Type certification is invariably completed with new aircraft, new equipment and pilots who know the test program.
So, it's reasonable to assume that the results these people obtain will be the very best that could be hoped for.
Lets advance the clock 20 years with the by now very tired airframe, carrying components whose tolerances are little looser than they ought to be (but still within limits)and a crew that is just expecting a normal take off. Even the rejected brief is a reflection of a legitimate expectation in the crew's mind that the runway will take the aircraft to a full stop. After all, the take off data and figures calculated before departure said so.
I think we can all understand and relate to the mind set here.
Now the reality - We're right up there approaching V1 and there are several loud bangs. Uncertainty as to what has really happened is followed by a decision to reject the take off. There is a resulting slight delay in the application of the retarding devices combined with less than optimal braking system performance.
Next thing - the aircraft is off the runway at the other end.
What went wrong ?
It is FAR too easy to criticise the crew for failing to initiate the rejected manoeuvre early enough. The true cause is a combination of ALL the factors described above.
The largest contributors IMHO, may well be:
1. the performance data is really no longer valid for the condition of the airframe and engines.
2. The gross weight of the aircraft may not be known sufficiently accurately. There may also be c of g error inputs.
This is a very complex issue that should NOT have the crew as the automatic cause of the over run.
Aircraft age and condition play a significant role in what occurs on the runway.
Maybe it's time to start looking at applying degradation factors to the performance tables to try and offset the effects of aircraft aging.
Good luck to the AAI guys.
Last edited by Arctaurus; 9th Nov 2004 at 19:42.