Friday, July 20, 2007

When malvolent factors collide...

It's generally a combination of all factors all colliding together (like Murphy's law) that shape such a serious incident. I take it now confirmed that the reverse of the right thruster had been disabled. Having said that, the effect of the reverse thruster at high speed is not necessarily high.

The design of the automatic braking of the Airbus has been criticized before, as it does not in all situations guarantee that the plane will actually brake in time. When to brake is sensed by a couple of things. It's better to let you know from different sources and other accounts where similar events developed:

Well, since all I can do is speculate, I'm leaving it to the following course of events:
  • The thrusters were not in operation, but their effect during landing is minimal. Not sure how much of a difference they would have made on this account.
  • The speed of the aircraft at landing was higher than normal. This may have caused hydro-planing and Airbus has a system where the rotation of the wheels need to be at 45knots minimum for the braking system to kick in. This is when automatic braking is in use.
  • The runway was too short to recover in any way possible. When the braking apparently started to work, the runway left was too short to bring the plane to a full stop. The pilot reverted his decision and attempted an emergency take-off.
Thus. the combination of all undesirable factors together:
  • Some mechanical disability that makes a difference (reverse thrusters disabled)
  • Probable failure of the plane to recognize it was on the ground, causing the braking not to kick in on time
  • Failure of the pilot to recognize this occurrence and apply braking manually (if possible)
  • Too short a runway to give more lee-way in the recovery of these emergency situations
  • Rain puddles on the runway (see rainspray) that caused the hydro-planing in the first place
The actual course of events can only be found out for sure when the report comes out. Some of these findings can only be truly confirmed with the data of the black box.

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