View Full Version : some qiz from 737's QRH
eagle737
7th May 2005, 01:53
#1. in checklist "AIR CONDITIONING SMOKE/FUMES"(NNC.0.2), it says:
"RECIRCULATION FAN SWITCH . . . . . . . . . . . . . . . . . . . . .OFF
......
If smoke/fumes stop:
Continue flight with the recirculation fan switch(es) OFF"
keep going with some place is still smoking? i can't accept this kind of smoking aircraft as a pilot, what will you do?
#2. in checklist "SMOKE/FUMES REMOVAL"(NNC.0.28), it says that set" LAND ALT 10000ft to increase the ventilation rate."
as far as i can understand now, the reason we set LAND ALT 10000ft is to decrease the differential pressure between the
selected LAND ALT and FLT ALT. so why 10000, why not 14000?
looking forward to any replies. thanks!
1) Hi Eagle, I'm afraid you misinterpreted the cklist: you turn the recirc fan off not because in doing so you will hide the problem (not recirculating air thus not seeing the smoke generated somewhere else), but because in this particular case the recirc fan is the source of smoke.
2) You set 10000ft to make the cabin climb at 10000ft, thus dumping more air overboard.
10000ft is the maximum before having to use crew oxygen.
I agree with you a higher altitude would be even better, if you are already on oxygen masks... but not 14000ft, as you don't want the passengers masks to be deployed with smoke in the cabin.
Maybe 13000ft....?
Cheers
Flight Detent
8th May 2005, 00:08
Right on LEM,
Would have been my words exactly!
Cheers, FD
eagle737
8th May 2005, 04:27
thank u for the replies!
for qiz #1, what if the smoke come from the forward cargo compartment but not recirc fan itself? waiting for the warning horn of cargo fire?
ifleeplanes
8th May 2005, 08:23
Id go with ASFKP. yes the recirc fan might be the sourse of the smoke however the reason its done here is to increase the ventilation since the overboard exhaust valve is driven open if the RIGHT Recirc fan is off and either pack is placed to HIGH
If you continue with the checklist under SMOKE/FUMES removal it states that @ 14000 ft or below Pressurization mode selector to manual and the Outflow Valve switch to open. You dont realy want to compound the problem at high level by turning smoke and fumes into a full depressurization as well. Your initally just increasing ventilation not depressurizing, the cabin will not climb at 10000ft min it will climb proportionaly (at a max of 2000ft min) to the LAND ALT.
Hi Gents, as usual we might be starting to confuse Classic and NG.
On the Classic, my understanding is the forward outflow valve will open if the recirc fan is off and the main outflow valve is open more than 3 degrees.
So during a normal flight turning off the recirc fan will not be sufficient to open the forward outflow valve.
NG might be different....
ifleeplanes
8th May 2005, 09:25
Could be right LEM I am talking NG.....and my memory was erased after the Classics...lol
The Puzzler
8th May 2005, 09:58
Puzzle me this....
Yeah, there is a difference between the classic and NG, and a difference between the -600/700 and -800/900. On the classic the forward outflow valve will open if the recirc fan is switched OFF. On the -600/700 the overboard exhaust valve (OEV) will open when the recirc fan is switched OFF, and on the -800/900 the OEV will open when the RIGHT recirc fan is switched OFF. One pack needs to be in HIGH as well on the NG.
As has already been mentioned, continuing the flight with the recirc fan off is referring to continuance to the nearest suitable airport for landing.
Hope this helps. :D
As has already been mentioned, continuing the flight with the recirc fan off is referring to continuance to the nearest suitable airport for landing.
Not necessairily:
If smoke\ fumes stop: Continue flight with the recirculation fan switch(es) OFF"
The Puzzler
9th May 2005, 08:00
Puzzle me this....
Unless you can positively confirm that the source of smoke or fire has been completely removed, a landing at the nearest suitable airport is required. That of course is the commanders call on the day (and what all the big bucks are for ;) ). The remark in the QRH assumes that the recirc fan was the source (as it is a prime candidate). You are quite correct LEM, but on the day the flight crew will have to make the final decision on whether to divert or not.
Agree, it's a crew call, not a QRH requirement.