Airworthiness Directives; Pilatus Aircraft LTD Model PC-6 Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes to adopt a new airworthiness directive (AD) that would apply to all Pilatus Aircraft LTD (Pilatus) Model PC-6 airplanes that are equipped with a certain stabilizer trim actuator. The proposed AD would require you to inspect the lower lug of the actuator for cracks, damage, or distortion; verify that the staked bearing is correctly installed in the bore of the lug; and repair any cracked, damaged, or distorted parts and reassemble any incorrectly installed staked bearing, as necessary. The proposed AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. The actions specified by the proposed AD are intended to detect and correct damage, distortion, or cracks in the lower lug assembly, which could result in failure of the lower lug. Such failure could lead to loss of the stabilizer trim actuator with consequent loss of control of the airplane.

DATES:

The Federal Aviation Administration (FAA) must receive any comments on this proposed rule on or before December 8, 2000.

ADDRESSES:

Submit comments in triplicate to FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 99-CE-77-AD, 901 Locust, Room 506, Kansas City, Missouri 64106. Comments may be inspected at this location between 8 a.m. and 4 p.m., Monday through Friday, holidays excepted.

Service information that applies to the proposed AD may be obtained from Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6371 Stans, Switzerland; telephone: +41 41 619 65 09; facsimile: +41 41 610 33 51. This information also may be examined at the Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT:

Roman T. Gabrys, Aerospace Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: (816) 329-4141; facsimile: (816) 329-4090.

SUPPLEMENTARY INFORMATION:

Comments Invited

How Do I Comment on the Proposed AD?

The FAA invites comments on this proposed rule. You may submit whatever written data, views, or arguments you choose. You need to include the rule's docket number and submit your comments in triplicate to the address specified under the caption ADDRESSES. The FAA will consider all comments received on or before the closing date. We may amend the proposed rule in light of comments received. Factual information that supports your ideas and suggestions is extremely helpful in evaluating the effectiveness of the proposed AD action and determining whether we need to take additional rulemaking action.

Are There Any Specific Portions of the Proposed AD I Should Pay Attention To?

The FAA specifically invites comments on the overall regulatory, economic, environmental, and energy aspects of the proposed rule that might suggest a need to modify the rule. You may examine all comments we receive before and after the closing date of the rule in the Rules Docket. We will file a report in the Rules Docket that summarizes each FAA contact with the public that concerns the substantive parts of the proposed AD.

We are re-examining the writing style we currently use in regulatory documents, in response to the Presidential memorandum of June 1, 1998. That memorandum requires federal agencies to communicate more clearly with the public. We are interested in your comments on whether the style of this document is clearer, and any other suggestions you might have to improve the clarity of FAA communications that affect you. You can get more information about the Presidential memorandum and the plain language initiative at http://www.plainlanguage.gov.

How Can I Be Sure FAA Receives My Comment?

If you want us to acknowledge the receipt of your comments, you must include a self-addressed, stamped postcard. On the postcard, write “Comments to Docket No. 99-CE-77-AD.” We will date stamp and mail the postcard back to you.

Discussion

What Events Have Caused This Proposed AD?

The Federal Office for Civil Aviation (FOCA), which is the airworthiness authority for Switzerland, recently notified the FAA that an unsafe condition may exist on all Pilatus Model PC-6 airplanes that are equipped with a stabilizer trim actuator, part number (P/N) 978.73.18.101, 978.73.18.102, or 978.73.18.103 (Electomech P/N EM-483-1, 483-2, or 483-3). The FOCA reports an incident of a cracked, damaged, and distorted lower lug of the horizontal stabilizer trim actuator. Analysis of this incident reveals that the staked bearing was loose, which caused excessive wear and failure of the actuator lower lug.

What Are the Consequences If the Condition Is Not Corrected?

Damage, distortion, or cracks in the lower lug assembly, if not detected and corrected, could result in failure of this part. Such failure could lead to loss of the stabilizer trim actuator with consequent loss of control of the airplane.

Is There Service Information That Applies to This Subject?

Pilatus has issued Service Bulletin No. 178, dated September 29, 1999.

What Are the Provisions of This Service Bulletin?

The service bulletin:

—includes procedures for inspecting the lower lug of the actuator for cracks, damage, or distortion, and assuring that the staked bearing is correctly installed in the bore of the lug; and

—specifies repairing any cracked, damaged, or distorted parts, as necessary, and reassembling any incorrectly installed staked bearing.

What Action Did the FOCA Take?

The FOCA classified this service bulletin as mandatory and issued Swiss AD HB 99-507, dated October 1, 1999, in order to assure the continued airworthiness of these airplanes in Switzerland.

Was This in Accordance With the Bilateral Airworthiness Agreement?

This airplane model is manufactured in Switzerland and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement.

Pursuant to this bilateral airworthiness agreement, the FOCA has kept FAA informed of the situation described above.

The FAA's Determination and an Explanation of the Provisions of the Proposed AD

What Has FAA Decided?

The FAA has examined the findings of the FOCA; reviewed all available information, including the service information referenced above; and determined that:

—the unsafe condition referenced in this document exists or could develop on other Pilatus Model PC-6 airplanes of the same type design that are equipped with one of the previously referenced stabilizer trim actuators;

—the actions specified in the previously-referenced service information should be accomplished on the affected airplanes; and

—AD action should be taken in order to correct this unsafe condition.

What Would the Proposed AD Require?

This proposed AD would require you to incorporate the actions in the previously referenced service bulletin.

Cost Impact

How Many Airplanes Would the Proposed AD Impact?

We estimate that the proposed AD affects 7 airplanes in the U.S. registry.

What Would Be the Cost Impact of the Proposed AD on Owners/Operators of the Affected Airplanes?

We estimate the following costs to accomplish the proposed inspection:

If any distortion, damage, or cracks are found during the proposed inspection, you would have to repair the actuator assembly in accordance with an FAA-approved repair scheme developed by the manufacturer.

The FAA has no way of determining how much incorporating each repair scheme would cost since the damage to each airplane would be unique.

Regulatory Impact

Would This Proposed AD Impact Various Entities?

The regulations proposed herein would 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. Therefore, it is determined that this proposed rule would not have federalism implications under Executive Order 13132.

Would This Proposed AD Involve a Significant Rule or Regulatory Action?

For the reasons discussed above, I certify that this proposed 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, under 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 U.S.C. 106(g), 40113, 44701.