AD/B747/174 Amdt 1 - Strut Midspar Fitting Lower Horizontal Clevis (Cth)

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

Boeing 747 Series Aeroplanes

AD/B747/174 Amdt 1

Strut Midspar Fitting Lower Horizontal Clevis 10/97

Applicability: Model 747 series aircraft with line numbers 1 through 886; equipped with Pratt and Whitney JT9D-3, -7, and -70 series engines, General Electric CF6-45/-50 series engines, or Rolls Royce RB211 series engines; and on which the strut/wing modification has not been accomplished in accordance with Boeing Alert Service Bulletin (ASB) 747-54A2157, Boeing ASB 54A2158, or Boeing ASB 747-54A2159, as applicable.

Requirement: Action in accordance with the technical requirements of FAA AD 97-12-03 Amdt 39- 10045.

Note: Boeing Alert Service Bulletins 747-54A2179 and 747-54A2179 Revision 1, and Boeing Service Bulletin 747-54-2118 and subsequent revisions refer.

Compliance: As specified in the requirement document with a revised effective date of 11 September 1997.

Background: The FAA received reports of fatigue cracking, stress corrosion cracking, and fracturing of the horizontal clevis of the inboard midspar fitting at the number 3 strut position. Such cracking and fracturing could result in drooping of the strut at the strut-to-wing interface, and consequent separation of the engine and strut from the aircraft.

Amendment 1 is issued in response to a new FAA AD which combines the requirements of FAA ADs 87-04-13 R1 (AD/B747/57 Amdt 1) and 96-25-01 in this directive. This amendment continues to require inspections to detect cracking, corrosion, and fracturing of the lower horizontal clevis; and adds corresponding inspections of the upper horizontal clevis, and replacement of discrepant parts with new parts, or rework, if necessary. This amendment also removes certain optional terminating actions. This latest FAA action is prompted by reports of cracking of the lower and upper leg of the horizontal clevis of the midspar fitting.