AD 94-12-12 ACTIVE

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-300 series airplanes, that requires replacement of the forward and aft hinge shims and the lower hinge fairings of the main cargo door with new shims and fairings. This amendment is prompted by reports of a slight separation between the end hinge shims and the cargo door; this separation can cause bending loads on the fasteners. The actions specified by this AD are intended to prevent fatigue failure of the hinge fasteners, loss of structural integrity of the cargo door hinge, possible loss of the cargo door, and subsequent rapid decompression of the airplane.

Final rule

94-12-12 BOEING: Amendment 39-8940. Docket 93-NM-173-AD. \n\n\tApplicability: Boeing Model 737-300 series airplanes, as listed in Pemco Aeroplex Inc. Service Bulletin 737-52-0012, dated February 9, 1993; equipped with a Pemco Aeroplex main deck cargo door that has been modified in accordance with Supplemental Type Certificate (STC) SA2969S0; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously.\n \n\tTo prevent fatigue failure of the hinge fasteners, loss of structural integrity of the cargo door hinge, possible loss of the cargo door, and subsequent rapid decompression of the airplane, accomplish the following: \n\n\t(a)\tWithin 12,000 landings from the date of STC SA2969S0 installation or within 6 months after the effective date of this AD, whichever occurs later, replace the forward and aft hinge shims and the lower hinge fairings of the main deck cargo door, with new shims and fairings, in accordance with Pemco Aeroplex Inc. Service Bulletin 737-52-0012, dated February 9, 1993. \n\n\t(b)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Atlanta Aircraft Certification Office (ACO), FAA, Small Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Atlanta ACO. \n\nNOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Atlanta ACO. \n\n\t(c)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(d)\tThe replacement shall be done in accordance with Pemco Aeroplex Inc. Service Bulletin 737-52-0012, dated February 9, 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pemco Aeroplex Inc. Service Bulletin 737-52-0012, dated February 9, 1993. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Small Airplane Directorate, Atlanta Aircraft Certification Office, Suite 210C, 1669 Phoenix Parkway, Atlanta, Georgia; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(e)\tThis amendment becomes effective on July 20, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing 737-300 series airplanes was published in the Federal Register on December 6, 1993 (58 FR 64198). That action proposed to require replacement of the forward and aft hinge shims and the lower hinge fairings of the main cargo door with new shims and fairings. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tTwo commenters support the proposal. \n\n\tOne commenters considers there is no justification for issuing the proposed rule, since most of the affected airplanes have already been modified in accordance with the proposed requirements. The FAA does not concur. Although the commenter has provided the FAA with data indicating that the proposed modification has been accomplishedon all airplanes currently on the U.S. Register, this data did not provide positive indication, verified by FAA personnel, that the modification had been accomplished on airplanes not currently on the U.S. Register. Should one of these affected airplanes be imported to the U.S. in the future, this AD is necessary in order to ensure that the required actions are accomplished on the airplane prior it being placed on the U.S. Register. Further, as is indicated in the final rule, operators are given "credit" for previously accomplishing the requirements of the rule; therefore, no further action is required on the part of the operators in these cases. \n\n\tAnother commenter contends that there is no justification for the proposed AD, since the Supplemental Type Certificate (STC) holder (Pemco) has not indicated that the referenced Pemco service bulletin concerns an airworthiness problem. The commenter states that Pemco has portrayed the service bulletin as addressing only a reliability problem. The FAA does not concur. In developing this AD action, the FAA reviewed the relevant data which indicated that this STC door design allows slight separation between the end hinge shims and the cargo door during pressurization cycles; such separation can cause increased bending loads on the door hinge fasteners. The FAA determined that this situation constitutes an unsafe condition since, if not corrected, it could lead to fatigue failure of the hinge fasteners, loss of structural integrity of the cargo door hinge, possible loss of the cargo door, and subsequent rapid decompression of the airplane. Regardless of whether or not the wording in the service bulletin describes the procedures specified within it as addressing an airworthiness problem, the FAA finds that accomplishment of those procedures will serve to eliminate the identified unsafe condition. \n\n\tOne commenter suggests that the wording that identifies the location of the affected cargo door be clarified. The commenter points out that the notice identified this door as the "main cargo door;" however, a more correct identification would be "main deck cargo door." The FAA concurs and has changed the pertinent wording in the final rule accordingly. \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 11 Model 737-300 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 2 airplanes of U.S. registry will be affected by this AD, that it will take approximately 280 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts will be provided by Pemco Aeroplex at no cost to the operators. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $30,800, or $15,400 per airplane. \n\n\tThe total cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. However, the FAA has been advised that all affected U.S.-registered airplanes have been modified previously in accordance with the requirements of this AD. Therefore, there is no cost impact of this AD on U.S. operators. \n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."\n\n List of Subjects in 14 CFR Part 39 \n\nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\nAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39 - AIRWORTHINESS DIRECTIVES \n\n1.\tThe authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended) \n\n2.\tSection 39.13 is amended by adding the following new airworthiness directive:

The service information referenced in this AD may be obtained from Pemco\nAeroplex Inc., P.O. Box 2287, Birmingham, Alabama 34201. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Small Airplane Directorate, Atlanta Aircraft Certification Office, Suite 210C, 1669 Phoenix Parkway, Atlanta, Georgia; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Curtis Jackson, Aerospace Engineer, Airframe Branch, ACE-120A, FAA, Small Airplane Directorate, Atlanta Aircraft Certification Office, Suite 210C, 1669 Phoenix Parkway, Atlanta, Georgia 30349; telephone (404) 991-2910; fax (404) 991-3606.