Loss of Thrust Both Engines at 35,000 ft in 737 Classic simulator.

[Centaurus]

Question. B737 Classic simulator. Assuming Loss of Thrust Both Engines at 35,000 ft. the cabin will lose pressure due to leakage. What would be the expected cabin rate of climb with both engines failed?

[BizJetJock]

I can't speak specifically for the 737, but other types where maintenance/acceptance check flights have included a leak rate test have had 2000fpm as the maximum acceptable.

[BARKINGMAD]

Following the practice of sensible airmanship and bearing in mind the Payne, Helios and the recent Cuban coast accident, I think as my ears and more enthusiastic venting of wind alerted me to the cabin RoC, I would be getting onto oxygen & establishing comms with my oppo as a priority before the hypoxia and decompression sickness became an issue.

If I had the capacity to note the cabin RoC for the hopefully submitted ASR, I would not expect any credit for this information.

And if it occurs in the simulator, who give a , as long as you carry out the appropriate actions?

Or is some TRI making a point for his/her own benefit?

[BOAC]

In real life it all depends on how leaky the tub is, so you can select what you like for the sim detail. We had a 737-500 in BA that leaked so badly it would not pressurise after take-off on 1 pack!.

[Centaurus]

And if it occurs in the simulator, who give a , as long as you carry out the appropriate actions?

Or is some TRI making a point for his/her own benefit?

On the latter comment, the answer is not in the slightest. On the former comment a reply to that is unnecessary. The reason for the question is that as a simulator instructor about to inflict a dual flameout or Loss of Thrust of Both Engines at high altitude, it behoves a competent instructor to thoroughly brief the students (or candidates) on what to expect and what to look for. Loss of thrust at high altitude is no laughing matter and things can happen rapidly. It is a training exercise - not thrown into the deep end as a test.

Because there will be a steady leaking of cabin air with both engines shut down at high altitude, most pilots under training would like to know whether the leak is like a rapid decompression or whether a lot less urgency. Trying to re-start an engine at high altitude when both have run down, as well as coping with a rising cabin altitude, is a high work load event to say the least. Any allied information that could aid the pilot in the decision making process would therefore surely be helpful. Hence the original question about expected rate of climb of cabin altitude following a double flame-out in a 737.

[BOAC]

......and the answer is 'how old is your piece of string'?

[de facto]

If you have loss of thrust on both engines,you follow the memory items to relight and all what you were taught(capt flies,fo does his share),NNC.......plus you need to keep on eye on the pressurization...if you expect it to reach 10000,Don o2 mask and if 14000 pax o2..simples.

[PEI_3721]

This situation is a good CRM exercise – knowledge, situation assessment, decision making, and action; manage the surprise of the situation which might not be detected until the cabin alt warning goes.
AFAIR the acceptable leak rate for an air-test was ~2000ft/min.
My last type required a descent for a relight, thus commence aircraft descent at 1000ft/min (FL300-250) – 5min, but cabin rising from 8000ft towards ambient at 2000ft/min – 3 min before 14000ft pax O2 action required. However, as the aircraft descends the change in pressure differential may reduce the leak rate, and there might be an opportunity for the APU to supply air.

Crew O2 early – less you forget. If time, consider why both engines should go out at the same time (if only to discuss with the instructor during debrief as to what he considers relevant to creating the situation).

[Denti]

(capt flies,fo does his share)

Would guess that depends on airline, we removed that automatic transfer of control quite a few years ago.

Apart from that i would agree, main issue is to relight at least one engine, pressurization is a secondary problem. And yes, our simulators show around 2000fpm cabin rate in that case, doesn't matter if it is the classic or NG. In reality i would expect higher leak rates on most classics though.

[framer]

I think as my ears and more enthusiastic venting of wind alerted me to the cabin RoC,

I guess that may happen but it hasn't been my experience. With two engines out your brain will be doing a fair bit of processing with regard to the immediate situation and I doubt any signals from your ears will get priority handling, especially at only 2000fpm.

[FlightDetent]

I respect this is originally a sim question. Yet perhaps, can someone of the knowledgeable bunch provide AMM limiting values for a seal/leak check?

[tom775257]

One of our A321s on an acceptance flight showed 5000'/min with both packs off!

[flyingchanges]

If you have loss of thrust on both engines,you follow the memory items to relight and all what you were taught(capt flies,fo does his share),NNC.......plus you need to keep on eye on the pressurization...if you expect it to reach 10000,Don o2 mask and if 14000 pax o2..simples.

Seeing as how your starting at a cabin altitude of 8,000 feet, I would say both of these are an absolute given.

[Down Three Greens]

On the A320 and A330 it is about 700 fpm...packs and bleeds offs

[de facto]

Seeing as how your starting at a cabin altitude of 8,000 feet, I would say both of these are an absolute given.

Pedantic but 35000 feet doesnt give 8000 ft of cabin altitude

Denti,
The left seat taking over controls is indeed a company SOP but with both gens off line during your attempt at a relight, i would think the left seat is the most sensible option to take over the flying unless obviously the right seat not being familiar with his memory items

[FlightDetent]

DTG: you run a very tight ship

Meanwhile, anybody yet with AMM airworthiness limit ?

[Skyjob]

During a ground leak test the pressure decay from 4.0 to 2.5 PSID takes 4-8 minutes; within this time with BEST performance, 4.0-3.0 takes 60 seconds, 3.0-2.5 a further 40 seconds.

[FlyingStone]

AFAIK most companies use 2000ft/min on acceptance checks, since the higher the leak rate, the more packs have to work to maintain cabin pressure, the more fuel the aicraft burns...

[Snakecharma]

Here in lies the difference between some sim exercises and reality.

What is going to cause a double flame out at cruise altitude? No fuel would be the obvious answer. Ice maybe the next option.

Other than that I can't think of anything too obvious that would cause the double flame out to occur.

A mechanical problem is unlikely to occur on both engines at the same time - the statistical probability of that is so remote as to make it not worth considering. (I suppose you could add in oil leak due to a servicing error - both engines being done at the same time by the same person making the same error - as happened on a 737 a few years ago, but if I recall correctly the oil ran away fairly quickly and it didn't make it to cruise, let alone sit there at 35 grand).

So if it is fuel, then you have run out - in which case you won't get a relight. Maybe the pumps have failed - but again the chances of more than one independent mechanical device failing at the same time is remote.

The fuel could have gone waxy due to extremely low temps - in which case an immediate relight isn't going to happen.

It could be intake icing due to gross mishandling - extended period in icing conditions without selecting engine anti ice. Again an immediate relight isn't likely to be successful.

So, what am I getting at?

I am not sure that the focus should be on getting an engine running again as the first priority. My thinking would be to make sure that you stay alive and not go hypoxic, don't get too slow and manage the flight path such that the aeroplane is controlled and heading in a helpful direction.

737's that I have done acceptance tests on (both ex factory and lease return) have shown leak rates around the 1800-2000 ft per minute mark, so you are not too far off a cabin altitude above 10000 ft.

The point is - don't rush and have a think. There is plenty of time before you hit the ground, you have a little time before your cabin altitude exceeds 10000 ft, just manage the aeroplane and people in it and manage things that come up as they come up.

[grounded27]

The greater factor is going to be DP, say you are at 8.6 psi @ 35K, your leak rate will slow exponentially as your cabin pressure decreases and as you descend the pressure outside increases. Descending through 20k you may be holding a much more comfortable cabin altitude with a slow Ft/MIN decay.