737NG emergency descent procedure...

[dustrat]

A quite interresting discussion with some boieng guys and some pilots regarding the fact to get the gear down or not during emergency descent training on the NG...
What are your opinion if you have any?

[Shaka Zulu]

It's not interesting at all, it doesn't work.
There have been various flight tests and it appears that the time required to get down to MSA or 10000' is virtually the same.

[Wizofoz]

....Follow the SOPs you've been given.

[Backtrack]

....and read the Flight Crew Training Manual.

[Centaurus]

Thing to keep in mind is to decide what speed should be used in the emergency descent. If big bang down the back and no comms from the back either, coupled with obvious massive depressurisation, then assume there is a significant structural danger. Note the IAS at time of depressurisation and don't go faster than that during the descent lest you tear the plane apart if the structure has already been weakened. This means a compromise between getting it down quickly to breathable altitudes while hoping the passenger oxy doesn't run out of puff (like the pun? I did..) and spearing down at high speed hoping it doesn't fall apart on the way. Most simulator sessions accent the high dive policy which is relatively easy when compared with the think it through slow speed descent assuming structural failure somewhere. The latter needs to be practiced as much as the former - but rarely is the case.

[Capt Chambo]

As others have said follow your SOP's.

Interestingly enough on the BBJ's some of the earlier BBJ1's (based on the -700 fuselage) have what they call a "soft" wing. On this model you slow the aeroplane to gear extension speed and carry out the emergency descent with the gear down. On the BBJ2's and later BBJ1's with the "hard" wing you descend without the need to slow to gear extension speed.

[80/20]

Stick to QRH which is specific to the tail number of each aeroplane - basically no winglets = gear up, some winglet versions = gear down (otherwise many winglet 737 would not meet CFR/JAR certification requirements) in additon as allways - use commander's/PIC's common sense based on the particular situation.

[CaptainSandL]

Just in case you have not got acess to the latest FCTM (Backtrack, not all operators issue it to their crews or reissue the updates), here is the extract. This section was changed on the 3-900 series FCTM on 31 Oct 05.

"Landing Gear Extended Descent
The rapid descent is normally made with the landing gear up. However, when structural integrity is in doubt and airspeed must be limited, extension of the landing gear may provide a more satisfactory rate of descent.
If the landing gear is to be used during the descent, comply with the landing gear placard speeds."

[80/20]

"Landing Gear Extended Descent
The rapid descent is normally made with the landing gear up."

The QRH emergency descent is a copy of the AFM which takes precedence over the FCTM. The AFM/QRH is specific to the airframe and many 737's with winglets actually have a different emergency descent procedure that includes gear down (to meet JAR/FAR certification requirements). As CaptainSandL correctly points out (Plan 1) FCTMs does not reflect this and the rapid descent description may actually be contradictive to AFM/QRH for some winglet B737s.

[unmanned transport]

Not reported ramp rash and she blew.

http://www.kirotv.com/news/5680634/detail.html

[hawk37]

Can anyone explain why adding winglets to 737's would require them to use gear down to meet emerg descent certification?
I'd have thought the added profile drag of winglets was more than the reduced induced drag, at the typical speeds of a high-speed emergency descent. Perhaps with the initial descent made near MMO, but still at a comparably low IAS, the rate of descent for the initial portion is less than without winglets.
Thoughts?
Hawk

[unmanned transport]

The AOA even of the canted winglets change when the wing AOA changes in a rapid descent.
It would also be interesting to see the flt. test data.

[oldebloke]

I'm surprised that the lessons learned have not been passed on!!
At the time of the Aloha 737 peelback some criticism had been levelled at the crew, in that they 'used' high speed descent,possibly agravating the situ.
The Industry then seemed to accept the Modus Operandi that in the event of an 'explosive' decompression,slow speed(actual) descend would be used to preserve structural integrity.In the event of a Pressurization concern(cabin warning horn above 10000')high speed clean descent would be used to expeditiously 'catch' the climbing cabin...
Possibly the training dept's haven't passed it on??
Keep it simple?
Cheers