AD 98-04-17

This amendment supersedes Airworthiness Directive (AD) 97-03-03, which applies to certain Pilatus Britten-Norman Ltd. (Pilatus) BN-2, BN-2A, and BN-2B series airplanes that do not have Modification NB/M/1571 generator terminal diodes installed. AD 97-03-03 currently requires the installation of higher capacity diodes on the generator switches regardless of whether the airplane is equipped with the original 50 amp DC generating system or a Modification NB/M/1148, which is a 70 amp system. This action retains the actions of AD 97-03-03, but modifies the applicability section to reflect that this AD does not apply to Pilatus BN-2, BN-2A, and BN-2B series airplanes with 50 amp DC generation systems installed. This AD is the result of reports that the applicability section of AD 97-03-03 is incorrect. The actions specified by this AD are intended to prevent a loss of electrical power to the navigation, communications, and lighting systems, which could impair the pilot's ability to maintain control of the airplane.

The incorporation by reference of Pilatus Britten-Norman Manufacturers Service Bulletin (SB) BN-2/SB.228, Issue 2, dated January 17, 1996, as listed in the regulations was previously approved by the Director of the Federal Register as of March 23, 1997 (62 FR 4909, February 3, 1997).

Final rule.

98-04-17 PILATUS BRITTEN-NORMAN LTD.: Amendment No. 39-10329; Docket No. 97-CE-12-AD; Supersedes AD 97-03-03, Amendment 39-9909.

Applicability: BN-2, BN-2A, and BN-2B series airplanes (all serial numbers), certificated in any category, that have Pilatus Britten-Norman (Pilatus) Modification NB/M/1148 (70 amp DC Generation System) incorporated, and do not have Pilatus Modification NB/M/1571 (Introduction of Increased Rated Diode-70 amp DC Generation System) incorporated.

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 (d) 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 within the next 50 hours time-in-service (TIS) after the effective date of this AD, unless already accomplished.

To prevent loss of electrical power to the navigation, communications and lighting systems, which could impair the pilot's ability to maintain control of the airplane, accomplish the following:

(a) Remove the diodes (quantity 2, part number (P/N) 340502014, type 10B1 or 10D1) installed on the terminals of the STBD (RIGHT) GEN and PORT (LEFT) GEN switches (SW2 and SW3), and install new approved diodes (quantity 2, P/N NB-81-5873, type 60S6) in accordance with the Accomplishment Instructions section in Pilatus Britten-Norman Aircraft Manufacturers Service Bulletin (SB) BN-2/SB.228, Issue 2, dated January 17, 1996.

(b) Accomplishment of paragraph (a) of this AD is considered incorporation of Modification NB/M/1571.

(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) An alternative method of compliance or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, Small Airplane Directorate, 1201 Walnut, suite 900, Kansas City, Missouri, 64106. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Small Airplane Directorate. Alternative methods of compliance previously approved for AD 97-03-03 are considered approved for this AD.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from theSmall Airplane Directorate.

(e) The removal and installation required by this AD shall be done in accordance with Pilatus Britten-Norman Aircraft Manufacturers Service Bulletin (SB) BN-2/SB.228, Issue 2, dated January 17, 1996.

(1) The incorporation by reference of Pilatus Britten-Norman Aircraft Manufacturers Service Bulletin (SB) BN-2/SB.228, Issue 2, dated January 17, 1996, was approved previously by the Director of the Federal Register as of March 23, 1997 (62 FR 4909, February 3, 1997).

(2) Copies may be obtained from Pilatus Britten-Norman, Ltd., Bembridge, Isle of Wight, United Kingdom, PO35 5PR. Copies may be inspected at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(f) This amendment supersedes AD 97-03-03, Amendment 39-9909.

(g) This Amendment (39-10329) becomes effective on March 23, 1998.

Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain Pilatus BN-2, BN-2A, and BN-2B series airplanes equipped with Pilatus Modification NB/M/1148 (a 70 amp generating system), but without generator terminal diodes installed in accordance with Modification NB/M/1571, was published in the Federal Register on July 7, 1997, (62 FR 36240). The action proposed to supersede AD 97-03-03, which requires installing type 60S6 diodes on the terminals of the STBD (RIGHT) GEN and PORT (LEFT) GEN switches (SW2 and SW3), regardless of the generating system being used on the airplane. This superseding action retains the same action as AD 97-03-03, but changes the applicability section so that it applies only to the Pilatus BN-2, BN-2A, and BN-2B airplanes that have Modification NB/M/1148 (70 amp DC generation system) incorporated, and do not have Pilatus Modification NB/M/1571 (Introduction of Increased Rated Diode - 70 amp DC generation system) incorporated. This action would not apply to certain Pilatus BN-2, BN-2A, and BN-2B series airplanes with a 50 amp DC generation system installed.

Accomplishment of this action would be in accordance with Pilatus Britten-Norman Ltd. Service Bulletin No. BN-2/SB.228, Issue 2, dated January 17, 1996.

The FAA's Determination
Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposed rule or the FAA's determination of the cost to the public.

After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

Cost Impact
The FAA estimates that 116 airplanes currently on the U.S. registry will be affected by this AD, that it will take approximately 1 workhour per airplane to accomplish this action, and that the average labor rate is approximately $60 an hour. Parts cost approximately $40 per airplane. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $11,600 for the fleet or $100 per airplane. For purposes of estimating the cost of this AD, the FAA is presuming that none of the owners/operators have accomplished any of the actions on any of the affected airplanes.

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 copy of the final 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, 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 USC 106(g), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by removing airworthiness directive (AD) 97-03-03, Amendment No. 39-9909, and by adding a new AD to read as follows: