10 January 2001
Cracked blade retaining rings
Transport Canada has received two Service Difficulty Reports describing cracking of the blade retaining ring halves (P/N 794345) on Hamilton Sundstrand (formerly Hamilton Standard) 14SF-5 and 14SF-7 propellers, which are installed on ATR-42 and DHC-8-100 aircraft, respectively.
The first cracked retaining ring was detected during a routine blade removal. The crack, which was 2 mm long and 1 mm deep, was emanating from the corner of the bore of the rear attachment bolt hole and running parallel to the outer top and bottom surfaces of the ring.
Analysis of this part indicated that the crack was not service induced, as determined by the absence of any signs of progressive formation on the fracture surface. The retaining ring material met hardness and strength specifications for the application and it was concluded that the most likely cause was an anomaly introduced during the manufacturing process.
The same operator submitted a second report identifying a crack approximately 2 mm long emanating from the retaining ring forward bolt hole.
Transport Canada strongly recommends a visual inspection in the area of the bolt hole bores of all retaining rings (P/N 794345) installed in Hamilton Sundstrand Model 14SF-5 and 14SF-7 propellers.
Further occurrences of cracking of these parts or any other defect 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. Philip Champion-Demers, Continuing Airworthiness, Ottawa, telephone (613) 941-7466, facsimile (613) 996-9178 or e-mail firstname.lastname@example.org.
For Director, Aircraft Certification
Chief, Continuing Airworthiness