Originally Posted by
Icarus2001
Maybe someone who is CURRENTLY flying the type would care to run the numbers for us so we can be informed as to the REAL difference is V speeds and flex?
Possibly. However, my understanding is that in the event of an engine failure under flex conditions, no additional thrust is required, the calculations are good for flex OEI. In reality pretty much all operators will add power to the live engine by either pressing TOGA, pushing TL forward of a detent or in some cases doing nothing as the aircraft adds power without pilot input.
So now does that mitigate 400 metres of missing runway as far as obstacles upwind are concerned?
Not really. The Airbus EFB (I'm assuming here that the 320 is similar to the bigger Busses) will try to give you a flex temp that results in balanced field length, often with a margin of less than 100m. If you've got 400m less runway than you thought you had, then an engine failure at V1 will give you a negative margin for either stopping or continuing. If you've continued and select TOGA, that will obviously help, but by how much? If it was only a small derate to start with, then TOGA won't make a big difference.