fear that's driving the issue? If there is a definitive safety margin, what is it? Is it greater than, say, not properly securing a line? Is it a difference along the lines of the difference in safety between putting one of those (overpriced) stainless steel heat deflectors on an exhaust pipe under a fuel line and not putting one on.

Very, very difficult to make educated decisions based on actual calculations and testing. At least for me.

I don't have the answer to your question, Bob, but it seems like it's kind of like buying any type of insurance - if you never need it, it's wasted money but if you NEED it, I'll bet you'll be glad you've got it! If you never suffer a fire because of aluminum fittings - no harm, no foul but would you wish you'd have spent the money on steel if a broken fitting causes a fire in flight?

It's a tough call. Were I in your position, I'd likely install the aluminum-fitted hoses with the intent to change them to steel at a predetermined "No Later Than" date...say three to five years? Some hose use might ease the sting of "unused".

 

[n5lp]

...The forum has been a tremendously valuable resource, but at times it's almost a curse, since there is so much information and so many opinions on any topic...

Yep. When I built my plane there was no internet information and there were no nearby builders. I was on my own; well I did have Tony's books.

I have been flying the airplane for many years now and have learned about more and more stuff that wasn't done the way so many think things have to be done and in truth I have truly found out some deficiencies, but then so has Boeing with the Dreamliner and Boeing has lots of really smart people working for them.

So I feel reasonably OK with the current state of my airplane, aluminum fittings and all, but have given quite a bit of thought about what I will do when the loss of medical time comes around. Knowing about all the wrongly done things I might very well just saw it up. Prorated over all those years, even with no resale, the expense will seem pretty worth it.

Besides, who would be interested in buying a worthless airplane with a fixed pitch prop? You see that was yet another thing I was ignorant about.

 

[Don Jones]

Exactly!!!

Here's a suggestion that might help Bob. Next nice day at the airport, go wandering around to open hangars to see if anyone has their cowl off of their certified airplane. Poke around - see what the industry does, what has been CERTIFIED by the FAA. It will make you feel alot better.

You're right - many builders without a lot of aircraft maintenance (or design) background simply don't know the difference between "good", "good enough", and "perfect". Don't be a non-finisher because you're afraid to say it is "good enough".

Paul

I agree with you Paul, my certified airplane has all aluminum fittings under the cowl on both oil and fuel. Yes, I prefer steel fittings under the cowl, but the certified industry seems to think aluminum is "good enough". I think sometimes we all get carried away by things like this.

 

[panhandler1956]

Build on

Bob,
I wonder how many folks would rush out to change their fwf lines if the industry announced some new 'unobtainium' alloy that was 10x better than steel? Not many...
I say build on and if the fittings bother you after you are flying you can save up for some nice pre made Bonaco's!

Btw I'm in the same boat as you.

 

[LettersFromFlyoverCountry]

I'll bet you'll be glad you've got it! If you never suffer a fire because of aluminum fittings - no harm, no foul but would you wish you'd have spent the money on steel if a broken fitting causes a fire in flight?

As with so many things, it becomes a question of evaluating risk. Some folks never learn to fly because something might happen. Is it an acceptable risk? It is for us partly because we've seen the data and determined it to be acceptable.

In this case, and many others like it, it's hard to make sound -- and most important: practical -- decisions without quality data.

I would, for example, probably like to have a ballistic parachute on the RV if I were in a position to need it. But I'm not installing one. What is more likely to happen, a plane getting into a position to need a 'chute, or an aluminum fitting failing? How often do aluminum fittings fail in this application. 1 in every 1,000 hours? How does that compare to steel fittings?

I have added other items because of an assessment of risk, a lift reserve indicator and a traffic alert system, for example. I'm also thinking of smoke system to make it easier for other traffic to find me when they need to. Is that overkill? Those are situations for which I have some data. I'm also making decisions on fireproofing the firewall based on Dan Horton's excellent research, but this is one of those areas where I find it difficult to separate fact from not-so-much-fact.

Anyway, I went ahead and put the firesleeve on , clamped it and installed it on the plane. I'm 56, I won't be flying for another year or so and I probably have only another 20 years of flying time left. The odds are I'll sell the 7A within 5-10 years and build an RV-12. If one of these fittings goes south within that period of time, heck, I'll just think about the parachute I won't be wearing, the quick release canopy latch I didn't bother building, the fire suppression system I didn't bother buying, the fireproof suit and gloves I didn't put on, while not flying at 1,500 AGL over the flat land with an airport in sight that I didn't use as a security blanket.

Somewhere between all of that, I'll pause to think, "I've had a good life."

 

[pierre smith]

You have many alternatives...

..Bob. My -10 had aluminum fittings for three years and my A@P buddy and I decided to go with Tom's (TSflightlines on here) stainless steel, firesleeved, teflon lined hoses, for both oil and fuel lines...an upgrade of sorts, during her recent annual/condition inspection.

Tweak your bird as time and money allows...what you're doing is definitely "good enough".

Best,

 

[DanH]

The "look at what they do in the certified world" advice is fine....but be sure you look at all they do, not just the superficial.

(a) The aluminum fitting risk is high-cycle vibratory fatigue. To duplicate the certified assembly you must also duplicate the hose clamping or, if free to move, the vibratory behavior of the hose assembly.

(b) Aluminum is also far more sensitive to imperfection. Consider the classic case of the Lycoming nose case propeller line elbow.....and the poor record of some vendors regarding bogus AN fittings.

(c) Consider the type of fitting used (and where) as compared to merely being "aluminum". Does anyone believe the 90 degree tube fitting in Bob's first post is as fatigue resistant as a straight hose end?

I recommend steel fluid fittings to homebuilders for all vibrating assemblies because they are forgiving of the unanticipated, at a very small weight penalty.

 

[LettersFromFlyoverCountry]

I do get that, Dan, but what you're talking about is possibilities. Is there ANY data at all that quantifies the safety margin?

Consider the type of fitting used (and where) as compared to merely being "aluminum". Does anyone believe the 90 degree tube fitting in Bob's first post is as fatigue resistant as a straight hose end?

What is the expected lifespan of a fitting? The reason I'm using this 90-degree fitting is one of tradeoffs. If I go out of the fuel pump with a straight line fitting, the line is going to impact the engine mount (I think I posted this somewhere months ago and Mahlon suggested angling the fitting out of the fuel pump aft, using a longer hose and angling away from the direct contact with the engine mount. If I were to use a straight-line fitting, I'd be using a much longer hose and making a long detour aft to achieve an acceptable bend to make the long journey forward. Are longer hoses more susceptible to vibration than shorter ones (there's no engine mount to clamp it to were I to go aft for any appreciable difference) and, if so, how much more susceptible.

I think there's a pretty good chance by focusing merely on the micro ( a fitting) we might be losing the bigger picture and the law of unintended consequences. We know, of course, of the penalties of weight and cost but what we don't know is what factors we might introduce that might be a safety issue in our attempts to eliminate another potential safety issue.

There are also other factors that enhance safety to be considered. For example, if I do a complete visual inspection of these fittings before every flight, I may be safer than someone with a steel fitting who mostly just checks the dispstick and kinda peeks through the oil door. But to what factor of X better?

This will all be better once we get those spiffy new electric engines.

 

[C-GRVT]

judgment

Having no particular expertise (speaking for myself), one is left to exercise best judgment.
Bob, your questions about lines and fittings underlines the challenge of that. Those whom I think have expertise and experience - Van's Aircraft, some of the professional engine builders, and some on this list and elsewhere arrive at different conclusions.
Van's provides aluminum fittings firewall forward. AeroSport installs steel AN fittings in its engines. Builders on this list post that aluminum is fine, or not, or that industrial fittings or speedshop hoses are OK to substitute for AN.
My suggestion - choose the option among those reasonably available that results in a larger, rather than smaller, margin of safety, as far as you can determine.
Absent actually knowing the margin of safety for a fitting, installed as it is, in that application, how can one justify any other choice?
So,for me - -
1. use steel - AeroSport does, it's stronger, does not gall, heat resistant, not much more money;
2. limited empirical data re. failures, and probably more than one cause, but seem to point in the direction of steel - the Lycoming prop line AD requiring steel instead of aluminum, the AirFlow Performance fuel injection flow divider fitting required change from aluminum to steel, the Pacific Cooler advice to use steel fittings in their coolers;
3. aircraft hose and AN fittings, since I don't know how others compare;
4. Eustace Bowhay's advice to pressure test all hoses to 1000 psi.

Not at all suggesting that other choices are wrong, but for me, with my limited knowledge, that seems the best course.
Bill Brooks
Ottawa Canada
RV-6A finishing

 

[LettersFromFlyoverCountry]

A long time ago there was an actual question that started this thread that even I'd forgotten about.

The answer is that the firesleeve should go to the actual curve of the elbow and be clamped after the nut onto the smaller tube.

 

[DanH]

Is there ANY data at all that quantifies the safety margin?

Yes...ordinary S-N data. In very, very rough terms, the steel fitting offers about double the fatigue resistance at the 10^7 to 10^8 cycles appropriate for engine applications. The gap widens as the number of cycles increases because the aluminum values get worse. If the applied vibratory load is less than the endurance limit for the steel fitting, fatigue life is more or less infinite, while the endurance limit for the aluminum fitting continues to slowly decrease.

Let's quantify 10^7 cycles. Hose vibration is likely to be at engine firing frequency. If we assume 2400 RPM for your 4-cyl 4-stroke, 100 million cycles is reached in 347 hours.

What is the expected lifespan of a fitting?

That's like asking "what is the expected life of a wing spar?". It depends upon the details of the application. You can have an infinite life for the aluminum fitting......if you eliminate any cyclical loading.

The reason I'm using this 90-degree fitting is one of tradeoffs. If I go out of the fuel pump....

Good, some details. You're exiting the fuel pump with a straight SAE pump fitting, then using the 90 degree tube end on your hose to turn directly forward? If so, the question becomes "Where does the hose clamp to the engine?". If the hose is left to flop around, engine vibration applies cyclical loading to the skinny little tube. Every shake is a tick of the clock toward end of life. However, if clamped well so the hose can't shake, the skinny tube sees no cyclical load and has an infinite lifespan.

BTW, not a fatigue issue but there is another twist (yes, a pun) to the above arrangement. The hose vibration would tend to be in the plane of rotation for the fitting's b-nut. A loose b-nut at the pump exit is a classic cause of aircraft fires. Fixating the hose would greatly reduce the probability.

With enough care about the installation aluminum fittings can be perfectly safe. Steel fittings allow homebuilders to make subtle installation errors and get away with it, long term. A superficial aluminum-vs-steel debate without considering installation details is like betting football based on the school fight songs.

 

[LettersFromFlyoverCountry]

Where does the hose clamp to the engine?". If the hose is left to flop around, engine vibration applies cyclical loading to the skinny little tube. Every shake is a tick of the clock toward end of life.

I was going to clamp it to the engine mount.

There's no area where it comes close to the engine

 

[DanH]

I was going to clamp it to the engine mount.

No, no, no. The engine moves. The pump is on the engine. Short distance between moving pump and stationary mount tube = high cyclical stress on the hose fitting.

There's no area where it comes close to the engine

Then you need fatigue-resistant fittings.

 

[TS Flightlines]

Bob-

Dan is right---you need motion , hence the need for a flexible hose. By looking at your picture, firesleeve up to the bend in the fitting---the hose liner is close to the exhaust, and even though it is not at the cylinders, there is still sufficient heat to distort the liner of a 701 hose. Just my opinion for whats its worth.
Tom

 

[LettersFromFlyoverCountry]

Dan is right---you need motion , hence the need for a flexible hose. By looking at your picture, firesleeve up to the bend in the fitting---the hose liner is close to the exhaust, and even though it is not at the cylinders, there is still sufficient heat to distort the liner of a 701 hose. Just my opinion for whats its worth.
Tom

There's a heat shield on the exhaust. My theory here is there's slack in the line that even if clamped to the engine mount, there's flex in the hose. But beyond that, if I don't stand the hose off the engine mount, it's going to chaffe the engine mount.

I don't suppose any of you guys are building a 7A with a vertical updraft Mattituck engine, are you?

Is anyone? If so, how did you run this line.

 

[DanH]

My theory here is there's slack in the line that even if clamped to the engine mount, there's flex in the hose.

So how much hose length do you have between the pump fitting and the engine mount tube? Got a side view photo?

 

[TS Flightlines]

how far

away is the hose from your exhaust shield? Just asking
Tom

 

[Walt]

Really hard to say by looking at a picture but I would say just put the firelsleeve on it and leave it just the way it is.

 

[LettersFromFlyoverCountry]

I stuck a video up on the blog after I fit the hose with firesleeve on it. Basically, it's a lost cause. I'm not comfortable with how it's going and I've got to start over again and remake lines and come up with a better routing. Unfortunately, I've blown my budget on this for a few months so I may just wait until warm weather to revisit things.

After 10 years, I'm REALLY sick of costly mistakes.

 

[Brantel]

Keep at it Bob. You will overcome it somehow someday... It will be worth it!!!

 

[LettersFromFlyoverCountry]

Heh. By the time this thing gets built, I'll be due for an RV-12.

 

[TS Flightlines]

Bob-

Stick with it. I know how frustrating it can be, to work so long and hard on something, then having to scrap it and start over. BUT---and I think that I can speak for all of those on this forum, help is available. Plumbing your engine isnt rocket science--no offense Paul-. It looks like you are on the right track. The more information we have, the better the solution we can come up with for you.
Tom

 

[LettersFromFlyoverCountry]

My strategy at the moment is to fake my own death, and then a sympathetic VAF will rush to South St. Paul to finish the project to sell it, in order to give the money to my widow.

Haven't quite figured out how the resurrection will occur yet, tho.

 

[DanH]

My strategy at the moment is to fake my own death.....

Probably more effective to focus and find a solution.

Does the 7A mount have enough room between mount ring and engine case to run the line up and forward? It works well with both -8 and -8A mounts. Here's are some old photos from the files:





The pump fitting is the 90 degree/w pressure tap seen in the video. Viewed from the left side it is clocked to about 10:30. The line gets a straight fitting. It is humped up over lower left mount casting on the case and run forward right along the sump bolt line....which means it can be clamped using the sump studs. It is also quite distant from any exhaust pipe. There is no flopping line and little cyclical stress, so the aluminum end fitting is fine.

 

[TS Flightlines]

a trip to St Paul--

In the winter?? Its cold enough in SC right now!
Instead of faking your death---try cryogenic freeze---then when a solution is found, you can thaw out! Just kidding. Look at Dan's pics---a solution is there!
Tom

My strategy at the moment is to fake my own death, and then a sympathetic VAF will rush to South St. Paul to finish the project to sell it, in order to give the money to my widow.

Haven't quite figured out how the resurrection will occur yet, tho.

 

[LettersFromFlyoverCountry]

Probably more effective to focus and find a solution.

It was a joke. Don't tell the insurance company, though.

It's what we do when it's 14 degrees at the hangar. You can't focus for more than a few seconds.

I'm looking at the pictures and trying to figure out the route you're taking here. I'm also going up to the Twin Cities RV Builders Group meeting next week to look at what I understand is a similar installation.

Mahlon had recommended going inside the mount/nose gear tube and down the center (sort of like what Van's IO-360 drawing shows for a 7, but I've got a couple of exhaust hangars blocking that route so maybe there's an up-and-down-again route to be had.

 

[TS Flightlines]

be sure

to keep us informed! Dont quit!
Tom

 

[JonJay]

Is there another choice for your fuel "inlet"

I'm looking at the pictures and trying to figure out the route you're taking here. .

Some servo's have different options for inlet and outlet locations. They dont always make it obvious. You might check and see if there is another port that might lend itself better for your line routing. I had to do this with my vert. draft set up with the Silverhawk.
On my Silverhawk I reversed my inlet so I could come into the right (looking forward) and reversed the outlet from the front to the back.
Once I did this my options opened way up and things started to fall into place.

 

[Walt]

A standard carb has about the same inlet location, when I had a carb I used a 45? fitting on the outlet which gave it room to go around the mount. I can send you a pic if you send me your email.

 

[LettersFromFlyoverCountry]

[email protected] or [email protected] or [email protected]

 

[RV7Guy]

Bob, Bob, Bob.

Ya know we've lived this journey with you for years. You really think you're gonna quit. I don't think so.

So, pull the skirt out of you know where, man up and complete the task.

Seriously, the build process provides a lifetime of memories. I can hear it know at the RV BBQ camp fire after you are flying, "yeah, I remember those fuel lines. They thought they were get the best of me, but I showed them. Hey Chad, get me a beer."

Hang it there Brother!!!!

 

[CMW]

Don't quit!

Bob,

Don't quit! I enjoy reading your posts and blog.

You said that the fuel line you got from Mattituck is too short, well the line I got from Mattituck is too long. Maybe we can trade. The hose I have has a 90 deg fitting on one end and a straight fitting on the other end and is approximately 26" long. I need the same configuration but only 15" long. Let me know if that will help you.

-Chris

 

[LettersFromFlyoverCountry]

Not quitting.

I'll check the dimensions on mine. It's probably the same hose, though. What are you building and what route are you taking for that line?

 

[CMW]

Bob,

I'm building an -8 with a Mattituck IO-360 vertical sump with Airflow Performance injection. The inlet to the fuel servo is on the rear right hand side so I have a fairly easy shot to the fuel pump. But, the hose as supplied is way too long as you can see from these crappy pictures.

Chris

 

[DanH]

Here you go Bob...had the cowl off the -8 this afternoon and remembered to get a few pictures for you. Yeah, it's not quite the same as your updraft, but it illustrates how it is possible to rig the hose inboard, well away from the hot stuff and securely clamped.