Not sure how accurate or representative that test on the AN2 was
The aircraft descended then would heve made a big pitch and power change to go to a climb.
I don't know enough about vortices generation? When they are at their maximum but this AN2 took off on a steady climb maybe 30 seconds ahead of the crash aircraft.
A true test would have had smoke emanating from the crash point and the aircraft 30 seconds ahead.
Again in the high altitude tests the AN2 should have been in a climb attitude with the chase aircraft 30 seconds behind which it was not on the test.
But a good example of taking off behind a much larger aircraft and the dangers of doing so.
Pace