Auto Descent following high Altitude Pressurisation Failure

[Centaurus]

It is clear that the Helios 737 accident involved a loss of pressurisation. Do any of the high level cruise corporate types (Global 500 for example) have an automatic pilot descent function based on sudden loss of pressurisation with accompanying delay in crew response to electronic warnings? If so, how does it work?

[LEM]

No airplane could incorporate that feature.

Too many pilot's input overrides necessary.

Too many risks associated with an unwanted activation.

You auto descend, then what?

We MUST assume there are alive pilots, in an airplane, otherwise the battle is lost anyway.

The challenge is having PROFESSIONAL pilots in the cockpit who behave in a PROFESSIONAL way.

You don't check your oxy valve?
Go home.

You don't check your pressurization AT LEAST at 10000ft?
Go home.

You don't know the recall items for the Cabin altitude warning?
Go home!

Auto descent?
The next step is to remove the pilots and control from the ground a fully automated airpl-fully automated airpl-fully automated airpl-fully automated airpl-fully automated airpl...

;)

[oldebloke]

Cent' yes these days the Emergency descent is performed on AutoPilot..WITH posative initial inputs by the Crew.(selecting Alt change/flt level change,idle power,once the nose down selecting SpeedBrakes,ATC,PAX, etc),all after the crew have donned the airhats..:ok:

[BizJetJock]

Errm, actually LEM several corporate models that I fly have exactly that system. If aircraft altitude is above 35k and cabin altitude reaches 13.5k then the autopilot goes into EMER DESC mode with associated red warnings. It turns left approximately 90 degrees, flies VMO/MMO -10kts and levels at 15000 feet. However without autothrottles the descent will take a very long time if nobody closes the throttles and/or extends the speedbrakes:hmm:

[jaja]

CENT, the CESSNA CITATION 3 have got an Auto Descent Mode, which activates in case of a decompression.

[Max Angle]

Got to be a good idea, if one of the pilots is still alive and kicking then they would do it themselves anyway, if they are both out cold it can't make the situation any worse.

[Capt Claret]

A question.

How does the pilot who performs the safety equipment check, including O2 on, know that the O2 is on?

[LEM]

Well... I'm amazed.

BizJetJock, those gadjets are typical of small bizjets... and as you say, without autothrottle the airplane will never descend.

:hmm:
However, that's quite interesting... I hope someone will provide more details on this feature, aircraft type etc...

Thanks

ps CaptClaret, he turns the oxygen valve on, if closed, then half tour back, as all divers know...

[Captain Stable]

...then check the gauge, check flow to the masks making sure as he does so that the pressure on the gauge doesn't drop. Ensure the microphones in the masks work and the switchover from boom to mask (whether manual or automatic) works, and that the masks are set to 100% O2 and flow set to normal.

[LEM]

Hi Captain Stable, unfortunately Mr.Boeing designed a dangerous trap for hs jurassic jets...

The gauge indicates pressure before the valve we have in the cockpit.

If the valve is turned closed, even depleting the line after the valve with several mask tests, will not move the indication at all.

And you know what?

Even if you make a good mask test, that doesn't mean the valve is open!

I personally managed to get TEN FULL MASK TESTS WITH THE VALVE FULLY C L O S E D, before the pressure in the line between the valve and the mask depleted.

Also, if the valve is almost completely closed, that means not very tightly, the line after the valve will slowly refill, giving the impression that there is pressure at the mask.

BUT if a pilot actually used the mask for breathing, the result will be NO FLOW.

B737 pilots BEWARE!

If all of us took a scubadiving course, that would be quite useful...:E

LEM

[LEM]

...as I'm still skeptical on this auto descent feature, I'd like to ask again (jaja for example) how that exactly works.

Is that really an Auto Descent (that means WITHOUT TOUCHING ANYTHING) the airplane will do it all alone, or is it just an aid that maybe "suggests" a heading, lower altitude etc... but can't actually close the thrust levers and so on...


Come on guys, enlighten us!

[Mad (Flt) Scientist]

I understand that at least some systems are truly automatic - provided the aircraft was on autopilot, it will engage a descent mode and - unless the crew stop it - will turn and descend as indicated. Not sure if the autothrottles will also retard, guess it depends on the AP/AT coupling in place. (They were testing it on one aircraft while I was there, but can't recall the details).

But the intent is that the aircraft gets down, on its own, to an altitude where the crew hopefully can regain consciousness, and does so in a way that is reasonably safe regarding speed limits, other traffic, etc. Certainly it's better than nothing, since we've seen what "nothing" leads to ....

[BIG//40/FL260]

On the Gulfstream V series, on activation of the cabin pressure low warning whilst operating with the autopilot and autothrottles engaged above FL400, the aircraft will turn left 90 degrees, power levers will retard to idle and the aircraft will descend at Mmo/Vmo to FL150 whereupon it will level off and maintain a speed of 250kt. The efficiency of the process is marred only by the lack of automatic control of the spoilers.

[ICT_SLB]

The GEX & GEX5000 both have the same system operating & triggered in the same way as the GV but it's a relatively new feature (beleive we tested it about 18 months ago) so it may not be on all aircraft in the fleet.