1AD/HU 269/69 - Alternator Circuit Protection - Modification

COMMONWEALTH OF AUSTRALIA CIVIL AVIATION ORDERS CIVIL AVIATION SAFETY AUTHORITY PART 105 SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Schweizer (Hughes) 269 Series Helicopters

AD/HU 269/69 Alternator Circuit Protection - Modification 6/80

Applicability: All 269 Series operating under Instrument Flight Rules (IFR) or Flights at Night in VMC.

Requirement: 1. Install a 5 ampere circuit protective device between the cable-coded P34A20 and the alternator switch (269A4613) and identify as “Alternator Field”.

Note: An inline fuse is an acceptable means of compliance.

2. Install a circuit protective device between the Alternator positive-cable and the bus. This protective device shall be of a value that will protect the particular sized cable installed and shall be identified as “Alternator”.

Note: A circuit protective device which meets the requirements of the cable and circuit protector coordination chart in ANO 108.32, Appendix 3, Table 6 will be an acceptable means of compliance.

Compliance: Within 100 hours time in service after 30 June 1980.

Background: A recent defect report highlighted the problem of smoke in the cockpit when the field circuit was grounded within the alternator. The above modification should prevent this type of defect and/or an earth on the alternator positive line which necessitates removal of all electrical power from the aircraft. This is a potential hazard in NVMC aircraft. Modification is also considered highly desirable for VFR aircraft.

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