View Full Version : "...if after 30 seconds....discharge...."

15th May 2003, 01:04
Many Engine Fire cklists call for the second bottle to be discharged after 30 seconds.
But from what?
The moment I have cut the fuel, or the moment I discharge the first bottle?
Personally I think this is a purely academic question, but some people are surprisingly picky on that!

Possum 15
15th May 2003, 01:39
"Discharge the second agent, if the fire warning remains 30 secs after the discharge of the first agent"

15th May 2003, 03:18
Well heres my 2 pennys worth.

I would rotate the fire handle and hold for 1 sec as stated in the QRH and then start my clock and await the 30 sec before discharging the other bottle if needed........



15th May 2003, 16:25
From KLM 737 Emergency Checklist:

".... rotate to the stop and hold for one second " first discharge

"If after 30 seconds the Engine Fire Warning Switch or Engine Overheat light remains illuminated:
Engine Fire Warning Switch.............Rotate to Remaining bottle"

So... as others have also stated here: rotate to first bottle, hold for one second and start timing. If all hasn't gone quiet and dark by then shoot the second bottle. If on the ground you can then time for thirty seconds again and if nothing has happened by then evacuation would be the next option. Obviously in the air this option would not be directly available which leads us to your other topic concerning emergency descents.

Max Angle
15th May 2003, 20:47
The Airbus ECAM counts down 30secs for you after you have fired the first bottle. Nice and easy.

Shaka Zulu
15th May 2003, 21:23
Quite obvious. But on the ground I would think of firing both bottles into one engine inside the 30 sec. Cos it will not do any further damage and you're making damned sure that the fire can't keep raging on.
In the air it's a different matter....

Max Angle
15th May 2003, 23:23
Quite agree, the Airbus (and Boeing I would think) drill for eng. fire on the ground says fire both bottles straight away. If it does not go out pretty fast you are going to evacuate anyway so you might as well give it both shots.

15th May 2003, 23:28
Confirm Airbus calls for firing BOTH bottles with no delay on the ground?

16th May 2003, 00:33
While on the ground, and with an engine fire warning on, what kind of information specifically will you be requesting from the ARFF commander ? (visible flames, smoke, etc...).

Shaka Zulu
16th May 2003, 00:57
Seems to be sensible, that Boeing prescribes the same medicine...

16th May 2003, 01:03
ARFF- No disrespect to you guys and girls, but I think by the time we had contact with you and you were near enough to see anything, our decision to evacuate would have been long taken. If we are still there when you arrive, anything you can tell us. Certainly any signs of fire.

LEM - certainly no delay - there is NO point in waiting. In the air, it is wise not to fire a bottle unless you need to, hence the pause to see if the first one works.

Shaka Zulu
16th May 2003, 02:54
I totally agree with the post made by BOAC :)

It does happen!

Cornish Jack
16th May 2003, 03:20
For those who wish to be REALLY picky and pedantic, the 30 seconds should start from the INDICATION of DISCHARGE - depending on type, that could take a second or so after actvation. So, pop the switch, wait for the discharge light, start timing....... should keep even the 'sim' guys happy!;)

16th May 2003, 07:47
BOAC, the point in waiting is the official 737 cklist which calls for 30 seconds delay in the air AND ON THE GROUND.
But I agree with you it would be better to disregard those 30 " on the ground. The problem is that any deviation exposes you to criticism....

Shaka Zulu
16th May 2003, 18:46
Any action you'll take will get criticism anyway.
I do sincerely think that you'll get a pat on the back anyway if
the engine hasn't burned down its socks.
It isn't a strange rationale right to fire both bottles into the engine after a sensible delay to see if it has worked or not....
Who can tell you not to do so for doing that?

16th May 2003, 21:42
Typical Boeing QRH NNCHL:
Engine fire switch................................ override, pull, rotate
No elaboration, easy. Done like dis at d sim all d time...

17th May 2003, 00:23
LEM - I cannot find a reference to 'wait 30 seconds' in the cklist we use - it says discharge both bottles into the engine in question. What is the EXACT wording of your evac cklist regarding bottles?

Possum 15
17th May 2003, 00:47
Once again le good ol'e AIRBUS FCOM:
"- AGENT 1 + 2 ....................DISCH"

17th May 2003, 02:16
Shaka, I don't agree with you: you are exposed to criticism only if you deviate from the established procedure, unless there is a good reason to do so.
Of course you'll get a pat on your back if all ends well!!!
But our scenario calls for a fire NOT extinguishing!
If after evacuation the airplane burns out, they will reproach to you the fact you have discharged both bottles without waiting the famous 30 seconds.

Swish 266, exactly as you say, IF AFTER 30 SECONDS the fire remains, discharge the 2nd bottle.


"... IF after 30 seconds the Fire Warning LIght remains illuminated:
No difference between in flight and on ground procedure.
My manuals could be obsolete, could anybody else check if this wording is still valid (737 classic)?


17th May 2003, 12:41
Thank you Bik, so the 30 seconds are confirmed.;)

17th May 2003, 18:09
It is a good point, LEM, and I've inadvertently drifted away into the evac cklist. I'll ask a few of our trainers what they think. To my mind, delaying the second bottle is pointless ON THE GROUND. You could be about to evacuate. Who wants to wait those extra 30 seconds to see if it works?

Shaka Zulu
17th May 2003, 19:01
Hmm Lem, good points made there. I think a little bit different now ;) Anyway on the ground i still sincerely think that waiting for 30 secs with passengers disembarking (decision has already been made anyway) it's pointless to wait and see if after 30 sec. the fire has extenguished.
I mean if you were not able to turn the aircraft away from a prevailing crosswind, the fire leaps quikly over the wing to the cabin and to the other side of the plane.
If the fire hasn't extinguished after 30 sec when bottle 1 is fired, you're about certain that the second bottle doesn't help either. Because probably the fire is already going further than the core of the engine. I do think that a little delay is there for a reason. So wait let's say 10 sec. or something, then discharge nr2 and get the hell outta there....

And again, in the air it's completely different reasoning, and 30 sec logic is well in place there.

Good subject for debate though on the ground.

18th May 2003, 01:40
Boeing proves to be too simplistic, sometimes, and Airbus more modern and appropriate!

18th May 2003, 09:08
Read the Boeing QRH 737 for Passenger Evacuation, it's covered there. If you have any further doubts about waiting for 30 seconds on the ground before firing the second bottle I suggest you contact Boeing or take it up with your Flight Safety Officer.

18th May 2003, 16:48
Pancho - I think you have, like me, been 'seduced' down the evac line, and I THINK LEM is referring to the execution of the engine fire drill BEFORE the evacuation, while the situation is being 'assessed' after the STOP, no?

18th May 2003, 21:54
I have a view that the amount of extinguishing agent provided by the manufacturer per "shot" will be based on the volume of space inside the engine cowlings. This volume can only take so much extinguishing agent. If you discharge both together, a significant amount will be forced outside the engine compartment and lost. If you fire one shot and then wait a period of time (and 30 seconds seems the standard), you will have the full quantity of the second shot left if the fire is not fully extinguished by the first shot, minimising the amount of agent lost outside the cowling.

Having said that, if the manufacturer's Flight Manual instructs you to fire both together, you should do so unless you have good reason not to.

19th May 2003, 09:54
One thing to consider if you fire both firex cylinders at the same time on the ground:
You only have two shots to put the fire out. If you fire the first cylinder and some time later the fire reignites, you have a second shot to put the fire out. What would you do if you have already fired both cylinders? If you have ever put a fire out with a fire extinguisher you will be aware that secondary flare up can occur if fuel and a source of ignition remain. I would be hanging out for the 30 seconds to see whether the first shot had worked before using up my last chance.

19th May 2003, 12:05
Interesting points made there.
All these prove that there's little to reinvent , today, in aviation.

In this example, with a fire on the ground, just follow the manufacturer's procedure: on an Airbus, discharge both bottles right away; on a 737 discharge the second one after 30 seconds.

19th May 2003, 15:00
You can talk about it as long as you like but I'm lucky if I last 30 seconds before I discharge :{ :{

19th May 2003, 15:31
'rwg' - are YOU talking about the second shot - if so, ........................ :O

hereford united
19th May 2003, 18:18
Stick to the checklist - ie if the required drill (as Boeing) says 'wait 30 seconds', do so. Two reasons:

1) Liability issues are protected if it all goes wrong because you 'only followed orders' (as they say)

2) as 'roundwego' says, there is some doubt about the effectiveness of an immediate second shot (ask his partner!! :eek: )

In any case, you always have the option of starting an evacuation during those 30 seconds if you feel uneasy about the wait.


duty lert

Shaka Zulu
19th May 2003, 21:48
Points taken guys, always good to broaden the horizon. Though I do think that some instructors have different believes about this issue. Probably because of the very same reasons we have discussed...
The big red line is easy to follow, probably is the best anyway.