5 March 2001
Tail rotor blade cracks
Transport Canada has recently received two Service Difficulty Reports (SDRs) describing cracks on tail rotor blades on AS 350 and AS 355 series rotorcraft.
As these rotorcraft evolved and the maximum gross weight increased, a factory modified trailing edge tab was introduced to increase the chord of the blade. This tab is bonded and rivetted onto the tail rotor blade trailing edge.
The first SDR described a chordwise crack, 40 mm long, which was found on the top and bottom blade surface. This crack originated from under the trailing edge tab.
The second report also described a chordwise crack on the top and bottom blade surface. This 15 mm crack also originated from underneath the trailing edge tab but was found only because the tab was completely removed for another unrelated reason.
The SDR database lists 40 reports of various defects and cracks on this particular blade. However, these are the first reports of cracks in this area of the blades.
Transport Canada strongly advises operators and maintainers to pay particular attention for cracks in this area when carrying out visual inspections.
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 Mr. Barry Caldwell, Continuing Airworthiness, Ottawa, Ontario, telephone (613) 952-4358, facsimile (613) 996-9178 or e-mail email@example.com.
For Director, Aircraft Certification
Chief, Continuing Airworthiness