AD 95-02-09

This amendment adopts a new airworthiness directive (AD), applicable to certain British Aerospace Model ATP airplanes, that requires inspections to detect damage, overheating, and proper operation of the DC connections and cooling fans in certain transformer rectifier units (TRU), and repair or replacement, if necessary. This amendment is prompted by a report of the loss of all DC electrical power, except for the battery emergency bus, due to failure of the TRU's, which occurred during flight. The actions specified by this AD are intended to prevent such failures that could lead to loss of essential electrical power required to continue safe flight of the airplane.

Final rule

95-02-09 BRITISH AEROSPACE (COMMERCIAL AIRCRAFT), LIMITED: Amendment 39-9128. Docket 93-NM-217-AD.
Applicability: Model ATP airplanes equipped with Ferranti Transformer Rectifier Unit TR202A (Pt. No. 84/59100) or TR202B (Pt. No. 84/60040), 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 prevent loss of essential electrical power required to continue safe flight of the airplane, accomplish the following:

(a) Within 225 hours time-in-service after the effective date of this AD, and thereafter at intervals not to exceed 625 hours time-in-service, accomplish paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this AD.

(1) Perform a visual inspection of the DC connections to detect any damage or overheating, in accordance with Ferranti Service Bulletin 24-20-171, dated September 1993. If any damage or overheating is found, prior to further flight, repair in accordance with a method approved by Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate.

(2) Perform a torque loading inspection of each DC connection to ensure that torque loads are within the limits specified in Ferranti Service Bulletin 24-20-171, dated September 1993; and, during this inspection, ensure that each terminal stud is secure in its mounting by visually observing that the stud does not rotate; in accordance with Ferranti Service Bulletin 24-20-171, dated September 1993.

(3) Perform a visual inspection of the cooling fan blades to detect any damage due to overheating, in accordance with Ferranti Service Bulletin 24-20-172, dated September 1993. If any damage is found, prior to further flight, replace the fan blade with a serviceable part in accordance with the airplane maintenance manual.

(4) Perform a functional test of the operation of the cooling fan by energizing the relay and confirming that cooling air exits from the grill on top of the unit, in accordance with Ferranti Service Bulletin 24-20-172, dated September 1993. Prior to further flight, repair or replace any malfunctioning or damaged cooling fan or cooling fan relay, in accordance with the airplane maintenance manual.

(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 inspections and test shall be done in accordance with Ferranti Service Bulletin 24-20-171, dated September 1993; and Ferranti Service Bulletin 24-20-172, dated September 1993. 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 Jetstream Aircraft, Inc., P.O. Box 16029, Dulles International Airport, Washington, DC 20041-6029. 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 March 16, 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 certain British Aerospace Model ATP airplanes was published in the Federal Register on February 18, 1994 (59 FR 8145). That action proposed to require inspections of the DC connections and cooling fans in certain transformer rectifier units (TRU) to detect damage or overheating and to ensure correct operation, and repair or replacement, if necessary.

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 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 theAD, 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 requirement.

Additionally, The FAA has recently reviewed the figures it has used over the past several years in calculating the economic impact of AD activity. In order to account for various inflationary costs in the airline industry, the FAA has determined that it is necessary to increase the labor rate used in these calculations from $55 per work hour to $60 per work hour. The economic impact information, below, has been revised to reflect this increase in the specified hourly labor rate.

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

The FAA estimates that 10 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours 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 $1,200, or $120 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: