Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above that would supersede an existing AD. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
A complete loss of both ignition systems occurred on a DHC-3 Otter when the lock wire hole in the ignition connector plug on the firewall broke out, allowing the plug to vibrate loose. A maintenance safety feature grounds out both magneto systems through a spring-loaded safety pin incorporated into the Cannon plug. The DHC-2 system is similar in design. Subsequent to the issuance of AD CF-2001-36 a complete loss of both ignition systems occurred on a DHC-2 Beaver resulting in engine failure and subsequent forced approach and landing. Investigation by the Transportation Safety Board determined the internal failure of the magneto firewall connector resulted in both magneto "P'' leads shorting to ground. A maintenance "safety'' feature through a spring-loaded safety pin incorporated in the firewall connector on many DHC-2 aircraft grounds out both magneto systems when the connector is disconnected. This connector type is readily identified when disconnected by the existence of three internal pins on the firewall and magneto harness side, one of which is shorted directly to ground.
The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.