AD/PA-31/43 - Alternate Air Door Magnetic Catch - Replacement/Modification

This Airworthiness Directive mandates a safety fix for specific Piper PA-31 aircraft (Navajo models). What it requires: Owners must replace or modify the magnetic catches on the alternate air doors (backup air intakes that open if the main engine air supply gets blocked) following the manufacturer's instructions in Piper Service Bulletin No. 479B. Which planes are affected: Only specific serial numbers of the PA-31-325 and PA-31-350 models built in the mid-1970s. Why it matters: Defective magnetic catches could allow these doors to open unexpectedly or fail to seal properly, risking loss of engine power if ice or debris blocks the main air intake. Deadline: The modification had to be completed before 1 August 1976. While this directive is historical, it remains enforceable until compliance is recorded in the aircraft's maintenance logs.

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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

View image in the official source Piper PA-31 Series Aeroplanes

AD/PA-31/43 Alternate Air Door Magnetic Catch -

Replacement/Modification

5/76

Applicability: Model PA-31-325 with S/Nos. 31-7400990 and 31-7512006 to 31-7612030. Model PA-31-350 with S/Nos. 31-5001 to 31-7652066.

Document: Piper SB No. 479B. Compliance: Before 1 August 1976.