Emergency Descent: Lowering landing gear

[Matey]

The B737 Flight Crew Training Manual contains the following guidance:

"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."

At normal cruise levels with a cruise speed generally around 250/M.77 on the NG the gear extension speed is not an issue (270/M.82), and the gear can be lowered without waiting to slow down. Upon reaching level off it could be necessary to slow down to the retraction limit of 235 knots.

[stilton]

With structural damage lowering the gear and a slower IAS descent is a good option otherwise a high speed descent is most effective.


And it doesn't matter if 'you've been skiing at flight level 130' maybe you were up to it but you didn't just go through a rapid decompression and had your cabin altitude go from 7000 to 37000+ in seconds with all the debilitating effects of that on your body.


So getting down to 10k if possible is important, you're not on the slopes

[FullWings]

So the idea that this is a panic meteorite re-entry manoeuvre IMHO needs to be rethought. I wait to be shot down, but note I comment only about the ROD when in an sufficient O2 environment. Remember, in B's QRH it suggests maintaining crz speed in descent if structural damage is in doubt. If it's OK for the people then it's OK all the time. Thus ROD will be less than max even at high levels.

I agree. On many routes I fly there are long periods with MSA in the teens: we carry enough oxygen for crew and pax and if necessary have pre-planned escape routes, therefore there is no hurry in the latter stages of the descent.

Priorities on decompression:

1) Pilot(s) go on O2 ASAP.
2) Confirm a safe altitude to descend to (not necessarily the MSA for the current leg).
3) Check if a turn back / offset / escape route is required.
4) Start descent.
5) Assess possible damage before going Mmo/Vmo.
6) Ease off the RoD some time before you reach your chosen altitude.

For a well-trained crew that has been paying attention during the flight, items 1-3 take very little time to accomplish but are fairly essential. An extra ten seconds thinking time is not going to harm anyone but diving into (unexpected) ground will.

I think the whole “get it down as fast as you can without thinking” ethos came from certification requirements and a certain breed of instructors from a few decades ago who focussed on things like “one knot fast”, “one degree off” or “two seconds too long", rather than the big picture of survival by being practiced and using intelligence in a non-normal situation.

[Bergerie1]

FullWings
Excellent good common sense!

[RAT 5]

FullWings & Bergerie 1
Excellent good common sense!

Sadly, in most airlines I've flown with & trained for they all followed the meteorite re-entry procedure all the way to 10,000'. There was never any discussion about other options/techniques. There was never any discussion about what to do if MSA was >10,000', other than level off at MSA. There was never any discussion about facts learnt from real-life encounters, even in their own company. Perhaps, due to this lack of discussion, there are even occasions where there has been a full-blown 02 emergency descent made from FL130?
It was always nose dive earthwards ASAP. No ATC coordination.
I was very glad to hear ICAO are reviewing the whole Crew-ATC coordination procedure and are considering recommending a single worldwide protocol. Finally.