AD/B737/15 Amdt 3 - Fuel Boost Pump Bypass Valve (Cth)

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

Boeing 737 Series Aeroplanes

AD/B737/15 Amdt 3

Fuel Boost Pump Bypass Valve 11/90

Applicability: Model 737 series aeroplanes listed in Boeing Service Bulletin 737-28A1072 Revision 4.

Requirement: 1. Action in accordance with Part I of Boeing Service Bulletin 737-28A1072 Revision 4.

2. Unless already modified in accordance with Part II of Boeing Service Bulletin 737-28A1072 Revision 2 or 3, action in accordance with Part II of Boeing Service Bulletin 737-28A1072 Revision 4.

3. For those aircraft which exhibited bracket preload when previously modified in accordance with Boeing Service Bulletin 737-28A1072 Revision 2 or 3; unless already accomplished, conduct an inspection of the suction feed bypass system for preloading in accordance with Boeing Service Bulletin 737-28A1072 Revision 4.

Note: FAA AD 90-15-17 Amdt 39-6673 refers.

Compliance: 1. At each maintenance interval coinciding with approximately 300 hrs time in service, until improved bypass valves are installed in accordance with Requirement 2.

2. Prior to 31 March 1992.

3. Prior to 31 March 1992.

Background: The manufacturer has determined that two separate incidents of engine flame out during cruise conditions was caused by small accumulations of water freezing in the Fuel Boost Pump Bypass Valve, and preventing fuel flow to the engine while on suction feed. Amendment 3 is raised in response to a revision of the country of origin AD which required modification of those aircraft not previously modified and an inspection for bracket preload for aircraft modified prior to Revision 4 of the Service Bulletin.