AD 97-24-11

This amendment adopts a new airworthiness directive (AD), applicable to certain Fokker Model F28 Mark 0100 series airplanes, that requires repetitive inspections of certain flanges and finger strips at rib 5.0 of the vertical stabilizer to detect fatigue cracking, and repairs, if necessary. This amendment also requires modifications that would strengthen the torsion box at rib 5.0 and prevent fatigue cracking; one of these modifications constitutes terminating action for the repetitive inspections. This amendment is prompted by reports indicating that, during full-scale fatigue testing, cracking has been found on the vertical stabilizer of the test article. The actions specified by this AD are intended to detect and prevent fatigue cracking in the subject area, which, if not corrected, could reduce the structural integrity of the vertical stabilizer.

Final rule

97-24-11 FOKKER: Amendment 39-10218. Docket 96-NM-185-AD.

Applicability: Model F28 Mark 0100 series airplanes having the serial numbers specified in Table 1 of this AD; certificated in any category.

TABLE 1
Serial Numbers of Airplanes Subject to this AD

11244 through 11460, inclusive
11463 through 11469, inclusive
11471
11474 through 11483, inclusive,
11489 through 11491, inclusive
11497 through 11499, inclusive
11501
11502
11504
11506
11507
11512 through 11515, inclusive
11517
11520

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 detect and prevent fatigue cracking in the vertical stabilizer, which consequently could reduce its structural integrity, accomplish the following:

(a) For airplanes having serial numbers 11244 through 11419, inclusive, and 11421: Except as provided by paragraph (c) of this AD, prior to the accumulation of 8,500 total landings or within 30 days after the effective date of this AD, whichever occurs later, perform an eddy current inspection to detect fatigue cracking in the left-hand and right-hand flanges and finger strips at rib 5.0 of the vertical stabilizer, in accordance with Fokker Service Bulletin SBF100-55-019, Revision 1, dated May 19, 1993.

(1) If no cracking is detected, repeat this inspection thereafter at intervals not to exceed 2,000 landings until the requirements of paragraph (b) of this AD are accomplished.

(2) If any cracking is detected, prior to further flight, repair in accordance with a method approved by the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate.

(b) For airplanes with serial numbers 11244 through 11419 inclusive, and 11421, accomplish the requirements of both paragraphs (b)(1) and (b)(2) of this AD:

(1) Except as provided by paragraph (c) of this AD, prior to the accumulation of 13,500 total landings, or within 6 months after the effective date of this AD, whichever occurs later, perform an eddy current inspection to detect fatigue cracking in the left-hand and right- hand flanges and finger strips at rib 5.0 of the vertical stabilizer, in accordance with Part 1 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-55-018, Revision 1, dated December 27, 1993.

(i) If no cracking is detected, prior to further flight, accomplish the requirements of paragraph (b)(2) of this AD.

(ii) If any cracking is detected, prior to further flight, repair in accordance with a method approved by the Manager, International Branch, ANM-116, and accomplish the requirements of paragraph (b)(2) of this AD.

(2) After accomplishing the requirements of paragraph (b)(1) of this AD, modify rib 5.0 of the vertical stabilizer by installing new stiffening, in accordance with Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-55-018, Revision 1, dated December 27, 1993. Accomplishment of this modification constitutes terminating action for the repetitive inspections required by paragraph (a) of this AD.

(c) The following exceptions apply with regard to the requirements of paragraphs (a) and (b) of this AD:

(1) Accomplishment of the inspection specified in paragraph (a) and (b)(1) of this AD is not required if the modification specified in paragraph (b)(2) is accomplished prior to the accumulation of 7,300 total landings on the airplane.

(2) Compliance with AD 91-18-15, amendment 39-8018, is not required if the requirements of paragraph (b)(2) of this AD are accomplished prior to the accumulation of 6,000 total landings on the airplane.

(d) For all airplanes: At the applicable times specified in paragraph (d)(1) or (d)(2), modify the Hi-lok bolt holes at rib 5.0 of the vertical stabilizer by cold expansion, in accordance with Fokker Service Bulletin SBF100-55-023, dated January 3, 1995.

(1) For airplanes that have been modified in accordance with the requirements of paragraph (b) of this AD prior to the effective date of this AD: Modify prior to the accumulation of either 10,000 landings after in-service modification, or 10,000 landings after delivery with factory modification, as applicable; or within 30 days after the effective date of this AD, whichever occurs later.

(2) For all other airplanes: Modify concurrent with accomplishing the requirements of paragraph (b) of this AD.

(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, International Branch, ANM-116. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, International Branch, ANM-116.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

(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 the following Fokker service bulletins, which contain the following list of effective pages:

Referenced Service
Bulletin and Date
Revision Level
Page Number
Date
Shown on Page

Shown on Page
SBF100-55-018,
Revision 1,
December 27, 1993
1-4, 8-16, 18, 19,
21-23, 25-28

5-7, 17, 20, 24,
29-31
1

Original
December 27, 1993

May 19, 1993
SBF100-55-019,
Revision 1,
May 19, 1993
1-3, 5, 9,

4, 6-8, 10-12
1

Original
May 19, 1993

August 11, 1992
SBF100-55-023,
January 3, 1995
1-17
Original
January 3, 1995

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 Services B.V., Technical Support Department, P.O. Box 75047, 1117 ZN Schiphol Airport, The Netherlands. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office ofthe Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 2: The subject of this AD is addressed in Dutch airworthiness directive (BLA) 93-069 (A), dated June 1, 1993.

(h) This amendment becomes effective on January 2, 1998.

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 January 14, 1997 (62 FR 1866). That action proposed to require repetitive eddy current inspections to detect fatigue cracking of the left-hand and right-hand flanges and finger strips at rib 5.0 of the vertical stabilizer, and repair, if necessary. That action also proposed to require modification of rib 5.0 by the installation of a stiffener to the torsion box; this modification would be preceded by an eddy current inspection to detect fatigue cracking, and repair, if necessary. Accomplishment of this modification constitutes terminating action for the repetitive inspection requirements. In addition, that action proposed to require another modification of rib 5.0 by cold-expanding certain bolt holes on the torsion box.

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

One commenter supports the proposed rule.

Requests to Extend the Compliance Time
Two commenters request that the compliance time for accomplishing the proposed eddy current inspection and modification of rib 5.0 of the vertical stabilizer [required by paragraphs (b)(1) and (b)(2) of the proposed AD, respectively] be extended from "prior to the accumulation of 13,500 total landings, or within 6 months . . ." to "prior to the accumulation of 16,000 total landings or within 12 months." One of these commenters states that it is currently performing the subject inspection and modification during its F100 "Q" check visit, which is currently scheduled at 16,000 flight hours or 16,000 landings, whichever occurs first. The commenter also states that ten of its airplanes, which have accumulated between 10,972and 14,976 flight cycles, have been inspected and modified. This commenter points out that no cracks have been detected on these airplanes. This commenter contends that accomplishment of the repetitive inspections required by paragraph (a) of the proposed AD at 2,000 flight cycle intervals will assure that the required level of safety is maintained.

The FAA does not concur with the commenters request to extend the compliance time. The FAA points out that the proposed compliance time of paragraphs (b)(1) and (b)(2) of the AD was developed in consideration of not only the degree of urgency associated with addressing the unsafe condition, but such factors as the manufacturer s and the foreign airworthiness authority s [i.e., Rijksluchtvaartdienst (RLD)] recommendations, the availability of required parts, and the practical aspect of installing the required modification within an interval of time that parallels normal scheduled maintenance for the majority of affected operators. The FAA also has consulted with the manufacturer and RLD and determined that 13,500 flight cycles represents the maximum number of flight cycles allowable for the affected airplanes to continue to operate prior to accomplishing the required inspections and modification without compromising safety. The proposed compliance times are based on results of fatigue tests and analysis of the effects of the thrust reverser loads on adjacent structure.

In addition, the FAA finds that the commenters have not submitted any data to substantiate why a 2,500 flight-cycle extension of the compliance time would not compromise safety, nor have the commenters addressed whether further inspections would be necessary to ensure the long term operational safety. However, under the provisions of paragraph (e) of the final rule, the FAA may approve requests for adjustments to the compliance time if sufficient data are submitted to substantiate that such an adjustment would provide an acceptable level of safety.

Conclusion
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 as proposed.

Cost Impact
The FAA estimates that 122 Fokker Model F28 Mark 0100 series airplanes of U.S. registry will be affected by this proposed AD.

Approximately 77 airplanes will be required to conduct repetitive inspections of the left-hand and right-hand flanges and finger strips at rib 5.0 of the vertical stabilizer. It will take approximately 10 work hours per airplane to accomplish each required inspection. The average labor rate is $60 per work hour. Based on these figures, the cost impact of these inspections required by this AD on U.S. operators of these airplanes is estimated to be $46,200, or $600 per airplane, per inspection.

Approximately 77 airplanes also will be required to accomplish the installation of steel reinforcement in the torsion box at rib 5.0 ofthe vertical stabilizer. It will take approximately 170 work hours per airplane to accomplish this modification (including a pre-modification inspection). The average labor rate is $60 per work hour. Required parts will cost approximately $27,000. Based on these figures, the cost impact of this modification required by this AD on U.S. operators of these airplanes is estimated to be $2,864,400, or $37,200 per airplane.

Approximately 122 airplanes will be required to accomplish the cold expansion of holes in the torsion box at rib 5.0 of the vertical stabilizer. It will take approximately 17 work hours per airplane to accomplish this modification, or approximately 8 work hours per airplane if this modification is done at the same time as the installation of steel reinforcement. The average labor rate is $60 per work hour. Required parts will cost approximately $206. Based on these figures, the cost impact of this modification required by this AD on U.S. operators of these airplanes is estimated to be between $83,692 and $149,572, or between $686 and $1,226 per airplane.

The cost impact figures discussed above are 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 RegulatoryPolicies 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 thefollowing new airworthiness directive: