Fuel Hoses

Hi All

This is all a bit of a sidebar to the original question but worth some time.  The concept in aviation is to get you to the ground as safe as possible.  There are 2 major definitions for fire protection within both EASA and the FAA terms.  We define the fire zone as the engine bay in general, where we are most likely to have a fire and we need to buy time if one occurs.  All the guidance can be found in AC20-135, free to download.  The key elements are the firewall, it should be fireproof.  Fireproof for this function states it will withstand 2000 F (1093C) for 15 minutes before burnthrough.  This includes wire pass throughs and any connections between the cockpit and the fire zone.  This explains why we do not use wood firewalls or aluminium, they simply fail far too fast.  The other major item to define is fire resistant, in that case the same temperature rating but now the limit is only 5 minutes.  We need to remember that not only fuel lines but oil lines should meet that standard.  

For certified the path is clear, they must comply and show this compliance in the testing leading up to a type certificate, TC.  For the amature built/ experimental world clearly we want  to be as near as possible to the same standards of safety.  I am in the camp that believes little to no attention is generally shown in the experimental world to the issue, especially homebuilt and kit built aircraft.  There are exceptions for sure, such as the VANS Aircraft kits where they have all the lines made to TSO standards the same as certified.  Indeed that level of care should be our goal for all aircraft.  

Cheers

RW/Roger,

Roger;

Accepted norms/practised are not empirical evidence, no matter how visually impressive the  result..

I applaud your professionalism and with it your desire to work/advise to the highest standards, however small, lightweight recreational aircraft, often constructed of materials not so commonly found in certified aircraft, do not lend themselves to encompassing the same levels of safety that a certified aircraft might have.

RW;

Have had a quick brows of your Advisory Circular 20-135 - the first information of note is that it's for certification/certified aircraft.

It seems to me that using this (advisory) document to encourage the comprehensive fitting of fire sleeves, to the sort of aircraft most Rotax engines are fitted to, is a bit like suggesting fitting airbags to a motorcycle. Not saying there may be a very slight benefit, under extremely unusual circumstances but that a motorcycle does not lend itself to the fitting of such a device and if one was fitted its effectiveness would questionable (Note: Airbag jackets for motorcycle/horse riders are available and may reduce the risk of thorax injury).

The second point is that a 1094 C (2000F ) fire for 5 minutes (the fire resistance standard for fuel/oil lines) in a composite/wood cowling, airframe will likly see  the demise of the aircraft and its occupants irrespective of what fire resistant systems are fitted. I think it extremely unlikly that the  fireproof standard of 1094 C/15 min could be achieved and still have an aircraft empty weight somewhere between 300 - 400 kg.

RW & Roger;

I am not suggesting that reasonable attempts to improve safety should not be incorporated when/where such innovation is likly or demonstrably cost effective and do not have a negative effect on other aspects of the aircraft's performance.

What I am suggesting is, unless you have empirical evidence to support your position on the comprehensive use of fire sleeves in small, lightweight recreational aircraft (powered by Rotax engines), you are by inference, implying a heightened level of safety that does not exist.

There are many articles on fire sleeve use over a couple of decades that support its use by many top experts and from the FAA. Herein the US it's an air raft standard.

Why play Russian Roulette with your safety when there is zero reason too.

It is called fire sleeve, and we focus on that name, as a fire in flight is quite a dire situation. But fire sleeve’s daily function is as a very effective means to insulate fuel lines from heat.  Good points for debate raised by all in this topic but a reminder that the current Rotax 912 Installation Manual addresses (more than once) protecting fuel lines from heat to help prevent vaporization of the fuel. One quote from CH 73-00-00 pg. 8: “All the fuel lines on the suction side of the fuel pump have to be insulated against heat in the engine compartment…”. The newer engines come with this installed (thanks Rotax) but for anyone out there installing or flying an older engine with rubber hoses on the suction side of the pump, please heed the current IM. Does it have to be orange fire sleeve to insulate? No. I’ve seen aluminum foil used. But always remember if after one bad day the attorneys get involved, everything is now on the table. 

Hi all

OK, so not going to beat a dead horse on the subject.  Best practice as discussed in an AC can be completely ignored on any experimental if that is what the builder wants.  (at least in the USA it can)  For many years people used vinyl fuel lines and plastic fittings.  Were they safe?  Hell no.  Do they work, sure to a point.  How many people were burned up because of that is simply a bit of empirical evidence I don't care to look at.  I can tell you I have done a large number of NTSB (under party status) investigations regarding Rotax powered aircraft and a large number did catch fire.  Could this have ended better if they had followed the best practice is the question and without hesitation?  I would say yes.  For the most part even a post crash fire is because some flammable liquid, oil or fuel, was released on to a hot exhaust or battery.  

Within the light sport standards there are existing requirements for an OEM to comply with similar fire safety requirements for both the firewalls and the flammable liquids.  The burden of such testing and approval falls to the OEM to declare that they have done so.  In my opinion there are very few of the over 135 recognized aircraft types on the FAA register that actually do however.  Next time you go look at one simply pick one thing, say firewalls where the wire harness enters the cockpit.  Look at the fittings and ask yourself , if my engine is on fire will it allow flame to enter the cockpit in under 15 minutes?  The next time you see some plastic block on a firewall it should give you pause.  

It is simply best practice, do what you can to mitigate risk is all I am saying.

So for homebuilders there is a lot you can do, check this out on firewalls for example.  (there are lots of similar things on fuel and oil hoses}

https://www.youtube.com/watch?v=Rs4ohdgulpE

Cheers