DenverBrian

Pressure that drops gradually, though - sufficient alarms for that? It seems that the insidiousness of pressure falling over many minutes, without big fat warnings as it's occurring, could lead to situations like Payne Stewart's flight.

username

I have some questions...

1 - do they have time to clear with ATC when they do the rapid descend? If not, it is a visual thing to avoid other aircraft?

2 - the pilot wearing mask thing - I guess they really don't need to unless the cabin pressure is certain altitude or above?

3 - I have once been delayed on a flight when they said the oxygen thing did not work. I guess they do serious check these things before departure - both the pilots and the FAs in the cabin? (Seeing how "thorough" some FAs do the safety check, I kind of worry..)

4 - I was once on a UA A320 which developed a loud humming noise once we got above a certain altitude. People said it was an air leak. The plane just kept flying with the FA denying anything was wrong. I guess somehow the system still checked out and there was no need to divert? (The humming noise was terrible though.)

Thanks.

DenverBrian

Humming could be from some slightly loose part on the exterior creating a resonant frequency at the right speed and pressure.

djmodifyd

1. They can declare an 'emergency decent' to ATC and just start descending. ATC will move other aircraft out of the way. Usually, though, the pilots will state they need to decent immediately and wait for the controller to say it is ok first rather than just descend.

2. they wear it in CASE the cabin altitude climbs. Well that is why they are supposed to wear it. Not because they need it at the current cabin altitude.

3. the O2 is def an MEL item.

4. ??

JSprague24

I'd long wondered about that. Thanks for the explanation!

Xeno

I am using ATH as a hub for going on to IST then back to ATH over to CHQ and finally back to USA via CDG-DTW on a 763.

I have not been able to keep up on media reports due to flying almost every day + appointments and making a presentation at an international conference.

I just asked DM line about this incident and the number I was given was for media only who in turn sent me to the corporate office number that only functions M-F.

I take it this is an isolated incident that has not triggered a review of like aircraft flying international routes, right?

jrl767

so far, that appears to be the case

HKG_Flyer1

Also, if this wasn't done, it would be impossible to open the A/C doors upon landing, as the pressure inside the plane would exceed the pressure outside, and plane doors are designed in such a manner to utilize such pressure differentials to help prevent doors, emergency exits, etc. from being able to come open during flight.

flyerCO

The pressure inside can still be higher than at ground when get to gate. Most aircraft have warning lights to alert crew. Airbus Warning info

This on top of ensuring door is disarmed is why GA waits for a thumbs up before opening door.

WillSkiGT

The Learjet Payne Stewart was on didn't have a low cabin pressure alarm. They were added post-accident.

All major commercial aircraft have them - the issue on the Helios flight was that the aircraft was climbing and the pilots were becoming increasingly hypoxic as the alarms were going off, so they couldn't think straight to understand what the alarms were telling them. The mechanic who worked on the aircraft right before the flight basically diagnosed the problem and asked the captain if he had checked if the bleed valves were open (they were set to manual instead of auto). Unintelligible response from the captain was the last ATC transmission.

jebr

The article made it to their website: https://kstp.com/news/two-delta-air-...dings/5500200/

vinnmann

This is probably a stupid question with hopefully a simple answer. Hypoxia is defined as an oxygen deficiency in tissue. If there is a rapid decompression, it is said that you can lose consciousness in a few seconds (5 or so). If I can fully exhale and not inhale for 30 seconds and not develop hypoxia, how will 5 seconds of no air during decompression cause hypoxia?

jeet

When you are in 'oxygen rich' environment - at sea level or well acclimatized at any altitude, your body is used to the conditions and holding your breath for 30 secs to a minute will not cause any adverse efftect.
But hypoxia due to rapid decompression is different as your body doesn't get time to get used to it. On top, not only lungs, but body tissue and blood also release oxygen as they can't hold on to it due to lower pressure and that affects brain function first - 'cerebral hypoxia'