Airworthiness Directive · Amendment 39-11851 · Boeing Model 737-100 and -200 Series Airplanes
Boeing Model 737-100 and -200 Series Airplanes
Model 737-100 and -200 series airplanes, line numbers 001 through 813 inclusive, certificated in any category.
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 737-100 and -200 series airplanes, that currently requires inspections to detect cracking of the support fittings of the Krueger flap actuator; and, if necessary, replacement of existing fittings with new steel fittings and modification of the aft attachment of the actuator. That AD also provides for an optional terminating modification that constitutes terminating action for the repetitive inspections. This amendment requires accomplishment of the previously optional terminating action. This amendment is prompted by reports of cracking due to fatigue and stress corrosion of the support fittings of the Krueger flap actuator. The actions specified by this AD are intended to prevent such cracking, which could result in fracturing of the actuator attach lugs, separation of the actuator from the support fitting, severing of the hydraulic lines, and resultant loss of hydraulic fluids. These conditions, if not corrected, could result in possible failure of one or more hydraulic systems, and consequent reduced controllability of the airplane.
To prevent possible failure of one or more hydraulic systems and consequent reduced controllability of the airplane, accomplish the following:
(a) Within one year after September 17, 1996 (the effective date of AD 96-17-04, amendment 39-9712), perform an eddy current inspection to detect cracking of the support fitting of the Krueger flap actuator on each wing, in accordance with Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notices of Status Change 737-57-1129 NSC 1, dated July 23, 1982; 737-57-1129 NSC 2, dated April 14, 1983; and 737-57-1129 NSC 3, dated May 18, 1995; or Revision 2, dated May 28, 1998.
(1) If no cracking is detected, repeat the inspection required by paragraph (a) of this AD thereafter at intervals not to exceed 3,000 hours time-in-service.
(2) If any cracking is detected, prior to further flight, accomplish the replacement and modification specified in paragraph (b) of this AD.
(b) Within 5 years after the effective date of this AD: Replace any existing aluminum support fitting of the Krueger flap actuator on each wing with a steel fitting, and modify the actuator aft attachment, in accordance with Boeing Service Bulletin 737-57-1129, Revision 2, dated May 28, 1998. Accomplishment of this replacement and modification constitutes terminating action for the repetitive inspections required by paragraph (a) of this AD.
Note 2: Replacement of the existing aluminum support fitting of the Krueger flap actuator on each wing with a steel fitting, and modification of the actuator aft attachment, prior to the effective date of this AD, in accordance with Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notices of Status Change 737-57-1129 NSC 1, dated July 23, 1982; 737-57-1129 NSC 2, dated April 14, 1983; and 737-57-1129 NSC 3, dated May 18, 1995; is considered acceptable for compliance with the modification required by paragraph (b) of this AD.
(c) As of the effective date of this AD, no person shall install on any airplane any aluminum support fitting identified in the “Existing Part Number” column of Paragraph 2.D. of Boeing Service Bulletin 737-57-1129, Revision 2, dated May 28, 1998.
