geniusintraining said:
......if the door opened the plane would implode and there would be pieces everywhere where they had the last blip on the radar...
Implosion occurs where there is a significant enough differential between an internal lower pressure and an external higher pressure, such as when a submarine hull implodes at crush depth under a high enough external hydrostatic pressure. Aircraft cabins are pressurized. That means they are of a higher pressure inside than the outside atmospheric pressure. If there's a sizable breach in the fuselage, say after a bomb detonates, the internal cabin pressure is rapidly forced outward, in an explosive manner, not inward in an implosive manner. This is known as explosive decompression. Air is forced from the cabin at a rate much faster than a humans lungs can normally expel air. Typically faster than 0.1 to 0.5 seconds. This can cause severe lung trauma, especially if the lungs are full of breathe at the instance of explosion.
RussB said:
What would happen on a Boeing 777 if at about 35,000 feet two people with stolen passports were sitting at emergency exits and opened them at about the same time?
Stowaway 1 would say to Stowaway 2 - "
Hey! Why do I always have to be the ugly one?"
Sorry, I couldn't help it.
As Ken pointed out,
Cabin doors are designed to make it nearly impossible to lose pressurization through opening a cabin door in flight, either accidentally or intentionally. The 'plug door' design ensures that when the pressure inside the cabin is greater than the pressure outside, the doors are forced shut and won't open again until the pressure is equalized. Cabin doors, including the emergency exits, open inwards, or must first be pulled inwards and then rotated before they can be pushed out through the door frame. This is because at least one dimension of the door is larger than the door frame.
RussB said:
...Would it trigger an emergency that would trigger the pilots to turn around, lose altitude and pass out before an emergency transmission could be transmitted?
The pressure differential on an aircraft is only for the normalization of the cabin air pressure so the occupants can breathe normally. It has nothing to do with the altitude of the aircraft.
Important info...
At higher altitudes, atmospheric pressure is much lower than at sea level. We say the air is much 'thinner', and that it has a lot 'less' oxygen. At high altitude the 'partial pressure' on the oxygen molecules in the air is reduced. The necessary amount of oxygen for human respiration, and the amount that is toxic, is set by the partial pressure of oxygen alone. Also at higher altitudes the air is much colder, which can cause hypothermia. Altitudes above 1500 metres (4,900ft) start to affect humans. Above 2,400 metres (8,000ft) the lack of oxygen can cause serious altitude sickness. Athletes attempt to acclimatize themselves to higher altitudes to gain a performance boost, but anything above 8,000 metres (26,000ft), known as the "Death Zone", is impossible for humans to acclimatize to.
Why do your ears pop on a plane?
As a plane climbs, the atmospheric pressure is decreasing. Higher pressure air trapped in your inner ear forces your ear drums outward. Your body equalizes the pressure in your ear with the atmospheric pressure by releasing the trapped air through tubes either side that run from your ears down to your throat, known as Eustachian tubes.
Losing cabin pressure at several thousand feet is detrimental to the occupants, but not essential to keeping the aircraft in the air. Many non-fatal cabin decompression incidents happen around the world every year where the plane is successfully landed. The effects of cabin decompression, however, could have an impact on the structure of the aircraft, or the pilots, which in turn could affect it's flight.
If the doors were to open suddenly, or any other opening large enough, then rapid decompression takes place. The speed and violence of the decompression is affected by the size of the cabin, the differential pressure between the inside and outside of the cabin, and the size of the breach. Rapid decompression typically takes more than 0.1 to 0.5 seconds, which allows the lungs to decompress more quickly than the cabin, reducing the risk of lung damage.
The pressurization system should be in auto. As the available oxygen is being forced from the cabin, the oxygen masks are deployed. Once cabin air pressure is equalized with the outside, and the occupants and crew have oxygen, they should be able to radio their status and make an emergency landing, or turn about. Rapid decompression doesn't start sucking people and seats out of the opening Hollywood style!
Another scenario is gradual decompression, where the cabin depressurizes at a slow enough rate that it goes unnoticed by the occupants. The aircraft may have failed to fully pressurize as it ascended to high altitude. It could be caused by a failure in the pressurization system, or a small enough hole somewhere in the fuselage. If the pilots weren't monitoring the pressurization indicators, or had left it in manual, then it can be too late to react when the signs of hypoxia start to set in. This is the starvation of oxygen to the cells of the body, eventually resulting in unconsciousness.
In the case of Flight MH370, they were saying this morning that the radar is very poor in that region, and that the search has been widened to the vast Indian ocean, which they think was the direction of their last known heading. This would be way off their plotted flight plan. One possibility is gradual decompression, where the pilots eventually reacted, but too late. They may have started changing their heading to turn around, but passed out before completing it. Auto pilot then kept the plane flying on the last entered heading until it ran out of fuel. One of many, many possibilities.
Until they find the aircraft and its black box, who knows?
George
