AD 2005-19-25 Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

Models named: 737-100, -200, -200C, -300, -400, -500 series. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-53-1230, dated June 13, 2002.

You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. Service Bulletin Reference (f) The term “special attention service bulletin,” as used in this AD, means the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1230, dated June 13, 2002. Repetitive Inspections (g) Before the airplane accumulates 20,000 total flight cycles, or within 4,500 flight cycles after the effective date of this AD, whichever occurs later: Do the inspection in paragraph (g)(1) of this AD; or, for airplanes with an external repair doubler installed at body station (BS) 390, do the inspection in paragraph (g)(2) of this AD in lieu of the inspection in paragraph (g)(1) of this AD for BS 390 only; inspections at all other body stations must be done in accordance with paragraph (g)(1) of this AD. Repeat the applicable inspection thereafter at intervals not to exceed 4,500 flight cycles. (1) Do an eddy current inspection for cracks of the surface area around the satellite holes of the radio altimeter cutouts between BS 390 and BS 450. Do the inspection with the fasteners installed in accordance with the special attention service bulletin. (2) For airplanes that have an external repair doubler installed at BS 390 only, in accordance with Boeing Service Bulletin 737-53-1117, Revision 1, dated April 6, 1989, do an eddy current inspection of the external doubler for cracks around the satellite holes of the radio altimeter cutout; and do an eddy current inspection for cracks of the fuselage skin along the aft edge of the doubler from S-28L to S-28R. Do the inspections with the fasteners installed in accordance with the procedures in Figure 1 of the special attention service bulletin. Repair (h) If any crack is found during any eddy current inspection required by this AD: Before further flight, repair the area by doing all applicable corrective and further investigative actions in accordance with the special attention service bulletin. Accomplishment of the repair terminates the repetitive inspection requirements of paragraph (g) of this AD for the repaired area. Where the special attention service bulletin specifies to contact Boeing for appropriate action; for instructions about how to repair certain conditions, including repairs at BS 390 “with doubler installed”; or where lack of specific repair instructions exist: Before further flight, repair using a method approved in accordance with paragraph (m) of this AD. Additional Inspection and Repair for Certain Airplanes (i) For any airplane in Group 1, 2, 3, 4, or 5 of the special attention service bulletin: Before or at the same time as the actions in paragraph (h) of this AD, inspect in accordance with Table 1 of this AD if both conditions in paragraphs (i)(1) and (i)(2) of this AD exist. (1) A skin crack at the cutout at BS 390 was found during any inspection, including the inspections required by paragraphs (g), (h), and (j) of this AD. (2) An external repair doubler has not been previously installed in accordance with Boeing Service Bulletin 737-53-1117, Revision 1, dated April 6, 1989. Table 1.—Service Information Inspect in accordance with either— The Accomplishment Instructions of Boeing Service Bulletin 737-53-1117, Revision 1, dated April 6, 1989— Figure 17 of the special attention service bulletin— A detailed inspection for cracks in the fuselage lower skin in the area of the electronics bay cooling duct cutout An eddy current inspection for cracks of the exhaust port duct cutout edge and the 6 fastener locations;   An eddy current and open-hole probe inspection for cracks of the satellite holes; and   A general visual inspection for corrosion of the area under the repair. Corrective Actions (j) If any crack at the equipment cooling duct cutout is found that is less than 3 inches in length during the inspection required by paragraph (i) of this AD: Before further flight, stop-drill the crack or cracks and install an external repair doubler in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1117, Revision 1, dated April 6, 1989; or repair in accordance with Part III of the special attention service bulletin. If the special attention service bulletin specifies to contact Boeing for appropriate Action: Before further flight, repair using a method approved in accordance with paragraph (m) of this AD. Accomplishment of the repair terminates the repetitive inspection requirements of paragraph (g) of this AD for the repaired area. (k) If any corrosion is found, or if any crack is found that is 3 inches in length or greater during the inspection required by paragraph (i) of this AD: Before further flight, repair using a method approved in accordance with paragraph (m) of this AD. Note 1: For the purposes of this AD, a general visual inspection is: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to ensure visual access to all surfaces in the inspection area. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or droplight and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.” Note 2: For the purposes of this AD, a detailed inspection is: “An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirror, magnifying lenses, etc., may be necessary. Surface cleaning and elaborate procedures may be required.” Optional Terminating Action (l) Installing preventive modification doublers in accordance with the special attention service bulletin, including the additional eddy current inspection with the fasteners removed (with no crack finding), terminates the repetitive inspection requirements of paragraph (g) of this AD. Where Figure 2 of the special attention service bulletin specifies to “eddy current countersink inspect and open hole probe inspect the 16 satellite holes,” and the airplane has an external repair doubler installed in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1117, Revision 1, dated April 6, 1989; that inspection is not required by this AD. If any crack is found during the eddy current inspection specified by this paragraph: Before further flight, discontinue the preventive modification and do the applicable actions in paragraph (h) of this AD. Alternative Methods of

This AD was prompted by reports of cracks in the lower lobe fuselage skin of the affected airplanes. We are issuing this AD to detect and correct fatigue cracks of the countersunk rivet holes, which could result in cracks of the fuselage skin of the lower lobe, and consequent rapid depressurization of the cabin.