737 QRH Cab Alt Warn and Emergency Des

[Kefuddle]

Hi 737 Experts,

I'm trying to trace back the reason why the 14,000' criteria was removed from the Cabin Altitude Warning memory items and Emergency Descent condition statement.

I hoped to go back over the old revisions but just discovered that they are not available on our document management system.

Anybody got any ideas?

[SHRAGS]

Not sure what the official reason is but I'd say it would go something like..."it's the wrong time to try and figure out if the cabin is going to reach 14,000' and pilots aren't that smart anyway (I'm one) so just put the pax oxygen on and be done with it".

[Kefuddle]

What about the Emergency Descent condition statement?

[Cloud Cutter]

In a word (or an airline name), Helios.

[Kefuddle]

These recent changes are nothing to do with Helios.

[FlyingTinCans]

It may have been to standadise the procedure with other Boeing types.

A few normal & non-normal procedures have been tweaked to bring them in line with more recent boeing types such as the 777.

However don't know 100% if this particular procedure was changed because of the above.

[masalama]

Pass oxy on

I'm very happy with the change, it says if cabin altitude uncontrollable after manual mode of the controller and there's not much between 10,000 &14,000 when cabins uncontrollable.

The other checklist that's changed for the better is the airspeed unreliable and that's great.

[Qwerti]

Interesting, if it's not for the sake of simplicity Im curious what incidents are hidden behind that.

Would be helpful if anyone who has a copy of a previous revision to post the exact wording here.


Looking again at the Rev Changes it must be done "for cross model standardisation"

[JeroenC]

Now you have to drop them even when able to level off <14000ft, but I guess that's an acceptable tradeoff between standardisation and change of occurance.

[sekmeth]

Old wording in condition statement

Condition: One or more of these occur:
* Cabin altitude cannot be controlled when the airplane is above 14.000 feet
* A rapid descent is needed.

[Kefuddle]

Hi,

Thanks for the replies.

Take the old sim scenario where the TRE creates a pressurisation problem after takeoff, hoping you don't notice, so that as you climb through 10,000 you get the cabin alt warning.

Conventional wisdom was that you would don your masks (although some didn't bother), stop the climb and request a descent to 9 or 10,000 feet. Now, because the 14,000' criteria has been specifically removed, that option is not available without extensive justification. The only course of action now is to don your masks, do the cab alt warm mems and a rapid descent to 10,000.

Of course, you can choose how to manage this, but now any deviation results in that tedious justification of not following the meme. Rapid descent in the terminal area? Hmmm.

[de facto]

Whenever a cabin altitude warning occurs or is expected to occur,o2 masks should defintively be worn.
In the scenario of a cabin alt occurs passing 10000 ft,masks would come on , a good look at the bleeds position and MSA while going through the cab alt NNC.
Obviously if your MSA is higher than 10000 ,good idea to continue the climb rather than starting an emergency descent.
Correct briefing, situational awarness,NNC knowledge tend to avoid unnecessary embarassement if not major **** ups.

[Derfred]

Boeing doesn't write checklists to make your sim session convenient for you.

[FlyingStone]

Of course, you can choose how to manage this, but now any deviation results in that tedious justification of not following the meme. Rapid descent in the terminal area? Hmmm.

If you're at FL150 when you get the cabin altitude warning horn and light, and your checkie fails you for not going LVL CHG, 340 KIAS with full speedbrake, I think you better change the company.