Events Leading to the AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to Piper PA31, PA31P, and PA31T series airplanes was published in the Federal Register on December 7, 1995 (60 FR 62776). The action proposed to supersede AD 88-05-05 with a new AD that would (1) retain the requirement of repetitively inspecting both the left and right MLG forward sidebrace for cracks, and replacing any cracked MLG forward sidebrace; and (2) require replacing both the left and right MLG forward sidebrace with a part of improved design, part number (P/N) 85165-02 (left) and 85165-03 (right) or P/N 85166-02 (left) and 85166-03 (right), as applicable, as terminating action for the repetitive inspection requirement. Accomplishment of the proposed inspections would be in accordance with Piper Service Bulletin No. 845A, dated October 9, 1987. The improved MLG forward sidebrace installations would be accomplished in accordance with the applicable maintenance manual.
Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposed rule or the FAA's determination of the cost to the public.
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.
Cost Impact
The FAA estimates that 2,384 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 8 workhours per airplane to accomplish the required replacement, and that the average labor rate is approximately $60 an hour. Parts cost approximately $1,000 per airplane (2 MLG forward sidebraces per airplane at approximately $500 per sidebrace). Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $3,528,320 or $1,480 per airplane. This figure is based on the assumption that no affected airplane owner/operator has accomplished the required replacement.
Piper has informed the FAA that parts have been distributed to owners/operators to equip 2,123 of the affected airplanes (4,246 MLG forward sidebraces of improved design). Assuming that each set of parts has been installed on an affected airplane, the cost impact of the required replacement upon U.S. owners/operators of the affected airplanes is reduced by $3,142,040 from $3,528,320 to $386,280.
The FAA's Aging Commuter Class Aircraft Policy
This AD is part of the FAA's aging commuter class airplane policy, which briefly states that, when a modification exists that could eliminate or reduce the number of required critical inspections, the modification should be incorporated.
The intent of the FAA's aging commuter airplane program is to ensure safe operation of commuter-class airplanes that are in commercial service without adversely impacting private operators. The FAA believes that a large number of the remaining 261 affected airplanes (2,384 affected airplanes - 2,123 airplanes with a set of parts distributed) that will be affected by this AD are operated in various types of air transportation. This includes scheduled passenger service, air cargo, and air taxi.
This AD allows 1,200 hours time-in-service (TIS) after the effective date of the AD before mandatory accomplishment of the design modification. The average utilization of the fleet for those airplanes in air transportation is between 25 to 40 hours TIS per week. Based on these figures, operators of commuter-class airplanes involved in commercial operation will have to accomplish the required replacement within 7 to 12 months after the AD becomes effective. For private owners, who typically operate between 100 to 200 hours TIS per year, this allows 6 to 12 years before the required replacement will be mandatory.
The FAA established the 1,200 hours TIS replacement compliance time based on its engineering evaluation of the problem. Among the issues examined during this engineering evaluation were analysis of service difficulty reports, the difficulty level of the inspection, and how critical the situation would be if cracks occurred in the subject area despite accomplishment of the repetitive inspections.
Usually, the FAA establishes the mandatory design modification compliance time on AD's affecting aging commuter-class airplanes upon the accumulation of a certain number of hours TIS on the airplane. For this action, the FAA is mandating the replacement for all operators "within the next 1,200 hours TIS after the effective date of this AD." The total TIS levels of the airplane fleet vary from under 1,000 hours TIS to over 5,000 hours TIS, and annual accumulation rates vary from 50 hours TIS to over 1,000 hours TIS. Establishing a long-term set compliance time of hours TIS accumulated on Piper PA31, PA31P, and PA31T series airplanes (such as 5,000 hours TIS) imposes an undue burden on the manufacturer of having to maintain a supply of replacement parts for the entire fleet when many airplanes in the fleet may never reach this compliance time.
Instead, the FAA believes that Piper should maintain parts for several years; in this case about 12 years to allow low-usage airplanes time to accumulate the 1,200 hours TIS after the effective date of the AD. The FAA has determined that the compliance time of this AD provides the level of safety required for commuter air service while still minimizing the impact on the private airplane owners of Piper PA31, PA31P, and PA31T series airplanes.
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 39Air 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.
Section 39.13 - [AMENDED]
2. Section 39.13 is amended by removing Airworthiness Directive (AD) 88-05-05, Amendment 39-5861, and by adding a new AD to read as follows: