What happened
On 29 November 2011, a DHC-8-402 Dash 8, registration G-JEDV, was operating a commercial passenger flight at FL240 over the Thames Estuary. During the cruise phase, cabin crew alerted the flight deck to a loud whistling noise emanating from the forward left door, which appeared to be properly closed. Shortly after this report, the flight crew observed a rapid increase in cabin altitude, accompanied by a red cabin pressure warning light.
In response to the loss of pressure, the commander initiated an emergency descent. The crew transmitted a mayday call and donned oxygen masks. Air Traffic Control (ATC) provided vectors for an approach to Gatwick Airport, descending the aircraft to FL100. However, the crew determined that a slower descent toward their original destination, Southampton Airport, was more appropriate to allow for the completion of checklists and passenger briefing. Upon reaching FL80, the pilots performed a manual depressurisation. The flight concluded with an uneventful landing at Southampton Airport, with no injuries reported to the 4 crew members or 50 passengers, and no damage to the aircraft.
The investigation
The investigation examined the aircraft' and the operational history of the fleet. It was noted by the operator that G-JEDV had been involved in several recent pressurisation incidents. While the specific cause of the depressurisation during this flight was not identified, the operator had previously replaced the door seal, the cabin pressure controller, and the pressurisation control panel following those prior events. No further pressurisation issues had been recorded on the aircraft following these replacements.