Some of the Aerobats had a quick release mechanism for the door. This was mainly an FAA thing whereby the crew were expected to wear parachutes whilst aerobatting. This is not so in the UK and many of the old 150s are just pinned but the 152s still often have the release. I can't recall any of the 172s having them - but who wants to flick a 172 anyway, they get bent enough by people trying to barrel roll them!! <img src="rolleyes.gif" border="0">