BOAC - Just answer the question. You either provide O2 or you drop down and fly lower the rest of the way...will a 737 do it or not. Simple question..no fencing, no debate, no arguments, no dancing..pull out your book...you either know or you don't.

40 posts later....

The B737 will, of course or it wouldn't be dispatched; simple as that. And, it will at FL 100.

GF

You pretty much described ETOPS fuel: Fly to the CP, have a decompression, drop to 10,000 and continue to the destination. No secrets.

when reality hurts (it just has!) - the answer was in the SECOND post. If you UNDERSTAND ETOPS you will know we need more information in order to answer the question properly . If you don't you are simply wasting our time.:ugh:

Imbracable Crunk:

Wouldn't diverting to the ETOPS diversion airport be more appropriate?

I wasn't digging for exact regs, just that, yes you can have a decompression, descend, and make it to an airport. I guess it's good I'm scheduled for an ETOPS refresher next week.

Since US west coast to PHNL is the conversation here, returning to departure or continuing to destination is pretty much the same thing.

Aterpster:, yes, KSBA to PHTO is the shortest and might be a better example but not a lot of difference

GF

One tech question: Is there such a thing as partial decompression? That is, You're unable to maintain normal cabin altitude at cruise, but say you descend to FL150 and find that cabin altitude holds steady at 8K. Would you continue in that condition? Or would you go on down to FL100?

g.f.

KSFO to PHTO is 2,013 n.m.
KSBA to PHTO is 2,065 n.m.
:)

As I said previously I only flew KLAX-PHNL-KLAX.

Once KSFO became closer than KLAX we were to divert to KSFO prior to the ETP. After the ETP we were required to divert to PHTO until PHNL became closer than PHTO.

Descending at max speed
 

Quote: Question: Why does the descent have to be at max speed ? Why risk a structural overspeed instead of a low-speed stall ? Surely the RoD is more important to get down to 10,000' asap ?

e.g. A320 QRH Emer Descent : "Descend at the max appropriate speed."
e.g. B737NG FCTM Rapid Descent : "Target speed MMO/VMO".

Explanation appreciated.

Hi Reverse Flight
I hope that someone else has not already answered this, if so, I hope that mine is on a par with theirs.
With reference to ETOPS/EROPS, twins will be certified to x amount of minutes e.g. 120, 180 min etc. This then equates to a radius circle of x amount of nm drawn around their suitable/adequate en-route alternate aerodromes. This distance, if published, is normally base on a descent at a certain speed, normally max or high speed, followed by en-route at a certain speed using, for example, MCT if OEI. In other words, in order to achieve that distance, within the certified time, we would need to fly at the published speeds. Other than the above, there are the other concerns which have already been mentioned e.g. depressurization and need to descend to oxygen system limiting altitude etc. Hope that I have put my thoughts down correctly and that it helps.

Davidjh

An emergency descent is at Vmo/Mmo, regardless of whether you are ETOPs or no.

OEI might be different matter. For OEI in ETOPS = go fast. OEI in mountains = driftdown.

No way!! Sometimes you need to descend slower.

An emergency descent is at the max "appropriate speed". If there's a big bang that might be relatively slow but it might also be Vmo. Judgement Captain!!

Were there to be structural problems, known or suspected, the descent speed would be slower than Vmo.

Your (small) ace is to turn to your diversion airport during the emergency descent when close to DPD.

It's called "airmanship".

Yeah, yeah. That's all in the QRH and POM and FCTM. That doesn't change a quarter of the way over the Pacific or a half way across Kansas.

Mad (Flt) Scientist, davidjh and mustafagander : you're all correct, and thanks for your guidance. Glad to learn something new everyday. :ok:

Are you sure about this? Look at an ETOPS manual, take the TAS @ 10,000 ft and multiply it by your approval time, i.e. B772 375 TAS x 2 hours = 750 nms..... but the area of operation is 840 nms, how come?

Why?

Whenrealityisapain.... what would you do if you couldn't descend to a low enough altitude for normal breathing, would you increase the amount of oxygen on-board, and if so, how?

Mutt

So you can the Maximum Diversion Distance according to my manual.

Two points:

Descent speed is not relevant to ETOPS operations, nor is actual speed flown during a diversion..

There is no regulatory limit on actual distance to a diversion when it happens

For whatever reasons that are currently above my pay grade, my company has elected M.79/310k as ETOPS driftdown speed. The manual cites the 180 minute limitation. It also states the Captain may change the speeds flown.

Your results may vary.

The messenger.

Just because your 'company' "has elected M.79/310k as ETOPS driftdown speed." does not affect how you fly it. That IS your 'pay grade'. If your tail is about to fall off after a bomb, I would suggest less than 'M.79/310k' might be wise?

BOAC,


As I wrote previously regarding Emegency Descent speed: Emergency descent =/= OEI Driftdown.