Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Airbus Model A300 series airplanes; Model A300 B4-600, B4-600R, and F4-600R series airplanes, and Model A300 C4-605R Variant F airplanes (collectively called Model A300-600 series airplanes); and Model A310 series airplanes. The NPRM published in the Federal Register on August 30, 2016 (81 FR 59546) (``the NPRM''). The NPRM was prompted by reports of failure of an aft hinge bolt assembly in the NLG aft doors. The NPRM proposed to require replacement of the aft hinge bolt assembly in the left and right NLG aft doors, with new aft hinge bolt assemblies. We are issuing this AD to prevent failure of an aft hinge bolt assembly in an NLG aft door while the airplane is in flight, which could lead to an in-flight loss of an NLG aft door, and damage to the airplane.
The European Aviation Safety Agency (EASA), which is the TechnicalAgent for the Member States of the European Union, has issued EASA AD 2016-0100, dated May 24, 2016 (referred to after this as the Mandatory Continuing Airworthiness Information, or ``the MCAI''), to correct an unsafe condition for all Airbus Model A300 series airplanes; Model A300 B4-600, B4-600R, and F4-600R series airplanes, and Model A300 C4-605R Variant F airplanes (collectively called Model A300-600 series airplanes); and Model A310 series airplanes. The MCAI states:
An occurrence has been reported of failure of a nose landing gear (NLG) door aft hinge bolt assembly, Part Number (P/N) A53612600000. The result of laboratory investigations revealed that the aft hinge bolt rupture was initiated by fatigue crack development in the under head radius of the bolt, due to the lack of radius roll over and in combination with a non-optimised design.
This condition, if not detected and corrected, could lead to in- flight loss of an aft NLG door, possibly resulting in damage to theaeroplane and injury to persons on the ground.
Prompted by these findings, Airbus developed a new design aft hinge bolt assembly P/N A53612713000, introduced as Airbus modification (mod) 13741, to replace the existing bolt P/N A53612600000. Since the introduction of that mod, additional stress calculations demonstrated that the new bolt assembly, P/N A53612713000, cannot sustain fatigue loads up to the design Limit of Validity (LOV) of the affected aeroplanes.
To address this potential unsafe condition, Airbus issued Service Bulletin (SB) A300-53-0397, SB A310-53-2144 and SB A300-53- 6186, to provide instructions for the repetitive replacement of the affected post-mod 13741 P/N A53612713000 aft hinge bolts.
For the reasons described above, this [EASA] AD requires the replacement of all P/N A53612600000 aft hinge bolt assemblies, installed on the left hand (LH) and right hand (RH) NLG aft doors, with post-mod 13741 P/N A53612713000 aft hinge bolt assemblies, and, subsequently,the implementation of a life limit for those new bolt assemblies.
You may examine the MCAI in the AD docket on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2016- 9052.
Comments
We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM and the FAA's response to each comment.
Request To Withdraw the NPRM
FedEx stated it does not agree that the proposed hinge bolt replacement is necessary, asserting that the severity of a failed condition does not equate to an unsafe condition on the airplane. FedEx explained that in the last 22 years of flight operations, it has not had a departure of the NLG door, nor has it seen any cracking of the aft hinge bolt.
From this statement, we infer that FedEx requested we withdraw the NPRM. We disagree with this request. Airbus has records of multiple instances of hinge bolt failures. Failure of an aft hinge bolt assembly in an NLG aft door while the airplane is in flight could lead to an in- flight loss of an NLG aft door, and damage to the airplane. We have not changed this AD in this regard.
Request To Allow Option for Repetitive Inspections
FedEx requested that a repetitive non-destructive test (NDT) technique be allowed as an option to replacing the affected bolts. FedEx stated that a routine NDT inspection would be best suited for this condition and that the affected bolts should only be replaced as an on-condition action. Further, FedEx stated that the proposed requirement to replace all affected bolts will be a financial burden on operators. FedEx also pointed out that the two bolts required for each airplane are $2,300, and these bolts will be required to be replaced every 10,000 flight cycles (approximately every 10 years). FedEx further requested that the FAA petition the EASA to revise the Airbus service information to permit the repetitive inspection as an option to the required bolt replacement.
We disagree with the commenter's request. The intent of this AD is to regularly replace the affected hinge bolt with a new one. The bolt loading and fatigue spectrum is complex, and the manufacturer is not able to substantiate a fatigue life to support a repeat inspection program. Therefore, we have made no changes to this AD in this regard. However, under the provisions of paragraph (k)(1) of this AD, we will consider requests for approval of an alternative method of compliance (AMOC) if sufficient data are submitted to substantiate that the change would provide an acceptable level of safety.
Request To Remove the Requirement To Replace Aft Hinge Bolts
United Parcel Service (UPS) requested that we revise the proposed AD to remove the requirement to replace aft hinge bolts. UPS contended that the more appropriate method for implementation of the repetitive 10,000-flight-cycle replacement of the hinge bolt assembly would be through a maintenance program revision, or incorporation into the Safe Life Airworthiness Limitation Items (SL ALI)--Part 1. Therefore, UPS recommended that we delete the proposed hinge bolt replacement, and
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instead coordinate with EASA to revise the SL ALI to include the hinge bolt assembly.
We disagree with the commenter's request. Only parts that are identified as a safe life part are incorporated into the SL ALI. The specified hinge bolt does not meet the Airbus Airworthiness Limitations Section (ALS) Part 1 criteria for a safe life part. The hinge bolt does not have fatigue testing or demonstrated fatigue life analysis, which is required for safe life parts. We have not changed this AD in this regard.
Request To Combine Certain Service Information
UPS requested that, if its request to revise the proposed AD to remove the hinge assembly replacement is unacceptable to the FAA, we revise paragraph (h)(3) of this proposed AD to require removal and installation of a new bolt using only Airbus Service Bulletin A300-53- 6182 and not list Airbus Service Bulletin A300-53-6186. UPS explained that the final result of the proposed AD is the replacement of the bolt in every case; however, Airbus Service Bulletin A300-53-6186 specifies doing an inspection of the bolt part number in addition to the replacement and is an added burden to the operator given the location of the identifying mark and the difficulty accessing that mark.
We disagree with the commenter's request because paragraphs (g) and (h) of this AD and the corresponding service information are necessary to distinguish between two different actions with different compliance times:
Paragraph (g) of this AD and corresponding service information for the introduction of the bolt's new design.
Paragraph (h) of this AD and corresponding service bulletin for regular bolt replacement, which includes an inspection for verification if the proper bolt part number was installed.
While it might bedifficult for operators to identify the part number of the bolt when it is installed on the aircraft, the bolt is scheduled to be removed so it should not be difficult to verify that the correct part was installed. We have not changed this AD in this regard.
Request To Update Illustrated Parts Catalog (IPC) To Show the Post- Modification Part Number
UPS requested that the FAA coordinate with EASA and Airbus to ensure that the IPC is updated to show only the post-modification part number prior to the AD being issued. UPS was concerned that an outdated IPC creates opportunities for installation of the original, non- compliant bolt assembly.
We infer that UPS was also requesting that we delay publication of the final rule pending revision of the IPC. We disagree with this request. Airbus has informed the FAA that the IPC is scheduled to be revised. However, we do not consider that delaying this action until after the release of the manufacturer's revised IPC is warranted, since sufficient information currently exists in this AD and the required service information to address the identified unsafe condition. We have not changed this AD in this regard.
Clarification of Corrective Action
We have clarified the corrective actions in the introductory text of paragraph (h) of this AD by referring to paragraph (k)(2) of this AD.
Conclusion
We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD as proposed except for minor editorial changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was already proposed in the NPRM.
Related Service Information Under 1 CFR Part 51
We reviewed the following Airbus service information.
Airbus Service Bulletin A300-53-0396, dated November 25, 2015.Airbus Service Bulletin A300-53-6182, dated November 17, 2015.
Airbus Service Bulletin A310-53-2142, dated November 17, 2015.
This service information describes procedures for replacement of the aft hinge bolt assemblies in the left and right NLG aft doors, with new aft hinge bolt assemblies. These documents are distinct since they apply to different airplane models and configurations.
We also reviewed the following Airbus service information.
Airbus Service Bulletin A300-53-0397, dated January 18, 2016.
Airbus Service Bulletin A300-53-6186, dated January 18, 2016.
Airbus Service Bulletin A310-53-2144, dated January 18, 2016.
This service information describes procedures for replacement of the aft hinge bolt assemblies in the left and right NLG aft doors, with new aft hinge bolt assemblies. The replacement includes an inspection to verify if the proper bolt part number was installed and repair if the proper bolt part number was not installed. These documents aredistinct since they apply to different airplane models and configurations.
This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.
Costs of Compliance
We estimate that this AD affects 157 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:
Estimated Costs ----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Replacement........................ 9 work-hours x $85 per hour $2,000 $2,765 $434,105
= $765. ----------------------------------------------------------------------------------------------------------------
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. ``Subtitle VII: Aviation Programs,'' describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in ``Subtitle VII, Part A, Subpart III, Section 44701: General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition
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that is likely to exist or develop on products identified in this rulemaking action.
This AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes to the Director of the System Oversight Division.
Regulatory Findings
We determined that this AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect 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.
For the reasons discussed above, I certify that this AD:
1. Is not a ``significant regulatory action'' under Executive Order 12866;
2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26,1979);
3. Will not affect intrastate aviation in Alaska; and
4. 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.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.