Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to Socata Model TBM 700 airplanes was published in the Federal Register as a notice of proposed rulemaking (NPRM) on April 9, 1997 (62 FR 17125). The NPRM proposed to require removing the MLG inboard doors and the door locking control mechanism (MOD 70- 065-32). Accomplishment of the proposed actions as specified in the NPRM would be in accordance with the Technical Instruction of Modification OPT70 KO59-32, dated December 1995, as referenced in Socata Service Bulletin 70-073, Amdt. 1, dated June 1996.
The NPRM was the result of an incident on one of the affected airplanes where the MLG inboard door locking hooks (hinges) corroded, caused the doors to jam, and prevented the MLG from extending. The FAA's analysis reveals that removing the MLG inboard doors will not cause any airplane safety or performance problems.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received by one commenter.
Comment 1: No Justification for AD Action
The commenter states that the FAA does not have substantiating engineering data to justify the unsafe condition proposed in the NPRM. This commenter believes that if the pilot-in-command is adequately accomplishing the preflight checks, then any corrosion in the MLG inboard door locking hooks (hinges) would be detected and then corrected. Thus, the MLG doors would not jam and prevent the MLG from extending.
The FAA does not concur that the commenter's determination that an unsafe condition does not exist is justified. The FAA analyzed the preflight procedures of the Socata TBM 700 airplanes and the preflight procedures of similar design airplanes. From this analysis, the FAA has determined that inspecting this area forcorrosion is considered action over and above normal preflight procedures that the pilot is authorized to perform. In addition, the FAA always tries to mandate modifications or replacements rather than repetitive inspections. Removing the MLG doors and the door locking control mechanism is a modification that would eliminate the need for repetitive inspections, eliminate the unsafe condition identified by this AD, and not cause any adverse operational effects on the affected airplanes. No changes have been made to the final rule as a result of this comment.
Comment 2: Proposed Alternative Method of Compliance
The commenter states that removing the MLG inboard doors as proposed in the NPRM results in approximately 3-4 knots of performance degradation, and raises the level of cabin noise in the aircraft. Socata has issued SB No. 70-076-32, which specifies actions to address the noise issue (the FAA does not mandate accomplishment of this SB through AD action). The commenter explains that accomplishing this noise modification imposes substantial expense on the affected airplanes owners. For these reasons, the commenter has submitted a proposed alternative method of compliance (AMOC) that includes procedures for lubricating the inner landing gear door hinges and repetitively inspecting the inner landing gear door hinges every 50 hours time-in-service (TIS). The proposed AMOC also includes preflight visual inspections of the main landing gear doors prior to each flight. The commenter would like the proposed AMOC approved as an alternative to the proposed requirement of removing the MLG inboard doors and door locking control mechanisms.
The FAA is currently in the process of reviewing the information contained in the proposed AMOC and is working with the commenter toward approving this AMOC. All owners/operators of Socata TBM 700 airplanes may contact the FAA at the address specified in paragraph (d) of the AD to receive this AMOC (when and if it isapproved) and to obtain the necessary documents pertinent to this AMOC.
The FAA's Determination
After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.
Compliance Time of This AD
The unsafe condition specified in this AD develops primarily because of slush/debris accumulating in the MLG inboard doors area while landing in certain runway environments. Corrosion could have already developed on an airplane previously operated in certain slush/debris runway environments, regardless of future operation of the airplane. For this reason, the FAA has determined that the compliance time of this AD should be specified in both hours time-in-service (TIS) and calendar time (whichever occurs first), in order to assure that corrosion is not allowed to go undetected over time.
Cost Impact
The FAA estimates that 47 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 3 workhours per airplane to accomplish this AD, and that the average labor rate is approximately $60 an hour. Socata will provide parts at no cost to the owners/operators of the affected airplanes. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $8,460. This figure is based on the presumption that no owner/operator of the affected airplanes has accomplished the required actions.
Socata has informed the FAA that parts have been distributed to equip approximately 30 of the affected airplanes. Presuming that each set of parts is incorporated on an affected airplane, the cost impact upon U.S. airplane owners/operators is reduced by $5,400 from $8,460 to$3,060.
Regulatory Impact
The 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.
For 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 copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption "ADDRESSES".
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, 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
1. The authority citation for part 39 continues to read as follows:
Authority: 49 USC 106(g), 40113, 44701. 39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: