Fire switches

[max alt]

Chaps,In the boeing QRH during an Evacuation without an engine fire warning it requires fire switches to be rotated in opposite directions.With an engine fire warning it requires engine fire SWITCHES to be rotated to the affected engine.Now I think that means rotating the fire switch left then right, thats illuminated, ie the one on fire putting both shots into it.Not left and right switches toward the engine on fire,only using one shot.Can anyone enlighten me.
Regads ,Max.

[wobblyprop]

on the 757 there are 2 fire bottles. The two engines have a fire handle each.

Pulling the fire handle isolates the engine, cutting off: fuel, bleed air, hydraulics.

Twisting the fire handle left or right fires bottle 1 or bottle 2 into that handle's engine.

So, with an engine fire you want to dump all available extinguishing agent into the affected engine. With no engine fire, as a precaution, you fire a bottle into each engine.

Hope that helps.

[spannersatcx]

Not a pilot, but I'll give you it from a technical side.

Not all 747's are the same, RR powered a/c have 2 bottles per engine, so rotating left then right will fire 2 bottles on the same engine.

GE and PW powered a/c have 2 bottles per wing. So if you rotate handle left then right you will fire the 2 bottles into that engine. None left for the other engine on that wing.

If you rotate 1 handle left and 1 handle right then 1 bottle is fire into each engine, that way ensuring each engine has a fire bottle dispensed into them.

[Captain Airclues]

On the 747 that I fly (GE) you have to rotate all of the switches in the same direction if you want to fire a bottle into each engine. As spannersatcx says, it looks as though all 747s are different.

Airclues

[max alt]

WP,Thanks for the reply,sorry to be pedantic but the QRH says,if engine fire warning received rotate engine fire SWITCHES to the affected engine.IE Left fire warning left switch left, right switch left.It does not say SWITCH.Thats the point.The eng fire on gnd drill says both bottles into the affected engine, total common sense.Its this evac drill with a fire wx that doesnt sit well with me.
Regards Max.

[Intruder]

Since you don't say what aircraft you fly or what configuration the fire bottles are, the only sane advice is to follow your QRH.

The answers already given demonstrate the differences in configurations among airplane/engine combinations...

[max alt]

Intruder,The a/c is 757 200 Rb211535e4,What I would Like to know and the point of this post is why the Philosphy change between the drills for fire wx evac,eng fire on the gnd.
Happy to be enlightened,
Max.

[Intruder]

That part is relatively simple...

No fire: Emphasis on prevention, with both sides equally likely to flash (or not).

Fire already: Suppress/extinguish while evacuating; more important than flipping a coin as to whether the other side will flash. After all, you'll be gone before you get a chance to look at the indications again...

[max alt]

Ok,so why put only one shot into the affected engine,when you could put two,by rotating the switch.Two being better than one,do you not agree.
Max.

[alexban]

From 737 QRH:
"..............
Engine and APU fire switches(All).......override and pull

If an engine fire light is illuminated:
Related fire switch...........Rotate and hold.
Rotate to the stop and hold for 1 sec."

This is the new QRH ,march28/2005.
It should be the same on the 757 ,i guess.Previously ,you were supposed to fire bottles in both engines,now only if you have fire.

Brgds Alex

[wombat77]

Well for what its worth the philosophy is more or less as has been pointed out previously but its along these lines.
If you have an evacuation without an engine fire, you fire one bottle into each engine -- just in case.
If you have an engine fire on the ground I'm sure your QRH will tell you to fire one and then after a prescribed period of time (probably 30sec) the second.
If you are doing an evacuation with a fire you should have already fired both and hence none left and you will be going for a quick trip outside. Which makes the ensuing Evac checklist redundant as far as the bottles go because there's none left, (assuming you only have 2 on the 757) but then if checklists where written for every occasion we would have a New York telephone book.
Hopes this helps but I'm not familiar with the 757 but I am with other boeings

[alexban]

wombat: the philosophy can be tricky sometimes ..:)
evacuation with an engine fire...very easy to imagine one where no bottle is already fired: engine fire on takeoff.
In such a case our SOP is reject then evacuation. No time for engine fire drills before evac.
The latest Boeing QRH changed the recomandation to discharge bottles 'just in case" as I said in the post above.
Now is just override and pull. Makes sense somehow.
Brgds Alex

[max alt]

Alexban,very interesting that your new QRH outlines the thoughts that I have on this.My preferred drill would always be to recall eng fire on gnd so both bottles go in the affected side then if still illuminated into the evac.I was hoping for a diffinitive answer,maybe it will come.
Thanks for the replies.
Max.

[wombat77]

Alexban, well you do have me intrigued, I have been in the checking training, management side of things for a lot longer than I care to remember, and up to now, emergency evacs have been considered as last choice due to the fact that somepeople usually get seriously injured in the event.
Possibly Boeing have decided that as the B737 is relatively close to the ground, (no offense ) to change there long standing reccomendations. For what its worth the latest ammendment for the 777 did not feature any chage in that area but when I get back from my current pairing I will try and track down a Boeing rep and see if he has an answer for you, usually a pretty slow process as they cover themselves in all sorts of protection before answering. Cheers.

[alexban]

wombat:
close to the ground....you got me here.Actually I understand what you're talking about,but as I said this is our SOP.
Regarding what I said about the QRH description of use of the fire switches,this is the last edition of the QRH ,from 28.03.2005.(737)
Boeing intends to unify the QRH for all it's types (i'm not sure about the 777).I've actually seen some demo pages of the new QRH,very interesting.I guess you may find some ex on myboeingfleet.com
Just for argument:suppose you have a fire on takeoff.You'll stop the plane,then do the fire drill,then if fire not out perform evacuation?
We'll ,our sop says that in this case stop the plane,and perform evac (which include part of the fire drill and save a lot of time)
It was demonstrated that the fire will enter the cabin in no more then 90 sec (no matter if a 737 or a 777),so better safe then sorry.
How many injuries you'll have on a evacuation?I guess fewer then if you'll evacuate in stress a full of smoke cabin.
Also one important change in the evacuation check it's that it's no longer a recall item.
Brgds...
Alex

ps wombat,you fly a jewel of a plane.Brgds