AD 96-05-02

This amendment adopts a new airworthiness directive (AD), applicable to certain Fokker Model F28 Mark 0100 series airplanes, that requires modification of a certain galley; repetitive inspections to detect damage and to determine the clearance of generator wires in the auxiliary power unit (APU); and repair or replacement of the damaged wires. This amendment is prompted by reports indicating that, during an unscheduled removal of a galley from the production line, the insulation of one of the generator wires of the APU was found damaged due to inadequate clearance with the adjacent structure. The actions specified by this AD are intended to prevent such damage, which could result in a short in the electrical wiring of the APU and, thus, pose a potential fire hazard.

Final rule

96-05-02 FOKKER: Amendment 39-9527. Docket 94-NM-122-AD.
Applicability: Model F28 Mark 0100 series airplanes; as listed in Fokker Service Bulletin SBF100-24-029, dated June 28, 1993; 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 (c) 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 a short in the electrical wiring of the auxiliary power unit (APU) and a potential fire hazard, accomplish the following:

(a) Within 250 flight hours after the effective date of this AD, accomplish paragraphs (a)(1) and (a)(2) of this AD.

(1) Modify Nordskog Galley Model 1-871, in accordance with paragraphs 2.A., 2.B., and 2.C. of the Accomplishment Instructions of Fokker Service Bulletin SBF100-24-029, dated June 28, 1993.

(2) Perform an inspection to detect damage of and to determine the adequacy of clearance of the generator wires, having part numbers (P/N) AJC0001A, AJ0001B, and AJC0001C, of the auxiliary power unit (APU), in accordance with Fokker Service Bulletin SBF100-24-029, dated June 28, 1993.

(i) If no wires are found damaged and they adequately clear the adjacent structure (positive clearance), no further action is required by this paragraph.

(ii) If no wires are found damaged, but they do notadequately clear the adjacent structure, repeat the inspection thereafter at intervals not to exceed 250 flight hours.

(iii) If any wire is found damaged, prior to further flight, modify the Nordskog Galley Model 1-871 in accordance with paragraph (b) of this AD, and repair or replace the damaged wire in accordance with the service bulletin. However, the modification and repair/replacement actions may be postponed for a maximum of 10 days after detection of the damage, provided that the APU generator is rendered inoperative in accordance with the Master Minimum Equipment List (MMEL), and that modification and repair/replacement actions are accomplished prior to reactivation of the APU generator.

(b) At the next removal of the Nordskog Galley Model 1-871, or within 9,000 flight hours after the effective date of this AD, whichever occurs first, modify the Nordskog Galley in accordance with Fokker Service Bulletin SBF100-24-029 (reference Nordskog Engineering Change Order 43589 Attachment), dated June 28, 1993. Accomplishment of this modification constitutes terminating action for the repetitive inspection requirements of this AD.

(c) 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.

(d) 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.

(e) The actions shall be done in accordance with Fokker Service Bulletin SBF100-24-029, dated June 28, 1993, including Nordskog Engineering Change Order 43589 Attachment. 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 Fokker Aircraft USA, Inc., 1199 North Fairfax Street, Alexandria, Virginia 22314. 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.

(f) This amendment becomes effective on April 3, 1996.

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 Fokker Model F28 Mark 0100 series airplanes was published in the Federal Register on December 9, 1994 (59 FR 236). That action proposed to require modification of a Nordskog Galley Model 1-871 galley. It also proposed to require repetitive inspections to detect damage and determine the clearance of generator wires in the auxiliary power unit (APU); and repair or replacement of the damaged wires.

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 requests that the rule be revised to delete proposed paragraph (a)(2)(i), which would require operators to conduct repetitive inspections if the initial inspection shows that no damage to the feeder cables exists and that thecables adequately clear the adjacent structure. This commenter, an operator, states that it has conducted a boroscope inspection of the APU generator cables on all of its airplanes, and has found nothing anywhere near the cables that could cause damage to them. This operator notes that its initial inspection, which was conducted using a flexible boroscope from the cockpit, provided an excellent view of both the cables and the drain enclosure. The inspection revealed that there is a clearance between the wiring and adjacent structure (drain screws) on the order of six inches.

The FAA concurs with the commenter's request. According to the Rijksluchtvaartdienst (RLD), which is the airworthiness authority for the Netherlands, the clearance between the drain screws and the APU feeder cable (generator wires) found on airplanes on the production line was on the order of one inch. This amount of clearance was considered to be inadequate, such that chafing or damage of the wire installation could occur. Also, according to the RLD, the reason that the referenced service bulletin specifies that the inspection be accomplished with a mirror is because the manufacturer considered that a mirror would give a better estimate of the clearance than could a boroscope inspection. However, the FAA, in consultation with the RLD, recently has concluded that, since the clearance between the drain screws and the wires has been determined to be on the order of 6 inches on all affected airplanes that have not already been modified in accordance with this AD, there is little reason to believe that chafing would occur. In light of this, the FAA finds that there is no need for a repetitive inspection of the wires. Therefore, the FAA has revised paragraph (a)(2)(i) of the final rule to indicate that, if no wires are found damaged as a result of the inspection and they adequately clear the adjacent structure (positive clearance), no further inspections are required.

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 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 52 airplanes of U.S. registry will be affected by this proposed 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. Required parts will cost approximately $1,000 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $58,240, or $1,120 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.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 USC 106(g), 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: