Toga vs Flex on the 320 series
Just a quick perf question referring to my current type, the 320 series.
Performing a flex take off, with a flex of say, 60 degrees, while using the "mean" V1, on a 3000m runway, a typical V1 is around 140. While this drops to around 120 when you use Toga.
I see you would use Toga to get airborne quicker, obstacles, windshear etc, however, why for a given config does the V1 drop so much?
The ASDR when going from Flex to Toga genearlly drops too, i.e. if you decided to Toga the ASDR is lower, however would you guys, if you decide to use TOGA at the last minute, re-do the perf calculations and use the lower V1, or is it acceptable to use your Flex V speeds, and select TOGA at the last minute? I can see this would be an issue if your field length limited, but if not, are there any significant issues in doing this?
Thoughts and comments appreciated!