Document ID: chunk:federal_register_of_legislation:F2008L02659:body:0:p2
Version: federal_register_of_legislation:F2008L02659
Segment Type: other
Provision Reference: 
Character Range: 2816–4192

considered to have occurred during operation, for reasons not fully understood.  Further loosening may have taken place in-service under influence of vibration.  As a result, poor contact caused electrical arcing during which extremely high temperatures were developed, leading to partial melting of the terminal.

   Investigation of some other burned contactors revealed evidence (flat spring lock washer) of a fully torqued terminal/stud connection when the overheating occurred.  The exact cause for the increase in temperature in the contactor and the terminal/stud could not be determined.  However, it could not be excluded that an increase of the temperature inside the contactor could lead to reduction of the reliability of the contactor stud/terminal connection due to loss of lock washer tension.  The affected Electrical Power Contactor is used on several locations in the electrical power system, i.e. Generator Line Contactor (GLC), Bus Tie Contactor (BTC), Auxiliary Power Contactor (APC) and External Power Contactor (EPC).

   This condition, if not corrected, could lead to further cases of overheating of terminals and studs of Electrical Power Contactors P/N SG02206, possibly resulting in the loss of electrical power systems, electrical arcing and fire/smoke in the cockpit.

James Coyne
Delegate of the Civil Aviation Safety Authority

13 June 2008