Document ID: chunk:federal_register_of_legislation:F2006L03418:body:0:p2
Version: federal_register_of_legislation:F2006L03418
Segment Type: other
Provision Reference: 
Character Range: 2826–4240

TIS.
             This Airworthiness Directive becomes effective on 26 October 2006.
Background:  Some EECs, returned from in-service to the manufacturer, had damaged transorbs.  A transorb is a diode type device in the EEC connect module that protects the EEC from the effects of lightning strikes by conducting the current to the ground.  A damaged transorb may compromise the EECs ability to protect circuits from damage during a lightning strike event.  Investigation has shown that the transorbs could be damaged due to an inadequate bonding between the aircraft and the engine.
             As the EEC aircraft power supply 0 Volt return line is clamped to the engine through a transorb while it is bonded to the aircraft, a difference in potential between the engine and the aircraft could result in a transorb damage.  To prevent this, an additional bonding lead must be installed between the aircraft and the engine.  In addition, all EEC units need to be electrically checked to find out if any transorb is damaged.
             The purpose of this Directive is to establish that at least one engine installed on an aircraft has an EEC installed with undamaged transorbs.  Rolls-Royce Deutschland Alert Service Bulletin TAY-73-A1703 describes the electrical check of two transorbs of the EEC on one engine of the aircraft.

James Coyne
Delegate of the Civil Aviation Safety Authority

15 September 2006