AD 98-08-01

This amendment adopts a new airworthiness directive (AD), applicable to certain Fokker Model F28 Mark 0070 and Mark 0100 series airplanes, that requires a one-time visual inspection to detect heat damage of the fuselage skin and stubwing structure. This proposal also would require either repetitive leak tests of the seals of the bleed air system, or repair of any heat-damaged structure, as necessary; and replacement of corrujoint seals with new improved seals. This amendment is prompted by the issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent the leakage of hot air from the corrujoint seals of the low- and high-pressure check valves located in the stubwings, which could result in heat damage to the fuselage skin and stubwing structure, and consequent reduced structural integrity of the airplane.

Final rule.

98-08-01 FOKKER: Amendment 39-10450. Docket 97-NM-249-AD.

Applicability: Model F28 Mark 0070 and Mark 0100 airplanes; as listed in Fokker Service Bulletin SBF100-53-084, dated July 6, 1996; if equipped with any corrujoint seal having part number (P/N) BE20061 (Rolls-Royce P/N 3405891); 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 (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, therequest should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent the leakage of hot air from the corrujoint seals of low- and high-pressure check valves located in the stubwings, which could result in heat damage to the fuselage skin and stubwing structure and consequent reduced structural integrity, accomplish the following:

NOTE 2: Inspections for heat damage, leak tests, seal replacements, and repairs accomplished prior to the effective date of this AD in accordance with Fokker Service Bulletin SBF100-53-081, dated July 7, 1995, are considered acceptable for compliance with the requirements of this AD, provided that no seal has been subsequently replaced with a seal having part number BE20061 (Rolls-Royce part number 3405891).

(a) Within 3,000 flight hours or 12 months after the effective date of this AD, whichever occurs first, perform a one-time visual inspection of the fuselage skin inthe left- and right-hand stubwings to detect heat damage; in accordance with Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-53-084, dated July 6, 1996.

(b) If no heat damage is found during the inspection required by paragraph (a) of this AD, prior to further flight, accomplish either paragraph (b)(1) or (b)(2) of this AD.

(1) Replace all corrujoint seals having P/N BE20061 (Rolls-Royce P/N 3405891) at the 7th stage low-pressure and 12th stage high-pressure check valves of the left- and right-hand bleed air systems with new improved corrujoint seals having P/N EU15969, in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF100-36-026, Revision 1, dated July 6, 1996.

(2) Perform a leak test of each corrujoint seal at the 7th stage low-pressure and 12th stage high-pressure check valves of the left- and right-hand bleed air systems, in accordance with Part 3 of the Accomplishment Instructions of Fokker Service BulletinSBF100-53-084, dated July 6, 1996.

(i) If any leakage is found at a seal, prior to further flight, replace that seal with a new improved seal having part number EU15969, in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF100-36-026, Revision 1, dated July 6, 1996.

(ii) If no leakage is found at a seal, perform an additional leak test of that seal within 250 flight hours after the initial test.

(A) If no leakage is found during the additional test of the seal, within 3,000 flight hours after the additional test, replace the seal with an improved seal having P/N EU15969, in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF100-36-026, Revision 1, dated July 6, 1996.

(B) If any leakage is found during the additional test of the seal, prior to further flight, replace the seal with a new improved seal having P/N EU15969, in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF100-36-026, Revision 1, dated July 6, 1996; and inspect the fuselage skin in the applicable left- or right-hand stubwing to detect heat damage, in accordance with Part 2 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-53-084, dated July 6, 1996.

(c) If any heat damage is found during the inspection required by paragraph (a) or paragraph (b)(2)(ii)(B) of this AD, prior to further flight, perform a detailed inspection of the fuselage skin and stubwing structure to detect the extent of heat damage, in accordance with Parts 4 and 5 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-53-084, dated July 6, 1996; and accomplish paragraphs (c)(1) and (c)(2) of this AD.

(1) Repair the affected structure, in accordance with Part 6 of the Accomplishment Instructions of Fokker Service Bulletin SBF100-53-084, dated July 6, 1996. And

(2) Replace all corrujoint seals having P/N BE20061 (Rolls-Royce P/N 3405891) at the 7th stage low-pressure and 12th stagehigh-pressure check valves of the left- and right-hand bleed air systems with new improved corrujoint seals having P/N EU15969, in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF100-36-026, Revision 1, dated July 6, 1996.

(d) As of the effective date of this AD, no person shall install a corrujoint seal having P/N BE20061 (Rolls-Royce P/N 3405891) on any airplane.

(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 SBF100-53-084, dated July 6, 1996, and Fokker Service Bulletin SBF100-36-026, Revision 1, dated July 6, 1996. 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 BLA 1995-076/2 (A), dated August 30, 1996.

(h) This amendment becomes effective on May 14, 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 0070 and Mark 0100 series airplanes was published in the Federal Register on November 28, 1997 (62 FR 63292). That action proposed to require a one-time visual inspection to detect heat damage of the fuselage skin and stubwing structure. That action also proposed to require either repetitive leak tests of the seals of the bleed air system, or repair of any heat-damaged structure, as necessary; and replacement of corrujoint seals with new improved seals.

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, the Air Transport Association (ATA) of America, on behalf of one of its members, requests that the AD include a statement excluding aircraft previously inspected and modified in accordance with the referenced Fokker service information. The ATA member indicates that it has already completed the inspection and modifications described in the service bulletins cited in the proposed AD. The FAA concurs that previously accomplished inspections and modifications need not be repeated; however, the commenters concern in that regard was already addressed in the proposed AD by the statement, "Compliance: Required as indicated, unless accomplished previously." That language reappears in this final rule. Therefore, no change to the final rule is necessary.

Similarly, the ATA requests that a provision be added to exclude airplanes on which the intent of the proposed AD has already been accomplished, including repairs that were generated to repair damaged structure, in accordance with Fokker Service Bulletin SBF100-53-081, which is not referenced in the proposed rule.

The FAA concurs that replacements and repairs accomplished prior to the effective date of this AD in accordance with the service bulletin referenced by the commenter are acceptable provided that no seal has been subsequently replaced with a seal having part number BE20061 (Rolls-Royce part number 3405891). This final rule, therefore, includes a note stating that inspections for heat damage, leak tests, seal replacements, and repairs accomplished prior to the effective date of this AD, in accordance with Fokker Service Bulletin SBF100-53-081, dated July 7, 1995, are considered acceptable for compliance with the requirements of this AD, provided that no seal has been subsequently replaced with a seal having part number BE20061 (Rolls-Royce part number 3405891).

The ATA, on behalf of another commenter, requests that a provision be added to allow the leak tests to be omitted if the inspection reveals no heat damage and if, prior to further flight, the corrujoint seals at the seventh state low pressure check valve and twelfth stage high pressure check valves are replaced with the improved corrujoint seals. The commenter states that accomplishment of these actions is similar to the optional method of complying with Fokker Service Bulletin SBF100-53-084.

The FAA concurs with the commenter s request. The FAA agrees that, if the inspection required by paragraph (a) of this AD reveals no heat damage, and if, prior to further flight, all affected corrujoint seals are replaced with the improved corrujoint seals, then accomplishment of the leak tests is not necessary. The FAA has revised and reformatted paragraph (b) of this final rule to include this provision.

The ATA also requests that the compliance time be extended from 12 to 18 months. The commenter states that 18 months is the accepted industry standard and further notes that, because of the areas to which access is needed, the work must be accomplished while an airplane is out of service for maintenance.

The FAA does not concur. In developing an appropriate compliance time for this action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but a number of other factors as well. Those included the recommendations of the manufacturer and foreign airworthiness authority, the availability of required parts, and the practical aspect of accomplishing the required actions within an interval of time coinciding with normal scheduled maintenance for the majority of the affected operators. Considering all of those factors, the FAA determined that the proposed compliance time represents the maximum interval in which the affected airplanes could continue to operate without compromising safety. In that regard, the commenter did not provide any data to substantiate that an extension of the compliance time would not compromise safety. In view of those factors, and the amount of time that has already elapsed since issued of the original notice of proposed rulemaking, the FAA has determined that further delay of these actions is, in general, not appropriate. The FAA may, however, approve a request for an adjustment of the compliance time under the provisions of this final rule if data are submitted to substantiate that such an adjustment would provide an equivalent 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 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.

Cost Impact
The FAA estimates that 131 Fokker Model F28 Mark 0070 and Mark 0100 series airplanes of U.S. registry will be affected by this AD.

The inspection will take approximately 3 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $23,580, or $180 per airplane.

The replacement of the corrujoint seals will take approximately 7 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $80 per airplane. Based on these figures, the cost impact of the replacement required by this AD on U.S. operators is estimated to be $65,500, or $500 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 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 theAdministrator, 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: