What happened
On 15 August 2015, a DHC 6-300, registration C-GSGF, was performing a geological survey flight departing from Weston Airport, Co. Kildare. Shortly after takeoff, air traffic control notified the flight crew that the aircraft's nose cone appeared to have fallen off. The crew confirmed that the nose cone from the right-hand electromagnetic (EM) pod had detached.
As the aircraft climbed, the crew experienced a significant amount of rightward yaw that was physically perceptible through the flight controls. To manage the instability, the pilot leveled the aircraft at 1,500 feet and issued a "PAN" call. The crew decided to divert to Dublin Airport, choosing the larger runway and more comprehensive emergency services available there. The aircraft landed safely at Dublin International without further incident or injuries to the two crew members and one passenger.
The investigation
The AAIU investigation focused on the maintenance history and the pre-flight inspection process. It was discovered that the aircraft had undergone a supplementary inspection the previous day, which required the removal of the EM pod nose and tail cones. During this maintenance, a sensor fault was detected, causing the re-installation of the nose cone to be halted. Consequently, only two of the sixteen required retaining screws were actually installed.
Investigators found that the maintenance personnel did not use flagging tape—a standard company practice—to indicate that parts had been removed. Furthermore, the two installed screws were located at the top of the pod and were not visible from the ground. During the pre-flight walkaround, the pilot, co-pilot, and maintenance engineers all failed to notice the missing hardware. The investigation also noted that the pilot's inspection was interrupted by a briefing from engineers, which may have served as a distraction.
Findings
- The primary cause of the incident was that the right-hand EM pod nose cone was not properly re-installed following a maintenance inspection.
- The failure to use flagging tape meant there was no visual cue for the crew that the re-installation was incomplete.
- The two installed screws were positioned in a way that they were invisible to anyone performing a ground-level inspection.
- Human factors, including confirmation bias and habituation, likely prevented the inspection personnel from detecting the missing screws.
- There was no specific emergency checklist available in the aircraft's flight manual supplement for the loss of a pod nose cone.