Depressurization - Airbus

[mutt]

The standard depressurization profile with a 22 minute chemical system calls for

[1]Speedbrakes
[2]VMO/MMO
[3]Idle Thrust
[4]Descent to 14,000 feet or higher if limited by obstacles.

For a scenario where you are limited by obstacles and have to level off and cruise at FL290, then FL250, then FL140 and finally 10,000 feet, what descent profile do you adopt to descend between these altitudes? Why?

Mutt

[gearpins]

there are very few location in the world were one has to level off at FL290,the Himalayas for example. When flying over such territory there is an escape route preplanned and to my knowledge one can be down to FL140 well within 22min.
to answer your question I would continue with the same drill do descend from intermediate levels-'cause its the fastest way:)

[inducedrag]

I would like to know if possible to do this descend in profile mode with max descend selected and altitude consternate of at or above in flight plane

[Coldbear]

Comming directly from the A320 TR course, this is what airbus sais:

Mask on - PF: Turn ALT and pull, Turn HDG and pull and pull speed. check your FMA and thust ilde. speed brakes only if no structural damage.
PNF: Signs ON, IGN ON, TCAS TA + 7700 + "Mayday", if cabin alt above 14000 deploy mask.

If you use max speed on decent it will take approx 4min to get to FL100. The checklist says "decent to FL100/MOA" - so if you are above the Himalayas then you'll need a excape plan/contingency route and also an equi time point.

Hope this helps a little :D

Martin

[Checkboard]

medically the most damage due to oxygen starvation is done at the highest altitude, so you decend as far as you safely can as quickly as you safely can so that the odd passenger who didn't get their mask on isn't sitting there breathing F390 air.

[kijangnim]

Greetings,
the profile you follow is max rate of descent and speed is applicable i.e., no structural damage, however please bare in mind that
EMERGENCY DESCENT can be specific for example in European Airspace,
you turn first, then you talk to ATC then you dive.

[mutt]

Coldbear, I'm not surprised that a TR course go into this in detail, as there just isnt enough time, but you can find that the escape plan is based on the complete descent profile and not just your ability to immediately get to 10,000ft. The profile that i list above is actually the profile that Airbus believes will give you the greatest distance for the 22 minutes oxygen.

I have no problem with the initial emergency descent profile, be it to FL290 or 10,000 feet, i'm more interested in knowing if it desirable that after leveling off at FL290, and just about getting some form of normality back into the passenger cabin, you then initate another max rate descent. Personally i would prefer to see a fast rate of descent without airbrakes, and adjust the depressurization profiles accordingly.

Mutt

[TyroPicard]

mutt
As time is the limiting factor travel at MMO then VMO for max GS - for your descent profile I think I would use:
290 to 240 OP DES clean
250 to 140 OP DES and Speedbrake
140 to 100 OP DES clean
Your company may have rules about descent rate approaching MSA which you may need to bear in mind.

[skeletor]

EMERGENCY DESCENT can be specific for example in European Airspace,
you turn first, then you talk to ATC then you dive.

Kijangnim, do you know where I can find where this is written? I don't doubt it, I'd just like to read up on it.

many thanks.