1AD/DC4/34 Amdt 1 - Electrical Distribution Bus

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Douglas DC4 Series Aeroplanes

AD/DC4/34

Amdt 1

Electrical Distribution Bus 4/97

Applicability: All DC-4 and C-54 aeroplanes.

Requirement: 1. Inspect the electrical distribution bus to ensure that at least 12.7mm (0.5 inch) clearance is maintained between the bus and protuberances likely to “ground” the bus in the nacelle areas.

Note 1: Particular attention should be given to the areas around the engine control pulleys and the pulley guide brackets.

2. Remove the large gauge nacelle-to-bus feeder cables, that are run in metallic conduits, from the conduits and inspect them for chafing or mechanical deterioration of the insulation.

Note 2: Oil-soaked insulation alone is not considered as sufficient cause to require the replacement of the cables.

3. If any cables are found to be damaged during the Requirement 2 inspection, replace the cables with cables conforming to Douglas Aircraft Company (DAC) specification BXS7008, per MIL-L-22759 or DAC specification DMS2426, per MIL-W-81381/12.

4. If not previously accomplished, inspect the electrical distribution bus to ensure that the supporting brackets are of an approved DAC standard quality and that cushioned non grounding cable clamps are used for clamping the bus onto the brackets. Replace any substandard brackets or clamps.

Note 3: FAA AD 48-09-02 and Douglas Service Letter A214TS-1245/SRD-530 dated 10 October 1947 refer.

Compliance: For Requirement 1 - Prior to 22 May 1997 and thereafter at intervals not to exceed 400 hours time in service.

For Requirement 2 - Prior to 22 July 1997 and thereafter at intervals not to exceed 8000 hours time in service.

For Requirement 3 - Prior to further flight. For Requirement 4 - Prior to 22 July 1997.

This Amendment becomes effective on 27 March 1997.

Background: Actions mandated by this Directive are designed to preclude the possibility of short circuits occurring in the electrical distribution bus running from nacelles number one to four, which is impractical to protect by circuit protection devices.

This Directive was originally issued in 1948, this amendment both amplifies the requirements and clarifies the compliance intervals.

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES