AD 95-20-07

November 17, 1995.

Information that applies to this AD may be examined at the Federal Aviation Administration (FAA), Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.

Christina Marsh, Aerospace Engineer, FAA, Atlanta Aircraft Certification Office, Campus Building, 1701 Columbia Avenue, suite 2-160, College Park, Georgia 30337-2748; telephone (404) 305-7362; facsimile (404) 305-7348.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain Piper PA24, PA28R, PA30, PA32R, PA32RT, PA34, PA39, and PA44 series airplanes was published in the Federal Register on February 22, 1995 (60 FR 9799). The action proposed to require repetitively inspecting (using dye penetrant or magnetic particle methods) the main gear side brace studs for cracks, and replacing any cracked main gear side brace stud.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the seven comments received from four different commenters.

Piper proposes that the AD require inspecting the Models PA32R-300, PA34-200, and PA34-200T airplanes equipped with the \9/16\-inch stud and that the AD exempt the PA28R series airplanes from the repetitive inspections. Piper states that, based on its data regarding the service history of the affected airplanes, all failures and main gear side brace stud cracks occurred on airplanes equipped with the \9/16\-inch stud. The proposal would require inspecting both the \5/8\-inch diameter stud and the \9/16\-inch stud. The FAA partially concurs. The PA28R series airplanes may have either the \9/16\-inch stud or the \5/ 8\-inch stud installed. All PA28RT series airplanes have \5/8\-inch diameter studs installed at manufacture. Although no incidents regarding failures or cracks on main gear side brace studs involving Piper PA28R series airplanes have been received, the FAA has determined that PA28R series airplanes equipped with the \9/16\-inch stud are of the same type design as the PA32R and PA34 series airplanes equipped with the \9/16\-inch stud. Therefore, the AD will continue to affect the PA28R series airplanes with \9/16\-inch studs installed. The FAA does concur that repetitive inspections of affected airplanes with a \5/8\-inch main side gear stud brace assembly installed are not justified. The AD is changed to require repetitive inspections of the \9/16\-inch main gear side brace studs on Piper PA28R, PA32R, and PA34 series airplanes with an option for terminating the inspections by installing a \5/8\-inch main gear side brace stud bracket assembly. This AD does not apply to the PA32RT and PA44 series airplanes.

One commenter recommends that the FAA supply additional information in the AD to verify the part number (P/N) of the main gear side brace stud on the PA28, PA32R, and PA34 series airplanes. The FAA concurs that additional information would be helpful in identifying the main gear side brace stud P/N. A note has been added to the AD specifying that there is no way of determining the main gear side brace P/N without removing the stud from the bracket assembly and measuring the shank diameter of the stud. If the shank diameter is \9/16\-inch, then the main gear side brace stud is either P/N 95299-00 or P/N 95299-02.

Another commenter questions the availability of replacement \9/16\-inch main gear side brace studs for all the affected airplanes. The FAA contacted the manufacturer to verify that sufficient replacement parts are available. Replacement main gear side brace studs for cracked studs are available and shall be installed as follows:

--For the Models PA28R-180, PA28R-200, PA28R-201, PA28R-201T, PA32R-300, PA34-200, and PA34-200T airplanes, the \9/16\-inch diameter studs, P/N 95299-00 and P/N 95299-02, are no longer available as replacement parts. A new bracket assembly (P/N 95643-06, P/N 95643-07, P/N 95643-08, or P/N 95643-09, as applicable) must be obtained from the manufacturer and incorporated if a cracked \9/16\-inch main gear side brace stud is found on these airplanes. This assembly includes the \5/ 8\-inch main gear side brace stud, and the incorporation of the entire bracket assembly eliminates the need for the repetitive inspections. --For the Models PA24 and PA24-250 airplanes, main gear side brace stud P/N 20829-00 shall be installed. --For the Models PA24-260, PA24-400, PA30, and PA39 airplanes, main gear side brace stud P/N 22512-00 shall be installed.

One commenter requests that the FAA include a figure that identifies the area requiring non-destructive inspection. The FAA has added Figure 1 to the AD to comply with this commenter's request.

A commenter recommends that the FAA provide more detail regarding the appropriate inspection method required by the AD. This commenter's concern stems from the allowance to perform either dye penetrant or magnetic particle inspections of the main gear side brace studs. The term ``dye penetrant'' by definition includes the full range of penetrant options from low sensitivity visible or color contrast penetrants to the various higher sensitivity fluorescent penetrants. The FAA concurs that the inspection method should be more detailed in the AD. The AD is revised to require the inspection of the main gear side brace stud using a Type I (fluorescent) penetrant method or using magnetic particle inspection methods. The FAA does not concur that the inspection should only be accomplished using magnetic particle methods, but maintains that the sensitivity of either method will detect main gear side brace stud cracks.

A commenter requests that the FAA clarify the term ``FAA-approved dye penetrant or magnetic particle inspection procedures.'' Information has been added to the AD that specifies that the FAA intends for the inspections to be accomplished at a facility that is approved by the FAA to perform either dye penetrant or magnetic particle inspections.

One commenter agrees with the proposal, but feels that the FAA should express the compliance time in landings instead of hours time-in-service (TIS). The FAA does not concur. Airplane owners/operators are not required to log the number of landings for this type design airplane. A correlation between the number of landings and the number of flight hours for an airplane fleet is a portion of the information (when available) used by the FAA in establishing appropriate compliance times. The FAA has re-evaluated this information and considers hours TIS as the best method of establishing a compliance time for this AD. The AD is unchanged as a result of this comment.

No comments were received regarding the FAA's estimate of the cost impact upon U.S. operators of the affected airplanes. The FAA did, however, miscalculate the number of airplanes that would be affected by the proposal. Upon further examination, the FAA has determined that 13,200 airplanes will be affected by this AD. No airplane models or serial numbers have been added to the Applicability section of the AD; therefore, this economic information change will not add any additional burden upon U.S. owners/operators of the affected airplanes over that which was already proposed.

In addition to the comments received, the FAA re-evaluated the proposed compliance time and decided that the initial inspection compliance time should be adjusted to account for those operators who already accomplished the inspection. The initial inspection compliance time has been rewritten to give credit to those operators already accomplishing the inspection at least once.

In addition, the FAA has included an inspection to detect an unapproved alteration of the main gear side brace bracket assembly. The FAA received documentation of several mechanics taking the \9/16\-inch stud bracket assembly and modifying it to accommodate the \5/8\-inch stud. The unapproved alteration is easy to detect because of the number of installed bushings. The \9/16\-inch main gear side brace stud bracket assembly contains two bushings and the \5/8\-inch main gear side brace stud bracket assembly contains one bushing. The FAA has included a note in the AD to specify that the ``PA34-200T Illustrated Parts Catalog (Revision dated May 1983, Piper P/N 761 589), Figure 45, Item 52, illustrates this one and two-bushing installation.''

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 the compliance change, the economic information correction, the addition of the inspection for unapproved main gear side brace stud bracket assemblies, minor editorial corrections, and the changes referenced above pertaining to the comments received as a result of the notice of proposed rulemaking. The FAA has determined that the addition, changes, and minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

The FAA estimates that 13,200 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 5 workhours per airplane to initially inspect both the right and left main landing gear side brace studs, and that the average labor rate is approximately $60 an hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $3,960,000. This figure represents the cost of the initial inspection, and does not reflect costs for repetitive inspections or possible replacements. The FAA has no way of determining how many main gear side brace studs may need replacement or how many repetitive inspections each owner/operator may incur.

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.

Air transportation, Aircraft, Aviation safety, Safety.

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:

1. The authority citation for part 39 continues to read as follows:

Authority: 49 USC 106(g), 40101, 40113, 44701.