Full and free movement

                                                                                          

A report on an accident to a homebuilt Jabiru aircraft which suffered a jammed rudder control on landing, causing it to leave the runway surface and turn over, injuring the occupants. The jam had apparently occurred as a result of insufficient clearance between the leading edge of the rudder and the trailing edge of the fin. 

                Although jamming of aircraft control surfaces is not common in flight, it can have catastrophic consequences. As the AAIB report points out, aerodynamic or inertial loads can distort aircraft skin during flight, and any possibility of such distortion causing a control jam should be avoided. A check that controls all move freely over their full range of movement should be carried out before every flight, and not just when sitting in the cockpit. Between routine maintenance inspections, a pilot would hope to

detect a potential similar jam by physically inspecting and moving the control surfaces during the walk-round, noting the gaps between parts as they move, and assessing the risk of a jam occurring. Unfortunately, in many aircraft, a check of full movement of the rudder controls can normally only be carried out while taxiing, so the visual inspection should consider the potential for jamming through minimal clearances, evidence of prior damage or distortion

accident of Jabiru aircraft