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Flight MH370 Depressurization Scenarios

Melbury's Brick

Senior Member.
Video report from Sky News....
http://news.sky.com/story/1224061/flight-mh370-13-things-you-need-to-know


It was aired today. Unlike most on this site, I hate flying and spend the entire journey hanging on to the headrest of the seat in front of me with white knuckles! My only interest in aircraft is that they get me where I want to go in one piece, so I'm not qualified to comment about Sky's video. It's really just another chunk of speculation.
 
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Mick West

Administrator
Staff member
Video report from Sky News....
http://news.sky.com/story/1224061/flight-mh370-13-things-you-need-to-know


It was aired today. Unlike most on this site, I hate flying and spend the entire journey hanging on to the headrest of the seat in front of me with white knuckles! My only interest in aircraft is that they get me where I want to go in one piece, so I'm not qualified to comment about Sky's video. It's really just another chunk of speculation.

They suggest there was a cabin depressurization. The pilots attempted to set the autopilot heading for back to Kuala Lumpur, but then passed out. So the plane flew until it ran out of fuel, somewhere in the middle of the Indian Ocean. The passengers would be on their oxygen masks for 15 minutes, then would pass out. Everyone would be dead, and the plane would continue flying.

It seems pretty clear that the plane did not just blow up, or crash where contact was lost. This explanation is not impossible - but still just one of several possible explanations.
 

Hama Neggs

Senior Member.
Wouldn't it take several minutes before the pilots passed out? They would have had to be preoccupied with more tasks than just dialing in a new heading.
 

Mark Barrington

Active Member
They suggest there was a cabin depressurization. The pilots attempted to set the autopilot heading for back to Kuala Lumpur, but then passed out. So the plane flew until it ran out of fuel, somewhere in the middle of the Indian Ocean. The passengers would be on their oxygen masks for 15 minutes, then would pass out. Everyone would be dead, and the plane would continue flying.

It seems pretty clear that the plane did not just blow up, or crash where contact was lost. This explanation is not impossible - but still just one of several possible explanations.
I don't know, wouldn't they first try to get to a low enough altitude to breathe before trying to set the autopilot? Is there some sort of scenario where the pilot's oxygen masks would not have been available?
 

WeedWhacker

Senior Member
Wouldn't it take several minutes before the pilots passed out? They would have had to be preoccupied with more tasks than just dialing in a new heading.

ALL pilots know that the immediate action in a decompression is to don the O2 masks. It's a "memory item" on the checklist. All pilots know of the brief time of useful consciousness at high altitude.



That Sky News video? The "former" airline pilot just wanted his 15 minutes of "fame", apparently.
 

Mick West

Administrator
Staff member
Here's an incident where they did not put on the masks, and the plane just kept flying:
http://en.wikipedia.org/wiki/1999_South_Dakota_Learjet_crash
http://www.ntsb.gov/doclib/reports/2000/AAB0001.pdf
 

WeedWhacker

Senior Member
Is there some sort of scenario where the pilot's oxygen masks would not have been available?

No, highly unlikely. Again, the first action is donning masks...they are a "quick don" design, can be swiftly grasped and placed on the head with one hand.



For a rapid decompression at high altitude, the masks are first, it is

"Oxygen masks ON, 100%"
"Communications, establish"

(That's verifying 100% O2 setting, and communication on the Interphone, and over the speakers, for the pilots to talk and hear each other).

An emergency descent must be initiated next, first the determination of whether or not there is structural damage. If damage is suspected, then the current airspeed is maintained, and not exceeded during the descent (this presumes that any increase in airspeed might be dangerous). If no structural damage is suspected, then the airspeed is allowed to increase to Mmo/Vmo, in order to achieved maximum rate.

This must be done with alacrity, since as mentioned, the Pax O2 only lasts about 15 minutes.
 

Mark Barrington

Active Member
ALL pilots know that the immediate action in a decompression is to don the O2 masks. It's a "memory item" on the checklist. All pilots know of the brief time of useful consciousness at high altitude.



That Sky News video? The "former" airline pilot just wanted his 15 minutes of "fame", apparently.
The Sky News video mentioned a scenario where the oxygen system for the pilots malfunctioned on a Helios airline flight in 2005. That's barely plausible. Still, it seems more likely they would be concentrating on losing altitude than setting the course back towards the point of origin.

I think this theory is unlikely, but if it were true, the new search area would be so far from anything that it might be just about impossible to find the plane. Doesn't the U.S. have an airbase in the middle of the Indian Ocean?

Edit: Diego Garcia: http://en.wikipedia.org/wiki/Diego_Garcia (and it's British, not U.S.)
 

Mick West

Administrator
Staff member
And another with a 737, thought to be a gradual decompression due to flight crew errors with the pressurization system. Again the plane continue to fly
http://en.wikipedia.org/wiki/Helios_Airways_Flight_522
It seems very unlikely. But clearly something very unlikely happened. I just hope we find out what.
 

WeedWhacker

Senior Member
The Sky News video mentioned a scenario where the oxygen system for the pilots malfunctioned on a Helios airline flight in 2005.

Actually, the major malfunction on that Helios flight was Human...both pilots mis-identified a cabin pressurization problem, and never even donned their masks!

http://en.wikipedia.org/wiki/Helios_Airways_Flight_522

That was a 'comedy" of errors...except it turned out tragically. They heard the cabin altitude warning, and thought it was the takeoff Config.
 

Mark Barrington

Active Member
Actually, the major malfunction on that Helios flight was Human...both pilots mis-identified a cabin pressurization problem, and never even donned their masks!

http://en.wikipedia.org/wiki/Helios_Airways_Flight_522

That was a 'comedy" of errors...except it turned out tragically. They heard the cabin altitude warning, and thought it was the takeoff Config.
You're right, of course. I was confused by how the incident was described in the video, which seemed to indicate an equipment malfunction, not human error.
 

Mick West

Administrator
Staff member
Actually, the major malfunction on that Helios flight was Human...both pilots mis-identified a cabin pressurization problem, and never even donned their masks!

http://en.wikipedia.org/wiki/Helios_Airways_Flight_522

That was a 'comedy" of errors...except it turned out tragically. They heard the cabin altitude warning, and thought it was the takeoff Config.

The analysis here a fascinating read. Page 112 (pdf 124) on:
http://www.aaiasb.gr/imagies/stories/documents/11_2006_EN.pdf

Apparently they did not put on their masks, as they did not realize they were needed.
 

Melbury's Brick

Senior Member.
The analysis here a fascinating read. Page 112 (pdf 124) on:
http://www.aaiasb.gr/imagies/stories/documents/11_2006_EN.pdf

Apparently they did not put on their masks, as they did not realize they were needed.

Which supports the point that people in any occupation can do the wrong, and sometimes inexplicable thing no matter how thorough their training. The idea someone "wouldn't have done this" or "wouldn't have done that" because they are trained pilots, or policemen, or emergency service personnel etc. is a cry we often hear from conspiracy theorists.

(Thanks Mick, for embedding the "Sky news" video. I couldn't make it happen for some reason.)
 

TWCobra

Senior Member.
The crew of MH370 reached FL350 and was beginning stable cruise. They replied to an instruction from KL ATC to switch to Ho Chi Minh ATC. That was the last transmission.

The Helios crew were climbing with numerous warnings going off, that they failed to interpret correctly. The 737 climbs fairly rapidly and the cabin never pressurised.

If the 777 had a pressurisation problem, a large red "Cabin Altitude" message would have appeared on the EICAS screen followed by the same alarm you get when an engine catches fire. As Weedwhacker says, the first action is to don the oxygen mask and make sure 100% oxy is selected.

Once that is done, the life and death emergency is pretty much finished and becomes more a matter of an expeditious descent.

There was no indication of a depressurisation when the crew responded to the frequency change. It only takes one of the pilots to respond correctly if it happens. It also would have triggered ACARS messages.

This scenario is unlikely.
 

Melbury's Brick

Senior Member.
More speculation that the plane continued to fly after last contact....

http://www.nytimes.com/2014/03/14/world/asia/missing-malaysia-airlines-flight-370.html?_r=0


 

ralph Leo

Member
With nothing being found and reports of the plane flying for 4 hrs after last contact is there any chance it was hijacked and flown somewhere and landed?
 

WeedWhacker

Senior Member
If the 777 had a pressurisation problem, a large red "Cabin Altitude" message would have appeared on the EICAS screen followed by the same alarm you get when an engine catches fire.


Exactly. For those unfamiliar, 'EICAS' is an acronym for "Engine Indication and Crew Alerting System". I have found an instructional video on YouTube (that appears to be part of some airline's CBT program...as designed by Boeing, no doubt). This is specific to the B767, but is very similar to a B777 in most respects:


EDIT: My use of the acronym "CBT" refers to 'Computer Based Training'...a method that is becoming more commonplace, at many airlines. In fact, for one of my Type Ratings, the actual "Oral" was in fact, conducted on the computer! "Times, they are a'changin!"

(Sorry for the interruption....MicroSoft decided to suddenly "take over" and add "Security updates" to my OS, right as I was typing).
 
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Pete Tar

Senior Member.
With nothing being found and reports of the plane flying for 4 hrs after last contact is there any chance it was hijacked and flown somewhere and landed?
The report of flying for four hours is someone's reported speculation, it's officially denied. It's unfortunately going to persist and confuse things.
(there is a very remote chance it was secretly diverted and landed, but airfields that can host a 777 tend to be visible from space, so it's really unlikely.)

When does the engine data transmission usually happen - is it part of the transponder signal or separate?
Is there a way for it to have sent data after all other contact was off?
 
J

Joe

Guest
The report of flying for four hours is someone's reported speculation, it's officially denied. It's unfortunately going to persist and confuse things.
(there is a very remote chance it was secretly diverted and landed, but airfields that can host a 777 tend to be visible from space, so it's really unlikely.)

When does the engine data transmission usually happen - is it part of the transponder signal or separate?
Is there a way for it to have sent data after all other contact was off?
 

TWCobra

Senior Member.
I have to say this now as it appears to be the most likely scenario. Barring further revelations I believe that this aircraft has had it's flight path interfered with by one of the pilots.

The lack of any wreckage coupled with the transponder being apparently turned off is the clue here.

There are no indications of terrorism or inflight breakup. A crew incapacitation would have resulted in a Helios type event and triggered numerous ACARS messages as the flight progressed. The aircraft would have been tracked as there is no reason that the transponder would have been switched off.

The US is moving towards the same conclusion IMHO.

http://www.washingtonpost.com/world...688034-aa68-11e3-b61e-8051b8b52d06_story.html

You are already seeing reports of pilots families being interviewed. This would be a routine investigatory function anyway but I predict we will start seeing more stories on this angle very shortly.

I hope I am wrong. Pilots occupy a position of trust in the community. But I have been saying this privately since day three of the event, where it was becoming apparent there was no wreckage to be found anywhere where it should be, and the news of the primary radar traces of an aircraft heading west.

I really do hope to be proved wrong.
 

Pete Tar

Senior Member.
Is there a difference between 'turned off' and 'stopped transmitting due to technical failure' so that it can be 100% determined it was turned off?
 

Pete Tar

Senior Member.
According to Rolls-Royce’s website, their aircraft engine data is transmitted via satellite feed. Rolls- Royce would analyze the data submitted and make recommendations to the airline for engine maintenance, as appropriate.
Yes but that might not apply definitely to this flight. I hope they clear this up via a statement.

ETA from ATS
 

Mick West

Administrator
Staff member
Is there a difference between 'turned off' and 'stopped transmitting due to technical failure' so that it can be 100% determined it was turned off?

I don't think so. When you turn a transponder to standby, or off, it just stops transmitting (as that's what the intent is).
 
J

Joe

Guest
Yes but that might not apply definitely to this flight. I hope they clear this up via a statement.

ETA from ATS
Yes but what TWcobra said makes the most sense . I heard the pilot had a flight simulator at his home ? Seems strange being he had so many flight hours ? http://www.hindustantimes.com/world...ry-plane-under-scrutiny/article1-1194558.aspx
 

Pete Tar

Senior Member.
Not really, could easily be a hobby passion.
But they're definitely widening their possible scenarios.
 

TWCobra

Senior Member.
I have Flight Simulator X set up on my desktop at home with a high end joystick.
I use it at the moment to make historical aviation recreations (you can see one on my YouTube channel) and it is also good for flight simulator check revision.
It is not unusual for pilots to do this.
I believe the MAS captain may have done a full simulated 777 cockpit. I don't think much should be read into that in relation to this incident.
 

Pete Tar

Senior Member.
 

WeedWhacker

Senior Member
You would think it would be hard to hijack and hide a jetliner with all the onboard electronics, radar and satellites in use today.

"IF" (and only being speculative here)...."IF" one's objective was to "hide" an airliner, and one knew the systems well enough...yes, turning off (or to 'STBY' in the case of transponders) is easily accomplished. Circuit Breakers could be pulled (opened), rendering any component then unpowered.

There is a LOT of room for 'speculation', however.....
 

Melbury's Brick

Senior Member.
Hijack seems to be back on the table, according to "sources"......

http://uk.reuters.com/article/2014/03/14/uk-malaysiaairlines-flight-idUKBREA2701C20140314
However (same report).......

Malaysian officials have already received some criticism for the way they have handled this so far. I guess there'll be more to come.
 

Pete Tar

Senior Member.
Yeah it's not really Malaysia's fault that it has to clear up confusion and deny rumours run with by the press.
 

Melbury's Brick

Senior Member.
Yeah it's not really Malaysia's fault that it has to clear up confusion and deny rumours run with by the press.
They now seem to be agreeing with the rumours that the flight continued long after the last contact.


Here's a rumour....Did Malaysian Airways deny the "flew on" theory because it may implicate one of their pilots and open the possibility that the airline could be criminally responsible? Would that action have perpetuated a search in the wrong place? That would clear the decks for an even uglier thought.....Would it be (in that scenario) in Malaysian Airlines interests that the plane never be found?
(I'm sounding a bit ct here.)

Either way, this is off topic re. depressurization and probably should be in the main "Speculation" thread.
 

Paul29

New Member
The discussions above imply that loss of pressure was accidental. I believe that it was intentional.
The pilot hijacked the aircraft and shutoff the transponder and communications.
He took it up to 45,000 feet (beyond max ceiling), put on his oxygen mask, dumped cabin pressure (people unprepared would have seconds to respond), and then flew the aircraft somewhere.

I lost a canopy at 50,000 with my mask hooked to the helmet but off my face. Seconds not minutes ...
 

WeedWhacker

Senior Member
He took it up to 45,000 feet (beyond max ceiling)...

The scenario of running the cabin altitude up to disable everyone in the cabin is possible, but it would not require the additional step of climbing the jet above its Service Ceiling. The same effect would be accomplished just as effectively at FL 350.

So, the reports of the climb to FL 450 seem doubtful...at least at this stage.
 

Pete Tar

Senior Member.
There is some question that taking it to that height is logistically impossible and highly likely to induce a stall. We have to not assume that figure is necessarily accurate.
The same effect could have been achieved at a lower height.
"lost a canopy" what does that mean? In a 777?
 

TWCobra

Senior Member.
There are other possible scenarios there. The 777 has oxygen generators for the passengers which last for 12 minutes. After that time, depressurising the cabin at normal cruising altitude is enough to incapacitate the passengers.

The cabin crew have oxygen bottles which they can use. Whether or not they would be very effective at 35000 feet, think of every film you have seen of climbers on Everest, is problematic.

The problem is that the higher you go, unless the oxygen is delivered under substantial pressure, it is not doing you any good.
 
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