AL 1999-03
11 August 1999
Nose Gear Door Torque Tube
A recent Service Difficulty Report has been received outlining the results of an investigation on the integrity of an operator's nose wheel door torque tube assembly. The investigation on the Canso PBY5A found visible external corrosion at the left aft operating arms; upon removal, severe internal corrosion was found. Upon removal of the right torque tube internal corrosion was discovered.
What prompted the investigation was a report issued by the United Kingdom's Air Accident Investigation Branch as a result of a Catalina crash upon landing that occurred 27 July 1998 in the Southampton water (AAIB bulletin No. 1/99 Ref. EW/C98/7/9 Category 1.1). The report concluded that the accident was caused by the severe corrosion in the nosegear operating mechanism torque tube.
The left door was suspected to have first torn off complete with most of the torque tube followed by the right door. A breach of the aft bulkhead ensued while the roof of the nose gear well separated at the riveted joints allowing water to enter into the front cabin. The aircraft sank so quickly that two of the fourteen occupants were unable to escape.
The UK report goes on further to explain that corrosion inside the tube would have been completely concealed from inspection as both ends were closed; the construction of the tube assembly, however, makes it possible for liquid to enter and remain undetected.
Transport Canada therefore recommends that the left and right torque tubes be removed and inspected for corrosion, particularly at the aft curved levers, at the next convenient maintenance opportunity.
Any defects or further occurrences should be reported by sending a Service Difficulty Report to Transport Canada, Continuing Airworthiness, Ottawa.
For further information contact a Transport Canada Centre, or call Mr. Robert Dixon, Continuing Airworthiness, Ottawa, telephone (613) 952-4308, facsimile (613) 996-9178 or e-mail dixonro@tc.gc.ca.
For Director, National Aircraft Certification
B. Goyaniuk
Chief, Continuing Airworthiness