Thursday, August 04, 2005

Air France Flight 358 - the Likely Cause!

When I first read the report in the Sydney Morning Herald about Air France Flight 358, a witness, Corey Marks, who saw the jet land, stated:

"Everything looked and sounded good. It hit the runway nice and all of a sudden, we heard his engines backing up."

He then added that the jet went straight into the valley and broke into two.

Based on his report, I jumped to conclusion that the jet started having problems because of the engine reversing, and suggested that there could have been asymmetric reversing, which could have then caused the aircraft to swing to one side, and plunged into the gully.

Asymmetric reversing is not completely impossible as in May 1991, an Air Lauda B767 experienced such an occurrence, unfortunately in the air. The asymmetric thrust of the worst possible kind, that is while in flight, subjected the aeroplane to so much stress that it broke up in flight. Read this chilling report of the accident findings.

On the ground, it would have swung the aircraft to one side, and unless the pilot is alert enough to prevent that, he would find the aeroplane on the grass strip besides the runway before he could say "Airbus 340".

After reading the news a bit more, and considering that there was heavy rain at the airfield, the most likely cause could be what is termed as aquaplaning.

Aquaplaning is akin to the aeroplane water-skiing on a thin film of water on the runway. The wheels or rather tyres are not in direct contact with the runway surface. When that happens, the pilot has no or very limited directional control over the aeroplane, apart from the additional difficulty of decelerating the plane.

The main cause of aquaplaning is water on the runway brought about by heavy rain or storm. The phenomenon is aggravated by poor tyre threads - OK, remember to check your car tyres before you drive around because it applies to you readers too, especially those living in the tropics where heavy rain is quite regular.

The speed at which aquaplaning occurs depends upon the tyre pressure – the higher the pressure, as would be the case for modern transport jets or military fighter-bombers, the higher the speed at which it would occur.

A combination of aquaplaning, poor tyre threads, tailwind (which could have been the case with passing thunderstorms), and higher than normal speed on landing (again, a likely case due to turbulence on the approach to land) could result in a landing distance that is 5 times longer than the normal case. This is of course the worst case scenario.

Braking would aggravate the sliding because the action would lock the wheels and set them up for skiing. But with modern aeroplane this is unlikely as the aeroplane braking system has what is called an anti-skid system. When the system senses a skid in the wheels, it automatically unlocks the wheels to mitigate against the condition conducive for skidding.

The best way to reduce the speed of the aeroplane, apart from landing at the correct speed and effecting a firm touchdown (to ‘break’ through the thin film of water on the runway so that the tyres contact the runway surface) is engine reversing.

What if it’s not your day, and asymmetric reversing occurs at that crucial moment.

Calamity!


Related post:
AIR FRANCE Crash at Toronto Airport

2 comments:

  1. http://flight358ptsdisorder.blogspot.com

    Flight 358, Air France, crash lands at Pearson International Airport in August 2005, with 309 people on board, everyone gets out okay, safe. Safe? Well, they all survived, yes, and thank their lucky stars, but one thing the news media has not mentioned in depth is the amount and degree of PTSD's that will emerge: post-traumatic stress disorders.

    Many of the passengers and some of the crew will find that they will experience post-traumatic stress disorders of various kinds, panic attacks, nightmares, fear of flying phobias, fear of heights, claustrophobia, etc., following the ordeal they survived. SOme will feel that they are living on borrowed time, and they will change the way they live their lives. Some will become more religious, some less religious. Many willl experience PTSD for the rest of their lives, and there will be lawsuits, yes, lawsuits, for "mental stress" endured in the crash landing and in the aftermath of their escape from the plane. HUGE LAWSUITS, worth millions of dollars. AIR FRANCE will be paying for this very stupid misake (trying to land in a fierce thunderstorm with lightning all around the airport, red alert, when in fact, the plane had enough fuel to fly to Montreal or Detroit or some safer place) of trying to land in red alert storm. Millions, billions of Canadian dollars. French francs.

    Let's look into this a bit:

    No complete passenger list has be released, but authorities released a partial list based on their nationality. Among the passengers were:
    101 French citizens, 104 Canadians, 19 Italians,
    14 Americans, 8 Indians and 7 British citizens.

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  2. Hello, I am interested in hearing from others

    ReplyDelete