'Contact lost' with Malaysia Airlines plane

[danlightbulb]

Hypoxia.

Here's the link:

Reddit - Dive into anything

www.reddit.com

Thanks.

Is this actually possible?

He then reaches again for a different set of cockpit controls, on the pressurization panel, he turns the OUTFLOW VALVE switches both to MAN, and the OUTLFOW MAN switches both to OPEN. Immediately Flight MH370 begins to rapidly bleed it's life giving internal pressure, and more importantly life sustaining air, from inside the passenger cabin and cockpit.

Perhaps our resident airplane pilots can confirm this, because it seems very strange to me that it could be so easy.

 

[esmozz]

Yeah - it is actually that easy.

 

[danlightbulb]

Yeah - it is actually that easy.

I am genuinely shocked that there is manual control over that.

 

[Trig]

Would a loss of cabin pressure not drop the masks?
Or is there a manual shut off for that as well..

 

[danlightbulb]

Would a loss of cabin pressure not drop the masks?
Or is there a manual shut off for that as well..

According to the reddit fictional story, the masks would drop but only have a 15 minute oxygen supply.


...Im still gobsmacked that the cockpit crew have the ability to oxygen starve the main cabin. Why in the hell would it be designed that way is beyond me.

 

[esmozz]

Would a loss of cabin pressure not drop the masks?
Or is there a manual shut off for that as well..

Yes - the masks should automatically deploy once the altitude in the cabin exceeds 14000ft. It might be possible to disable this function by pulling a circuit breaker in the cockpit but I'm not really sure - its not something I've ever considered needing to know how to do.

 

[Trig]

According to the reddit fictional story, the masks would drop but only have a 15 minute oxygen supply.


...Im still gobsmacked that the cockpit crew have the ability to oxygen starve the main cabin. Why in the hell would it be designed that way is beyond me.

I've not read the reddit thread tbh..

As for shutting off oxygen in the cabin, perhaps for some last ditch fire suppression? Passengers mask up and you vent the cabin.

 

[Trig]

Yes - the masks should automatically deploy once the altitude in the cabin exceeds 14000ft. It might be possible to disable this function by pulling a circuit breaker in the cockpit but I'm not really sure - its not something I've ever considered needing to know how to do.

Might I suggest not checking it the next time you are in a plane, I suspect trying to explain why to the boss would probably raise some eyebrows...

 

[Penfold101]

According to the reddit fictional story, the masks would drop but only have a 15 minute oxygen supply.


...Im still gobsmacked that the cockpit crew have the ability to oxygen starve the main cabin. Why in the hell would it be designed that way is beyond me.

Pressurisation failure - no point in having all the systems operated by computer without a backup in case you have a sensor or valve failure for instance.

Masks will drop if the cabin altitude drops below 10,000 ft or so. Pilots also have a limited supply of oxygen, and the cockpit is connected to the main cabin anyway, so if the air pressure drops there then it does for the pilots too.

Also, if you go back to the days of earlier aircraft without computers, this was all controlled manually by the Flight Engineer anyway, operating the outflow valves against the airflow from the engines to increase or decrease the cabin altitude at a comfortable rate.

 

[mid_gen]

...Im still gobsmacked that the cockpit crew have the ability to oxygen starve the main cabin. Why in the hell would it be designed that way is beyond me.

Because ultimately, whenever you board a plane, you place your life in the hands of the professional pilots in control of the aircraft.

There are innumerable ways they could intentionally or otherwise kill everyone on board. If a pilot goes bad...well you're **** out of luck and no amount of safeguarding is going to stop bad things happening. Fortunately it very, very rarely happens.

 

[esmozz]

According to the reddit fictional story, the masks would drop but only have a 15 minute oxygen supply.


...Im still gobsmacked that the cockpit crew have the ability to oxygen starve the main cabin. Why in the hell would it be designed that way is beyond me.

It designed so that in event of failure of both the automatic and standby pressurisation systems the crew can try to keep the cabin pressurised using direct control of the valve that controls the pressure. (I've had to do it a couple of times and its a right pain in the ****)

Also - as the aircraft descends the valve tends to open to depressurise the aircraft, upon landing it should drive fully open. If you were planning to land on water however you would want to manually close the value just prior to touchdown to stop the aircraft flooding.

 

[Lysander]

Also - as the aircraft descends the valve tends to open to depressurise the aircraft, upon landing it should drive fully open. If you were planning to land on water however you would want to manually close the value just prior to touchdown to stop the aircraft flooding.

Indeed, and in the story he fully opens the valve to let in as much water as possible.

Captain Shah then goes down the checklist he has brought with him, and makes a few last setting changes on MH370. He opens the same outflow valve he had used so many hours ago, and ensures that the APU is set to maximize water ingress and allow water to quickly enter the plane after it has ditched, hoping that the plane will sink quickly, should it somehow remain mostly intact upon landing. He sets the gear and the terrain override switches to OVRD.

Now this is interesting, so the story does mention the landing gear. What good is setting that switch to override going to do?

 

[esmozz]

Indeed, and in the story he fully opens the valve to let in as much water as possible.



Now this is interesting, so the story does mention the landing gear. What good is setting that switch to override going to do?

It simply disables the warning systems (EGPWS - Enhanced ground proximity warning system). It's basically a system that calls out 'TOO LOW, TERRAIN' or 'TOO LOW, GEAR' if the aircraft thinks you are descending into the ground or too low without having the gear extended. With those two cases thats all the system does but it can provide a whole range of warnings and guidance if necessary in other situations.

To be honest the reddit thread is completely fictional with some fairly big problems in its narrative - its probably best not to read to much into it.

 

[Allnamestaken]

Shattered?
Planes arent made of glass you know...

There are certain models and tests that have been done that will, within a certain degree of error, show how things happened based on what they know from the bits they have found so far.

I've heard that word used to describe the way the plane breaks up when planes hit the ground at very high speeds approaching mach 1, the way the impact destroys the plane etc.

lol