Drag.
There was actually a flying exercise at JATE called Regal Mount where u/t staff were subjected to a profile of steep turns and application of positive and zero G to demonstrate the necessity for correct load restraint. It was also an excuse for Flying Section to "horse it about a bit" which was deeply gratifying.
This, however, in no way gave an excuse for dangerous low flying. I was guesting on JATE some years after leaving and remonstrated with that pilot after a DZ inspection on an MSP at Larkhill which put us below the surrounding terrain, and on Salisbury Plain that was V. difficult. He countered by saying that he was a QFI and knew his job, until South Cerney.