the more i think of it the clear it is that:
(1) the crew made incredible job! chapeau bas! this situation must have been tried in all sims by whoever had a chance to try it - nobody so far has claimed successful landing. Two years after the accident! And the crew has done it in some 40 seconds
(2) from what i read and analyze the flying crew actions (a) at first tried to reach the airport and miss the obstacles on the way and only then (b) concentrated on just landing the plane. For me this explain why they first went for distance - aviate - and only later for speed to flair and land.
After reading comment from Cloud Bunny i did some
very rough estimations and it appeared that (the numbers are for
single wing of B777 with area of 215m2, excluding the fuselage drag):
- 3deg AoA the geometrical wing drag area would be equivalent to about 17m2 with Cd=0,05 => drag 0,85
- 8deg AoA the geometrical wing drag area would be equivalent to about 36m2 with Cd=0,07 => drag 2,54
- 12deg AoA the geometrical wing drag area would be equivalent to about 44m2 with Cd=0,08 => drag 3,44
- 14deg AoA the geometrical wing drag area would be equivalent to about 58m2 with Cd=0,09 => drag 5,22
estimated difference in geometrical drag area for 30deg flaps (over 25deg ) would be some 5m2 with Cd=0,3 => drag 1,5.
The overall wing drag estimation would be:
- flaps 30 + AoA 8deg : 1,5 + 2,54 = 4,05
- flaps 25 + AoA 12deg : 0,0 + 3,44 = 3,44
Result: total drag was reduced but this gain was not significant (about 10-15%) and was quickly lost due to constantly growing AoA.
so
SFLY had a point - confirmed by experience from Boeing sims - reducing flaps had much smaller effect than i have expected.
(the calculations are very rough and are for comparison only
- do not build your next a/c with these numbers
)