Suitable firewall

[Peasant_Pilot]

Afternoon everyone, im interested to see peoples firewall setups on the engine side, what material are you using? im assuming Stainless sheet but would be interested to see peoples thoughts

 

Thanks

 

Rob

[skippydiesel]

My last aircraft, a 2000, ATEX Zephyr/Rotax 912ULS, has a ply wood firewall, with some silvery  stuff that looks like air conditioning insulation. Great little aircraft, very quite in/outside the cockpit. No complaints.

[Marty_d]

I used galv steel.  The plans called for 0.018" (around .5 mm) but I think I went slightly thicker, just what was available at the time.

[skippydiesel]

I occasionally wonder what preventative actions (beyond good aircraft mechanistically/systems maintenance) would save my life, should I experience an in flight fire in your typical recreational aircraft ??

 

My gut feeling - all the SS (& similar) firewalls, colourful fuel & oil hose fire-sleeves would amount to zilch! So much marketing hype!

 

Why? Well most of our aircraft are light weight aluminium or other alloys, composite, wood, fabric or a combination of all - not the sort of materials that stand up well to the intense heat of a fuel or oil fire being fanned by a high speed air blast.

 

May be the installation of some sort of in-flight fire extinguishing system, might help but then the aircraft may be so burdened that flight is rendered  impossible ( the ultimate safety system).

 

I guess I will just do my best  to maintain my little beauty's engine/systems to the highest standard I can and hope that this is sufficient to reduce the chances of an in-flight fire to a very low probability.

Edited February 4, 2022 by skippydiesel

[Geoff_H]

At the end of the day ( a strange statement lol,) a firewall is about limiting the temperature rise of the cockpit side of the firewall.  An interesting one is for the CozyIV.  It uses aluminium, light but conducts heat rather well, coupled with fiberfrax, a sheet of "stuff" that is a very good insulator of high temperature heat and is very light. I saw a demonstration of this stuff over 30 years ago, thin blanket of fiberfrax one side a hand the other an oxytorch! Impressive! But I was told that it's low temperature heat conduction characteristics are not so good.  

[Thruster88]

10 hours ago, skippydiesel said:

 

 

My gut feeling - all the SS (& similar) firewalls, colourful fuel & oil hose fire-sleeves would amount to zilch! So much marketing hype!

 

 

I guess I will just do my best  to maintain my little beauty's engine/systems to the highest standard I can and hope that this is sufficient to reduce the chances of an in-flight fire to a very low probability.

I see you having a dig at expensive certified aircraft parts however if you search the ATSB data base for in flight engine fires you will see that they are very rare in Australia compared to RAAus types by a huge margin.  

 

AN fittings, steel braid oil and fuel lines, fire sleeves, proper fuel drain lines on components that could leak if a fault develops, robust correctly designed electrical systems all cost money. I think it is cheap.

 

Carburetor over flow lines should be routed out of the cowl at least.  

 

[Peasant_Pilot]

11 hours ago, skippydiesel said:

I occasionally wonder what preventative actions (beyond good aircraft mechanistically/systems maintenance) would save my life, should I experience an in flight fire in your typical recreational aircraft ??

 

My gut feeling - all the SS (& similar) firewalls, colourful fuel & oil hose fire-sleeves would amount to zilch! So much marketing hype!

 

Why? Well most of our aircraft are light weight aluminium or other alloys, composite, wood, fabric or a combination of all - not the sort of materials that stand up well to the intense heat of a fuel or oil fire being fanned by a high speed air blast.

 

May be the installation of some sort of in-flight fire extinguishing system, might help but then the aircraft may be so burdened that flight is rendered  impossible ( the ultimate safety system).

 

I guess I will just do my best  to maintain my little beauty's engine/systems to the highest standard I can and hope that this is sufficient to reduce the chances of an in-flight fire to a very low probability.

I think that's probably the best way to look at it, realistically making sure everything that could start a fire in the first place is maintained and manufactured correctly in the first place is a big factor

[Peasant_Pilot]

40 minutes ago, Thruster88 said:

I see you having a dig at expensive certified aircraft parts however if you search the ATSB data base for in flight engine fires you will see that they are very rare in Australia compared to RAAus types by a huge margin.  

 

AN fittings, steel braid oil and fuel lines, fire sleeves, proper fuel drain lines on components that could leak if a fault develops, robust correctly designed electrical systems all cost money. I think it is cheap.

 

Carburetor over flow lines should be routed out of the cowl at least.  

 

It's interesting really, I mean most RAAUS members and pilots are members to make flying more affordable. I think spending the time and money(and doesn't always have to be stupid amounts of money) on safety and redundancy is still just as critical.

[facthunter]

In Flight fires are close to the most dangerous things you encounter with powered flying. Get it back on the ground (safely) is a priority. Don't crash. You are already on fire..  Also hot oil is pretty good at burning also and easily lights up on a hot exhaust. These barriers just give you time. A firewall fuel and oil shut off might help also.  Nev

[turboplanner]

2 hours ago, facthunter said:

 A firewall fuel and oil shut off might help also.  Nev

The purpose of the fuel tap is to give control of fuel in the engine compartment dripping or spraying on hot exhausts or contributing to a fire.

In some lucky cases turning the fuel off quick enough will see a fuel drip originated fire go out. It would be unusual if this wasn't the layout in a GA aircraft, but worthwile checking the layout of an RA aircraft where people in the past have said things like "I don't have an of/off tap" or "I always leave it on, what's the point?" It's a relatively easy fix.

Oil is more likely to be ignited on hot exhausts (I've seen a lot of petrol spills just vapourise off without flashing). rigid steel oil lines last forever but can crack from vibration and spray oil, loose or cracked fuel filters will leak or spray, loose fittings will leak or spray,  overfull sumps will push oil droplets out of the dipstick tube, etc. It pays whereever possible to have the oil filler at the lowest point where the oil can be sucked out of a drain hole, and the pipes and connectors routed away from exhaust manifolds. A couple of minutes check on your kit built aircraft could save a bad situation in flight.

[Yenn]

Will you know you have an engine fire before it is too late. Sure the main aim is to reduce the fuel available by shutting it off. A good firewall allows you time to respond and no firewall means that when you know you are in trouble it is too late. S.S. and gal steel are the preffered options, just about anything else is either inefficient or too expensive.

[Geoff_H]

3 minutes ago, Yenn said:

Will you know you have an engine fire before it is too late. Sure the main aim is to reduce the fuel available by shutting it off. A good firewall allows you time to respond and no firewall means that when you know you are in trouble it is too late. S.S. and gal steel are the preffered options, just about anything else is either inefficient or too expensive.

Aluminium and fiberfrax is far lighter and approximately same cost as Stainless. Aircraft Spruce sell it probably cheaper than stainless.  A special high temperature glue is used. It will also be infinitely slower to heat whatever is behind the firewall

[onetrack]

If you're concerned about oil or fuel spray hitting a hot exhaust, the simple solution is an exhaust shielding arrangement - and ensuring that pipes and hoses are routed well away from hot areas.

 

[skippydiesel]

I recon you are all living in hope,  rather than reality - a fire in a RAA class aircraft (single engine, lightly built, possibly of flammable or low melting point materials, no inflight fire suppression)  is most  likely to end in death. Your best prevention/ action chance of survival is top notch maintenance.

[Old Koreelah]

11 minutes ago, skippydiesel said:

… Your best prevention/ action chance of survival is top notch maintenance.

Totally agree, Skip.

As well the normal fire sleeves, shields, etc, I have a fire extinguisher plumbed into the engine bay. Weighs about 2kg and might make a difference in certain situations, but there are lots of ways a fire could begin.

We do our best but probably can’t anticipate every cause.

[turboplanner]

46 minutes ago, Old Koreelah said:

Totally agree, Skip.

As well the normal fire sleeves, shields, etc, I have a fire extinguisher plumbed into the engine bay. Weighs about 2kg and might make a difference in certain situations, but there are lots of ways a fire could begin.

We do our best but probably can’t anticipate every cause.

There are many types of fires, other than an immediate conflagration where you can't get down.

One of them is an electrical short, where you have a surprisingly long time from a very noticeable small, in which case, if the wiring has been done correctly you can turn the master switch off, isolating all wiring from the battery. 

[Peasant_Pilot]

I think the extra measures are well worth it.

 

Iv seen fire extinguisher kits for engine bays on race cars with remote activation before which were a cool setup. 

[onetrack]

A problem with fitting fire extinguishers to RA-Aus aircraft, is that even small fire extinguishers aren't light. Also, if you're planning on using a dry powder extinguisher, you have the potential problem of a strong airstream blowing the powder away from the seat of the fire.

[skippydiesel]

13 hours ago, turboplanner said:

There are many types of fires, other than an immediate conflagration where you can't get down.

One of them is an electrical short, where you have a surprisingly long time from a very noticeable small, in which case, if the wiring has been done correctly you can turn the master switch off, isolating all wiring from the battery. 

I agree that there is more than one source (many??) and electrical is one.

 

I also agree that this is probably the one that has the best potential to be stopped/extinguished by isolating the problem (master switch off).

 

The other two most likely sources are fuel & oil.  Neither of which has the immediacy (response time) of an electrical off switch. 

 

I have never heard of an off valve for crankcase oil and although you can turn of fuel from the cockpit, by the time you are aware of the fire, turn off the fuel supply, there will still be fuel, on the engine side, for many more seconds.

 

How many seconds, of an air blasted fire (high intensity) does it take  to consume the structural supports for the engine and/or enter the cockpit ?

[turboplanner]

13 minutes ago, skippydiesel said:

although you can turn of fuel from the cockpit, by the time you are aware of the fire, turn off the fuel supply, there will still be fuel, on the engine side, for many more seconds.

The Fuel selector tap stops fuel spraying from cracked pipes/burnt lines, removing the initial flame source. Anything flammable may be on fire, but you've bought yourself time. I was taught to sideslip the aircraft down to try to redirect flames out of the cockpit on the way down. I've had a few engine fires on vehicles which I've put out without much escalation of flames (of course that's much easier on the ground with a bucket of water).

13 minutes ago, skippydiesel said:

 

How many seconds, of an air blasted fire (high intensity) does it take  to consume the structural supports for the engine and/or enter the cockpit ?

You realise you've been discussing getting the maximum air blast through an engine compartment...............maybe this is another potential need.

You probable need to do your own research on fire crashes, maybe on the NTSB site to get any sort of gauge, but from my memory, most make it to the ground, and if you can refocus on making a rough forced landing where you don't break a leg you'll have made the best of your chances.

[skippydiesel]

Turbs, my question "How many seconds, of an air blasted fire (high intensity) does it take  to consume the structural supports for the engine and/or enter the cockpit ?" was rhetorical./ There are just too may variables.

[Methusala]

Quickest way down with lowest airspeed is to spin it - recover closest to ground that you dare and then forced landing. Evacuate...!

[facthunter]

Having "Nothing" is hardly a good proposition  where something fairly simple will help. The idea is to stop the flame penetrating the cabin for a relatively short time. Also the AIR blast is much below the speed of the air going past the cowl In a conventional Cessna baffled and gasketed at the edges I doubt it's a 1/4 freestream speed.. Cowl gills are also an aid. Closing them can almost seal the engine area. Firewall SOV's are almost universal in planes carrying  any decent  payloads and with radials there's a zone behind the main part of the engine well protected from fire. Many of these set ups give you a good chance of controlling and extinguishing the fire in the air.

  When an engine has a giant blow up it can  dislodge/damage the Cowls and create a lot of drag as well as a lot of air blast and have OIL everywhere including the windscreen. Nev

[skippydiesel]

Although this Forum is open to all interested parties, I dont see too may GA/Certified aircraft being discussed - hence my referral to RAA class aircraft, as a catch all for the aeroplanes most of us fly.

 

Most fixed wing aircraft will have an engine bullhead (to attach the engine to if nothing else) the question comes down to, in an engine fire situation, the material the bulk head is either made of or covered in, that will deliver a sufficient protection (for crew & components essential for flight)  for enough time, to facilities a landing & evacuation. 

 

Its not just the bullhead of course - its all those control/fuel/power penetrations.

 

Again I suggest that most of the existing fire litigation techniques/materials, we have for RAA class aircraft, are so much window dressing - your best bet is fire prevention by paying a lot of attention to maintenance..

Edited February 6, 2022 by skippydiesel

[Old Koreelah]

2 hours ago, turboplanner said:

… I was taught to sideslip the aircraft down to try to redirect flames out of the cockpit on the way down…

Sideslipping is such a useful tool, but since fitting flaps I’ve rarely used it. Time for a bit more practise.

Was once told not to sideslip with flaps deployed; anyone got advice?