COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Beechcraft 50 (Twin Bonanza) Series Aeroplanes AD/BEECH 50/28 Wheel Well Fuel Lines 4/79 Applicability: All models. Requirement: Replace all aluminium fuel lines upstream of the fuel selector valve in each main landing gear wheel well with lines fabricated from stainless steel. Note: This requirement does not include the large diameter fuel tank interconnect line situated in the aft section of the wheel wells. Compliance: Before 1 July 1979. Background: In the event of an uncontained engine compartment fire it is known that flames will be directed by the slipstream into the main landing gear wheel wells, through which unprotected aluminium fuel lines of small diameter are located. Should any line burn through upstream of the fuel selector valve an uncontrollable amount of fuel will be added to the fire and the integrity of the wing main spar will be endangered. In order to reduce this threat, the aluminium fuel lines are to be replaced with those of stainless steel.