Germanwings Airbus A320: The search for clues to solve mystery of air crash tragedy
Once again, air crash investigators are desperately struggling to reach an inaccessible site to make sense of the latest crash of an jetliner.
Today, they are again scaling inaccessible mountains in the French Alps seeking clues to the mysterious crash of a Germanwings Airbus A320. The ultimate prize in all these undertakings are the famous black boxes which, some TV shows would have us believe, are the Holy Grail of air crash investigation.
The black boxes will be of enormous help in solving this latest crash. They can confirm, or disprove, some of the theories flying about the airwaves and the internet about what caused this latest tragedy. But the question arises: do we still need them? One of the leading theories is that the aircraft, which was travelling from Barcelona in Spain to Dusseldorf in Germany, suffered a sudden decompression as it reached its maximum cruising altitude of 38,000 feet some 45 minutes after taking off.
The air at cruising altitude does not contain enough oxygen to keep passengers and crew conscious for more than, at most, a minute or so. Even before losing consciousness, the ability of the crew, and passengers, to function is seriously hampered as a condition known as hypoxia. Victims often start to giggle, then rapidly become confused and unable to function. Pilots fail to perform the simplest of tasks.
On a normal flight, air is pumped into the cabin and the cockpit until there is enough oxygen to keep everybody alive and functioning for the duration of the flight.
Although it's hard to notice, the increased cabin pressure causes the skin of the aircraft to swell like a balloon, but any weaknesses can cause a hole to suddenly appear, allowing life-giving air to escape.
Explosive decompression is rare but has been known to happen, often aided by metal fatigue and corrosion. The doomed Germanwings jet was 24 years old. Could it have suffered a devastating decompression?
Some clues certainly point in that direction. One was the fact that the aircraft started a rapid descent within a minute of reaching cruising altitude.
It's standard procedure in the event of decompression for pilots to lose height as quickly as possible and reach an altitude of at least 10,000 feet where the air is more breathable. If hypoxia is affecting pilots they can rapidly find the simplest of tasks beyond them.
The second of the black boxes - known as a cockpit voice recorder - should be able to tell from the sound of the pilot's voice if hypoxia is a factor in this crash, while the main box - the flight data recorder - will reveal any sudden changes in cabin pressure.
Of course, hypoxia can also result from a failure of the aircraft to properly pressurise in the first place. Failure of the pressurisation system was certainly a factor in the 2005 crash of a Helios Airways 737 into a Greek mountain after overflying its destination because the pilots were unconscious from hypoxia.
Over the next few days, as relatives of the victims of this crash cope with the terrible personal tragedy that has befallen them, investigators will be poring over information from various sources to determine exactly what happened.
The truth is that old-fashioned tin-kicking - sorting through the wreckage - will continue to be a major feature of air crash investigation for many years to come.
Gerry Byrne is the author of Flight 427: Analysis of an Air Disaster (Copernicus Books)