AD 98-02-03

This amendment adopts a new airworthiness directive (AD), applicable to certain Fokker Model F28 Mark 0100 and Mark 0070 series airplanes, that requires modification of the hook and latch engagement assemblies of the engine cowl doors, measurement of the aerodynamic mismatch between the fixed cowl and lower cowl door, and repair, if necessary. This amendment is prompted by reports of operational experience that indicate that an aerodynamic mismatch may exist between the fixed engine cowl and the lower cowl door, and may be the result of one or more hooks of the engagement assemblies not engaging adequately. This condition may cause the other hooks to carry loads higher than they were originally designed to carry, and could result in the failure of those hooks that are engaged. The actions specified by this AD are intended to prevent possible separation of the lower cowling from the airplane due to failure of the hooks of the engagement assemblies.

Final rule

98-02-03 FOKKER: Amendment 39-10285. Docket 95-NM-94-AD.
Applicability: Model F28 Mark 0100 and Mark 0070 series airplanes as listed in Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71-019/1, dated February 28, 1997; certificated in any category.

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 notbeen eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent separation of the lower cowling from the airplane due to failure of the hook and latch engagement assembly of the cowl door, accomplish the following:

(a) Accomplish the requirements of paragraph (b) of this AD at the latest of the times indicated in paragraphs (a)(1), (a)(2), and (a)(3) of this AD:

(1) Prior to the accumulation of 2,500 total flight cycles; or

(2) Within 2,500 flight cycles since the last inspection performed in accordance with Fokker Service Bulletin SBF100-71-003, dated April 14, 1989; Revision 1, dated August 8, 1989, or Revision 2, dated November 21, 1994; or

(3) Within 30 days after the effective date of this AD.

(b) At the time specified in paragraph (a) of this AD, accomplish the actions specified in either paragraph (b)(1) or (b)(2) of this AD, as applicable:(1) For airplanes specified in Part 1 of Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71- 019/1, dated February 28, 1997: Modify the hook and latch engagement assemblies of the left and right engine cowl doors, and inspect to determine the aerodynamic mismatch between the fixed cowl and lower cowl door; in accordance with Part 1 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71-019/1, dated February 28, 1997.

NOTE 2: Accomplishment of the modification of the hook and latch engagement assemblies of the left and right engine cowl doors, in accordance with Part 1 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-003, dated April 14, 1989; Revision 1, dated August 8, 1989; or Revision 2, dated November 21, 1994; is considered acceptable for compliance with the applicable modification specified in paragraph (b)(1) of this amendment.

(2) For airplanes specified in Part 2 of Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71- 019/1, dated February 28, 1997, excluding those airplanes subject to paragraph (b)(1) of this AD: Perform a one-time inspection to determine the aerodynamic mismatch between the fixed cowl and the lower cowl door, in accordance with Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71-019/1, dated February 28, 1997.

(c) If the aerodynamic mismatch measured between the fixed cowl and lower cowl door is less than or equal to 4.5 mm, no further action is required by this AD.

(d) If the aerodynamic mismatch measured between the fixed cowl and lower cowl door is greater than 4.5 mm, prior to further flight, perform a one-time inspection to measure the mis-engagement between the left and right engine hooks of the fixed cowl door and the clevis fittings of the lower cowl door; in accordance with Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71-019/1, dated February 28, 1997.

(1) If the mis-engagement is less than or equal to 6.5 mm, no further action is required by this AD.

(2) If the mis-engagement is greater than 6.5 mm: Within 1 year after measuring the mis-engagement required by this paragraph, modify the mid-clevis fitting on the right and left engine lower cowl door; in accordance with Part 3 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71-019/1, dated February 28, 1997. After accomplishment of this modification, no further action is requiredby 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, 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, International Branch, ANM-116.

NOTE 3: 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 Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, as revised by Fokker Service Bulletin Change Notification SBF100-71- 019/1, dated February 28, 1997. 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 of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 4: The subject of this AD is addressed in Dutch airworthiness directive 1989-049/3 (A), dated June 28, 1996.

(h) This amendment becomes effective on February 20, 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 and Mark 0070 series airplanes was published in the Federal Register on November 5, 1996 (61 FR 56925). That action proposed to require modification of the hook and latch engagement assemblies of the engine cowl doors, measurement of the aerodynamic mismatch between the fixed cowl and lower cowl door, and repair, if necessary.

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.

Request to Extend the Compliance Time
Two commenters request that the compliance time for accomplishing the proposed inspection specified in paragraph (a)(2) of the AD be changed from "Within 2,500 flight cycles since the last inspection ..." to " Within 2,500 flight cycles or3,500 flight hours since the last inspection ... , whichever occurs later." One of these commenters states that it is currently accomplishing the proposed inspection on its fleet of Fokker Model F28 Mark 0100 series airplanes during its regularly scheduled maintenance checks at 3,500 flight hour intervals. The commenter notes that the proposed 2,500 flight cycle inspection time may fall short of its currently scheduled 3,500 flight hour maintenance check.

The FAA does not concur with the commenters' request to change the compliance time. The FAA points out that the proposed compliance time of paragraph (a)(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, and the practical aspect of inspecting the affected airplanes within an interval of time that parallels normal scheduled maintenance for the majority of affected operators.

Based on the average utilization rate of the worldwide fleet of Fokker Model F28 Mark 0100 series airplanes (approximately 1 flight hour per flight cycle), the request to include a 3,500 flight hour compliance time option, if granted, would be approximately equal to 3,500 flight cycles. This option would result in a 1,000 flight cycle extension to the compliance time. The commenters have not provided any data to substantiate why extending the compliance time by approximately 1,000 flight cycles would not compromise 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.

Service Bulletin Change Notification
One commenter states that certain errors were found in the service information referenced in the proposed AD.Paragraph C.(2) of Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-019, dated March 21, 1996, should refer to Figure 5 (not Figure 4) for dimensions X and Y. Additionally, Figure 5 of the service bulletin should refer to Figure 6 (not Figure 5) for tool geometry.

The FAA agrees with the commenter. Since issuance of the proposal, Fokker has issued Service Bulletin Change Notification (SBCN) SBF100-71-019/1, dated February 28, 1997, which revises paragraph C.(2) of Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-019 to correctly reference Figure 5 for dimensions X and Y. The final rule has been revised to reference SBCN SBF100-71-019/1, dated February 28, 1997, in addition to the previously referenced service information.

In addition, the FAA has determined that the reference in Figure 5 to Figure 5 (rather than Figure 6) for tool geometry is merely a typographical error, since paragraph C.(2) of Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-71-019 states "As a reference, to obtain the correct measurements, use tool as shown in Figures 5 and 6." However, the FAA has forwarded information regarding this error to Fokker Services.

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 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.

Cost Impact
The FAA estimates that 124 Fokker Model F28 Mark 0100 and 0070 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 3 work hours per airplane to accomplish the initial inspection and modification, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $22,320, or $180 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.

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 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 the following new airworthiness directive: