From earlier in
the thread, I believe someone stated that certification standards mandate that
Go Around thrust is effective within 8 seconds of throttle application. However,
it is usually effective in less time, such as 5 seconds.
I believe it was also noted that was from a stable approach with engines
powered up - not flight idle, at a very slow speed - way behind the inertia
curve. I think I recall someone said it would likely have taken 10+ seconds to spool AND overcome the existing sink rate.
The 8 second requirement is from idle - hence the need for a specific "approach" idle schedule. Normal GA performance is better than that because they're usually initiated from well above approach idle. If Asiana had firewalled the throttles they would have had (at least) 95% of go-around thrust within 8 seconds (assuming they hadn't already hit the ground)(I think for the 777/PW4090 go-around and takeoff are the same - there are some airplane/engine combinations where go-around is a little less than max TO). As to how long it would take to recover from their -30 knot airspeed and rapid sink rate - I'm not qualified to answer - that's not something I've ever seen.