Nine people, including the pilot, were believed to have been killed in the plane while it made a flight at 25,000 feet across Australia from Perth. Without the pilot, it eventually ran out of fuel and crashed 3200 km away on the shores of the Gulf of Capentaria in Queensland. The circumstances of the accident appear to be similar to the crash of the Lear Jet which took the life of the famous golfer, Payne Stewart in the United States a few months ago.
Although there are no official confirmation of the cause from the Civil Aviation Authority until it has completed the investigation, a likely scenario would be a slow depressurization of the aircraft cockpit and cabin. This will consequently result in hypoxia - a lack of oxygen in the blood.
Can you recognize hypoxia? The answer is no.. you may become euphoric and gradually loose consciousness. Can you feel the depressurization ? The answer is yes, if it is a rapid depressurization because your ears will pop out ! If the depressurization is very slow, then you may not be aware unless you look at the cabin altitude indicator. All modern aircraft, including the Boeing 777, has a cabin warning system, in the form of a warning horn, that sounds in the cockpit when the cabin altitude exceeds 10,000 feet.
If the cabin in the aircraft continues to depressurize to above 13,500 feet, the passenger oxygen masks automatically deploy and a pre-recorded emergency announcement activates. (Now you know why you have to pay careful attention to the emergency briefings every time you fly!). In the Boeing 777, up to about 43,000 feet, the aircraft can still maintain a comfortable cabin altitude of 8000 feet.
Airline pilots have been trained and tested regularly on depressurization procedures. Amongst other steps, they have been trained to don their oxygen masks immediately and descent to 10,000 subject to terrain clearance. If you are sitting quietly, your time of useful consciousness will be 30 seconds at 40,000 feet, 75 seconds at 30,000 feet and three minutes at 25,000 feet. This is the period between the individual being deprived of his oxygen supply and becoming so affected by hypoxia that he is unable to cope with an emergency. See the Helios Crash Investigation.
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