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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NM-181-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Bombardier Model DHC-7-100, -101, -102, and -103 series airplanes. This proposal would require inspecting the endcaps of the main landing gear selector valve for leaks of hydraulic oil and, if leaks are detected, replacing the leaking endcaps or the entire selector valve. This proposal would also require eventual replacement or rework of certain selector valves, which would terminate the repetitive inspections. This action is prompted by a report of the collapse of the main landing gear due to an external leak of hydraulic oil in the landing gear selector valve, resulting from a fracture of the endcap. This action is intended to prevent leaks of hydraulic oil from the main landing gear selector valve, which could result in the collapse of the main landing gear. 

# DATES:

Comments must be received by November 13, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-181-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-181-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text. 

The service information referenced in the proposed rule may be obtained from Bombardier, Inc., Canadair, Aerospace Group, P.O. Box 6087, Station Centreville, Montreal, Quebec H3C 3G9, Canada. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, New York Aircraft Certification Office, 10 Fifth Street, Third Floor, Valley Stream, New York. 

# FOR FURTHER INFORMATION CONTACT:

James E. Delisio, Aerospace Engineer, ANE-171, FAA, New York Aircraft Certification Office, 10 Fifth Street, Third Floor, Valley Stream, New York 11581; telephone (516) 256-7521; 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. 

Submit comments using the following format: 
    - Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
    - For each issue, state what specific change to the proposed AD is being requested.
    - Include justification (e.g., reasons or data) for each request.

                    Comments are specifically invited on the overall regulatory, economic,                           ( print page 60596)                        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 No. 2000-NM-181-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-114, Attention: Rules Docket No. 2000-NM-181-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

Transport Canada Civil Aviation (TCCA), which is the airworthiness authority for Canada, notified the FAA that an unsafe condition may exist on certain Bombardier Model DHC-7-100, -101, -102, and -103 series airplanes. TCCA advises that an investigation of the collapse of the main landing gear of a Model DHC-8 series airplane identified the cause as an external hydraulic oil leak in the landing gear selector valve due to a fracture of the endcap. Model DHC-7 series airplanes have the same parts in their main landing gears. 

TCCA further advises that inspection of main landing gear selector valves undergoing bench testing have revealed additional cases of fatigue failure in the endcaps. In addition, main landing gear selector valves which have not been upgraded to part number (P/N) 57420-5 configuration are more susceptible to internal leaks, and excessive internal leaks can also contribute to the collapse of the main landing gear. This condition, if not corrected, could result in leaks of hydraulic oil from the main landing gear selector valve, which could result in the collapse of the main landing gear. 

## Explanation of Relevant Service Information 

Bombardier has issued Alert Service Bulletin A7-32-103, dated September 3, 1999, which describes procedures for repetitive visual inspection of the endcaps of the main landing gear selector valve for leaks of hydraulic oil and replacement of the endcaps with new serviceable parts, if leaks are found. The service bulletin also describes procedures for rework or replacement of certain selector valves with new improved parts, which would eliminate the need for the repetitive inspections. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition. TCCA classified this service bulletin as mandatory and issued Canadian airworthiness directive CF-99-31, dated December 21, 1999, in order to assure the continued airworthiness of these airplanes in Canada. 

## FAA's Conclusions 

These airplane models are manufactured in Canada and are type certificated for operation in the United States under the provisions of § 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, TCCA has kept the FAA informed of the situation described above. The FAA has examined the findings of TCCA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States. 

## Explanation of Requirements of Proposed 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, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously. The FAA is also preparing a proposed AD, which will address a similar unsafe condition on Bombardier Model DHC-8-100, -200, and -300 series airplanes. 

## Cost Impact 

The FAA estimates that 32 airplanes of U.S. registry would be affected by this proposed AD, that it would require 1 work hour per airplane to accomplish the proposed inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed inspection on U.S. operators is estimated to be $1,920, or $60 per airplane. 

The FAA also estimates that it would require 5 work hours per airplane to rework or replace the main landing gear selector valve and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed rework or replacement on U.S. operators is estimated to be $9,600 or $300 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 proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. 

Should an operator elect to replace the endcaps and perform the optional repetitive inspections prior to replacing the main landing gear selector valve, it would take approximately 1 work hour per airplane to conduct each inspection. Based on these figures, the cost impact of the optional repetitive inspections is estimated to be $60 per inspection per airplane. 

## Regulatory Impact 

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 proposal would not have federalism implications under Executive Order 13132. 

                    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                           ( print page 60597)                        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. 

§ 39.13 

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

**Bombardier, Inc.**                                 (Formerly de Havilland, Inc.): Docket 2000-NM-181-AD.                             

*Applicability:*                                Model DHC-7-100, -101, -102, and -103 series airplanes, serial numbers 003 through 113 inclusive; certificated in any category.                             

# 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 (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 the collapse of the main landing gear due to leaks of hydraulic oil from the main landing gear selector valve, accomplish the following: 

## Inspection 

(a) Within 100 flight cycles after the effective date of this AD, perform a general visual inspection of both endcaps of the main landing gear selector valve for the presence of hydraulic oil, in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A7-32-103, dated September 3, 1999. If no hydraulic oil is detected on either endcap, repeat the inspection at intervals not to exceed 400 flight hours until the requirements of paragraph (c) are accomplished. 

# Note 2:

For the purposes of this AD, a general visual inspection is defined as: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or drop-light, and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.” 

## Replacement or Modification 

(b) If any hydraulic oil is detected on either endcap: Prior to further flight, perform the actions specified in either paragraph (b)(1) or (b)(2) of this AD. 

(1) Replace the existing aluminum endcaps, part number (P/N) 34629, with new stainless steel endcaps having P/N 52982, in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A7-32-103, dated September 3, 1999. 

(2) Replace the main landing gear selector valve with a valve having P/N 57420-5A, in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A7-32-103, dated September 3, 1999. 

# Note 3:

Use care when removing the endcaps, so that the internal components do not fall on the ground and get damaged.

(c) Within 12 months after the effective date of this AD: Perform the actions specified in either paragraph (c)(1) or (c)(2) of this AD, in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A7-32-103, dated September 3, 1999. Accomplishment of either paragraph (c)(1) or (c)(2) terminates the repetitive inspection requirement of this AD. 

(1) If a main landing gear selector valve having P/N 57420-1 or 57420-3 is installed, remove it and replace it with a valve having P/N 57420-5A. 

(2) If a main landing gear selector valve having P/N 57420-5 is installed, remove it and replace it with a valve having P/N 57420-5A or modify the valve to the P/N 57420-5A configuration (Modification 7/2742). 

## Alternative Methods of Compliance 

(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), FAA. 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 4:

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

## Special Flight Permits 

(e) Special flight permits may be issued in accordance with §§ 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. 

# Note 5:

The subject of this AD is addressed in Canadian airworthiness directive CF-99-31, dated December 21, 1999. 

Issued in Renton, Washington, on October 4, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-26093 Filed 10-11-00; 8:45 am] 

BILLING CODE 4910-13-P