Airworthiness Directive · Amendment 39-15617 · Boeing Model 737-300, -400, and -500 Series Airplanes
Boeing Model 737-300, -400, and -500 Series Airplanes
This AD applies to all Boeing Model 737-300, -400, and -500 series airplanes, certificated in any category.
We are adopting a new airworthiness directive (AD) for all Boeing Model 737-300, -400, and -500 series airplanes. This AD requires inspecting to determine if certain carriage spindles are installed, repetitive inspections for corrosion and indications of corrosion on affected carriage spindles, and if necessary, related investigative action and corrective action. This AD also provides optional terminating action. This AD results from a report of corrosion found on carriage spindles that are located on the outboard trailing edge flaps. We are issuing this AD to detect and correct corrosion of the carriage spindle, which could result in fracture. Fracture of both the inboard and outboard carriage spindles, in the forward ends through the large diameters, on a flap, could adversely affect the airplane's continued safe flight and landing.
Comply with this AD within the compliance times specified, unless already done.
Within 30 days after the effective date of this AD, inspect the carriage sub-assembly to determine whether an affected carriage spindle with a high velocity oxy-fuel (HVOF) thermal coating is installed, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-57A1304, dated June 2, 2008. A review of airplane maintenance records is acceptable in lieu of this inspection if the part number and/or serial number of the carriage can be conclusively determined from that review. If no affected carriage spindle is installed, no further action is required by this paragraph.
For airplanes on which any affected carriage spindle is installed: At the later of the times specified in paragraphs (g)(1) and (g)(2) of this AD, do a detailed inspection (or, as an option for the forward end of the spindle only, a borescope inspection technique may be used) of the spindle for corrosion and potential indications of corrosion of the carriage spindle, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-57A1304, dated June 2, 2008. Do all applicable related investigative actions and corrective actions before further flight. Repeat the detailed inspection (or, as an option for the forward end of the spindle only, the borescope inspection) and certain related investigative actions (i.e., the gap-check or optional non-destructive test (NDT) ultrasonic inspection) at the applicable compliance times specified in the service bulletin.
(1) Within 30 days after the effective date of this AD.
(2) Within 90 days after the installation of a new HVOF-coated spindle.
Note 1: Boeing Alert Service Bulletin 737-57A1304, dated June 2, 2008, references Boeing Alert Service Bulletin 737-57A1277, Revision 1, dated November 25, 2003, for further information on accomplishing the related investigative actions.
If any corrosion, cracking, or severed spindle is found during any inspection required by paragraph (g) of this AD: Within 10 days after the inspection, or within 10 days after the effective date of this AD, whichever occurs later, submit a report of the inspection results to the Manager, Airline Support, Boeing Commercial Airlines Group, as specified in Note 2 of paragraph 1.D., “Description,” of Boeing Alert Service Bulletin 737-57A1304, dated June 2, 2008. Information collection requirements contained in this AD have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.
(i) Replacement of an HVOF-coated carriage spindle with a non-HVOF coated carriage spindle in accordance with Boeing Alert Service Bulletin 737-57A1304, dated June 2, 2008, terminates the requirements of this AD for that carriage spindle only.
As of the effective date of this AD, an HVOF-coated spindle may be installed on an airplane provided the actions required by paragraph (g) of this AD are done on that spindle.
