AD 95-05-01

This amendment adopts a new airworthiness directive (AD), applicable to all British Aerospace Model BAe 146-100A, -200A, and -300A series airplanes, that requires conducting closed loop tests to determine the setting of the underfrequency trip level on suspect generator control units (GCU), and either the correction of discrepancies or replacement of the GCU. This amendment is prompted by several malfunctions of in-service GCU's due to the effects of setting the underfrequency trip level too high. The actions specified by this AD are intended to correct GCU's that may have the underfrequency level set too high, which could result in the unwanted shut down of an electrical generator; this condition may lead to loss of all generated electrical power on the airplane when other generator faults or failures occur.

Final rule

95-05-01 BRITISH AEROSPACE REGIONAL AIRCRAFT LIMITED, AVRO INTERNATIONAL AEROSPACE DIVISION (Formerly British Aerospace, plc; British Aerospace Commercial Aircraft Limited): Amendment 39-9168. Docket 94-NM-126-AD.
Applicability: All Model British Aerospace Model BAe 146-100A, -200A, and -300A 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 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 (b) 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 correct generator control units (GCU) that may have the under-frequency trip level set too high, which could lead to the unwanted shut down of an electrical generator, accomplish the following:

(a) Within 6 months after the effective date of this AD, check the part and serial number on the data plate of each generator control unit (GCU). If the part number is one of those affected and the serial number is listed in Addendum 1 of GEC-Marconi Service Bulletin HGE 24-23, dated March 11, 1994, prior to further flight, conduct a closed loop test to determine the setting of the underfrequency trip level, in accordance with that service bulletin.

(1) Ifthe level exceeds that specified in GEC-Marconi Service Bulletin HGE 24-23, dated March 11, 1994, prior to further flight, adjust the level in accordance with that service bulletin; or replace the GCU with a serviceable unit, in accordance with Avro Service Bulletin S.B. 24-103, dated March 24, 1994.

(2) Prior to further flight, after adjustment or replacement of the GCU as required by paragraph (a)(1) of this AD, conduct the post assembly testing in accordance with Avro Service Bulletin S.B. 24-103, dated March 24, 1994.

(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, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(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 closed loop test and adjustment shall be done in accordance with GEC-Marconi Service Bulletin HGE 24-23, dated March 11, 1994. The replacement and post assembly test shall be done in accordance with Avro Service Bulletin S.B. 24-103, dated March 24, 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 British Aerospace Holding, Inc., Avro International Aerospace Division, P.O. Box 16039, Dulles International Airport, Washington DC 20041-6039. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on April 13, 1995.

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 British Aerospace Model BAe 146-100A, -200A, and -300A series airplanes was published in the Federal Register on November 16, 1994 (59 FR 59179). That action proposed to require checking the part and serial number on the data plate of each GCU to identify discrepant units, and conducting closed loop tests on affected GCU's to determine the setting of the underfrequency trip level. That action also proposed to require either adjusting the underfrequency trip level or replacing the discrepant GCU with a serviceable unit, and conducting post assembly testing.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received.

The commenter supports the proposed rule.

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. The FAA 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 added to this final rule to clarify this long-standing requirement.

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

The FAA estimates that 43 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 total cost impact of the AD on U.S. operators is estimated to be $2,580, or $60 per airplane.

The total 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.

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. 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: