AD 95-12-12 ACTIVE

This amendment adopts a new airworthiness directive (AD) that is applicable to certain de Havilland Model DHC-8-102, -103, and -106 series airplanes. This action requires repetitive operational testing of the stall warning computers to ensure activation of the associated stick shakers, and replacement of non-operational stall warning computers with new or serviceable units. This action also provides an optional terminating action for the repetitive operational tests. This amendment is prompted by a report that, during a routine test, the stick shakers of the stall warning system did not activate, due to contamination of the weight-on-wheels contacts in the stall warning computer. The actions specified in this AD are intended to ensure that such contamination is detected. Contamination of the stall warning computers could lead to incorrect logic detection of the weight-on-wheels signal, and subsequent loss of the stick shaker function.

Final rule; request for comments

95-12-12 DE HAVILLAND, INC.: Amendment 39-9262. Docket 95-NM-104-AD.
Applicability: Model DHC-8-102, -103, and -106 series airplanes, serial numbers 003 and subsequent; equipped with Safe Flight stall warning computers having part number (P/N) 3605-4, -5, or -6; and on which Modification 8/2072 has not been installed; 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 use the authority provided in paragraph (c) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD.Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent incorrect logic detection of the weight-on-wheels signal, and subsequent loss of the stick shaker function, accomplish the following:

(a) Within 50 hours time-in-service after the effective date of this AD, unless previously accomplished within the last 400 hours time-in-service: Perform an operational test to determine activation of the stick shakers of the No. 1 and No. 2 stall warning computers, in accordance with Bombardier Alert Service Bulletin S.B. A8-27-73, dated November 25, 1993. Thereafter, repeat the operational test at intervals not to exceed 450 hours time-in-service. If any stick shaker does not activate, prior to further flight, replace the non-operational stall warning computer with a new or serviceable unit in accordance with the alert service bulletin.

(b) Replacement of stall warning computers having part number (P/N) 3605-4, -5, or -6 with new stall warning computers having P/N 3605-8, in accordance with Bombardier Service Bulletin S.B. 8-27-76, dated October 31, 1994, constitutes terminating action for the repetitive operational test requirements of this AD.

(c) 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, 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, maybe obtained from the New York ACO.

(d) 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.

(e) The operational test and replacement shall be done in accordance with Bombardier Alert Service Bulletin S.B. A8-27-73, dated November 25, 1993, and Bombardier Service Bulletin 8-27-76, dated October 31, 1994. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Bombardier, Inc., Bombardier Regional Aircraft Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(f) This amendment becomes effective on June 28, 1995.

Transport Canada Aviation, which is the airworthiness authority for Canada, recently notified the FAA that an unsafe condition may exist on certain de Havilland Model DHC-8-102, -103, and -106 series airplanes equipped with Safe Flight stall warning computers having part number (P/N) 3605-4, -5, or -6, and on which Modification 8/2072 has not been installed. Transport Canada Aviation advises that, during a routine "air mode" test of the stall warning system, the stick shakers did not activate. Investigation revealed that the weight-on-wheels relay contacts within the stall warning computer had become contaminated. This condition, if not corrected, could lead to incorrect logic detection of the weight-on-wheels signal, and subsequent loss of the stick shaker function.

Bombardier has issued Alert Service Bulletin S.B. A8-27-73, dated November 25, 1993, which describes procedures for repetitive operational testing to ensure activation of the stick shakers of the No. 1 and No. 2 stall warning computers, and replacement of non-operational stall warning computers with new or serviceable units. Transport Canada Aviation classified the alert service bulletin as mandatory and issued Canadian airworthiness directive CF-95-06, dated April 10, 1995, in order to assure the continued airworthiness of these airplanes in Canada.

Bombardier has also issued Service Bulletin S.B. 8-27-76, dated October 31, 1994, which describes procedures for replacing Safe Flight stall warning computers having P/N 3506-5, -6, or -7 with new stall warning computers having P/N 3506-8 (Modification 8/2072). The new stall warning computers have additional internal monitoring; installation of the new computers will increase reliability. Accomplishment of this replacement would eliminate the need for the repetitive operational tests.

This airplane model is manufactured in Canada and is type certificated for operation in the United States under the provisionsof 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 AD action is necessary for products of this type design that are certificated for operation in the United States.

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 AD is being issued to detect contamination of the weight-on-wheels relay contacts in the stall warning computer; such contamination could lead to incorrect logic detection of the weight-on-wheels signal, and subsequent loss of the stick shaker function. This AD requires repetitive operational testing of the No. 1 and No. 2 stall warning computers to ensure activation of the associated stick shaker, and replacement of non-operational stall warning computers with new units. This AD also provides an optional terminating action for the repetitive operational test requirements. The actions are required to be accomplished in accordance with the service bulletins described previously.

The FAA is considering further rulemaking action to require the replacement of Safe Flight stall warning computers with units having P/N 3506-8. However, the proposed compliance time (6 months) for this replacement is sufficiently long so that notice and time for public comment would be practicable.

As a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. TheFAA points out that all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been included in this rule to clarify this long-standing requirement.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule.Interested persons are invited to comment on this 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 under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 95-NM-104-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and thatit is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 95-NM-104-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The service information referenced in this AD 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; or at the FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Peter Cuneo, Aerospace Engineer, Systems and Equipment Branch, ANE-172, FAA, New York Aircraft Certification Office, Engine and Propeller Directorate, 10 Fifth Street, Third Floor, Valley Stream, New York 11581; telephone (516) 256-7506; fax (516) 568-2716.