Or where there is vibration.
@alioth Why do you need/want it to be flexible? The normal way is to use aluminium tubing aft of the FW. Cheap, strong, light, takes any fuel whatsoever and lasts for centuries. The only reason to use a flexible hose is when flexibility is needed, like firewall fwd.
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 .
@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…
Do you fit firesleeves on top of the steel braid as well ?
Yes.
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.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.
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.