Airworthiness Directives; The New Piper Aircraft, Inc. (Formerly Piper Aircraft Corporation) Models PA31T, PA31T1, PA31T2, and PA31T3 Airplanes

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received. Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket. Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket No. 90-CE-61-AD.'' The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Central Region, Office of the Assistant Chief Counsel, Attention: Rules Docket No. 90-CE-61-AD, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.

Discussion

The FAA has determined that reliance on critical repetitive inspections on aging commuter-class airplanes carries an unnecessary safety risk when a design change exists that could eliminate or, in certain instances, reduce the number of those critical inspections. In determining what inspections are critical, the FAA considers (1) the safety consequences if the known problem is not detected during the inspection; (2) the probability of the problem not being detected during the inspection; (3) whether the inspection area is difficult to access; and (4) the possibility of damage to an adjacent structure as a result of the problem. These factors have led the FAA to establish an aging commuter-class aircraft policy that requires incorporating a known design change when it could replace a critical repetitive inspection. With this policy in mind, the FAA conducted a review of existing AD's that apply to Piper Models PA31-350 and PA31T3 airplanes. Assisting the FAA in this review were (1) The New Piper Aircraft, Inc.; (2) the Regional Airlines Association (RAA); and (3) several operators of the affected airplanes. From this review, the FAA has identified AD 84-08-06, Amendment 39- 4851, as one that should be superseded with a new AD that would require a modification that would eliminate the need for short-interval and critical repetitive inspections. AD 84-08-06 currently requires the following on Piper Models PA31T, PA31T1, PA31T2, and PA31T3 airplanes:

--Repetitively inspecting the fuselage station (FS) 332 bulkhead for cracks, reinforcing the FS 332 bulkhead (Piper Kit 764-983) if all cracks found do not exceed certain limits, and replacing the bulkhead assembly with a reinforced replacement bulkhead assembly (part number 45583-16 or 45583-17) if any crack is found that exceeds certain limits. Accomplishment of the inspections required by AD 84-08-06 is in accordance with Piper Service Bulletin (SB) No. 773, dated December 19, 1983; and --Allowing for the provision of incorporating Piper Kit 764-983 or part number 45583-16 or 45583-17 bulkhead assembly as terminating action for the repetitive inspection requirement. The incorporation of Piper Kit 764-983 is accomplished in accordance with the instructions provided with the kit, and the reinforced bulkhead assembly installations are accomplished in accordance with the applicable maintenance manual.

Based on its aging commuter-class aircraft policy and after reviewing all available information related to this subject including the referenced service information, the FAA has determined that AD action should be taken to eliminate the repetitive short-interval inspections required by AD 84-08-06, and to prevent structural failure of the horizontal stabilizer and the aft fuselage attachment caused by cracks in the FS 332 bulkhead, which, if not detected and corrected, could result in loss of control of the airplane. Since an unsafe condition has been identified that is likely to exist or develop in other Piper Models PA31T, PA31T1, PA31T2, and PA31T3 airplanes of the same type design, the proposed AD would supersede AD 84-08-06 with a new AD that would (1) retain the requirement of repetitively inspecting the FS 332 bulkhead for cracks, reinforcing the FS 332 bulkhead (Piper Kit 764-983) if any crack is found that does not exceed certain limits, and replacing the bulkhead assembly with a reinforced bulkhead assembly (part number 45583-16 or 45583-17) if any crack is found that exceeds certain limits; and (2) require incorporating a stabilizer forward spar attachment bulkhead reinforcement (Piper Kit 764-983) or a reinforced bulkhead assembly (part number 45583-16 or 45583-17) as terminating action for the repetitive inspections. Accomplishment of the proposed inspections would be in accordance with Piper SB No. 773A, dated May 3, 1984. The incorporation of Piper Kit 764-983 would be accomplished in accordance with the instructions to this kit (Revised June 18, 1990), and the reinforced bulkhead installations would be accomplished in accordance with the applicable maintenance manual. The FAA estimates that 736 airplanes in the U.S. registry would be affected by the proposed AD, that it would take approximately 60 workhours per airplane to accomplish the proposed replacement, and that the average labor rate is approximately $60 an hour. Parts cost approximately $782 per airplane. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $3,225,152 or $4,382 per airplane. This figure is based on the assumption that no affected airplane owner/operator has accomplished the proposed replacement. Piper has informed the FAA that parts have been distributed to enough owners/operators to equip 348 of the affected airplanes. Assuming that each set of parts has been installed on an affected airplane, the cost impact of the proposed AD upon U.S. owners operators of the affected airplanes would be reduced by $1,524,936 from $3,225,152 to $1,700,216. 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 388 affected airplanes (736 affected airplanes--348 sets of parts distributed) that would be affected by the proposed modification AD are operated in various types of air transportation. This includes scheduled passenger service, air cargo, and air taxi. The proposed AD allows 600 hours time-in-service (TIS) after the effective date of the proposed 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 would have to accomplish the proposed modification within four to six months after the proposed AD would become effective. For private owners, who typically operate between 100 to 200 hours TIS per year, this would allow three to six years before the proposed modification would be mandatory. The FAA established the 600 hours TIS replacement compliance time based on its engineering evaluation of the problem. Among the issues looked at in 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 proposing to mandate the modification for all operators

``within the next 600 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 Models PA31T, PA31T1, PA31T2, and PA31T3 airplanes (such as 5,000 hours TIS) would impose the 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 six years to allow low-usage airplanes time to accumulate the 600 hours after the effective date of the AD. The FAA has determined that the compliance time of the proposed rule provides the level of safety required for commuter air service while still minimizing the impact on the private airplane owners of Piper Models PA31T, PA31T1, PA31T2, and PA31T3 airplanes. The regulations proposed herein would 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 proposal would 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) if promulgated, 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 draft regulatory evaluation prepared for this action has been placed 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, Safety.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing Airworthiness Directive (AD) 84-08-06, Amendment 39-4851, and by adding a new AD to read as follows:

The New Piper Aircraft, Inc. (formerly Piper Aircraft Corporation): Docket No. 90-CE-61-AD. Supersedes AD 84-08-06, Amendment 39-4851.

Applicability: The following model and serial number airplanes, certificated in any category, that do not have either Piper Kit 764- 983 (stabilizer forward spar attachment bulkhead reinforcement) incorporated at Fuselage Station (FS) 332 or have a part number (P/ N) 45583-16 or P/N 45583-17 bulkhead assembly installed:

------------------------------------------------------------------------ Models Serial No. ------------------------------------------------------------------------ PA31T............................ 31T-7400002 through 31T-8120104. PA31T1........................... 31T-7804001 through 31T-8104101, 31T- 8304003, and 31T-1104004 through 31T- 1104007. PA31T2........................... 31T-8166001 through 31T-8166032, 31T- 8166034 through 31T-8166065, 31T- 8166067 through 31T-8166071, and 31T- 8166073 through 31T-8166075. PA31T3........................... 31T-8275001, 31T-8275003 through 31T- 8275012, 31T-8275014 through 31T- 8275017, 31T-8275025, and 31T- 8375001 through 31T-8375005. ------------------------------------------------------------------------

Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (h) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. Compliance: Required as indicated in the body of this AD, unless already accomplished.

To prevent structural failure of the horizontal stabilizer and the aft fuselage attachment caused by cracks in the FS 332 bulkhead, which, if not detected and corrected, could result in loss of control of the airplane, accomplish the following: (a) Within the next 200 hours time-in-service (TIS) after the effective date of this AD, unless already accomplished (compliance with AD 84-08-06), and thereafter at intervals not to exceed 200 hours TIS until the modification required by paragraph (c), (d), or (e) of this AD is incorporated, inspect (using dye penetrant methods) the FS 332 bulkhead for cracks. Accomplish the inspections in accordance with the INSTRUCTIONS section of Piper Service Bulletin No. 773A, dated May 3, 1984. (b) The initial dye penetrant inspection type must be utilized for all future repetitive inspections. Dye penetrant inspection types consist of Type I: fluorescent; Type II: non-fluorescent or visible dye; and Type III: dual sensitivity. (c) If cracks are found during any of the inspections required in paragraph (a) of this AD and no crack exceeds the limitations specified in Piper SB No. 773A, dated May 3, 1984, prior to further flight, repair the cracks in accordance with Piper SB No. 773A, dated May 3, 1984, and reinforce the FS 332 bulkhead by incorporating Piper Kit 764-983 in accordance with the instructions to Piper Kit 764-983, Revised June 18, 1990. (d) If cracks are found during any of the inspections required in paragraph (a) of this AD and any crack exceeds the limitations specified in Piper SB No. 773A, dated May 3, 1984, prior to further flight, replace the bulkhead assembly with a reinforced bulkhead assembly, P/N 45583-16 or P/N 45583-17. Accomplish this replacement in accordance with the applicable maintenance manual. (e) Upon the accomplishment of the third repetitive inspection required by this AD (600 hours TIS after the effective date of this AD), unless already accomplished as required by paragraph (c) or (d) of this AD, accomplish one of the following, as applicable: (1) If cracks are found and no crack exceeds the limitations specified in Piper SB No. 773A, dated May 3, 1984, repair the cracks in accordance with Piper SB No. 773A, dated May 3, 1984, and reinforce the FS 332 bulkhead by incorporating Piper Kit 764-983 in accordance with the instructions to Piper Kit 764-983, Revised June 18, 1990; (2) If cracks are found and any crack exceeds the limitations specified in Piper SB No. 773A, dated May 3, 1984, replace the bulkhead assembly with a reinforced bulkhead assembly, P/N 45583-16 or P/N 45583-17, in accordance with the applicable maintenance manual; or (3) If no cracks are found, either reinforce the FS 332 bulkhead by incorporating Piper Kit 764-983 in accordance with the instructions to Piper Kit 764-983, Revised June 18, 1990; or replace the bulkhead assembly with a reinforced bulkhead assembly, P/N 45583-16 or P/N 45583-17, in accordance with the applicable maintenance manual. (f) Incorporating Piper Kit 764-983 or installing reinforced bulkhead assembly, P/N 45583-16 or P/N 45583- 17, as required by paragraphs (c) and (d) or (e) of this AD is considered terminating action for the repetitive inspection requirement of this AD.

(g) Special 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. (h) An alternative method of compliance or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, Atlanta Aircraft Certification Office (ACO), Campus Building, 1701 Columbia Avenue, suite 2-160, College Park, Georgia 30337-2748. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Atlanta ACO.

Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Atlanta ACO. Note 3: Alternative methods of compliance approved in accordance with AD 84-08-06 (superseded by this action) are not considered approved as alternative methods of compliance with this AD.

(i) All persons affected by this directive may obtain copies of the document referred to herein upon request to The New Piper Aircraft, Inc., 2926 Piper Drive, Vero Beach, Florida 32960; or may examine this document at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106. (j) This amendment supersedes AD 84-08-06, Amendment 39-4851.

Issued in Kansas City, Missouri, on January 10, 1996. Michael Gallagher, Manager, Small Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-485 Filed 1-18-96; 8:45 am] BILLING CODE 4910-13-U