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Are Electronics A Safe Way To Fly?
by Paul McGoldrick
Having gotten off a ten hour flight from London a few days before, the loss of Air France’s AF447 A330-200 Airbus en-route from Rio to Paris was a reminder that humans are vulnerable to mistakes, misdesigns, and Mother Nature.
It now seems clear that somewhere between the Arquipélago de Fernando de Noronha (Brazilian tourist territory about 350 miles Northeast of the mainland city of Natal) – probably on its own navigation, for such a low traveled route, to the civilized Cape Verde Islands and then on to The Canaries, Madrid, and Paris – a catastrophic event took place.
The debris field from the flight is reportedly so huge that it is clear that the airplane came apart at its cruising altitude, said to be Flight Level 350 (35,000 feet). That is sort of good news for the 228 souls on board. A decompression, however it occurred, would have rendered them all unconscious in a couple of seconds and they would have suffered no pain at all. Forget the briefing you get on the ground about the oxygen masks coming down and you putting on yours first… That is very different from the tragedy of Aero Peru’s Boeing 757 Flight 603 from Lima (Peru) to Santiago de Chile that literally landed, unknowingly, on the Pacific Ocean at 400 knots and where all the passengers and crew drowned horribly after the aircraft cart-wheeled and sank, slowly filling with water. That accident was caused by a blocked pitot tube (covered with Scotch tape for when the plane was being washed) which the technology-challenged air traffic control operators didn’t twig because they didn’t understand that the altitude readings they were getting were telemetry from the plane and not from some fancy radar equipment.
So why did the Airbus come apart?
A lot is being made of the weather that can be encountered near the Equator, in what is called the Intertropical Convergence Zone (ITCZ) where the trade winds of the Northern and Southern hemispheres associated with the warm waters cause enormous columns of moisture to rise from the oceans, as high as 50,000 feet, and often causing thunder activity.
I have often been battered about in the ITCZ, which moves North and South over the seasons. The worst was in a South African Airways Boeing 747-200 en-route from Mauritius to Johannesburg. The flight deck told the cabin crew to expect a rough time, although they could not predict how rough because the weather radar was poor at indicating the altitude of thunderheads, particularly ones lower than the flight path. They did not believe that they would be able to fly around the ridge of activity. The crew advised the only passenger in the front cabin – me – that I would probably be more comfortable if I got a few extra drinks down me before we got there. Advice I followed.
When we got to the storm front there was, initially, not much more activity than you would expect in such a large airplane. But then it really hit, and for about twenty minutes the plane was thrown up and down 400 – 500 feet at a time. It was truly terrifying. The cabin crew preferred to take to the cabin floor, rather than in their full-harness seats, wedging themselves under seats. Company policy or previous experiences? I don’t know.
Since that flight I have never been concerned about the structural integrity of the 747.
Is it any different from the A330?
Air accidents are never about a single incident; they happen as the result of the follow-up to the initial indicator. Airbus technology is heavily an engineering one and not one for the hands-on pilot. In a 747, for example, problems with thrust settings in turbulence can be felt through the adjusters. They cannot in an A330. Once you enter a moisture field, frozen at that, the groundspeed readings from a pitot become totally unreliable and there would be a tendency to increase thrust because of stall warnings. That puts additional pressure on the airframe, one that is not fully tested for much higher speed conditions at higher altitudes. The plane also becomes much less responsive to directional changes and we know from previous ovestress accidents that the composite tail plane of the A330 is far from being a perfect structure.
Reports are that a huge “oil” slick was seen by searchers on the ocean surface which was, presumably, fuel, suggesting that the plane did not blow up because of the contents of its tanks. But, at the same time, the captain on a flight from Lima to Madrid of the Spanish carrier Air Comet, passing further North, “saw in the distance a strong and intense flash of white light, followed by a downward, vertical trajectory which broke up into six segments."
The telemetry sent by satellite back to Air France has not been fully disclosed, but it probably has more clues than are being talked about as yet. If that fault telemetry coincides with the fifteen minutes that the pilots fought for control of the aircraft I think we may be looking at the one nightmare event that pilots pray never to have to deal with: a fire in the attic. A fire, that is, in the space above the passenger compartment.
That is an impossible problem to have to deal with.
How could such a fire start? Lightning? A metal aircraft is a huge Faraday cage such that everything internal should be protected from electrical discharges external and, typically, hits are on the ends of the wings and on the tail plane. But through the intensity of the storm, or with just sheer bad luck, what if there was a hit on one of the antennas on the fuselage? A deliberately non-grounded object? Or because of the stress of flying too fast there was actually an opening created at an external fixture, like an antenna or pitot? Pilots have also recorded lightning strikes where pin holes were punctured in the fuselage.
And the explosion seen by the Air Comet crew? White equals oxygen. With decompression all those masks dropped in the cabin with the oxygen system activated in the attic. A spark or electrical short would have created an incredible explosion.
We may never know the cause of this accident, or the telemetry might tell all. Our hearts go out to the relatives and friends of those lost.
We might have known more, immediately, about this incident if the pilots had been able to make a radio call. Why are airliners on long ocean crossings still communicating with air traffic control by SSB on shortwave? If the telemetry can be sent home to mother by satellite, why cannot cockpit communications? And why are we still relying on pitot measurements as a primary system for speed indications when we have GPS?
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