AL 2007-03R1
10 June 2009
Control cable inspection
This Revision is further to the original issuance of the Service Difficulty Alert (SDA), wherein your attention was brought to a Twin Otter accident in French Polynesia. The investigation is now complete, with the cause attributed by the investigating body, to the failure of the up elevator control cable in the vicinity of the fairlead located at airframe station 426.
Viking Air Limited has conducted a survey of operators to gain knowledge of in-service cable wear on the DHC-6 aircraft. As a result of this survey, revisions to the maintenance recommendations have been developed. All operators should have received these publications in the form of Temporary Revisions (TR) to the pertinent maintenance publications from Viking Air.
These recommendations should be reviewed by all operators for consideration in their maintenance planning.
Transport Canada is issuing this SDA to ensure that operators and maintainers are aware of, and are following the latest Instructions for Continued Airworthiness (ICA) for the Twin Otter, which includes Inspection Requirements Manual PSM 1-6-7 and Service Bulletin 6/523 - Special Inspection of Control Cables for Wear and Corrosion. Additionally PSM 1-6-2, 1-63-2 and 1-63S-2 contain cable inspection criteria.
In addition to the cable inspection requirements, periodic replacement of cables are required according to TCCA Airworthiness Directive CF-2000-14 which mandates the DHC-6 Structural Components Service Life Limits Manual PSM 1-6-11.
Viking Air has issued DHC6-SL-27-002, dated 18 March 2009, “Flight Control Cable Return Program” requesting DHC-6 operators to provide information to Viking, of all control cables found damaged as a result of in-service wear or corrosion prior to the recommended service life limit.
Transport Canada supports this initiative and recommends all DHC-6 operators comply with this request.
Any further defects or occurrences should be reported to Transport Canada, Continuing Airworthiness, Ottawa, via the Service Difficulty Reporting (SDR) program.
For further information regarding this SDA, contact a Transport Canada Centre, or Mr. Paul Jones, Continuing Airworthiness, Ottawa, telephone 613-952-4431 or by email at cawwebfeedback@tc.gc.ca
For Director, Aircraft Certification
Derek Ferguson
Acting Chief, Continuing Airworthiness