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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

Piper PA-23 (Apache and Aztec) Series Aeroplanes

AD/PA-23/86 Ammeter Cable Clamp - Inspection

and Replacement

Applicability: All model PA-23 all serial numbers.

3/93

Requirement: 1. Inspect the clamp securing the cable which connects the battery to the ammeter.

2.     If the clamp is metal and does not have a cushion insulation lining, remove the clamp and inspect the cable for damage.

3.     If the cable is damaged, repair or replace the cable as required.

4.     Secure the cable to the aircraft tubular structure using a cushioned (insulated) type clamp meeting Specification MS-21919 as detailed in FAA-AC 43.13-1A. Ensure clamps are correctly sized to secure the cable firmly and that the cable is aligned so that it passes centrally through the clamp axis.

5.     Ensure cables are free from rubbing by the co-pilots control column.

6.     If existing clamps have insulation liners, ensure that these are undamaged. Compliance:              Within 25 hours time in service after 4 Mar 1993.

Background:  An investigation into a Piper PA-23 aircraft fire, conducted by BASI, revealed that the cable connecting the ammeter to the battery had melted coincident where it passed through a metal supporting clamp. This caused a fire behind the instrument panel and resulted in cabin and fuselage destruction. Inspection also indicated that poor routing of the ammeter cable had allowed the co-pilots control column to rub against the cable.