Assuming that you wish to exit a plain loop at or above the entry point in a reasonably powerful aircraft, what is the last point that you can take corrective action if you realise that your airspeed is low?
The problem with powerful aircraft is that their loops are so big, that it's impossible to judge visually if you have sufficient height to complete the loop safely when you are at the top.
Rather than relying on visual judgement of the height available, pilots of these aircraft have previously determined target values for speed, and height they aim to achieve at the top of a loop, known as 'gates'.
If their speed and height are within the 'gates' then they are safe to continue down the second half of the loop. If not, they now have a small window of opportunity to roll erect and fly away.
They would aim to do this by the 45 degrees pitch down position from the top of the loop. Beyond this point the 'window of opportunity' rapidly closes, and is, of course, fully closed at the vertical point, where they are committed to continue the loop.
Factors affecting the height gained during the upward half of the loop, and the minimum height required to complete the downward half of the loop, such as aircraft weight, air temperature/pressure/humidity(density) will vary on the day, and the 'gates' required at the top of the loop, particularly the 'gate' for height, should be based on the worst case.
MJ
