Suitable firewall

[Old Koreelah]

1 hour ago, Methusala said:

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

Interesting idea. If the pilot is capable of a recovery, it might be safer for the airframe than a fast dive that could rapidly exceed VNE. Yesterday I flew high to avoid being tossed around, but a fire at that level is a worry.

[facthunter]

A spin recovery usually ends up in a dive where you pull about 2.5 G and can have a fair chance of flicking into another spin if you misjudge the Pull out under pressure. If you have effective flaps you probably won't bother with Sideslipping but why not ? if the situation demands it and the POH doesn't rule it out AND you have done it(properly) recently at  safe heights. Slipping is done at fairly slow speeds if it's to be effective and you MUST be competent. Nev

[turboplanner]

1 hour ago, skippydiesel said:

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.

It would be worth taking a very close look at one; they have a pretty good record at not causing in-flight fires and keeping them contained.

1 hour ago, skippydiesel said:

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

It's called a firewall in cars and aircraft and in cars and GA does an excellent job of isolating a fire.

The less penentrations the better and there are some great examples of "bundling" conectors - fire resistant connectors carrying multiple cables to prevent gaps.

 

Where single cables or pipes must pass through there are virtually unlimited sizes of rubber grommets which grip both the cable and firewall, and these provide enough delay for you to get to the ground.

 

It's probably more important to prevent smoke gettig into the cabin than flames, so there should be no gaps at all.

1 hour ago, skippydiesel said:

 

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..

Up to a point but in the sitiations I mentioned earlier, they will save your life.

While an inflight collision which bursts the fuel tank give you little hope of survival there are plenty of accident reports showing the occupants got safely on the ground before the aircraft went up.

[skippydiesel]

I still have my doubts - Bulkhead/Firewall ? - seems to me that firewall is just a fancy word for a bulkhead either made of something fire resistant or covered with something similar.

I just cant get my head around being reliant on IT (in a RAA class aircraft) to do anything other than lighten your pocket for the illusion of enhanced safety.

 

I agree that resitting smoke/fumes is possible, at least for a short time, which may be enough to get you to the ground (hopefully survivable) however ply wood with a heat blanket will probably serve you as well as a fancy metal bulkhead.

 

When you make vague references to aircraft mid airs etc are you talking RAA class or GA certified?

 

A burst fuel tank,  well away from hot engine components/electrical short, is literally a long way from an engine compartment.

 

 

[turboplanner]

3 minutes ago, skippydiesel said:

I still have my doubts - Bulkhead/Firewall ? - seems to me that firewall is just a fancy word for a bulkhead either made of something fire resistant or covered with something similar.

I just cant get my head around being reliant on IT (in a RAA class aircraft) to do anything other than lighten your pocket for the illusion of enhanced safety.

 

I agree that resitting smoke/fumes is possible, at least for a short time, which may be enough to get you to the ground (hopefully survivable) however ply wood with a heat blanket will probably serve you as well as a fancy metal bulkhead.

 

When you make vague references to aircraft mid airs etc are you talking RAA class or GA certified?

 

A burst fuel tank,  well away from hot engine components/electrical short, is literally a long way from an engine compartment.

 

 

You're better staying away from design, rather than getting involved and not knowing what the terms are, what the current standards are for performance etc.

[skippydiesel]

3 hours ago, turboplanner said:

You're better staying away from design, rather than getting involved and not knowing what the terms are, what the current standards are for performance etc.

Are you referring to yourself?

[turboplanner]

6 hours ago, skippydiesel said:

Are you referring to yourself?

No, I put in the five years of study to learn the steps of designing. I was referring to anyone who doesn't know what the product is called and what it has to do.;they can't get from that point to a finished product which doesn't have flaws, so best leave it to a professional.

[Geoff_H]

I suggest that you look at GA designs and copy one of them.  That way you could fail to some nuance but overall you will probably get the best result.  I would not copy a RAA nor an amateur built aircraft.  Their designs have a high degree of problems.  One of the things that worried me is the high proportions of plastic fuel lines that I have seen.

I am designing and building a composite Cri Cri aerodynamic similar aircraft.  I have found that it is extremely time consuming with very little previous designs to call upon, I have to research so much and end up making something  similar that has been previously designed.  It has worn me down and I am seriously looking at abandoning the prokect.  I have had 40 years of designing and trouble shooting mechanical equipment, I also have a degree in mechanical engineering.  To get it right on your own is possible but what if you get it wrong?  What design review process do you use?  How do you make sure that the reviewer is doing a good job.  I worked for a company in Dallas that did nuclear design ( not me).  They put the checker in a room, no telephones, no other personally allows in, max checking time without break was one hour.

 

What I am trying to say is don't do your own thing, use the greater knowledge of the professional flying community, unless you have professional training, even then consult other very experienced people.

[turboplanner]

21 minutes ago, Geoff_H said:

I suggest that you look at GA designs and copy one of them.  That way you could fail to some nuance but overall you will probably get the best result.  I would not copy a RAA nor an amateur built aircraft.  Their designs have a high degree of problems.  One of the things that worried me is the high proportions of plastic fuel lines that I have seen.

I am designing and building a composite Cri Cri aerodynamic similar aircraft.  I have found that it is extremely time consuming with very little previous designs to call upon, I have to research so much and end up making something  similar that has been previously designed.  It has worn me down and I am seriously looking at abandoning the prokect.  I have had 40 years of designing and trouble shooting mechanical equipment, I also have a degree in mechanical engineering.  To get it right on your own is possible but what if you get it wrong?  What design review process do you use?  How do you make sure that the reviewer is doing a good job.  I worked for a company in Dallas that did nuclear design ( not me).  They put the checker in a room, no telephones, no other personally allows in, max checking time without break was one hour.

 

What I am trying to say is don't do your own thing, use the greater knowledge of the professional flying community, unless you have professional training, even then consult other very experienced people.

I feel for you, have spent a lot of my life designing prototypes; biggest project was a Prime Mover with this brief.

• Needs to be synonymous with our brand
• Need it now
• 14 litre engine
• 18 speed Roadranger
• 44,000 lb diffs
• sleeper cab

It's nothing to fit, grind, reweld an item 40 times before it fits and then find you can't get your fingers in to undo a cap next to it. That's why initial design on prototypes is so expensive.

 

When you get stressed out, walk away from it; usually overnight there's be a lightbulb moment with another way to do it.

 

[facthunter]

Unless you are working on Carbon fibre etc There's already a great deal of information to be sourced from many places like the EAA and tony Bingelis books as an example. FAR 23 covers a lot of simple design aspects  . There's no need to start from scratch and try  to re invent the wheel. .Nev

[skippydiesel]

I dont think anyone is trying to design/reinvent the firewall/wheel here.

 

It seems advice/opinion is being sought as to a functional material, from which to make a firewall ie a material which will  confer heat/fume resistance, to an engine bay fire,  for sufficient time , so that the crew can land & survive

 

With the risk of stating the obvious -  it seems necessary to point out that  the engine bulkhead has several functions, one of which may be to act as a "firewall" should a fire break out within the engine compartment. Its primary functions are,to be a structural component of the airframe, separate the "crew" from noise & fumes generated by the engine and often to be the structure to which the engine is attached, through its mounting system, to the airframe (have I missed anything?).

 

RAA class aircraft are super light, using martials unlikely to maintain structural integrity when subject to a high heat situation (no matter the exotic/expensive material used to construct/cover the engine bulkhead itself ).

 

To me, this debate is much like that of the fire sleeve one - merely slipping a brightly coloured (& expensive) fire sleeve over a fuel/oil hose does little for fire resistance - proper terminations (rarely fitted) at each end are required to get any real benefit. Sure strategical placed fire sleeve may confer a degree of heat insulation,  reduce the chance of  hose damage &  fuel "vapour lock"from  from near by exhaust systems however other techniques, cheaper  & potentially more effective  (not so visually attractive perhaps) are just as good/better.

[Old Koreelah]

3 hours ago, skippydiesel said:

… the engine bulkhead has several functions, one of which may be to act as a "firewall" should a fire break out within the engine compartment. Its primary functions are,to be a structural component of the airframe, separate the "crew" from noise & fumes generated by the engine and often to be the structure to which the engine is attached..

Plywood covered by a skin of steel ticks all those boxes. 

[Geoff_H]

Why use steel?  Heat conductivity of 45w/mK and weight of 7.6k kg/M3. When Aluminium 1/3 the weight and back the aluminium with 13mm Fiberfrax heat conductivity of 0.22w/mK and weight of 96kg/M3  so much lighter so much more (approx 250times) more heat insulation.  A longer time before your plywood bulkhead starts to smolder and fill the cabin with smoke.  It is also a driven system.

 

[Geoff_H]

Proven system.

[skippydiesel]

2 hours ago, Geoff_H said:

Proven system.

In what way???

[Geoff_H]

Used in many composite aircraft.  Titan developed it and promotes it.

[facthunter]

I wouldn't go for aluminium. When it's thin you'll melt a hole in it in no time. You are the first person I've ever heard to recommend it as a firewall component. Nev

[Geoff_H]

It is only a carrier of the thermal barrier.  The barrier is also glued to the bulkhead ( special high temperature glue).  The aluminium is essentially mechanical protection.  Definitely used in aircraft.

[Geoff_H]

It seems like you doubt it?

[facthunter]

Are You talking to me?  Well it has a pretty low melt point so what use is it then?  It's actually flammable in some situations where it's used in cladding'   Nev

[Geoff_H]

It is just the mechanical protection.  Thermal protection provided by the insulation.  Insulation glued to firewall for structural support.  I really don't care if you don't believe the facts.  I know Cozy use it from over 30 years ago. I have written the last on this.

[skippydiesel]

Geoff - there is no offence intended - just us Doubting Thomas's - the trouble with much of your agreement is you keep throwing in references to GA type aircraft - way heavier, bigger engines, etc etc.

 

I have no doubt that the heavier, more complex, more powerful the aircraft the more lily a "firewall" will buy the crew time to land and abandon ship.

 

I just doubt the effectiveness, of such a feature,  at the very light end of the sport.

[onetrack]

Interestingly, the bloke in the blog below is building a Cozy, and he changed from the specified aluminium for the firewall, to stainless steel - without giving the reasons.

If I was building an aircraft, I think I would be inclined to favour stainless steel over aluminium for the firewall sheeting.

 

http://cozy1537.blogspot.com/2018/06/chapter-15-firewall-cutting-and-fitting.html

 

Skippy, while I would basically agree with your principle of maintenance to a high standard as a primary fire prevention move, the Swiss cheese principle says that you double that up with good firewall design, to further cover the 0.001% chance of an inflight fire.

[facthunter]

The concept of redundancy is a feature of aircraft systems. Nev

[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 preferred options, just about anything else is either inefficient or too expensive.

This was meant to be posted several days ago, but didn't.

The original question was what could be used. Some have said aluminium, but I wonder would they stand up an be counted if aluminium melted in a fire wall. History has shown that aluminium will not stand up to temperatures that occur forward of the firewall. That is the reason that most fuel fittings are steel.