Airworthiness Directive · Amendment 39-16406 · Fuselage
The Boeing Company Model 737-100 and -200 Series Airplanes
This AD applies to The Boeing Company Model 737-100 and -200 series airplanes, certificated in any category; line numbers 1 through 848 inclusive.
We are adopting a new airworthiness directive (AD) for certain Model 737-100 and -200 series airplanes. This AD requires repetitive inspections for cracking and damaged fasteners of certain fuselage frames and stub beams, and corrective actions if necessary. For certain airplanes, this AD also requires repetitive inspections for cracking of the inboard chord fastener hole of the frame at body station 639, stringer S-16, and corrective actions if necessary. For certain airplanes, this AD also requires an inspection to determine the edge margin of the lower chord. For airplanes with a certain short edge margin, this AD requires repetitive inspections for cracking, and corrective actions if necessary; replacing the lower chord terminates the repetitive inspections. This AD requires an eventual preventive modification. For certain airplanes, doing the modification or a repair terminates the repetitive inspections for the repaired or modified frame only. For airplanes on which the modification or repair is done at certain body stations, this AD requires repetitive inspections for cracking of certain frame webs and inner and outer chords, and corrective actions if necessary. For certain other airplanes, this AD requires a modification which includes reinforcing the body frame inner chords, replacing the stub beam upper chords and attach angles, and reinforcing the stub beam web. This AD results from reports of fatigue cracks at certain frame sections, in addition to stub beam cracking, caused by high flight cycle stresses from both pressurization and maneuver load. We are issuing this AD to detect and correct fatigue cracking of certain fuselage frames and stub beams, and possible severed frames, which could result in reduced structural integrity of the frames. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and result in rapid decompression of the fuselage.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
For airplanes on which a repair (Part III of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061) or preventive modification (Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061) has not been done in accordance with Boeing Service Bulletin 737-53-1061 as of the effective date of this AD: Before the accumulation of 15,000 total flight cycles or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, do the inspections required by paragraphs (g)(1) and (g)(2) of this AD, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. Repeat the inspection at the time specified, until the terminating action required by paragraph (l) of this AD is done.
(1) Do a detailed inspection (Part I of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992) for cracks and damaged fasteners of the fuselage frames and stub beams. If no crack or damaged fastener is found, repeat the inspection thereafter at intervals not to exceed 4,500 flight cycles.
(2) Do an eddy current inspection (Part IV of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992) for cracking of the inboard chord fastener hole of the frame at body station 639, stringer S-16. If no crack is found, repeat the inspection thereafter at intervals not to exceed 15,000 flight cycles.
Note 1: Access and restoration instructions, as detailed in the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, are not required by this AD. Operators may do those actions in accordance with their maintenance practices.
(h) For airplanes on which the body station 597 frame was changed as of the effective date of this AD, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, dated May 28, 1982; Revision 1, dated December 16, 1983; Revision 2, dated April 18, 1986; or Revision 3, dated June 15, 1989: Within 3,000 flight cycles after the effective date of this AD, do a detailed inspection for cracking of the frame, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. Repeat the detailed inspection thereafter at intervals not to exceed 4,500 flight cycles. Installation of new radius fillers in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, terminates the inspections required by this paragraph.
(i) For airplanes on which a stub beam lower chord with 1/4 -inch diameter fasteners at body station 597 is installed as of the effective date of this AD, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 1, dated December 16, 1983; Revision 2, dated April 18, 1986; or Revision 3, dated June 15, 1989: Within 3,000 flight cycles after the effective date of this AD, do a detailed inspection for short edge margins. If the short edge margin is determined to be less than 1.5D (diameter), before further flight, do a detailed inspection for cracking of the stub beam lower chords, in accordance with Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. Repeat the detailed inspection thereafter at intervals not to exceed 4,500 flight cycles, if the edge margin is less than 1.5D. If the edge margin is greater than or equal to 1.5D, no further action is required by this paragraph. Replacing the lower chord in accordance with Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, terminates the repetitive inspections specified in this paragraph.
Except as required by paragraph (k) of this AD, if any crack or damaged fastener is found during any inspection required by this AD, before further flight, repair if cracking and damaged fasteners are within the specified limits, or do a preventive modification if cracking or damaged fasteners are outside the specified limits, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992.
Where Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, specifies to contact Boeing for repair instructions: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (n) of this AD.
Before the accumulation of 75,000 total flight cycles: Do the preventive modification in accordance with Part II, or repair in accordance with Part III, of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. The modification or repair terminates the repetitive inspection requirements of this AD for the repaired or modified frame only, except as required by paragraph (m) of this AD.
For airplanes on which a repair or modification at body station 616 or 639 is done: Within 24,000 flight cycles after doing the repair or modification, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, do a detailed inspection for cracking of the body station 616 and 639 frame webs, inner chord, and outer chord near stringer S-16, in accordance with Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992.
(1) If no cracking is found, repeat the inspection thereafter at intervals not to exceed 4,500 flight cycles.
(2) If any cracking is found, before further flight, repair the cracking using a method approved in accordance with the procedures specified in paragraph (n) of this AD.
