PPRuNe Forums - View Single Post - Air North Brasilia Crash in Darwin (Merged)
Old 24th Jun 2012, 12:22
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sheppey
 
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The longer you stay glued to the ground the better, because that's the best place to have an emergency if you really must have one.
Interesting point of view which many will agree with. I guess we all have our personal opinions based often on personal experience.
I have always favoured a low V1 based on research papers that state most runway accidents are caused by a late abort when it was never necessary in the first place. A burst tyre is more likely at high speed than low speed and the general rule espoused by McDonnel Douglas aboout 30 years ago, was that it is safer to continue the take off from 15 knots below V1 rather than risk extended abort distance with a buggered tyre and associated brake loss that wheel. The statistical chances of hitting an obstacle after take off following engine failure after V1 are far less than the probability of a cocked up abort at high speed which is how some aircraft have crashed because of an over-run.

The higher the V1 the more the energy needed to stop with resultant hot brakes. Historically, overruns caused by an abort beyond V1 have occured because of indecision/uncertainty or even incompetency by the crew. If a late abort on a heavy weight take off occurs for whatever reason, there is the possibility of the brakes being beyond their energy limits and thus brake failure. For all these reasons this writer takes the view that a low VI if available, is a safer proposition in terms of the go decision rather than sweating out an unecessarily high V1 and the demonstrated dangers of a high speed abort. I would be much happier with a 20 knot spread between V1 and VR than having V1 =VR or maybe a couple of knots below.

Last edited by sheppey; 24th Jun 2012 at 12:27.
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