It is indeed possible (or certainly was) for the rear seat occupant's AEA to interfere with the controls if the front seat occupant applies large aileron inputs without warning.
Whilst on a Hawk refresher course, I flew in the back on a weather check with a pilot who decided to practise his aerobatic sequence. He hadn't briefed me about the content of the sequence, nor did he call each manoeuvre. So I was caught by surprise when he suddenly applied full aileron without warning and the bomb flap snagged on one of my kneepads (this was just before the days of external turning trousers), being caught by the velcro flap securing the kneepad pocket (again, later suits had a different kneepad pocket design).... Fortunately I quickly freed it - but it had certainly surprised him!
Last edited by BEagle; 14th Jan 2011 at 19:23.