Incident Details
On September 14 and 15, 2018, crews of a Bombardier Dash 8 Q400 (DHC-8-402) operated by PLL LOT encountered cabin pressurization issues while descending to land at Warsaw Okęcie Airport (EPWA). During these commercial flights, the decompression panel located in the rear wall between the cabin and the baggage compartment became dislodged. Passengers exiting the aircraft complained of blocked and painful ears. The crews recorded the occurrences in the aircraft technical log (LDP-60) but did not file Air Safety Reports (ASR).
Technical Analysis
After the first pressurization loss and panel dislodgement, maintenance actions consisted only of reinstalling the panel. Following a subsequent pressurization loss, a technical analysis identified damage to the seal of the rear cargo door (AFT BAGG DOOR). The damaged seal was replaced. During evaluation of the rear cargo door closing procedure by ground personnel, it was noted that the door was being closed (latched) forcefully, which may reduce seal service life. In the operator's fleet, a total of four in-flight pressurization irregularities were attributed to faulty rear cargo door seals. Two involved seal abrasion, and two involved moisture accumulation and freezing of condensate in the door seal. According to manufacturer reliability analysis, the Cumulative Unscheduled Removal Rate (Cum URR) for Q400 rear cargo door seals across the fleet was 84 removals since entry into service. The manufacturer had not established a separate programme for inspection and replacement of these seals.
Preventive Actions
The operator registered the event in its SMS database and classified it according to established criteria. The safety board requested the Q400 fleet engineer to analyse the recurrence of in-flight pressurization loss due to rear cargo door seal damage and to review the inspection/replacement frequency. The engineer reported that during winter, seal condition checks and lubrication were recommended during L50 maintenance checks. Instructions were issued to technical services on proper fault analysis and rectification procedures for pressurization loss and panel dislodgement. The Q400 fleet safety pilot requested statements from captains involved regarding the events and the reasons for not submitting ASRs. The events were described in the Q400 fleet safety bulletin No. 09,10/2018, distributed to pilots on December 7, 2018. Given that seal damage may result from improper door closing by ground personnel, it was proposed that the engineer, together with ground handling, develop an informational bulletin reminding ground staff of correct door closing procedures and distribute it to contracted ground organisations. During recurrent SMS pilot training, the principles of filing ASRs and recording defects or suspicions in the LDP-60 were reinforced.