Yeah, the math I did is as follows to figure out how long it takes the aircraft to hit the ground:
d = displacement (distance to the ground in this instance) (122 m = 400')
v = initial velocity (zero, since the aircraft is hovering at altitude, or moving along the horizontal plane, which we're ignoring for these purposes)
t = time
a = acceleration, in this case, due to gravity
d = vt + (a/2)*t^2
122 m = 0*t + ((9.8 m/s/s)/2)*t^2
122 m = 4.9 m/s/s *t^2
squareroot(122 / 4.9) s = t
t = 4.98 seconds
it takes less than 5 seconds for the aircraft to fall from 400 feet AGL, assuming it falls straight down and does not reach terminal velocity.
Here's a graph, so you can see how long you have depending on how high the aircraft is (y axis is altitude in metres, x axis is time to the ground in seconds)
This graph and math doesn't take into account the time it takes for the aircraft to save itself, this is just an analysis of falling things.
