Airworthiness Directive · Amendment 39-11660 · Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes
Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes
Superseded. A later AD replaced this one: AD 2013-09-10. Comply with the one in force.
All Model 737-100, -200, -200C, -300, -400, and -500 series airplanes; 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 all Boeing Model 737-100, -200, -200C, -300, -400, and - 500 series airplanes. This AD requires repetitive inspections to detect cracking of the lower corners of the door frame and cross beam of the forward cargo door, and corrective actions, if necessary. This AD also requires eventual modification of the outboard radius of the lower corners of the door frame and reinforcement of the cross beam of the forward cargo door, which would constitute terminating action for the repetitive inspections. This amendment is prompted by reports indicating that fatigue cracks have been detected in the lower corners of the door frame and cross beam of the forward cargo door. The actions specified by this AD are intended to prevent fatigue cracking of the lower corners of the door frame and cross beam of the forward cargo door, which could result in rapid depressurization of the airplane.
To prevent fatigue cracking of the lower corners of the door frame and cross beam of the forward cargo door, which could result in rapid depressurization of the airplane, accomplish the following:
(a) Within 1 year or 4,500 flight cycles after the effective date of this AD, whichever occurs later, perform a high frequency eddy current (HFEC) inspection to detect cracking of the lower corners (forward and aft) of the door frame of the forward cargo door in accordance with Boeing 737 Nondestructive Test Manual, Part 6, Section 51-00-00, Figure 4 or Figure 23.
(1) If no cracking is detected, repeat the HFEC inspection thereafter at intervals not to exceed 4,500 flight cycles, until the requirements of paragraph (c) of this AD have been accomplished.
(2) If any cracking is detected during any inspection required by paragraph (a) of this AD, prior to further flight, accomplish the requirements of paragraphs (a)(2)(i) AND (a)(2)(ii) of this AD, which constitute terminating action for the repetitive inspections required by paragraph (a)(1) of this AD.
(i) Accomplish the requirements of paragraph (a)(2)(i)(A) OR (a)(2)(i)(B) of this AD, and install a cross beam repair and reinforcement modification of the cross beam in accordance with Boeing Service Bulletin 737-52-1100, Revision 2, dated March 31, 1994.
(A) Repair the door frame of the forward cargo door in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair or modification method to be approved by the Manager, Seattle ACO, as required by this paragraph; and paragraphs (a)(2)(ii), (b)(2), (b)(3)(ii), and (c)(2) of this AD; the Manager's approval letter must specifically reference this AD.
(B) Replace the door frame of the forward cargo door with a new door frame in accordance with Boeing Service Bulletin 737-52-1100, Revision 2, dated March 31, 1994.
(ii) Modify the repaired or replaced door frame of the forward cargo door in accordance with a method approved by the Manager, Seattle ACO, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings.
(b) Within 1 year or 4,500 flight cycles after the effective date of this AD, whichever occurs later, perform a detailed visual inspection to detect cracking of the cross beam (i.e., upper and lower chord and web sections) of the forward cargo door in accordance with Boeing Service Bulletin 737-52-1100, Revision 2, dated March 31, 1994.
Note 2: 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.”
(1) If no cracking is detected, repeat the inspection thereafter at intervals not to exceed 4,500 flight cycles until the requirements of paragraph (c) of this AD have been accomplished.
(2) If any cracking is detected on the lower chord section of the cross beam during any inspection required by paragraph (b) of this AD, prior to further flight, repair in accordance with a method approved by the Manager, Seattle ACO, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings.
(3) If any cracking is detected on any area excluding the lower chord section of the cross beam (i.e., upper chord and web section) during any inspection required by paragraph (b) of this AD, prior to further flight, accomplish the requirements of paragraph (b)(3)(i) or (b)(3)(ii), as applicable, of this AD, which constitute terminating action for the repetitive inspections required by paragraph (b)(1) of this AD.
(i) For airplanes with line numbers 1 through 1231: Install a cross beam repair and preventative modification of the outboard radius of the lower corners (forward and aft) of the door frame in accordance with Boeing Service Bulletin 737-52-1100, Revision 2, dated March 31, 1994.
Note 3: Due to implications and consequences associated with cracking, this AD does not allow the option of replacing the door frame as an alternative method of compliance to installing the preventative modification.
(ii) For airplanes with line numbers 1232 and subsequent: Install a cross beam repair and preventative modification of the outboard radius of the lower corners (forward and aft) of the door frame in accordance with a method approved by the Manager, Seattle ACO or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings.
(c) Within 4 years or 12,000 flight cycles after the effective date of this AD, whichever occurs later: Install the preventative modification of the outboard radius of the lower corners (forward and aft) of the door frame and the reinforcement modification of the cross beam of the forward cargo door in accordance with paragraph (c)(1) or (c)(2) of this AD, as applicable. Accomplishment of paragraph (c)(1) or (c)(2) of this AD, as applicable, constitutes terminating action for the repetitive inspections required by paragraphs (a)(1) and (b)(1) of this AD.
(1) For airplanes with line numbers 1 through 1231: Accomplish the preventative modification and the reinforcement modification in accordance with Boeing Service Bulletin 737-52-1100, Revision 2, dated March 31, 1994.
(2) For airplanes with line numbers 1232 and subsequent: Accomplish the preventative modification and the reinforcement modification in accordance with a method approved by the Manager, Seattle ACO or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings.
(d) For all airplanes on which modifications of the forward lower corner of the door frame and the cross beam of the forward cargo door were accomplished in accordance with Boeing Service Bulletin 737-52-1100, dated August 25, 1988, or Revision 1, dated July 20, 1989, or in accordance with the requirements of AD 90-06-02, amendment 39-6489: Within 4 years or 12,000 flight cycles after the effective date of this AD, whichever occurs later, install the reinforcement modification of the aft corner of the door frame of the forward cargo door in accordance with Boeing Service Bulletin 737-52-1100, Revision 2, dated March 31, 1994. Accomplishment of such modification constitutes terminating action for the repetitive inspections required by this AD.
Note 4: Accomplishment of Boeing Service Bulletin 737-52-1100, Revision 2, dated March 31, 1994, does not supersede the requirements of AD 90-06-02, amendment 39-6489.
