Explosive decompression/auto descent??

[ZQA297/30]

Staying away from any speculation on the B737 accident, how hard would it be to engineer a "loss of pressurisation" mode in modern autopilots?
If cabin pressure sensed above (say) 15,000' for more than 60 seconds, or 30,000' for 30 seconds, with no "horn cancel" from pilots, auto squawk 7700, wait 30 seconds, turn off airway, and start auto descent to a safe altitude for the sector.
No need to get bogged down in the details here, just airing the general concept for discussion.

[wiggy]

What level are you going to descend to?

[ZQA297/30]

How about 10,000', or MSA for the sector/area, whichever is higher?

[Pointer]

should not be too difficult hooking the EGPWS data base into the FMC...? But this means taking a chance of the automation doing something you might not want?

General, following procedures, they "should" lead you to a descent even if you don't use Ox so you level-off and regain consiousness? But that offcourse is second guessing....



My thoughts are for the families who lost their lovedones...

Pointer

[ZQA297/30]

The presumption is, that after waiting a decent while for a pilot response, no response probably means that the pilots are"out of it". If the are aware, they can cancel any time.
On the other hand, getting down to breathable air should bring the pilots back into the loop, hopefully once they get back below 20/25,000'.
Not sure how long it takes to regain consciousness at 20,000' after a spell at "over 350".

[FoxHunter]

I believe an auto descent system is available in some business type aircraft.

[GlueBall]

How about just properly checking the cockpit oxygen masks and supply, and checking the cabin altitude warning system...instead of building a 3rd system to correct failures: 1 (pressurization) and 2 (oxygen). :ouch:

[Blacksheep]

Provided they are operating correctly, the current precautionary systems should provide adequate protection. It makes no difference whether decompression is rapid, or slow and insideous. As cabin altitude reaches 10,000 feet a warning should sound, and at a cabin altitude of 13,000 feet oxygen masks should auto-deploy. Accidents like the golfer's business jet must be the result of cascade failures.

In the Helios incident, speculative reports suggest that the pilots were incapacitated while some at least of the passengers were conscious. Many of the victims recovered from the crash site were reportedly wearing oxygen masks. Among several other possible cascade failure explanations, the one that would best explain why the crew did not initiate a descent would be that they received no warning, failed to don oxygen masks and passed out. If I were to suggest any modification, rather than have a system that overrides both the AFCS and the crew to initiate a descent, it would be to include redundancy into the cabin pressure warning system. Just thinking of the possible failure modes for an auto-descent system makes me tremble...

[ZAGORFLY]

I am glad that you are offering some more valuable advise to this forum.

As many of us know if an airbus override the TOD an EICAS message is trigged. How difficult and expensive would be to have a EICAS link with the Autopilot and start a desend if no action from the crew are detected within 30-60 sec. ?(for this kind of emmergency) Regarding where to go we would let the IRS to guide the plane where there are no objects at 10,000 .
This would create at least a more survivable enviroment for somebody else to intervene and at least to confirm the emmergency in board by radio receiving maybe valid instruction to bring the plane close to a point/speed/configuration that will enable the AUTOLAND,
what do you think? Hollywood science?

I just hope that this forum will not serve for a show of intelligence and aviation knowledge but will promote safety. I hope that some body will ask the industry to act to avoid that a even very low probability of double incapacitation will occur a third time.

[Grunf]

If I might say,

you would rather like to avoid "explosive" decompression (rapid as well) since that can be a nice signal of structural failure.

Discussion is OK as long as everything is within the "envelope". Explosive, or better, rapid decompression is accounted for but still it has its regulations guided limits.

Cheers

[flyburg]

Just out of curiousity,

I had been told that the concorde had exactly such a system installed. taking into account that with an explosive decompression at 60.000' there's no way you could put on the mask's in time. Does anybody know if this is in fact true?

Thanks.

[Flight Detent]

Hi Guys,

I understood the Concorde had this feature already installed because of the altitudes it operated, though not sure of the details.

Cheers, :zzz:

[Bumz_Rush]

both have the system, given certain pre conditions, basically AP in, and over 41000....not used it yet....hope never tooooo....Bumz

[jaja]

the CESSNA CITATION 3 has an Automatic Descent Mode function.

If AP on, altitude >35000`, cabin altitude > ~12000`, then the ADM function kicks in.
That means A/C turns 90 deg. left, and descents at MMO/VMO to 15000`. Only thing you have to do, is throttles to idle, and extend the speedbrakes.

Fantastic system, should be on all jets !

[mustafagander]

I don't think I would like it much jaja, when our MSA is FL220 and our escape route requires fairly precise tracking. Have a look at route L888 for starters.

[jaja]

"I don't think I would like it much jaja, when our MSA is FL220 and our escape route requires fairly precise tracking. Have a look at route L888 for starters."

Well, the ADM system on the CITATION is not new. With todays EGPWS, is should not be a problem. Just let database of the EGPWS "talk" to ADM system, to keep you safe in those few areas where FL150 is to low.

[SLFguy]

Why the 90 degrees left?

[Bunk-Rest]

Oh please ................... .

[SLFguy]

"Oh please.........."


Yet another helpful intelligent response....

[Confabulous]

SLFguy,

The aircraft turns 90 degrees for one reason - jets normally route via airways, or 'motorways in the sky'. If you just descend straight ahead there's a good chance you'll have a midair or a near miss with an aircraft below you going in the same or the ooposite direction. Turning 90 degrees takes you off the airway and (hopefully) into less busy airspace.