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

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-8-102, -103, -106, -201, -202, -301, -311, and -315 series airplanes. This proposal would require repetitive inspections for discrepancies of certain rear spar fittings between the flex shaft of the flap secondary drive and the wing-to-fuselage structure, and corrective action if necessary. This proposal also provides for an optional modification of the flex shaft installation, which would terminate the repetitive inspections. This action is necessary to find and fix damage and subsequent failure of the rear spar fittings, which could result in loss of the wing. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by December 29, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-154-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. 2003-NM-154-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 and Propulsion Branch, ANE-171, FAA, New York Aircraft Certification Office, 10 Fifth Street, Third Floor, 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 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 2003-NM-154-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. 2003-NM-154-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-8 series airplanes. TCCA has informed the FAA that discrepancies (chafing, wear damage, cracking) have been found on the rear spar fittings (part numbers (P/N) 85320053, 85322060, and 85334180), located between the flex shaft of the flap secondary drive and the wing-to-fuselage structure. These discrepancies are due to inadequate clearance between the fittings and the flex shaft of the flap secondary drive mechanism, caused by vibration of the flex drive during flap extension/retraction. Such discrepancies could affect the fatigue life of the fittings, which could result in failure of the fittings and consequent loss of the wing.

Explanation of Relevant Service Information

Bombardier has issued Service Bulletin 8-27-83, Revision ‘A’, dated February 8, 2002, which describes procedures for repetitive inspections for discrepancies (chafing, wear damage, cracking) of certain rear spar fittings between the flex shaft of the flap secondary drive and the wing-to-fuselage structure, and corrective action if necessary. The service bulletin also provides procedures for an optional modification of the flex shaft, which would eliminate the need for the repetitive inspections. The inspections and corrective action are as follows:

• A visual inspection to determine the wear damage of each rear spar fitting, which includes the following actions:

If wear damage is found, measure the depth of the wear; and if wear depth is less than the limits specified in Table 1 of the service bulletin, continued operation is allowed for 4,000 flight cycles without blending out the wear; when 4,000 flight cycles have been accumulated, the wear damage must be blended out and must be within the limits specified in Table 3 of the service bulletin. After blending the fitting must be re-inspected (high frequency eddy current (HFEC) inspection) for any remaining discrepancies (wear, cracking). Discrepancies must be repaired before further flight. If no discrepancies are found the inspection is to be repeated at intervals not to exceed 12 months.

If the wear depth is outside the limits specified in Table 1 of the service bulletin, but is less than the limits specified in Table 2 of the service bulletin, temporary operation is allowed for 400 flight cycles without blending out the wear; when 400 flight cycles have been accumulated, the wear must be blended out and within the limits specified in Table 3. The inspection is to be repeated at intervals not to exceed 12 months.

If the wear depth is greater than the limits specified in Table 2, or after blending is greater than the limits specified in Table 3, or cracking is found after temporary operation, the fitting must be replaced before further flight.

• A HFEC inspection for cracking of damaged areas after continued operation and after blending out wear damage. If no cracking is found and the blended wear is within the limits specified in Table 3, permanent continued operation is allowed. If cracking is found or blended wear exceeds the limits specified in Table 3, the fitting must be replaced before further flight.
• Replacement of the rear spar fittings includes removal of the existing fittings, removal of old sealant, inspection of each hole through the rear spar and fuselage for damage, repair of any damage before further flight, and application of new sealant, installation of new fittings, and application of anti-corrosive compound.
• The optional modification of the flex shaft includes installation of new brackets on the rear spar, rework of the torque tube support fittings in the flap primary drive, installation of a new torque tube retainer tray assembly, and installation of additional clamps to stabilize the flex shaft.

The service bulletin also describes procedures for functional tests after doing all applicable actions.

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-2001-42, dated November 23, 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 AD

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, except as discussed below.

This AD allows flight with wear damage, provided that (1) the wear damage is within the limits specified in the service bulletin, (2) no cracking is found, and (3) established inspection procedures would find wear damage in structure at intervals permitting repairs to be done before reduced structural integrity of the fuselage could occur.

To be consistent with the findings of the TCCA, this proposed AD allows operators to continue the repetitive inspections instead of doing the terminating action. In making this determination, we consider that, in the case of this AD, long-term continued operational safety is adequately assured by doing the repetitive inspections to detect discrepancies before they represent a hazard to the airplane, and by doing repairs within the specified time limits.

Differences Between Proposed AD, Canadian Airworthiness Directive, and Service Information

The service bulletin and Canadian airworthiness directive refer only to a “visual inspection” for discrepancies of the rear spar fittings. We have determined that the procedures in the service bulletin should be described as a “detailed inspection.” Note 1 has been included in this proposed AD to define this type of inspection.

Although the service bulletin specifies to submit certain information to the manufacturer, this proposed AD does not include such a requirement.

The applicability specified in the service bulletin and Canadian airworthiness directive includes Model DHC-8-314 airplanes; however, those airplanes are not U.S. type certificated and are not included in the applicability in this proposed AD.

Cost Impact

The FAA estimates that 218 airplanes of U.S. registry would be affected by this proposed AD.

It would take about 16 work hours per rear spar fitting (two fittings per airplane) to accomplish the proposed inspection, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the inspection proposed by this AD on U.S. operators is estimated to be $453,440, or $2,080 per airplane, per inspection cycle.

The cost impact figure discussed above is based on assumptions that no operator has yet done any of the proposed requirements of this AD action, and that no operator would do 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 do 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 modification, if done, would take about 16 work hours, at an average labor rate of $65 per work hour. Required parts would cost about $365 per airplane. Based on these figures, we estimate the cost of the optional terminating modification to be $1,405 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.