What happened
During aircraft preparations, ground handling agents removed various covers, including pitot tubes, from the aircraft. During this process, the horizontal stabiliser bungs remained in place. Despite the ground crew working around the rear of the aircraft multiple times, the bungs were not identified. Following the ground works, the flight crew performed external inspections. The first officer specifically noted a focus on the rear of the aircraft and removed the tail stand, yet neither pilot noticed the bungs. CCTV footage reviewed during the investigation also failed to show the bungs while the aircraft was parked or taxiing, suggesting the bungs were either improperly installed or the 'remove before flight' conspicuity flags were not visible as intended.
The investigation
Investigators examined the ground handling agent's training and equipment. While the training required agents to retain the bungs, it lacked specific instructions regarding their storage. Because the containers used by the agent held multiple sets of bungs, it was impossible to verify which equipment had been removed from which specific aircraft. Furthermore, while existing airline checklists required crews to account for removed covers, there was no specific pre-flight procedure to check for the presence of horizontal stabiliser bungs. The crew's ability to detect the bungs relied entirely on seeing the conspicuity flag, which was not visible in this instance.
Findings
- The horizontal stabiliser bungs were likely incorrectly installed or the tether rope and conspicuity flag were not positioned as designed.
- The lack of formal procedures for the storage and accountability of the bungs prevented a positive assurance check by both ground and flight crews.
- The design of the bungs did not sufficiently ensure they would be easily identifiable if installed incorrectly.
- The operator had not performed a specific risk analysis regarding the hazards introduced by a control surface bung remaining installed during flight.