AD 96-25-08

This amendment adopts a new airworthiness directive (AD), applicable to all de Havilland Model DHC-7 series airplanes, that requires performing a review of the airplane maintenance records to determine if any insulation blankets have been repaired or changed during service, and various follow-on actions, if necessary. This amendment is prompted by reports of corrosion forming on areas of the airplane structure where black film thermal insulation blankets are used. The actions specified by this AD are intended to prevent such corrosion, which could result in degradation of the structural capability of the airplane fuselage and consequent sudden loss of cabin pressure.

Final rule

96-25-08 DE HAVILLAND, INC.: Amendment 39-9851. Docket 95-NM-265-AD.
Applicability: All Model DHC-7 series airplanes, certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 (e) 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 degradation of the structural capability of the fuselage and sudden loss of cabin pressure, accomplish the following:

(a) Within six months after the effective date of this AD, perform a review of the airplane maintenance records to determine if any insulation blankets have been repaired or changed during service, in accordance with de Havilland Service Bulletin S.B. 7-21-30, dated July 6, 1994.

(b) If no insulation blanket has been repaired or changed, no further action is required by this AD.

(c) If any insulation blanket has been repaired or changed, prior to further flight, perform a visual inspection to detect black film insulation of the air conditioning system, in accordance with de Havilland Service Bulletin S.B. 7-21-30, dated July 6, 1994.

(1) If no black film insulation is detected, prior to further flight, perform a review of the airplane modification records to determine if any kit listed in "Table 1-Modification List" has been installed, in accordance withthe service bulletin.

(i) If no kit listed in "Table 1-Modification List" is found to be installed, no further action is required by this AD.

(ii) If any kit listed in "Table 1-Modification List" is found to be installed, prior to further flight, perform the various follow-on actions in accordance with the service bulletin. (The follow-on actions include an inspection to detect black film insulation, removal of any black film insulation, an inspection to detect corrosion, repair of corroded structure, and installation of new silver blankets.) However, in lieu of repairing corroded structure in accordance with service bulletin, the repair of any corrosion shall be done in accordance with a method approved by the Manager, New York Aircraft Certification Office (ACO), FAA, Engine and Propeller Directorate.

(2) If any black film insulation is detected, prior to further flight, perform the follow-on actions in accordance with the service bulletin. (The follow-on actions include removal of any black film insulation, an inspection to detect corrosion, repair of any corroded structure, and installation of new silver blankets.) However, in lieu of repairing corroded structure in accordance with service bulletin, the repair of any corrosion shall be done in accordance with a method approved by the Manager, New York ACO.

(d) As of the effective date of this AD, no person shall install black Orcon film insulation, part number AN46B/AN36B, on any airplane.

(e) 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 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.

(f) 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.

(g) The actions shall be done in accordance with de Havilland Service Bulletin S.B. 7-21-30, dated July 6, 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.

(h) This amendment becomes effective on February 3, 1997.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all de Havilland Model DHC-7 series airplanes was published in the Federal Register on September 30, 1996 (61 FR 51062). That action proposed to require performing a review of the airplane maintenance records to determine if any insulation blankets have been repaired or changed during service, and various follow-on actions, if necessary.

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 50 de Havilland Model DHC-7 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $3,000, or $60 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 adding the following new airworthiness directive: