5 January 2005
Transport Canada was informed by the Service Difficulty Reporting program that maintenance personnel discovered an oil leak in the outboard side of the left nacelle.
After cleaning, oil was observed running down the oil return line (cooler to tank) where a wire bundle was found fretting against the damaged line.
Damage found to wires for the hydraulic and oil firewall shut-off valves
Investigation revealed a wire that had chafed through was arcing against the oil tube causing a pinhole in the tube. The burnt wire supplies power to the hydraulic firewall shut-off valve. The arcing also damaged the power wire for the oil shut-off valve that is encased in the same wire bundle. The operator inspected the remaining aircraft in their fleet discovering one other aircraft with similar damage.
The hydraulic and engine oil shut-off valves are a fail-safe design. If these burnt wires were left undetected, the power supply could have been interrupted preventing the valves from closing.
Transport Canada strongly recommends operators inspect this area for chafing or burnt wires at their earliest convenience. Any defects discovered should be repaired in accordance with the published instructions.
Any further defects or occurrences should be reported to Transport Canada, Continuing Airworthiness, Ottawa, via the Service Difficulty Reporting program.
For further information, contact a Transport Canada Centre, or Mr. Steve Dudka, Continuing Airworthiness, Ottawa, telephone (613) 952-4361, facsimile (613) 996-9178 or e-mail email@example.com.
For Director, Aircraft Certification
Chief, Continuing Airworthiness
Note: For the electronic version of this document, please consult the following Web address: https://tc.canada.ca/en/aviation/aircraft-airworthiness/aircraft-certification