post 2898 Basil asked about retracting flaps straight to Flaps 20.
Basil,
Vref 135 from the 777 performance pages is for a 440,000 lbs a/c(I don't recall BA 038's weight).
Stall speeds at 440K -
Flaps 30 108
Flaps 25 110
Flaps 20 115
The flap retraction was done 115-118 kts(I've seen/recall different numbers). If the 777 would allow it there's a chance that a retraction to Flaps 20 at those speeds could have triggered a stall. I have to believe, based on Vso multipliers, that the AOA would have been mucher and I'm guessing it would outweight any configuration drag reduction.
I'd believe that an immediate retraction to Flaps 20 at Vref might be the best plan. Sadly, the AAIB report doesn't give the next guys any knowledge.
How quickly can guys be expected to react? With training and awareness it could be done fairly quickly. How quick does a trained pilot apply rudder with an engine failure?
For non pilots the difference for most Boeing a/c(that I know of) and I'm assuming Airbus' Flaps 2 is that the leading edge slats are in the mid, or takeoff, configuration. Most single engine configurations are based on mid/takeoff slats to reduce the drag associated with greater flap extensions.
My previous post explained how the largest stall speed reduction occurs in the first flap position(Flaps 1, Flaps 2, Slats EXT, etc). The last flap settings are just the opposite, mostly drag, with little stall speed reduction.
That is also why, as Basil mentioned, Flaps 20 is an important step in reducing drag, with a relatively small stall speed increase, to allow the a/c to accelerate rapidly during a go-around.