1AD/B737/118 - Standby Hydraulic System - Hydraulic Fuse Operation

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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Boeing 737 Series Aeroplanes

AD/B737/118 Standby Hydraulic System - Hydraulic

Fuse Operation

7/98

Applicability: Model 737-300, 400 & 500 series aeroplanes having line numbers 1001 through 2791 (inclusive).

Requirement: 1. For aeroplanes listed in Boeing Service Bulletin 737-29-1070 dated 8 June 1995, interchange the location of the hydraulic fuse and the flow limiter of the standby hydraulic system of the leading edge so that the hydraulic fuse is positioned upstream of the flow limiter in accordance with Boeing Service Bulletin 737-29- 1070 dated 8 June 1998.

2. For aeroplanes listed in Boeing Service Bulletin 737-29-1071 dated 16 May 1996, replace the existing hydraulic fuses in the standby hydraulic system with new fuses that are not adversely affected during low temperature operation, in accordance with Boeing Service Bulletin 737-29-1071 dated 16 May 1996.

Note: FAA AD 98-07-16 Amdt 39-10436 dated 7 May 1998 refers.

Compliance: 1. Within 18 months or 4000 flight hours after the effective date of this Directive whichever is the later.

2. Within 18 months or 4000 flight hours after the effective date of this Directive, whichever is the later.

This airworthiness directive becomes effective on 18 June 1998.

Background: Tests have shown that the standby hydraulic system is designed such that possible adverse operation of the hydraulic fuses could result in the loss of all standby hydraulic system pressure and consequent severely reduced controllability of the aeroplane during certain flight phases. This AD mandates the incorporation of two Boeing Service Bulletins which correct this situation.