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Summary

Summary

Over a period of four days the aircraft operated twenty sectors with a high pitch squeal emanating from the L2 door. The squeal reportedly occurred at the top of climb and during cruise, and stopped when power was reduced and descent commenced. On some sectors the squeal was not reported. On other sectors it was controlled by lowering the cabin differential pressure. At times the squeal was so loud that ear muffs were worn by the cabin crew, and passengers were seated away from the area. The investigation was unable to determine who issued the verbal instruction which resulted in the ear muffs being issued. After many attempts at rectification the aircraft was removed from service and ferried to Melbourne. During the flight a licensed aircraft maintenance engineer was able to remove some trim and closely inspect the door. He found that above certain pressure differentials and airspeeds the lower door seal was able to flutter. The door was examined and found to be rigged to the upper limit allowed by the maintenance manual.The door assembly was rerigged to the lower limit. During a subsequent verification flight, the seal was found to be secure. The adjustment required was small, the door being lowered less than four mm. The investigation disclosed that many factors had inhibited the early detection and rectification of the problem. These included; - an inadequate system of recording cabin defects, - flight crews did not always record that the defect existed, - flight attendants gave incomplete reports to flight crews, - a lack of timely advice to maintenance management, and - the difficulty in visually identifying the seal flutter. The investigation also found there had been inadequate communication links between: - flight attendants and the company's cabin safety management, - the flight attendants union and the company cabin safety management, - cabin safety management and maintenance, and - flying operations, cabin safety management and maintenance. While it is undesirable to have a defect existing for so many sectors, this particular defect was difficult to detect in normal service and was not found until after the door trim was removed and the seal closely inspected in flight. The major safety concern was that on some sectors the cabin crew wore ear muffs which could have prevented them from immediately responding to some other problem, should one have occurred. Safety actions taken. The operator is introducing a system of recording cabin defects that will stand alone from the technical report used by flight crews. This will require appropriate certification to transfer technical items into the maintenance log, and will also enable cabin crews to have access to a running history of cabin reports. The operator has also instituted an enhanced communications structure that will allow pilot reports to be rapidly conveyed to maintenance management, ensuring direct contact between operations, maintenance and cabin safety management. The operator's cabin safety management has advised cabin crews to make immediate telephone contact with them in the event of similar problems occurring.
 
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