The CAA Airworthiness Department issued at the end of October 2012 the long awaited guidance material for ageing engine continuing airworthiness.
This guidance material has been produced following a number of accidents over a period, involving the serious failure of high calendar time engines or their accessories. Over a prolonged calendar time engine parts risk deterioration due to corrosion and the hardening of materials such as seals, gaskets, diaphragms and flexible pipes. This leaflet has been compiled to accommodate historic engine types and their ancillary equipment which are typically without manufacturer-recommended calendar time backstops available.
The Guidance Leaflet evolved following extensive consultation with industry in which the HAA played an important role providing a great deal of technical advice and expertise. The HAA had provided technical advice to the AAIB during the investigation of the accident to Percival Provost G-AVWF that occurred in July 2009. In particular the HAA were able to suggest that a likely cause of the catastrophic engine failure in this accident was a history of hydraulic locking events that had probably not been identified. There was also some evidence of corrosion on vital engine components such as the master connecting rod gudgeon pin that may have also contributed to the engine failure.
Arising from this investigation the AAIB recommended that the CAA consider issuing guidance to operators to increase the calendar inspection processes of vital parts of aero engines where time life between inspections was not being consumed because of low utilisation.
This Leaflet 70-80 is the result of that work and now represents useful and sound guidance to both engineers and operators who may not be so familiar with the potential risk of corrosion or damage occurring to an engine between engine time life inspections.
Go to the Engineering Section on this website and click on the Engines Section to view a copy of this Leaflet. For full information and a complete copy of the downloadable Leaflet 70-80 go to -http://www.caa.co.uk/docs/33/CAP562RFS.pdf
http://www.caa.co.uk/docs/33/CAP562RFS.pdf