What happened
On 19 June 2022, an Extra EA 3/00/L, registration G-ZXEL, was performing a public aerobatic formation display near Duxford Airfield, Cambridgeshire. During a formation loop, the pilot experienced sudden, violent pitch oscillations of approximately ± 20° accompanied by a loud banging noise from the rear of the aircraft. The control stick began moving fore and aft without pilot input.
Recognizing a potential structural failure, the pilot maneuvered the aircraft away from the formation and climbed to a safe altitude, prepared to bail out if necessary. After approximately 30 seconds, the oscillations and noise ceased. A subsequent inspection by other pilots in the formation revealed that the elevator trim tab had detached from its hinges and become embedded in the rudder, causing damage to the vertical tail and rudder.
Despite the incident, the pilot performed a low-speed handling check at 4,000 feet, determined the aircraft remained controllable, and completed a successful landing at Duxford.
The investigation
The AAIB examination of G-ZXEL determined that while the trim tab had detached from the elevator, it remained connected to the aircraft via control cables. This allowed the tab to flap in the slipstream, which drove the elevator up and down and caused the physical impact against the rudder.
Investigation into the hardware revealed that the inboard hinge was the incorrect part, providing only one-third of the required bonding area. Furthermore, the outboard hinge had been improperly installed with insufficient adhesive. While the exact origin of the incorrect hinge could not be identified, evidence suggested a prior repair had been performed.
Further inspections of the operator's fleet revealed that other aircraft, including G-ZEXL, G-OFFO, and G-GEJS, exhibited cracked or loose trim tab hinges. Analysis of these components showed that the primary issue across these aircraft was the application of insufficient glue during the manufacturing process.
Findings
- The elevator trim tab detached due to the installation of an incorrect hinge type at the inboard location.
- Insufficient adhesive had been applied to the outboard hinge bonding surface.
- The flapping of the detached tab, held by control cables, caused the pitch oscillations and the striking of the rudder.
- Inspections of other aircraft in the fleet confirmed a pattern of insufficient glue application during the manufacturing of trim tab hinges.