Airworthiness Directive · Amendment 39-11623 · Boeing Model 737 Series Airplanes
Boeing Model 737 Series Airplanes
Model 737-100, -200, -300, -400, and -500 series airplanes; line positions 1 through 2135 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 (e) 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 adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737 series airplanes, that requires a one-time inspection of the main landing gear (MLG) axle flange to detect cracking, and follow-on corrective actions. For certain airplanes, this amendment also requires replacement of the original brake mounting gasket with a more durable aluminum-nickel-bronze gasket, and installation of new shear studs, if necessary. For certain airplanes, this amendment requires modification of the mounting flange holes of the brake torque tube. This amendment is prompted by reports of cracking in the axle flange and by reports of deterioration of the brake mounting gasket. The actions specified by this AD are intended to prevent fracture of the MLG axle and separation of the wheel from the MLG, and consequent reduced controllability of the airplane.
To prevent fracture of the main landing gear (MLG) axle and the separation of the wheel from the MLG, and consequent reduced controllability of the airplane, accomplish the following:
(a) For Model 737-100 and -200 series airplanes equipped with AlliedSignal (ALS/Bendix) brake assembly installations having Boeing part numbers (P/N) 10-61063-14, -18, or -21, on which the original gaskets have been replaced with aluminum-nickel-bronze gaskets in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991: Except as provided by paragraph (d) of this AD, within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the requirements of paragraphs (a)(1), (a)(2), and (a)(3) of this AD.
(1) Perform either a one-time magnetic particle inspection or a one-time high frequency eddy current inspection of the MLG axle flange to detect cracking, except that a high frequency eddy current inspection may only be accomplished if the axle flange has not been repaired previously and coated with a nickel sulfamate finish. The magnetic particle inspection or high frequency eddy current inspection is to be accomplished in accordance with procedures specified in paragraph B. of the “Recommended Operator Action” section of Boeing All Operators Telex (AOT) M-7272-96-1442, dated March 29, 1996. If any cracking is detected, prior to further flight, repair the MLG flange, in accordance with Boeing Overhaul Manual 32-11-11, or other method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.
(2) If any corrosion or fretting is found during accomplishment of the inspection required by paragraph (a)(1) of this AD: Prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.
(3) Accomplish the modification of the brake torque tube mounting holes, in accordance with AlliedSignal Service Bulletin 2601042-32-003, dated March 15, 1997.
(b) For Model 737-100 and -200 series airplanes equipped with AlliedSignal (ALS/Bendix) brake assembly installations having Boeing P/N 10-61063-14, -18, or -21, on which the original gaskets have not been replaced with new aluminum-nickel-bronze gaskets in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991: Except as provided by paragraph (d) of this AD, within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the requirements of paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD.
(1) Perform either a one-time magnetic particle inspection or a one-time high frequency eddy current inspection of the MLG axle flange to detect cracking, except that a high frequency eddy current inspection may only be accomplished if the axle flange has not been repaired previously and coated with a nickel sulfamate finish. The magnetic particle inspection or high frequency eddy current inspection is to be accomplished in accordance with procedures specified in paragraph B. of the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996. If any cracking is detected, prior to further flight, repair the MLG flange, in accordance with Boeing Overhaul Manual 32-11-11, or other method approved by the Manager, Seattle ACO.
(2) If any corrosion or fretting is found during accomplishment of the inspection required by paragraph (b)(1) of this AD: Prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.
(3) Accomplish the modification of the brake torque tube mounting holes, in accordance with AlliedSignal Service Bulletin 2601042-32-003, dated March 15, 1997.
(4) Accomplish the modification of the affected brake mounting hardware in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991.
(c) For Model 737-100, -200, -300, -400, and -500 series airplanes other than those identified in paragraphs (a) and (b) of this AD: Except as provided by paragraph (d) of this AD, within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the requirements of paragraphs (c)(1), (c)(2), and (c)(3) of this AD.
(1) Perform either a one-time magnetic particle inspection or a one-time high frequency eddy current inspection of the MLG axle flange to detect cracking, except that a high frequency eddy current inspection may only be accomplished if the axle flange has not been repaired previously and coated with a nickel sulfamate finish. The magnetic particle inspection or high frequency eddy current inspection is to be accomplished in accordance with procedures specified in paragraph B. of the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996. If any cracking is detected, prior to further flight, repair the MLG flange, in accordance with Boeing Overhaul Manual 32-11-11, or other method approved by the Manager, Seattle ACO.
(2) If any corrosion or fretting is found during accomplishment of the inspection required by paragraph (c)(1) of this AD: Prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.
(3) Accomplish the modification of the affected brake mounting hardware in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991.
Note 2: Accomplishment of the magnetic particle or HFEC inspections of unrepaired axle flanges in accordance with Boeing Telex M-7272-96-1442, dated March 29, 1996, concurrent with or after installation of an aluminum-nickel-bronze gasket and shear studs, is considered acceptable for compliance with the requirements of paragraphs (a)(1) and (c)(1) of this AD.
(d) The actions required by paragraphs (a), (b), and (c) of this AD may be accomplished at the time specified in paragraph (d)(1) of this AD, provided that the action specified in paragraph (d)(2) is accomplished.
(1) Within 1 year or 4,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the actions specified in paragraph (a), (b), or (c) of this AD, as applicable; and
(2) Within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, perform a detailed visual inspection to detect fretting or corrosion of the axle flange bolt holes. If any fretting or corrosion is detected, prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.
Note 3: For the purposes of this AD, a detailed inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”
