Incident Overview
On 29 November 2011, a DHC-8-402 Dash 8, registration G-JEDV, was cruising at flight level (FL) 240 over the Thames Estuary when the cabin began to depressurize. A cabin crew member reported a loud whistling noise from the forward left door, although the door appeared closed and the flight deck indicated it was secure. The cabin altitude initially increased at nearly 500 ft/min, then accelerated rapidly, triggering the cabin pressurization warning.
Emergency Response
The pilots initiated an emergency descent. The commander began the descent while the co-pilot transmitted a mayday call and both donned oxygen masks. Air traffic control cleared the aircraft to descend to FL100 and vectored it for an approach to Gatwick Airport. During the descent, the noise from the door increased, the cabin altitude rose quickly, and a red cabin press warning activated, indicating loss of cabin pressure.
Subsequent Actions
After assessing the situation, the pilots determined there was no damage to the aircraft and no injuries to the 50 passengers or 4 crew members. They decided to continue with a slow descent to their intended destination, Southampton Airport, rather than a rapid descent into Gatwick. This approach allowed time to complete checklists and brief for landing, and was considered more comfortable for passengers. At FL80, the pilots performed a manual depressurization and flew an uneventful approach, maintaining a low rate of descent, and landed safely at Southampton.
Cause Investigation
The cause of the depressurization was not determined. The operator noted that G-JEDV had experienced several pressurization events prior to this incident. Following this occurrence, the door seal, cabin pressure controller, and pressurization control panel were replaced. As of the time of reporting, no further pressurization problems had been encountered.