US safety regulators are recommending a series of check on certain Boeing 757-200 converted freighters, after an incident in which the main cargo door opened during flight.
The US FAA has stopped short of issuing an airworthiness directive but, in a safety information bulletin, highlights the occurrence in February 2021 during which the main door opened while the DHL Air aircraft was climbing out of Leipzig.
While the crew observed a sudden cabin pressure problem, there was no instrument indication that the door had malfunctioned or opened.
The aircraft had been modified by Precision Conversions, including installation of the hydraulically-operated main cargo door, plus mechanical latches and locking hooks to secure it shut during flight.
Proximity sensors provide signals to confirm the door is locked and latched, and a warning system is supposed to alert the crew to potential anomalies.
Precision Conversions’ most recent revision of its 757 operations manual is supplemented with specific procedures for opening and closing the main door.
Its maintenance manual also contains particular servicing and testing processes including cleaning of view-port mirrors and windows, and painting of latches and lock pins.
The FAA bulletin recommends that operators perform ‘door-open’, ‘door-closed’ and ‘latched and locked’ test procedures, detailed in the Precision Conversions documents, every 5,000 cycles.
Operators should inspect view-port mirrors and windows for “smudges, debris and other contaminants”, it adds, and check the latches and lock pins for “paint defects” – carrying out the documented cleaning and painting procedures if required.
Crews should also follow procedures for operating in cold weather, including removal of snow or ice around the cargo door and its mechanisms, and consider the need for additional inspections in freezing fog or icing conditions.
Although the bulletin only mentions the Leipzig incident, Russian federal air transport regulator Rosaviatsia referenced a similar occurrence to a Precision Conversions 757-200 freighter operated by Yakutia, as part of a notification on a series of in-flight door events in December 2014.
While the jet was being unloaded at Magadan on 5 December 2014, the main cargo door was periodically opened and closed over a period of 8h in snow, gusting winds, and temperatures of around minus 20-25°C.
The aircraft took off for Shijiazhuang in China the following day, with no freight on board, but the crew received a warning that the cargo door was not secure, followed by the door’s lifting to its fully-open position.
It subsequently returned to Magadan where its landed safely. Inspection of the jet found compacted ice and snow in the vicinity of the door locking mechanisms and proximity switches.
