AD 96-22919

[Federal Register Volume 61, Number 175 (Monday, September 9, 1996)] [Proposed Rules] [Pages 47459-47462] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-22919]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-194-AD] RIN 2120-AA64

Airworthiness Directives; de Havilland, Inc., Model DHC-8-100 and -300 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of comment period.

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SUMMARY: This document revises an earlier proposed airworthiness directive (AD), applicable to de Havilland Model DHC-8-100 and -300 series airplanes. That proposal would have superseded a previously- issued AD that currently requires repetitive inspections to detect cracks of the upper drag strut trunnion fittings of the nose landing gear and to verify tightness of the fitting attachment bolts. It also would have required the

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installation of a modification to terminate the repetitive inspections. This new action revises the proposed rule by proposing to require a different terminating modification. This action is prompted by data indicating that the previously proposed terminating modification is not effective. The actions specified by the proposed AD are intended to prevent failure of the upper drag strut trunnion fittings of the nose landing gear, which could lead to collapse of the nose landing gear.

DATES: Comments must be received by September 30, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 93-NM-194-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays. The service information referenced in the proposed rule may be obtained from Bombardier, Inc., Bombardier Regional Aircraft Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Jon Hjelm, Aerospace Engineer, Airframe Branch, ANE-172, FAA, Engine and Propeller Directorate, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York 11581; telephone (516) 256-7523; fax (516) 568-2716.

SUPPLEMENTARY INFORMATION:

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 shall 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 summarizing 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 Number 93-NM-194-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, Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 93-NM-194-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an airworthiness directive (AD), applicable to certain de Havilland Model DHC-8-100 and -300 series airplanes, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on February 7, 1994 (59 FR 5554). That NPRM would have superseded AD 93-08-03, amendment 39-8550 (58 FR 25549, April 27, 1993), which currently requires repetitive inspections to detect cracks of the upper drag strut trunnion fittings of the nose landing gear and to verify tightness of the fitting attachment bolts. It also requires replacement of the fittings or fasteners, if necessary. AD 93-08-03 was prompted by reports of cracks detected in two trunnion fittings which retain and support the nose landing gear upper drag link. The requirements of AD 93-08-03 are intended to prevent failure of the upper drag strut trunnion fittings of the nose landing gear, which could lead to collapse of the nose landing gear. The NPRM would have added a requirement to the AD to modify the upper drag strut trunnion fittings and fasteners of the nose landing gear. Once the modification was installed, the repetitive inspections could be terminated.

Actions Since Issuance of Previous Proposal

Since the issuance of that NPRM, Transport Canada Aviation, which is the airworthiness authority for Canada, has advised the FAA that the modification proposed as terminating action for AD 93-08-03 has been determined to be ineffective. Data indicate that installation of Modification 8/1880, which is described in de Havilland Service Bulletin S.B. 8-53-45, dated July 12, 1993, may recreate the original problem that the AD intends to correct.

Explanation of New Relevant Service Information

De Havilland has issued Service Bulletin S.B. 8-53-49, dated June 30, 1995, that describes procedures for installing Modification 8/2139. This modification entails the installation of strengthened drag link trunnion fittings and adjacent right-angled support fittings, both of which will reduce premature fatigue. Additionally, the modification involves the installation of fasteners with larger diameters to attach the fittings, and installation of a new sensor support bracket. Transport Canada Aviation approved the technical content of this service bulletin and issued Revision 3 of Canadian airworthiness directive CF-92-18, dated August 2, 1995, in order to assure the continued airworthiness of these airplanes in Canada. That revised Canadian airworthiness directive specifies that Modification 8/2139 is an optional terminating action for the repetitive inspections required of the drag strut trunnion fittings (required by the original issue of CF-92-18). Additionally, de Havilland has issued Revision ``D'' of Service Bulletin S.B. A8-53-40, dated June 30, 1995. This revision is essentially identical in its technical content to the previous revisions of the service bulletin, but contains updated effectivity information and new references to Modification 8/2139.

FAA's Conclusions

This airplane model is manufactured in Canada 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, Transport Canada Aviation has kept the FAA informed of the situation described above. The FAA has examined the findings of Transport Canada Aviation, reviewed all available information, and determined that similar AD action is necessary for products of this type design that are certificated for operation in the United States.

Explanation of the New Proposed Requirements of the Rule

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this new proposed AD would

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supersede AD 93-08-03 to continue to require inspection to detect cracks of the upper drag strut trunnion fittings of the nose landing gear, inspection to verify tightness of the fitting attachment bolts, and replacement of the fittings or fasteners, if necessary. Additionally, this new proposed AD would require the installation of Modification 8/2139. When accomplished, this modification would terminate the need for the currently required inspections. The modification would be required to be accomplished in accordance with de Havilland Service Bulletin S.B. 8-53-49, described previously. The proposed AD also would limit the applicability of the rule to exclude those airplanes on which Modification 8/2139 has been installed previously. The manufacturer has installed Modification 8/2139 prior to delivery of airplanes having serial numbers 396 and subsequent. Airplanes so modified are not subject to the unsafe condition addressed by this proposed AD. Paragraph (a) of the proposed AD has been revised to reference Revision ``D'' of de Havilland Service Bulletin S.B. A8 53-40, dated June 30, 1995, as an additional appropriate source of service information.

Differences Between the Proposed Rule and Related Canadian AD

Operators should note that, whereas the Canadian AD allows installation of Modification 8/2139 as an optional action, this proposed AD would mandate its installation as terminating action. The FAA has determined that long term continued operational safety will be better assured by modifications or design changes to remove the source of the problem, rather than by repetitive inspections. Long term inspections may not be providing the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous repetitive inspections, has led the FAA to consider placing less emphasis on special procedures and more emphasis on design improvements. The proposed modification requirement is in consonance with these considerations.

Reopening of Period for Public Comment

Since the changes made to this proposal expand the scope of the originally proposed rule, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Cost Impact

The FAA estimates that 146 airplanes of U.S. registry would be affected by this proposed AD. Accomplishment of the currently required inspections takes approximately 1 work hour per airplane, at an average labor rate of $60 per hour. Based on these figures, the cost impact of the currently required inspection actions on U.S. operators is estimated to be $8,760, or $60 per airplane, per inspection. The proposed modification action would take approximately 18 work hours per airplane to accomplish the proposed actions, at an average labor rate of $60 per work hour. Required parts would cost approximately $3,325 per airplane. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $638,725, or $4,405 per airplane. The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. However, based on the effective date and compliance time of AD 93-08-03, it can be reasonably assumed that the majority of affected U.S. operators already have initiated and are currently conducting the inspections required by that AD.

Regulatory Impact

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 proposed regulation (1) is not a ``significant regulatory action'' under Executive Order 12866; (2) is not a ``significant rule'' under the 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 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, 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 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

De Havilland, Inc.: Docket 93-NM-194-AD. Supersedes AD 93-08-03, amendment 39-8550.

Applicability: Model DHC-8-102, -103, -301, -311, and -314 series airplanes; having serial numbers 003 through 395, inclusive, but excluding serial numbers 011, 362, and 391; on which Modification 8/2139 (as described in de Havilland Service Bulletin S.B. 8-53-49, dated June 30, 1995) has not been accomplished; certificated in any category.

Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 (d) 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, unless accomplished previously. To prevent failure of the upper drag strut trunnion fittings of the nose landing gear, which could lead to collapse of the nose landing gear, accomplish the following: (a) Within 500 landings after May 27, 1993 (the effective date of AD 93-08-03, Amendment 39-8550), unless accomplished within the last 500 landings, conduct a visual inspection of both upper drag strut trunnion fittings of the nose landing gear to detect cracks; and conduct an inspection of the fitting attachment bolts to verify tightness; in accordance with de Havilland DHC-8 Alert Service Bulletin S.B. A8-53-40, Revision `A', dated June 12, 1992; or Revision `B', dated February 24, 1993; or Revision `D', dated June 30, 1995. (1) If no crack is detected in the upper drag strut trunnion fittings of the nose landing

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gear, and no looseness is detected in the fitting attachment bolts, repeat the inspections at intervals not to exceed 1,000 landings until the modification required by paragraph (b) of this AD is accomplished. (2) If any crack is detected on either fitting, prior to further flight, replace both fittings with confirmed crack-free fittings in accordance with the service bulletin. After such replacement, the inspections required by this paragraph must continue at intervals not to exceed 1,000 landings until the modification required by paragraph (b) of this AD is accomplished. (3) If any fitting attachment bolt is found to be loose during the initial inspection, prior to further flight, replace the fasteners (nut, washer, and bolt) that secure the fitting, in accordance with the service bulletin. After such replacement, the inspections required by this paragraph must continue at intervals not to exceed 1,000 landings until the modification required by paragraph (b) of this AD is accomplished. (4) If any fastener is found to be loose during any repetitive inspection required by this AD, prior to further flight, tighten the bolt to the value specified in the service bulletin. (b) Within 6 months after the effective date of this AD, install Modification 8/2139 in accordance with de Havilland Service Bulletin S.B. 8-53-49, dated June 30, 1995. Installation of this modification constitutes terminating action for the inspection requirements of this AD. (c) Installation of Modification 8/2139, in accordance with de Havilland Service Bulletin S.B. 8-53-49, dated June 30, 1995, constitutes terminating action for the inspections required by this AD. (d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, New York Aircraft Certification Office (ACO), ANE-170, FAA, Engine and Propeller Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, New York ACO.

Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York ACO.

(e) 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.

Issued in Renton, Washington, on September 3, 1996. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-22919 Filed 9-6-96; 8:45 am] BILLING CODE 4910-13-U