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Flexible fuel hose aft of the firewall

I’m having to replace a flexible fuel hose on a permit aircraft (from the fuel selector on the floor, to a fitting on the cabin side of the firewall) which has perished. The existing hose that’s perished was Pirtek R1T-06 which turns out is a type of flexible hydraulic hose. I don’t want to just replace like for like since there are better options actually designed for fuel!

Unfortunately we have fairly limited options where I live for buying things like this locally unless it’s for a boat, but the ISO 7840 fuel hose that they use looks pretty good to me as an option (with the added benefit of fire resistance, although it’s behind the firewall). Of course I could just get some hose online from LAS but it’d be more convenient to run up to the local marine supplies shop and get some ISO 7840 spec hose. The other alternative is R9 but apparently the classic car world has had issues getting R9 (including pipe that’s not actually R9 marked up as such).

What generally are people using for firewall-aft flexible fuel hoses for homebuilts/permit aircraft? Experiences with certain fuel hose types? The installation for now only ever runs on avgas.

Last Edited by alioth at 22 Feb 11:23
Andreas IOM

I use the standard automotive stuff, so did the factory that built my plane and so do all others on my field. The factory used poor quality, though, several bits had to be replaced after only two or three years – cracks where bent.

One day I ought to enrobe those fuel hose in fire-retardant stuff, but it does not feel like urgent. Actually has anyone ever heard of a fire in a 912 motor compartment?

Running on car MoGas 99% of the time.

Last Edited by at 22 Feb 11:30
EBZH Kiewit, Belgium

Are the fittings an issue e.g. are they NPT (US) or ISO (metric)? The hoses around US engines and on US aircraft generally are NPT. There is a long history around ISO fittings which enable firms like Socata to shaft people for €1000 for a €100 hose – because the fittings are “owned” by Aeroquip in France.

Regarding the hose itself, the absolute top end gold standard for fuel and oil hoses is a teflon fireproof hose (ignore the thickened section at the RH end of it – there is something inside that)

It has no life limit, no shelf life limit, and is dirt cheap (of the order of €100 for NPT, possibly much more for ISO) so there is no point in using anything lesser. I would not use anything else anywhere in any aircraft which I was going to be sitting in, because an in-flight fire is going to really ruin your day

I recall reading an accident report of a homebuilt where the pilot was dealing with a big fuel fire in the cockpit, and obviously crashed and killed himself.

Note that most switches used in GA are not sealed so e.g. the PTT switch could ignite vapour, if the concentration was around the right area i.e. ~14%.

There is an alternative construction of the firesleeve which is moulded on – example here. That style of sleeve costs a bit more, though the hose in that drawing is with ISO fittings and cost me about €300 from Saywells in Worthing, UK, or would cost about €1000 from Socata. Saywells is a good firm for making up hoses.

Administrator
Shoreham EGKA, United Kingdom

alioth wrote:

What generally are people using for firewall-aft flexible fuel hoses for homebuilts/permit aircraft?

I am using aluminum tubing, because it came with the kit. If there is no pump there (no pressure) I think anything compatible with fuel will do. I would go for marine hose instead of automotive. The Marine stuff tends to be more general and consistent, sort of.

ENVA ENOP ENMO, Norway
There are two sides with firesleeves: Basically this sounds like a good idea but then you don´t see the real hose and its condition, cracks and all. Should there be a big hidden leak the firesleeves will not help, there will be fire anyway when things go wrong. With real avgas there will be no problem for a long time with common NBR hoses from any hydraulics supplier . In case of Mogas you will want to check conditions of hoses more often as the material is not really gas proof, if it is not teflon or Viton. Anyway I´d see my next hydraulics company and have new hoses made with real quality press fittings at prices of 10 or 20 €€ a hose typically, not this ridiculous hose clamp junk going with some “aviation type” hoses. Of course this is only an option with uncertified aircraft that does not require lifed labelled hoses – unless your inspector will accept professionally made press fitting types. When those hoses are OK for up to 300 bar on any hydraulic machine with staff working all day close to them they should be OK for him for Mogas with no pressure at all, be it aviation or not. As to metric types, I had to change oil, gas and air hoses on the Yak – 10 years lifed – about 36 each a set, the complete set at below € 900.- three years ago, from a Yak supplier in Lithuania, EASA form 1. The “firesleeves” are leatherlike but I wouldn´t bet they are fireresistant, but all air hoses are fit for the 50 bar air system on the Yak. This hose change was most likely a “repair job” , EASA speak. The old hoses were returned to the supplier …. Vic

vic
EDME

Basically this sounds like a good idea but then you don´t see the real hose and its condition, cracks and all. Should there be a big hidden leak the firesleeves will not help, there will be fire anyway when things go wrong

I agree, but the visual check is possible only during services, and avgas leaks are obvious via discolouration of the firesleeve. And all the rest of the time (flying) the firesleeve gives protection to the hose. Plus it reinforces it, in a way which makes it IMHO much safer to tie it to e.g. the engine mounting frame.

The hoses I am thinking of have stainless steel braid over the teflon hose anyway

so the teflon hose is not visible.
Administrator
Shoreham EGKA, United Kingdom
The teflon hoses have a different failure mode than “rubber” hoses that I had in mind regarding cracks that come with age and mogas exposure. You should keep an eye on those , mounted in an aircraft or a car, same problem after a certain time. But then these are low price and fittings are easy to find, plus very flexible for some applications, not so with teflon. For these you need the specific press fittings that suit teflon , hose clamps no great idea with them. Do you fit firesleeves on top of the steel braid as well ? Does not hurt anyway …. Vic
vic
EDME

Do you fit firesleeves on top of the steel braid as well ?

Yes.

Administrator
Shoreham EGKA, United Kingdom

@alioth, in case you don’t find what you want in your local boatyard, you might try an agricultural engineer. They are used to fixing hoses 24/7 at harvest time. Then next time you put down in a silage field to tow a glider which didn’t quite make it home, your machine will have something in common with the Claas working in the next field…

Glenswinton, SW Scotland, United Kingdom

alioth,
R9 which is ethanol proof is readily available and is definitely the way to go. There are various manufacturers the most popular being Gates Barricade ( Bit expensive though).
When I replaced the hoses on my Sportcruiser I used R9 purchased from:-
http://www.flexiducting.co.uk/
They do Gates and also their own brand R9 which is cheaper and which I used and is fine .

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