AD 97-20-10 R1

This amendment revises an existing airworthiness directive (AD), applicable to certain de Havilland Model DHC-8-100, -200, and -300 series airplanes, that currently requires modification of the attitude and heading reference systems (AHRS). That action was prompted by a report of loss of power to both AHRS s during flight due to a faulty terminal block to which the signal ground for the AHRS s is connected. The actions specified by that AD are intended to prevent simultaneous power loss to both AHRS s, which could result in reduced controllability of the airplane. This amendment reduces the applicability of the existing AD.

Final rule

97-20-10 R1 DE HAVILLAND, INC.: Amendment 39-10697. Docket 98-NM-70-AD. Revises AD 97-20-10, Amendment 39-10147.
Applicability: Model DHC-8-100, -200, and -300 series airplanes; serial numbers 3 through 472 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 (b) 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 simultaneous power loss to both attitude and heading reference systems (AHRS), which could result in reduced controllability of the airplane, accomplish the following:

(a) Within 400 hours time-in-service after November 3, 1997 (the effective date of AD 97-20-10, amendment 39-10147), modify the AHRS's, in accordance with Bombardier Alert Service Bulletin S.B. A8-34-117, Revision `C', dated February 14, 1997.

(b) 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, may be obtained from the New York ACO.

(c) 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.

(d) The modification shall be done in accordance with Bombardier Alert Service Bulletin S.B. A8-34-117, Revision `C', dated February 14, 1997. This incorporation by reference was approved previously by the Director of the Federal Register as of November 3, 1997 (62 FR 50861, September 29, 1997). 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, Engine and Propeller Directorate, New York Aircraft Certification Office, 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.

NOTE 3: The subject of this AD is addressed in Canadian airworthiness directive CF-97-01R2, dated August 13, 1997.

(e) This amendment becomes effective on September 11, 1998.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by revising AD 97-20-10, amendment 39-10147 (62 FR 50861, September 29, 1997), which is applicable to certain de Havilland Model DHC-8-100, -200, and -300 series airplanes, was published in the Federal Register on June 16, 1998 (63 FR 32771). The action proposed to reduce the applicability of the existing AD.

Comments
Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were submitted in response to the proposal or the FAA's determination of the cost to the public.

Conclusion
The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

Cost Impact
The FAA estimates that 167 de Havilland Model DHC-8-100, -200, and -300 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 4 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $10 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $41,750, or $250 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Regulatory Impact
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.

For the reasons discussed above, I certify that this action (1) is not a significant regulatory action under Executive Order 12866; (2) is not a significant rule under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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. 106(g), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-10147 (62 FR 50861, September 29, 1997), and by adding a new airworthiness directive (AD), amendment 39-10697, to read as follows: