Incident 13 May 15

[JG3]

<< surprising how well even half a kilo of powder works>>

 

Just a caution about dry powder extinguishers in aircraft. There was an incident where one such extinguisher accidentally discharged in flight. The dry powder, being electrostatic, immediately coated the windscreen and all the windows. and couldn't be wiped off, just kept clinging on. Complete loss of visibility. He was only able to land by peering out a small vent in the side window......

 

 

[turboplanner]

I carried an aerosol extinguisher (made in Tasmania) until it was well out of date, then replaced it with a proper aircraft one, plumbed into the engine bay.

That's a great idea but what about an electrical short behind the instrument panel?

 

 

[turboplanner]

The one I use cost $26 from supercheap , comes with a plastic holder which I riveted below my control stick but also added extra duct tape to hold it in place , wouldn't want it rolling around under the rudder pedals. The 914 fuel set up in my plane uses 2 electric pumps plumbed together but are powered separately inside the cabin behind the instrument panel, I've always been worried about a fire behind the panel and petrol feeding the fire

If there's an inflight fire, you will need to keep flying the aircraft, and act very quickly.

The extinguisher also needs to be restrained to about the same g level as a car seat belt to minimise the chance of it breaking away in flight as you mention.

 

Wrestling with duct tape at this time may not work, and it might be better to fabricate a quick release pull pin.

 

 

[jetjr]

I thought powder extinguishers were not recommended for enclosed spaces for a few reasons?

 

Aircraft can carry Halon but cant get them easily anymore .....and they carry aviation specialised pricing

 

Anyone have access or suppliers?

 

 

[Guest Andys@coffs]

So....your on fire and have heaps of altitude to loose before you can escape your chariot.........Things are looking grim......what focus do you put on VNE....is this the one time that you'll push past it?

 

Choice of two evils...what do you do?

 

Andy

 

 

[rhtrudder]

I did wonder about the powder inside the cabin, it's got a trigger so the whole lot doesn't empty at once, I may have to think of a better holding down system.

 

 

[Old Koreelah]

That's a great idea but what about an electrical short behind the instrument panel?

It's installed so that if need be I can reef it out and hand spray. I also have an automatic battery isolator to cut the juice.

 

 

[Maritime_Ev]

I thought powder extinguishers were not recommended for enclosed spaces for a few reasons?Aircraft can carry Halon but cant get them easily anymore .....and they carry aviation specialised pricing

Anyone have access or suppliers?

True, ABC powder is nasty stuff and I certainly wouldn't recomend using it in an enclosed space normally, but sometimes it is a matter of priorities.

 

It's also very bad for your electronics, they may still work a day later but once they've been contaminated it is only a matter of time before they will fail.

 

Problem is that there are not a lot of alternatives available; Halon (or FM200) will do the job but is difficult or impossible to get for a private person.

 

CO2 you can't use in an enclosed space and it won't do much out in the open when there's a breeze (except for liquid fires perhaps). Also you will need a fair bit of it to be effective (packed in a heavy pressure cilinder).

 

I have a foam extinguisher (AFFF) at home and one in the car, which work fine, but as with the CO2 you need a bit of it to be effective so probably not suitable for use in the air.

 

 

[facthunter]

I wouldn't rule CO2 out. It's going to cool anything you spray it on quickly, which helps. If you fill the cabin you need to have your nose near an airvent. It's not poisonous as carbon monoxide is. It works by excluding air.

 

Regarding descending quickly depends on structural integrity and turbulence . TIME is the essence of in flight fire. Full flap at a lower speed or faster clean may have a similar ROD. If you have a field that's really good and close it might be your decision to fly clean and faster to go there, but if it's a fair distance you have to make the call weighing the factors.. If it's in the engine you have probably shut the fuel off anyhow, so it's a deadstick arrival and don't prang an already burning aircraft . Nev

 

 

[Geoff13]

So....your on fire and have heaps of altitude to loose before you can escape your chariot.........Things are looking grim......what focus do you put on VNE....is this the one time that you'll push past it?Choice of two evils...what do you do?

 

Andy

I dont think I would want to exceed Vne until my clothes were burning. Far more important to work out and practice maximun possible rate of descent whilst keeping the aircraft within safety parameters. There is not much point getting on the ground quickly if it is uncontolled. Far more important to know and practice besr rate of descent imho

 

 

[rhtrudder]

I wouldn't rule CO2 out. It's going to cool anything you spray it on quickly, which helps. If you fill the cabin you need to have your nose near an airvent. It's not poisonous as carbon monoxide is. It works by excluding air.Regarding descending quickly depends on structural integrity and turbulence . TIME is the essence of in flight fire. Full flap at a lower speed or faster clean may have a similar ROD. If you have a field that's really good and close it might be your decision to fly clean and faster to go there, but if it's a fair distance you have to make the call weighing the factors.. If it's in the engine you have probably shut the fuel off anyhow, so it's a deadstick arrival and don't prang an already burning aircraft . Nev

Looked at CO2 and it seems like the units are to big

 

 

[Ungrounded]

Someone recently tried selling me some "Sapphire" extinguishers for a computer room. Very expensive and I have no idea if the system is available in smaller extinguisher sizes. But it seems to tick a lot of boxes. No powder to obscure the view. Purpose built to NOT cause damage to electronics. Reportedly harmless to people and the environment.

 

PDF Brochure link below mentions "Military and aviation vehicles" so I guess it may be a good match for aircraft?

 

Just thought I'd mention it. And "No" I didn't end up buying them...

 

https://www.ansul.com/en/us/pages/ProductDetail.aspx?productdetail=SAPPHIRE+Systems+-+Halocarbon

 

https://www.wormald.com.au/fire-products/fire-extinguishers/sapphire-mri-fire-extinguishers

 

https://www.wormald.com.au/__data/assets/pdf_file/0008/155447/Wormald_AUS_SapphireBrochure.pdf

 

 

[jetjr]

Followed up today

 

Halon is out, almost cant get approved use permit any more apparently, was told +$10K for annual permit to handle it. Some big Aviation places have exemptions, Boeing, Qantas, DOD??

 

Can get ~ 0.6 kg (1.5kg) Halotron $250 plus some freight no doubt, other place was ~ $340

 

Larger 1.1kg (2.3kg) model is only $40 dearer

 

0.6kg model is only little but should be suited to small aircraft use I was told

 

And 5 yr life, 6 max

 

Appears theres someone out pinging small aircraft units as they have sold lots in last few months to replace old Halon ones picked up by inspectors

 

 

[Guest Maj Millard]

I have always carried a small , half kilo, fire extinguisher within easy reach with me just in case . After reading the nightmare that Geoff went through I found out the thing was 3 years out of date and didn't work at all. Does everyone else carry one?

Yes I carry one......

 

 

[Aldo]

Interesting conversation but a couple of points, remember you only need to remove one of the three elements in the fire triangle (I think they use four now, chemical, shouldn't be an issue in a light aircraft) to stop the fire.

 

1. Aircraft cabin fire foam is the best alternative (electrical is not an issue as max voltage is generally 32 volt RA/GA) foam is wet and will remove the heat from components and also smother reducing the available oxygen and if used correctly (not sprayed everywhere) will not obscure the view out the window.
    
    
   
2. Halon - BCF (difficult to get) is a great extinguisher but is an oxygen scavenger and as such you as PIC can't breathe either , so you say open the door or window/vent as soon as you do that the heat in the fire will reignite with the return of oxygen. I have been in an engine room (on an offshore drilling rig) with a halon un-commanded release and it is not a situation you want to find yourself in at altitude - 10 seconds and you can't breathe.
    
    
   
3. Halatron - available but as above just not as effective as Halon
    
    
   
4. All fires shut off the electrical supply but remember residual heat will still be there see point 1 above.
    
    
   
5. Engine compartment fire shut off fuel & electrical supply and get the nose down as far as you can (wouldn't worry about vne at this stage) - excess air = excess oxygen, fire will go out as it is too rich to burn, additional airflow will assist in cooling the hot areas, need to be careful on pulling out of the dive though as you may stall the aeroplane and end up with an additional problem.
    
    
   

 

 

Aldo

 

 

[Maritime_Ev]

Interesting conversation but a couple of points, remember you only need to remove one of the three elements in the fire triangle (I think they use four now, chemical, shouldn't be an issue in a light aircraft) to stop the fire.

 

1. Aircraft cabin fire foam is the best alternative (electrical is not an issue as max voltage is generally 32 volt RA/GA) foam is wet and will remove the heat from components and also smother reducing the available oxygen and if used correctly (not sprayed everywhere) will not obscure the view out the window.
    
    
   
2. Halon - BCF (difficult to get) is a great extinguisher but is an oxygen scavenger and as such you as PIC can't breathe either , so you say open the door or window/vent as soon as you do that the heat in the fire will reignite with the return of oxygen. I have been in an engine room (on an offshore drilling rig) with a halon un-commanded release and it is not a situation you want to find yourself in at altitude - 10 seconds and you can't breathe.
    
    
   
3. Halatron - available but as above just not as effective as Halon
    
    
   
4. All fires shut off the electrical supply but remember residual heat will still be there see point 1 above.
    
    
   
5. Engine compartment fire shut off fuel & electrical supply and get the nose down as far as you can (wouldn't worry about vne at this stage) - excess air = excess oxygen, fire will go out as it is too rich to burn, additional airflow will assist in cooling the hot areas, need to be careful on pulling out of the dive though as you may stall the aeroplane and end up with an additional problem.
    
    
   

 

 

Aldo

With a bit of streching there are now even 5 classes of extinguishers, ABC for solids, liquids and gasses, class D for metal fires (which require a special powder) and E for (high voltage) electrical fires. Although the E class is a bit of a missnomer, an electrical fire is just a class A fire that you shouldn't get wet. We have a couple of class D extinguishers on board for putting out litium battery fires, I guess they'll become more common once electrical aircraft and cars get more mainstream.

 

The reason you only need a very small amount of Halon or powder is that they work as a negative catalyst, they don't get 'used up' like evaporating water (in AFFF) or need to remove the oxigen to a non-flamable level (like CO2).

 

From what I picked up at a bunch of more and and less advanced fire fighting courses over the years is that the cooling effect of CO2 (and to some extend foam) is quite limited, the main effect has to come from removing the oxigen from the fire.

 

On all larger ships there's a total flooding system for the engine room in case of a large fire (with the benefit that ships are generally air tight on the bottom...) there have been quite a few stories where ventilation was started hours after the fire was put out and just re-ignited because there was still enough heat for ignition (which is usually the end of the ship since you only have a single shot of CO2).

 

 

[turboplanner]

Procedure at race tracks for a fuel fire is to go in first with CO2 to displace oxygen. The hot components will reflash if nothing else is done, so a second person moves in with foam. The CO2 man moves closer, then the foam man and so on until they get on top of the fire.

 

 

[Oscar]

Geoff - apologies for the slow response here, but other things have intervened.

 

An 'autopsy' of my old brick-type pump revealed a number of things.

 

At the base of the pump, there is a small circuit-board with what is probably a switching power transistor of the 13003 form factor, which is riveted to the base plate of the pump - presumably so the base-plate acts as a mounting for the circuit board and a heat-sink for the transistor.

 

The actual pump mechanism is a pair of coils that - presumably - are switched so that the 'piston' of the pump oscillates; there are simple valves at the intake and output ends of the pump 'cylinder'; it would be hard to get a more simple mechanism. I can't readily see how a mechanical failure of the pump could cause a seizure leading to a combustive situation - more likely, it would just cease to pump effectively.

 

The hole blown through the plastic ident. plate in your piccy, is already in the casing; it appears that it is used as an inlet for the pressure foam filling around all the components - which makes sense for sound attenuation ( or in less complicated terms, shuts the damn thing up from rattling your teeth when in operation). The entire inside of the pump is filled with this very dense, yellow foam and is obviously done by injecting the foam as a liquid.

 

The foam will sustain combustion when subject to flame/heat and produces a vast amount of acrid, almost black-coloured smoke.

 

There is NO electrical component anywhere near the hole on the casing that could cause arcing off the casing; our best guess is that the heat from the circuit board failing ignited the foam and what you had was a very small bomb in action, that blew the foam away from the hole in the casing which then became a vent. It probably required the foam to be burnt away toward the casing to the extent where the surface area of the casing cooled the remaining foam below its ability to sustain combustion before the smoke abated - hence the delay after you cut off the power before the smoke started to clear.

 

FWIW: my sparky is also the co-owner of our aircraft and we are intensely interested in avoiding what happened to your aircraft. Our conclusions from your experience and our investigations are:

 

We will still use a Facet brick-type pump, because the incidence of what happened to you appears to be incredibly rare. HOWEVER:

 

We will mount it with stand-offs beneath the feet, to give the base-plate room to 'breathe';

 

We will wire it up through a 5-amp circuit breaker in case of electronic 'hiccups';

 

We will twist the power and earth feed wires tightly together and a) put a cable clamp around them, and b) put a braided fibreglass 'sheave' wrapping around all of that, so an excessive resistance will melt the wiring insulation and trigger the circuit breaker before setting fire to the pump foam - and we'll add a slow-blow 5-amp. fuse to the power supply circuit as a redundant safety.

 

As an addendum: the standard Rotax (and Jabiru) alternators are subject to voltage spikes which can possibly fry electronics. We are using a CAMit alternator with more reliable regulation.

 

As a final point: what happened to you may be just a freak failure of the electronics - or may be an entirely predictable result of a bodgie installation. If it is the latter, a good electrical engineer should be able to give you a qualified opinion.

 

 

[Guest ozzie]

Oscar gives two reasons why it might be a good thing to fit a pump. Mogas can have vapour problems. Might not happen in colder climates, and there's the back up factor.A fuse protects the wiring.. It's rating should be appropriate to the current the wiring can take. If a pump was faulty and had say bearing failure the fuse won't protect it till the current goes way above normal, and causes it to pop if it's a Circuit breaker, or melt if a fuse. It won"t necessarily guarantee protection against fire or smoke if it heats up slowly. Nev

consider a thermal protection device, a lot of pumps use them.

 

 

[jetjr]

Just make sure power supply is fused and switched

 

 

[Oscar]

[*]Engine compartment fire shut off fuel & electrical supply and get the nose down as far as you can (wouldn't worry about vne at this stage) - excess air = excess oxygen, fire will go out as it is too rich to burn, additional airflow will assist in cooling the hot areas, need to be careful on pulling out of the dive though as you may stall the aeroplane and end up with an additional problem.

 

 

 

Aldo

 

Seriously - the idea that one should ignore VNE is not something that should be taken lightly. If it becomes a decision to be roasted or ignore VNE, than I can see the argument - but if anything less, then exceeding VNE may be the equivalent of diving out of the tenth-floor window vs. being lightly scorched while awaiting the fire crews.

 

VNE is not JUST a mystical figure above which the wings MIGHT fall off. It is also not 'just' a figure with a 10% safety factor for the sake of providing an observable limit.

 

Amongst things that may have contributed to the VNE figure for a specific aircraft are: flutter, reversing controls, locked controls.

 

Any decent attempt to snuff the fire, is worth it - provided that does not result in an incontrovertible plummet into the ground.

[Aldo]

[*]Engine compartment fire shut off fuel & electrical supply and get the nose down as far as you can (wouldn't worry about vne at this stage) - excess air = excess oxygen, fire will go out as it is too rich to burn, additional airflow will assist in cooling the hot areas, need to be careful on pulling out of the dive though as you may stall the aeroplane and end up with an additional problem.

 

 

 

Aldo

Seriously - the idea that one should ignore VNE is not something that should be taken lightly. If it becomes a decision to be roasted or ignore VNE, than I can see the argument - but if anything less, then exceeding VNE may be the equivalent of diving out of the tenth-floor window vs. being lightly scorched while awaiting the fire crews.

 

VNE is not JUST a mystical figure above which the wings MIGHT fall off. It is also not 'just' a figure with a 10% safety factor for the sake of providing an observable limit.

 

Amongst things that may have contributed to the VNE figure for a specific aircraft are: flutter, reversing controls, locked controls.

 

Any decent attempt to snuff the fire, is worth it - provided that does not result in an incontrovertible plummet into the ground.

 

Oscar

 

The "wouldn't worry about VNE at this stage" comment was in relation to getting an engine compartment fire out and nothing more. You are well and truly intelligent enough to understand what a force fed fire will do in a very short time.

 

[facthunter]

A fuse only protects the wiring circuit. That's what it is there for. A slow failure of a motor or other items doesn't always cause a fuse to blow so a thermal responsive feature is required incorporated in the particular item. ( as Ozzie says) Not rocket science.

 

Regarding the foam involved in this matter. It has very good thermal insulating properties and I have seen it CAUSE overheating of serviceable components in some installations. used continuously as the heat just can't escape. Any electrical component that generates heat must be capable of cooling in all conditions of service.. Nev

 

 

[Oscar]

A lot of good thoughts on here; Geoff's report has done very good work in causing people to think about causes and options for action.

 

Obviously, prevention - as far as possible - is the first line of defence. Both electrical and fuel are the obvious contenders for causing problems and while that is a glaringly obvious no-brainer statement, it is so very easy to do something that seems innocuous enough but could have bad consequences. 'Aircraft standards' for installation are sometimes pretty impenetrable to read but really do need to be considered.

 

Something that hasn't been discussed, is Personal Protection. I'll bet that just about all of us have trawled through maybe the eBay 'aircraft parts' or similar pages and noticed ads for Nomex overalls , and probably thought 'maybe a good idea', then dismissed it because - let's be honest - the idea of stepping out of your wee little plain-Jane Jab or whatever dressed like someone out of Top Gun is rather likely to cause others to think 'What a WANKER'.

 

Yet thoughtful clothing choices can make a considerable difference to your potential injuries / incapacitation from fire - or at least add a bit of time to get on the ground and out of there. We are strapped in with basically no room to reduce our exposure to a source of flame, and needing our hands and feet to continue to operate the controls. Just good leather shoes, woolen socks, non-synthetic material trousers etc. plus a pair of Nomex overalls would at the very least add protection from both panel fires and anything coming through the firewall, for longer than more dangerous types of clothing.

 

It's interesting that in some other sports, the attitude towards personal protection is very much oriented in favour of the best level of personal protection. Motorcycl;ists (with any intelligence, anyway) adopt what is called ATGATT: 'All The Gear, All The Time'. Those full leather suits with body armour incorporated, gloves with carbon-fibre finger protection etc. are not worn because it makes us look like grand prix racers - it is worn because sliding down the road at 100 kph does really nasty things to the human body. Serious motorcyclists consider the lightly-clad 'thong nongs' to be the 'wankers'.

 

So - a question: what do people think about someone flying with in Nomex overalls - even ones with fairly obviously 'Air Force' or 'Navy' badges removed that have been purchased as good second-hand equipment from a Surplus store? Is the reaction generally that they are a bit of a poseur or that they are cautious and concerned about their safety? I freely admit that I have had thoughts both ways about this idea, but I anm starting to come to the idea that a pair of Nomex overalls is not silly (and maybe I'd strip them off immediately after landing, rather than wander into the clubhouse wearing them..)

 

 

[facthunter]

Just wear them as if it's normal. Better than wearing gold sleeves with black armbands around an aerodrome...Nev