Airworthiness Directive · Amendment 39-16565 · Stabilizers
The Boeing Company Model MD-90-30 Airplanes
This AD applies to all The Boeing Company Model MD-90-30 airplanes, certificated in any category.
We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires repetitive high frequency eddy current inspections for cracking on the hinge bearing lugs of the left and right sides of the center section ribs of the horizontal stabilizer, and related investigative and corrective actions if necessary. This AD was prompted by reports of cracks found on either the left or right (or in one case, both) sides of the center section ribs of the horizontal stabilizer. We are issuing this AD to detect and correct cracking in the hinge bearing lugs of the center section of the left and right ribs, which could result in failure of the hinge bearing lugs and consequent inability of the horizontal stabilizer to sustain the required loads.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
At the applicable time in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, except as required by paragraph (n) of this AD, do a high frequency eddy current (HFEC) inspection for cracking on the hinge bearing lugs of the left and right sides of the center section ribs of the horizontal stabilizer, and do all applicable related investigative actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010. Do all applicable related investigative actions before further flight.
(h) If during any inspection required by paragraph (g) of this AD, no cracking is found, repeat the inspection required by paragraph (g) of this AD thereafter at intervals not to exceed 1,680 flight cycles.
(i) If during any inspection required by paragraph (g) or (h) of this AD, any crack is found having a length between Points `A' and `B' less than or equal to 0.15 inch and crack length between Points `C' and `D' less than or equal to 0.05 inch, as identified in Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010: Before further flight, blend out the crack; and within 1,000 flight cycles after doing the blend out, do an HFEC inspection of the blend out on the center section rib hinge bearing lug; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010. Repeat the HFEC inspection of the blend out thereafter at intervals not to exceed 400 flight cycles until the replacement specified by paragraph (j) is done.
(j) If any cracking is detected during any inspection required by paragraph (i) of this AD, before further flight, replace the horizontal stabilizer center section rib with a new horizontal stabilizer center section rib, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010.
(k) If during any inspection required by paragraph (g) or (h) of this AD, any crack is found having a length between Points `A' and `B' greater than 0.15 inch or crack length between Points `C' and `D' greater than 0.05 inch, as identified in Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010: Before further flight, replace the horizontal stabilizer center section rib with a new horizontal stabilizer center section rib, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010.
(l) For any airplane having a horizontal stabilizer center section rib replaced during the actions required by paragraph (j) or (k) of this AD: Before the accumulation of 7,200 total flight cycles on the new horizontal stabilizer center section rib, do the actions required by paragraph (g) of this AD, and do all applicable actions specified in paragraphs (h), (i), (j), and (k) of this AD.
Actions accomplished before the effective date of this AD according to Boeing Alert Service Bulletin MD90-55A016, dated December 16, 2009, are considered acceptable for compliance with the corresponding actions required by paragraphs (g), (h), (i), (j), and (k) of this AD.
Where Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, specifies a compliance time “after the original issue date on the service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
