View Full Version : b737 eMERGENCY dESCENT

15th May 2003, 00:12
During a typical cruise we are well below (737 classic) VLO and VLE.
So why don't we lower the gear also, for an emergency descent?

I mean, there are cases in which we don't want to really set MMO/VMO....

Notso Fantastic
15th May 2003, 02:19
Idle power, speedbrakes up, turn, nose over. Putting the gear down isn't helped by reduced 'g'. You can extend, but better to get down quickly. Accelerating will produce a whopping descent, with the gear down, it will be difficult to get speed up without excessively steep body angles- tried it in the sim. I think better to leave the gear alone- something to forget down in a shaken-up situation!
You seem to be doing a tech course with holes in it!

15th May 2003, 02:50
I thought one the first considerations was "structural integrity"?

If this in doubt and the a/c is hanging together best not to increase speed and, I guess, make too much of a radical change to the configuration.

Remember too that pressurisation problems are not the only reason for an emergency descent - if you have an uncontrollable fire and or smoke in the cabin you want to land asap.

15th May 2003, 20:22
There should be no blinding hurry to keep up the speed to barber pole in an emergency descent. If the problem is depressurisation there is enough oxygen for twelve minutes of passenger usage. At even 4000 ft per minute from 37,00 to 10,000 ft - thats a little under seven minutes of oxy use.

15th May 2003, 21:10
Of course you are presuming that their masks have dropped!

What if they have'nt or the supply does'nt feed? We are talking seconds and not minutes and hence no time for dilly dalying around.

Get down

Shaka Zulu
15th May 2003, 21:19
Yeah but no reason to do it in a blinding rush either.
Besides there are 4 masks per 3 seats.

Interesting point about the gear. It just seems for standardisation and emergency purposes better to leave the gear alone.
Can't go wrong as it has been demonstrated. And the gain is not much. Since you'll lose time in the beginning part of the descent, and gain in the latter part.

Easier for us I'd say to just pull the s/b, retard and go as the banana

15th May 2003, 22:12
In the event of rapid loss of pressure, you are not going to hang around for too long! Sheer self-preservation will tell you to go down and bear in mind it's going to feel pretty cold if it's -45 degrees C outside!

15th May 2003, 22:59
That's exactly because of structural integrity that one may wish to maintain , let's say, 250 kts indicated.
What descent rate do you get at that speed without the gear?