In an aircraft, if it's red, you don't touch or mess with it unless you knwon what you are a doing, or nasty things can happen.
This is an example, which almost cartainly true:
10/08/1947 American Airlines DC-4
As a prank, a captain riding in the jump seat engaged the gust lock in flight. The command pilot, not knowing the gust lock had been engaged, rolled the elevator trim tab with no response. When the jump seat captain disengaged the gust lock, the aircraft went into into a steep dive, executed part of an outside roll and become inverted. Neither the command nor jump seat captain had seat belts on and they accidentally feathered No. 1, 2 and 4 engines when they hit the controls with their heads. No one realized it at the time but the feathering reduced power and allowed the co-pilot, who was strapped in, to pull out of the dive 350 feet from the ground.
Last updated: 16 February 2015