03-25590. Airworthiness Directives; Bombardier Model DHC-8-102, -103, -106, -201, -202, -301, -311, and -315 Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Bombardier DHC-8-102, -103, -106, -201, -202, -301, -311, and -315 airplanes, that currently requires inspections to detect breakage in the struts of the rear mount strut assemblies on the left and right engine nacelles, and replacement of any broken struts. The existing AD also requires eventual replacement of all currently installed struts with new and/or reworked struts, as terminating action for the inspections. This action would require new repetitive inspections of the strut assemblies for cracking of struts replaced per the existing AD, and replacement of any cracked strut with a new, machined strut. This action also would change the applicability of the existing AD by adding certain airplanes and removing certain other airplanes, and would include an optional terminating action for the repetitive inspections. The actions specified by the proposed AD are intended to prevent failure of the engine rear mount struts, which could result in reduced structural integrity of the nacelle and engine support structure. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by November 10, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-266-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 [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2001-NM-266-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 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Bombardier, Inc., Bombardier Regional Aircraft Division, 123 Garratt Boulevard, Downsview, Ontario M3K 1Y5, 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:

Jon Hjelm, Aerospace Engineer, Airframe Branch, ANE-171, FAA, New York Aircraft Certification Office, 10 Fifth Street, Third Floor, Valley Stream, New York 11581; telephone [phone]; fax [phone].

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 action 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, 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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2001-NM-266-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. 2001-NM-266-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On February 14, 1994, the FAA issued AD 94-04-09, amendment 39-8829 (59 FR 8393, February 22, 1994), applicable to certain Bombardier Model DHC-8-100 and DHC-8-300 airplanes, to require inspections to detect breakage in the engine rear mount strut assemblies, and replacement of broken struts. That AD also requires eventual replacement of all currently installed struts with new and/or reworked struts, as terminating action for the inspections. That action was prompted by several reports of failure of the engine rear mount struts, due to fracture at one of the rosette welds on the shank of the strut where full weld depth was not achieved during manufacture. The requirements of that AD are intended to prevent failure of the engine rear mount struts, which could reduce the structural integrity of the nacelle and engine support structure.

Actions Since Issuance of Previous Rule

Since the issuance of AD 94-04-09, we have been advised by Transport Canada Civil Aviation (TCCA), which is the airworthiness authority for Canada, of reports from the manufacturer and operators of Model DHC-8-100 and DHC-8-300 airplanes indicating that replacement struts installed per that AD have developed cracks. Therefore, the engine rear mount strut has been redesigned and is pressed fit assembled instead of welded which improves the endurance of the strut to prevent failure due to cracking and/or fracture.

Explanation of Relevant Service Information

Bombardier has issued Service Bulletin 8-71-24, dated August 21, 2001, which describes procedures for replacing the existing rear mount struts in a nacelle with new, improved struts. TCCA previously issued Canadian airworthiness directive CF-2001-20, dated May 16, 2001, to ensure 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 section 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 us informed of the situation described above. We have 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 supersede AD 94-04-09 to require new repetitive inspections of the strut assemblies for cracking of the struts replaced per the existing AD, and replacement of any cracked strut with a new, machined strut. This proposed AD also would change the applicability of the existing AD by adding certain airplanes and removing certain other airplanes, and would include an optional terminating action for the repetitive inspections.

Consistent with the findings of TCCA, this proposed AD would allow repetitive inspections to continue in lieu of the terminating action. In making this determination we considered that long-term continued operational safety in this case will be adequately ensured by repetitive inspections to find cracking before it represents a hazard to the airplane.

Changes to the Applicability of the Existing AD

This proposed AD would expand the applicability in the existing AD to include Model DHC-8-102, -103, -106, -201, -202, -301, -311, and -315 airplanes; serial numbers 003 through 509 inclusive. Model DHC-8-102 and -103 series airplanes, serial numbers 003 through 310 inclusive; and Model DHC-8-301, -311, and -314 series airplanes, serial numbers 100 through 311 inclusive, were identified in the existing AD.

Additionally, this proposed AD would remove Model DHC-8-314 airplanes, which were added to the applicability of the existing AD but are not U.S. type-certificated.

Cost Impact

There are approximately 192 airplanes of U.S. registry that would be affected by this proposed AD.

The actions that are currently required by AD 94-04-09 take approximately 16 work hours per airplane to accomplish, at an average labor rate of $65 per work hour. Required parts are provided by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the currently required actions is estimated to be $1,040 per airplane.

The new detailed inspection that is proposed in this AD action would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the proposed inspection on U.S. operators is estimated to be $12,480, or $65 per airplane, per inspection cycle.

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. 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.

The optional terminating action, if done, would take approximately 16 work hours per strut to accomplish, at an average labor rate of $65 per work hour. Required parts would cost approximately $800 per strut. Based on these figures, the cost impact of the optional terminating action is estimated to be $1,840 per strut, 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 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

[Amended]

2. Section 39.13 is amended by removing amendment 39-8829 (59 FR 8393, February 22, 1994), and by adding a new airworthiness directive (AD), to read as follows:

Bombardier, Inc. (Formerly de Havilland, Inc.): Docket 2001-NM-266-AD. Supersedes AD 94-04-09, amendment 39-8829.

Applicability: Model DHC-8-102, -103, -106, -201, -202, -301, -311, and -315 airplanes; serial numbers 003 through 509 inclusive; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the engine rear mount struts on the left and right engine nacelles, which could result in reduced structural integrity of the nacelle and engine support structure, accomplish the following:

Repetitive Inspections

(a) Within 1,000 flight hours since installation of any new or reworked rear mount strut per the replacement required by paragraph (b) of AD 94-04-09, amendment 39-8829, or within 250 flight hours after the effective date of this AD, whichever is later; do a detailed inspection for cracking of each rear mount strut in the left and right engine nacelles.

Note 1:

Bombardier Service Bulletin 8-71-24, dated August 21, 2001, does not contain inspection procedures for the detailed inspection required by paragraph (a) of this AD; however, the definition of a detailed inspection is specified in Note 2 of this AD.

Note 2:

For the purposes of this AD, a detailed inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

(1) If no crack is found, repeat the inspection at intervals not to exceed 250 flight hours, until accomplishment of paragraph (b) of this AD.

(2) If any crack is found, before further flight, replace the strut with a new, improved strut per Bombardier Service Bulletin 8-71-24, dated August 21, 2001. Repeat the inspection thereafter at intervals not to exceed 500 flight hours, for that nacelle only.

Optional Terminating Action

(b) Replacement of both rear mount struts in a nacelle with new, improved struts, by doing all the actions specified in the Job Set-up, Procedure, and Close-out sections of the Accomplishment Instructions of Bombardier Service Bulletin 8-71-24, dated August 21, 2001, ends the repetitive inspections required by this AD for that nacelle only. Replacement of both rear mount struts on both the left and right engine nacelles ends the repetitive inspections required by this AD.

Parts Installation

(c) As of the effective date of this AD, no person shall install an engine rear mount strut, P/N 87110016-001, -003, -005, -007, -009, or -011, on any airplane.

Alternative Methods of Compliance

(d) In accordance with 14 CFR 39.19, the Manager, New York Aircraft Certification Office, FAA, is authorized to approve alternative methods of compliance for this AD.

Note 3:

The subject of this AD is addressed in Canadian airworthiness directive CF-2001-20, dated May 16, 2001.

Issued in Renton, Washington, on October 3, 2003.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.