Air Accidents Investigation Branch
Summary:
During a formation display routine the aircrafts elevator trim tab detached at its hinges. The tab was still attached to the aircraft via control cables, and this caused it to flap in the slipstream causing the elevator to move up and down and causing a loud banging noise as it repeatedly struck the side of the rudder. The pilot was able to control the aircraft and make a successful landing.
The elevator trim tab had detached due to a combination of the wrong hinge type being fitted (with only one third of the glue bonding area compared to the type of hinge that should have been fitted) and insufficient glue having been applied. Other aircraft with cracked hinge tabs were found which indicated that insufficient glue had also been applied between the hinges and the tab structure. The aircraft manufacturer has since published a Service Bulletin to mandate more frequent visual detailed inspections of the trim tab hinge areas and has advised the trim tab manufacturer to ensure that sufficient glue is used when bonding the hinges.