B737 Engine fire on ground

[finals24]

Can anyone shed light on the following:
All the Operators I have worked for require that Memory items are to be completed by the FO unmonitored AND both bottles should be fired WITHOUT waiting for 30secs between.
I have recently been informed that this is not the procedure adopted by some companies who require that the 30sec interval is taken on the ground as well as in the air. The rationale, I am told, is that firing both bottles one after the other is less effective in putting the fire out. I cannot find any definitive Boeing advice on the subject - can anyone help please?

[nick14]

Is there not something in the FCTM about it? Our policy is both bottles on the ground.

[Pin Head]

also no need to confirm on the ground I believe.

my battery is dead on my iPad but recall that the engine fire NNC is carried out, respecting the 30secs unless CP then calls evacuation and as per the reference item you dump both of them in.

[nick14]

Again have a look in the FCTM but we still confirm as firing the bottles into the wrong engine is a significant issue.

[FlyingStone]

AFAIK Boeing SOP is to perform the Engine Fire (...) NNC and only evacuate if you can't extinguish the fire.

Operators with more common sense use the "Airbus" approach, that is perfectly applicable to 737 - discharge both bottles and commence evacuation immediately.

I disagree with the confirmation of engine fire switches on ground. You are loosing precious time that could be used to start evacuation. Even if you discharge the bottles in to the wrong engine - for which you would have to ignore the large red engine fire switch and use that annoying override button that is much more stiff on the real aircraft than in the sim (hint: frequency of use) - the worst case scenario is that you can't extinguish the fire, but you'll be far away from the aircraft by the time it becomes an issue.

[nick14]

How long does it take to check and say "confirm" ?? Come on let's be realistic here. The decision to evacuate should also only be taken after the completion of the memory items and after confirmation with ATC/ground fire services etc. It should not be taken lightly as there will be injuries.

Believe me, I have seen people misdiagnose it!!

[finals24]

Guys the question is SHOULD you wait 30sec before firing the 2nd bottle when on the ground? Different companies appear to have different SOPS - is there a reason for this?

[RAT 5]

It is astonishing why different operators choose to operate the same system differently. Surely the manufacturers have a standard method. I've flown for both philosophies. When we asked for an explanation it usually turned out to be whim of the CP; rarely the manufacturer's recommendation.

Explanations for waiting 30secs.
"the discharge tubes would be blocked by too much discharge, so no advantage in flow rate of extinguishent."

Not waiting:
"allows max rate of discharge of extinguishent, even if the tubes are blocked in the first instant."
"avoids distraction during a critical situation: avoids forgetting if distorted by events."

Pays yer money takes yer choice.

What might be more a grey area is what to do, ref' evac, if the fire goes out. Someone said evac as soon as the bottles have been discharged: others say ask the firefighters, who should be outside, what they can see. IMHO the tower would be too far away. In the B737 EVAC QRH the whole procedure is written without a break. What do guys thing about re-checking the situation half way thought the QRH - e.g. fire warning plus outside information - before ordering the evac?
Does anyone have an SOP to cover the scenario or is it always down to Captain's discretion?

[Avenger]

Discharging Fire Bottles during an Evacuation Boeing FCTM

The evacuation NNC specifies discharge of the engine or APU fire bottles if an engine or APU fire warning light is illuminated. However, evacuation situations can present possibilities regarding the potential for fire that are beyond the scope of the NNC and may not activate an engine or APU fire warning. The crew should consider the following when deciding whether to discharge one or more fire bottles into the engines and/or APU:

• if an engine fire warning light is not illuminated, but a fire indication exists or a fire is reported in or near an engine, discharge both available fire bottles into the affected engine


The question of delay in firing the second bottle is not really applicable as the time taken from the turning of the fire handle, checking the orange discharge light and observing the result is usually more than 30 seconds anyway. In our SOPS, No confirmation is required to discharge a bottle on the ground but as mentioned it if you discharge into a running engine its an opportunity lost.

The amount of time the Halon has to act on the fire is more important than the quantity, and discharging the second bottle too soon may just result in pushing out the Halon present before it has had to to suffocate and start its job.

No need to rush.. take the example of BA!

[RAT 5]

The amount of time the Halon has to act on the fire is more important than the quantity, and discharging the second bottle too soon may just result in pushing out the Halon present before it has had to to suffocate and start its job.

That is a very relevant technical comment and surely one which the boffins at the manufacturers should specify. It is a specialised scenario better known about by the pyrotechnic chappies than airline managers. Indeed, via 4 different members of the B737 family, B757/767 and 9 operators I've been told every which way to behave in this supposedly straight forward scenario.
Are there any knowledgeable fire engineers out there to comment?

[lomapaseo]

That is a very relevant technical comment and surely one which the boffins at the manufacturers should specify

That's what training is for.

Manufacturers don't talk directly to crew except via "must do statements" approved by the FAA, and communicated by the operating certificate holder.

I have seen numerous cases of training sylabus that left open or unsaid the reason why. The answer was available only going through the instructor and his or her interpretation. In many cases the background explanation was not critical to flying as long as you followed your training.For those few cases where you feel it important, start by challenging your instructor :)

[finals24]

Thanks RAT 5 and Avenger - I agree that logically the elapsed exposure to Halon is more important, although that is not supported by any specific knowledge on the subject! This is potentially a very important issue and it is frustrating that SOP's are seemingly developed in some ignorance in the absence of clear direction from the Manufacturer or Regulator.

[de facto]

What do guys thing about re-checking the situation half way thought the QRH - e.g. fire warning plus outside information - before ordering the evac?
Yes please!
Concerning firing the halon,i was told that in the air,the second discharge is kept in case the fire relights...once discharged,it fire fights for an hour..
Not much possible to evacuate in the air...

On the ground,the possibility to evacuate means delaying the back up of the second is not deemed as important as in the air.
In any case,follow your company SOP,always review your action before a delicate ,potentially irreversable decision such as an evacuation.

I agree,this specific is an annoying ongoing issue.
In such a situation,not waiting for 30 secs would my way for on the ground,especially as the QRH fitted in my aircraft does not mention a delay.

[RAT 5]

The thought about checking the result of firing the bottles before ordering the EVAC is my unofficial opinion, and will depend on outside information. The lights out may not be enough to be confident the fire is out. The reason for the question is because the QRH (B737) does not include a 'note' "choose one....." to consider this. Cadets assume that once started the EVAC QRH must be finished.

[TheChitterneFlyer]

I confess to not knowing anything about the B737. However, I would ask the question... "How many fire bottles do you have"? The B707 had two bottles per wing and if both bottles were discharged into, say, No 1 Engine, No 2 engine would not have any fire suppression capability for the remainder of the flight. As for an engine fire on the ground, well, I would strongly support the option of throwing everything you have at the fire and getting the hell out of there... Captains decision of course!

[RAT 5]

Yes: but the question ( and it is purely technical and should be answered by the boffins who designed the system) is what is the best way to 'throw everything at it' to achieve the best chance of extinguishing the fire. Is it 1 bottle, wait, 2nd bottle, or both ASAP? I suspect pilots have only an opinion based on what their respective SOP says. I doubt they've ever tried it. I doubt airline engineers have ever tried it. I hope and trust the fire extinguisher & engine designers have done so.

[lomapaseo]

Have a go at this

What is Halon? How does Halon Work? Is Halon legal? Is Halon Safe? (http://www.h3rcleanagents.com/support_faq_2.htm)

lasting chemical reactions take time