What happened
On 14 December 2016, a DHC-8-402 Dash 8 (Q400), registration G-PRPC, was performing a commercial passenger flight departing from Manchester Airport. During the takeoff roll, the outboard engine access panel on the number one engine failed at its hinge attachment points and separated from the aircraft. The detached component struck the vertical stabiliser and the VOR/LOC antennas, causing impact damage to the airframe. The panel eventually came to rest on a grass verge near the runway. There were no fatalities and no injuries among the 4 crew members or 27 passengers on board.
This event followed a nearly identical incident involving the same aircraft's number one engine panel just one month earlier, which also resulted in a panel loss during takeoff.
The investigation
The AAIB investigation focused on the maintenance performed the previous night, which included an oil level check on the number one engine. It was established that the engineer had closed the access panel, but the locking pins had not properly engaged with the receiving fixtures on the nacelle. This left a small gap that was not visually apparent.
Investigators examined the pre-flight inspection conducted by the pilot, which was performed in low-light conditions using a torch. CCTV footage confirmed the inspection took place but did not reveal the panel defect. The investigation also looked into the maintenance technique, noting that engineers often close the upper latches first. This method can lead to the panel being seated incorrectly, where the latches appear closed even though the pins are not engaged. Furthermore, the investigation found that the aircraft's purple paint scheme reduced the visual contrast of any shadow cast by a gap in the panel.