Airworthiness Directive · Amendment 39-17374 · Stabilizers
The Boeing Company Airplanes
This AD applies to The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011.
We are adopting a new airworthiness directive (AD) for all The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 airplanes. This AD was prompted by reports of cracks of the hinge bearing lugs of the center section ribs of the horizontal stabilizer. This AD requires repetitive high frequency eddy current (HFEC) inspections for cracking of the left and right rib hinge bearing lugs of the aft face of the center section of the horizontal stabilizer; measuring crack length and blending out cracks; and replacing the horizontal stabilizer center section rib, if necessary. We are issuing this AD to detect and correct cracking in the hinge bearing lugs of the horizontal stabilizer center section ribs, which could result in failure of the lugs, and consequent inability of the horizontal stabilizer to sustain the required limit loads and loss of control of the airplane.
For Group 1 airplanes, as identified in Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011: Before the accumulation of 23,000 total flight cycles, or within 4,383 flight cycles after the effective date of this AD, whichever occurs later, do a high frequency eddy current (HFEC) inspection for cracking of the left and right rib hinge bearing lugs of the aft face of the center section of the horizontal stabilizer, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011. For any crack-free lug, repeat the inspection thereafter at intervals not to exceed 8,200 flight cycles.
If, during any inspection required by paragraph (g) of this AD, any crack is found: Before further flight, measure the length of the crack between the points specified in Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011. Do the action in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011.
(1) If the crack length between points ‘A' and ‘B' is less than or equal to 0.15 inch and the crack length between points ‘C' and ‘D' is less than or equal to 0.05 inch: Before further flight, blend out the crack, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011. Within 15,600 flight cycles after doing the blendout, do an HFEC inspection of the blendout on the center section rib hinge bearing lug for cracking, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011.
(i) If no cracking is found, repeat the inspection thereafter at intervals not to exceed 3,900 flight cycles.
(ii) If cracking is found during any inspection of the blendout, before further flight, do the replacement required by paragraph (h)(2) of this AD, and do the inspections required by paragraph (h)(2) of this AD at the times specified in paragraph (h)(2) of this AD.
(2) If the crack length between points `A' and `B' is greater than 0.15 inch or the crack length between points `C' and `D' is greater than 0.05 inch: Before further flight, replace the horizontal stabilizer center section rib with a new horizontal stabilizer center section rib, using a method approved in accordance with the procedures specified in paragraph (l) of this AD. Repeat the inspection required by paragraph (g) of this AD one time before the accumulation of 23,000 total flight cycles on the new horizontal stabilizer center section rib, and thereafter at intervals not to exceed 11,300 flight cycles.
For Group 2 airplanes, as identified in Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011: Before the accumulation of 23,000 total flight cycles, or within 4,383 flight cycles after the effective date of this AD, whichever occurs later, do an HFEC inspection for cracking of the left and right rib hinge bearing lugs of the aft face of the center section of the horizontal stabilizer, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011. For any crack-free lug, repeat the inspection thereafter at intervals not to exceed 11,300 flight cycles.
If, during any inspection required by paragraph (i) of this AD, any crack is found: Before further flight, measure the length of the crack between the points specified in, and in accordance, with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011.
(1) If the crack length between points ‘A' and ‘B' is less than or equal to 0.15 inch and the crack length between points ‘C' and ‘D' is less than or equal to 0.05 inch: Before further flight, blendout the crack, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011. Within 15,600 flight cycles after doing the blendout, do an HFEC inspection of the blendout on the center section rib hinge bearing lug for cracking, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011.
(i) If no cracking is found, repeat the inspection thereafter at intervals not to exceed 5,800 flight cycles.
(ii) If cracking is found during any inspection of the blendout, before further flight, do the replacement required by paragraph (j)(2) of this AD, and do the inspections required by paragraph (j)(2) of this AD at the times specified in paragraph (j)(2) of this AD.
(2) If the crack length between points ‘A' and ‘B' is greater than 0.15 inch or the crack length between points ‘C' and ‘D' is greater than 0.05 inch: Before further flight, replace the horizontal stabilizer center section rib with a new horizontal stabilizer center section rib, using a method approved in accordance with the procedures specified in paragraph (l) of this AD. Repeat the inspection required by paragraph (i) of this AD one time before the accumulation of 23,000 total flight cycles on the new horizontal stabilizer center section rib, and thereafter at intervals not to exceed 11,300 flight cycles.
Although Boeing Alert Service Bulletin MD80-55A069, dated January 19, 2011, specifies to submit certain information to the manufacturer, this AD does not include that requirement.
