Airworthiness Directives; Bombardier Model DHC-8-301, -311, and -315 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-8-301, -311, and -315 airplanes. This proposal would require determining the modification number of the angle of attack (AOA) sensor vanes; testing the movement of the affected vanes to evaluate sticking against both the upper and the lower vane travel end stops; and corrective action, if necessary. This action is necessary to prevent an incorrect AOA indication to the stall warning system in flight, which could result in an inadvertent stall and consequent loss of control of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by May 26, 2004.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-297-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. 2002-NM-297-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, 1600 Stewart Avenue, Westbury, New York.

FOR FURTHER INFORMATION CONTACT:

Ezra Sasson, Aerospace Engineer, Systems and Flight Test Branch, ANE-172, New York Aircraft Certification Office, FAA, 1600 Stewart Avenue, suite 410, Westbury, New York 11590; telephone (516) 228-7320; fax (516) 794-5531.

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 2002-NM-297-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. 2002-NM-297-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-8-301, -311, and -315 airplanes. TCCA advises that the manufacturer of the angle of attack (AOA) sensor vane has determined that a damper within the AOA sensor in some vanes can leak oil. Such leakage could cause the vane to stick against the upper or the lower travel end stop. Although no problems with sticking AOA vanes have been reported on the subject airplanes, other airplanes using similar sensor designs have experienced AOA split indications during takeoff roll, which resulted in rejected takeoffs. A sticking vane would provide the stall warning system with an incorrect AOA reading at airspeeds below approximately 100 knots; above airspeeds of 110 knots, the airflow would release a stuck vane. This condition, if not corrected, could result in an incorrect AOA indication to the stall warning system in flight, which could cause an inadvertent stall and consequent loss of control of the airplane.

Explanation of Relevant Service Information

Bombardier has issued Alert Service Bulletin A8-27-94, Revision “A”, dated February 5, 2002, which describes procedures for an initial movement test of the AOA sensor vane to evaluate sticking against both the upper and the lower vane travel end stops. The service bulletin also includes procedures for related investigative and corrective actions.

The initial movement test includes placing a gram gauge (dynamometer) against the AOA sensor vane, and recording the gauge reading as the vane is moved away from both the upper and the lower travel end stops. The related investigative action is repeating the movement test one time for sensor vanes that have measurements of less than 110 grams.

The related corrective action is replacing any AOA sensor vane if any movement shows certain gram gauge readings from either the upper or lower position. If the gram gauge reading is between 110 and 170 grams, the service bulletin recommends replacing the AOA sensor vane within six months or 1,000 flight hours, whichever occurs first. If a gram gauge reading is 170 grams or more, the service bulletin recommends replacing the AOA sensor vane within 5 calendar days. The service bulletin specifies that only post-MOD “J” sensors be used for replacement.

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-2001-46, dated December 3, 2001, to ensure the continued airworthiness of these airplanes in Canada.

Bombardier Alert Service Bulletin A8-27-94, Revision “A”, dated February 5, 2002, references Rosemount Aerospace Alert Service Bulletin 0861CAB-27A-07, dated September 28, 2001, as an additional source of service information for doing the vane movement test of the AOA sensors. The Rosemount service bulletin is included in the Bombardier service bulletin. This service bulletin also includes procedures for sending reports of test findings to Rosemount Aerospace, and for sending removed sensors to Rosemount Aerospace for modification.

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, 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, except as discussed below.

Differences Among the Proposed AD, Service Bulletins, and the Canadian Airworthiness Directive

The Rosemount Aerospace service bulletin (which is included in the Bombardier service bulletin) contains procedures for sending reports of test findings to Rosemount, and for sending removed sensors to Rosemount for modification. This proposed AD would not include those requirements.

Both the Bombardier service bulletin and the Canadian airworthiness directive have a compliance time for the initial movement test, and for replacement of certain sensor vanes of 1,000 flight hours or 6 months, whichever occurs first. This proposed AD would require that operators perform the initial test within 1,000 flight hours or 18 months after the effective date of this proposed AD, whichever occurs first; and the replacement within 1,000 flight hours or 18 months, whichever occurs first, after accomplishing the movement test in which certain measurements are found. We find that this compliance time represents an appropriate interval for affected airplanes to continue to operate without compromising safety. This difference has been coordinated with TCCA.

Cost Impact

The FAA estimates that 57 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 1 work hour per airplane to accomplish the proposed inspection to determine the modification letter, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $3,705, or $65 per airplane.

The cost impact figure discussed above is 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.

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.