AD 98-06-26

This amendment adopts a new airworthiness directive (AD), applicable to certain Fokker Model F28 Mark 0100 series airplanes, that requires repetitive inspections to detect corrosion in the wheel axles of the main landing gear (MLG) sliding members; and rework of any corroded areas, an inspection to detect cracks in the wheel axles, and replacement of any cracked sliding member. This AD provides for interim actions that may be accomplished in lieu of the repetitive inspections. This AD also requires eventual modifications of the main wheel brake units and the MLG sliding members; when accomplished, these modifications terminate the repetitive inspections and interim actions. This amendment is prompted by a report of failure of an MLG wheel axle during push back of an in-service airplane from the terminal. The actions specified by this AD are intended to prevent failure of the MLG wheel axle due to problems associated with corrosion and cracking.

Final rule

98-06-26 FOKKER: Amendment 39-10404. Docket 93-NM-193-AD.

Applicability: Model F28 Mark 0100 series airplanes equipped with Dowty Aerospace main landing gear (MLG) part number 201072011, 201072012, 201072013, 201072014, 201072015, or 201072016; 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 (g) 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 failure of the MLG wheel axle due to problems associated with corrosion and cracking, accomplish the following:

(a) Within 30 days after the effective date of this AD, remove the MLG wheels and brakes and perform a visual inspection to detect corrosion and cracking in the wheel axles of the MLG sliding members in accordance with Fokker Service Bulletin F100-32-079, Revision 1, dated October 4, 1993, and paragraph 2.A. of the Accomplishment Instructions of Dowty Aerospace Service Bulletin F100-32-63, Revision 2, dated September 23, 1993.

(b) Following accomplishment of the inspection required by paragraph (a) of this AD, accomplish either paragraph (b)(1) or (b)(2) of this AD.

(1) Repeat the inspection required by paragraph (a) of this AD thereafter at intervals not to exceed 3 months in accordance with Fokker Service Bulletin SBF100-32-080, dated October 4,1993, and Dowty Aerospace Service Bulletin F100-32-64, Revision 1, dated February 18, 1994, until the actions required by paragraph (e) of this AD are accomplished. Or

(2) Accomplish paragraphs (b)(2)(i), (b)(2)(ii), and (b)(2)(iii) of this AD at the times specified in those paragraphs in accordance with Fokker Service Bulletin SBF100-32-083, dated March 23, 1994.

(i) Within 3 months after the accomplishment of an inspection required by paragraph (a) or (b)(1) of this AD: Rework the axles in accordance with Part 2 of the Accomplishment Instructions of the service bulletin. Repeat this rework thereafter at intervals not to exceed 12 months or 2,200 landings, whichever occurs first. And

(ii) Prior to or concurrent with accomplishing the initial rework specified in paragraph (b)(2)(i) of this AD: Replace the main wheel brake units in accordance with Part 1 of the Accomplishment Instructions of the service bulletin. And

(iii) Within 3 months after the firstaccomplishment of the rework required by paragraph (b)(2)(i) of this AD: Begin performing interim inspections ("sampling program") to detect corrosion and cracking in the wheel axles of the MLG sliding members, in accordance with Part 3 of the Accomplishment Instructions of the service bulletin. Perform these inspections at the intervals specified in the service bulletin until the actions required by paragraph (e) of this AD are accomplished.

(c) If any corrosion is found during any inspection required by this AD, prior to further flight, rework the affected area and perform a non-destructive testing (NDT) inspection to detect cracks in the MLG wheel axles, in accordance with Appendix A of Dowty Aerospace Service Bulletin F100-32-63, Revision 2, dated September 23, 1993 (if corrosion is found during the initial inspection required by this AD); or Dowty Aerospace Service Bulletin F100-32-64, Revision 1, dated February 18, 1994 (if corrosion is found during a repetitive inspection required by this AD); as applicable. After rework, perform repetitive inspections of the affected area in accordance with paragraph (b)(1) of this AD until the actions required by paragraph (e) of this AD are accomplished.

(d) If any crack is found during any inspection required by this AD, prior to further flight, replace the affected sliding member with a serviceable sliding member in accordance with Dowty Aerospace Service Bulletin F100-32-63, Revision 2, dated September 23, 1993 (if any crack is found during the initial inspection required by this AD); or Dowty Aerospace Service Bulletin F100-32-64, Revision 1, dated February 18, 1994 (if any crack is found during a repetitive inspection required by this AD); as applicable. After replacement of the affected sliding member, perform the repetitive inspections in accordance with paragraph (b)(1) of this AD until the actions required by paragraph (e) of this AD are accomplished.

(e) At the next major gear overhaul, or within 5 years after the effective date of this AD, whichever occurs first: Rework the sliding member, and replace the main wheel brake units in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF100-32-081, dated March 23, 1994. Accomplishment of these actions constitutes terminating action for the repetitive inspections and the interim actions specified in paragraph (b) of this AD.

NOTE 2: Fokker Service Bulletin SBF100-32-081 refers to Dowty Aerospace Service Bulletin F100-32-64, Revision 1, dated February 18, 1994, as an additional source of service information for accomplishment of the rework and replacement.

(f) As of the effective date of this AD, no person shall install a Dowty Aerospace MLG, part number 201072011, 201072012, 201072013, 201072014, 201072015, or 201072016, on any airplane unless the requirements of this AD have been accomplished on that MLG. Following its installation, the repetitive inspections required by paragraph (b) ofthis AD shall be accomplished on that MLG.

(g) 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.

(h) 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.

(i) The actions shall be done in accordance with the following Fokker service bulletins or Dowty Aerospace service bulletins, as applicable, which contain the specified effective pages:

Service Bulletin
Referenced and Date

Page Number
Revision Level Shown on Page
Date
Shown on Page
Fokker SBF100-32-079,
Revision 1,
October 4, 1993
1-3

4
1

Original
October 4, 1993

August 2, 1993
Fokker SBF100-32-080,
October 4, 1993
1-4
Original
October 4, 1993
Fokker SBF100-32-081,
March 23, 1994
1-6
Original
March 23, 1994
Fokker SBF100-32-083,
March 23, 1994
1-6
Original
March 23, 1994

1-3

4
2

Original
September 23, 1993

July 29, 1993

Appendix A

1-2
Original
July 29, 1993

Appendix B

Dowty Aerospace
F100-32-63,
Revision 2,
September 23, 1993
1
2
September 23, 1993

1-6
1
February 18, 1994

Appendix A

1-2
Original
September 23, 1993

Appendix B

1
Original
September 23, 1993

Appendix C

Dowty Aerospace
F100-32-64,
Revision 1,
February18, 1994
1
1
February 18, 1994

The incorporation by reference of these documents 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 No. 93-108/2 (A), dated November 1, 1993.

(j) This amendment becomes effective on April 24, 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 as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on September 9, 1996 (61 FR 47462). That supplemental NPRM proposed to require repetitive inspections to detect corrosion in the wheel axles of the main landing gear (MLG) sliding members; and rework of any corroded areas, an inspection to detect cracks in the wheel axles, and replacement of any cracked sliding member. That supplemental NPRM proposed to provide for interim actions that may be accomplished in lieu of the repetitive inspections. That supplemental NPRM also proposed to require eventual modifications of the main wheel brake units and the MLG sliding members; when accomplished, these modifications terminate the repetitive inspections and interim actions.Consideration of Comments Received
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 Allow Terminating Action to be Optional Rather Than Mandated
The Air Transport Association (ATA) of America, representing a member airline, requests that the terminating action of this AD be allowed as an option to the repetitive inspections rather than be mandated. This commenter states that the Dutch airworthiness directive does not mandate the modification as terminating action.

The FAA does not concur with this request and, as cited in the supplemental NPRM, the FAA has determined that long-term continued operational safety will be better assured by design changes to remove the source of the problem, rather than by repetitive inspections. However, under the provisions of paragraph (g) of the final rule, the FAA may consider requests for approval of an alternative method of compliance if sufficient data are submitted to substantiate that such an alternative method would provide an acceptable level of safety.
Request to Use Long-Term Inspections to Ensure Level of Safety

The ATA, on behalf of one member, states that the member does not agree with the FAA's statement (in the preamble of the NPRM) that "Long-term inspections may not be providing the degree of safety assurance necessary for the transport airplane fleet." This commenter also states that the concept that inspections do not provide the degree of safety required runs contrary to established industry principles and FAA advisory material. In addition, the commenter states that the Certification Maintenance Requirements (CMR's) are an example whereby repetitive tasks are defined as operating limitations in order to detect latent failures that could lead to hazardous or catastrophic failure conditions. Further, the commenter states that damage tolerance concepts for structuralelements similarly rely on a well-defined inspection program to maintain safety by ensuring that fatigue cracking is detected before the critical crack length is reached.

The FAA does not concur that the statement regarding long-term inspections is inappropriate for inclusion in the final rule, although the FAA agrees that clarification of this statement may be necessary. The FAA requires CMR items and damage tolerance inspections to ensure compliance with the airworthiness standards for type certification. The FAA also maintains that the requirement for such inspections is a result of a design methodology, and these inspections are necessary for maintaining the type design in an airworthy condition. However, the FAA points out that the inspections required by this final rule result from in-service cracking in a known area, which could lead to an unsafe condition. For this reason, the FAA has determined that the statement that "long term inspections may not be providing the degree of safety assurance" is appropriately used in this case because an unsafe condition exists.

Request to Allow Operators to Revise Maintenance Inspection Programs
The ATA, representing two member airlines, requests adding a new provision to the final rule that would allow an alternative to the accomplishment of the inspection procedures required by this AD. This alternative action would specify that if operators revise their maintenance inspection programs to include the actions specified by this AD, then the AD would no longer be applicable and these operators could use an alternative recordkeeping method to that required by the AD. The ATA further recommends that the FAA not be involved in the continued oversight of the proposed inspection since it will likely continue for the life of the airplane. One operator states that the inspection procedure could be controlled more efficiently and allow more adaptability if it were included in each operator's FAA-approved maintenance program, which could be coordinated with each operator's FAA principal maintenance inspector (PMI). This operator also states that if a regulatory mandate is required by the FAA, a better option would be to incorporate the most recent inspection procedures as an Airworthiness Limitation through the F100 Maintenance Review Board (MRB) process rather than issuance of a new AD.

A second commenter maintains that its inspection program has provided the required level of safety and that no failures of MLG axles have occurred since the introduction of the inspection program in 1994. Another commenter states that industry principles and FAA advisory material accept inspection programs as a satisfactory means of monitoring structural integrity and that the adequacy of such programs has been demonstrated by in-service experience.

The FAA does not concur with the commenters' requests to revise their maintenance inspection programs to include the actions specified by this AD. TheATA's suggested alternative to accomplishment of the actions required by this AD would permit each operator to determine whether and how often these actions should be accomplished. In light of the identified unsafe condition, however, the FAA has determined that allowing this degree of operator discretion is not appropriate. Therefore, this AD is necessary to ensure that operators accomplish the required actions in a common manner and at common intervals.

Requests to Extend Compliance Periods for Modification of the MLG
The ATA, representing a member airline, states that the compliance time for accomplishment of the modification required by paragraph (e) of the proposal is too stringent and that a typical period for landing gear overhaul is in the range of 3 to 5 years. One commenter states that the timing of the mandated modification does not fit into any normal aircraft check period and, as such, will force carriers to take airplanes out of service and obtain otherwise unneeded landing gear assemblies. This commenter maintains that the delivery schedule for the number of airplanes that would be required to support the industry would make it impossible to comply with the proposed AD. The commenter states that any mandate to modify the MLG at any time that is not flexible enough to be accomplished during each carrier's established landing gear overhaul period also should be opposed.

These commenters request changing the proposed compliance time specified in paragraph (e) of the proposal from "At the next major gear overhaul, or within 4,400 landings after accomplishment of the initial inspection required by paragraph (a) of this AD, whichever occurs first..." to "At the next major gear overhaul, or within 4 years after the effective date of the proposed rule, whichever occurs later...." The FAA infers from these remarks that the commenters request an extension for accomplishment of the modification.

The FAA concurs partially with these requests. The FAA concurs with the requests to extend the compliance time for completion of the modification and considers that the repetitive inspections required by paragraphs (a) and (b) of this AD will provide an adequate level of safety until such modification is completed. The FAA has determined that extending the compliance time will provide operators additional time to complete the modification and, at the same time, allow sufficient time to adequately address the unsafe condition. However, the FAA does not concur with the request to change "whichever occurs first" to "whichever occurs later" because it has determined that "later" (which refers to the next scheduled maintenance) does not provide a definitive compliance time.

The FAA concurs with the request to change the compliance time specified in paragraph (e) of this final rule from "within 4,400 landings." However, the FAA does not concur with the request to change the number of landings to 4 years and, instead, has determined that 5 years is more appropriate because it corresponds more closely to most operators' "heavy" maintenance schedules. Paragraph (e) of the final rule is changed to read "At the next major gear overhaul, or within 5 years after the effective date of this AD, whichever occurs first...." Request to Revise the Cost Estimate to Include the Terminating Actions

Two commenters request a revision of the cost impact information, below, to more accurately reflect the cost associated with accomplishment of the terminating modification. These commenters state that accomplishment of the terminating action requires removal of the MLG from the airplane and rework in the shop, and that because this action will be outside the usual maintenance for the MLG, operators may incur additional cost due to the need for a loaner gear to support the shop repair cycle.

The FAA does not concur with these requests to revise the cost estimate. The FAA points out that the compliance time for accomplishment of the terminating action has been extended in this final rule. This extension will likely allow operators to accomplish the terminating action during a major gear overhaul. Therefore, there is no additional cost associated with the removal of the MLG outside regularly scheduled maintenance. 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 125 Fokker Model F28 Mark 0100 series airplanes of U.S. registry will be affected by this AD.

It will take approximately 14 work hours per airplane to accomplish the required visual inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impactof the visual inspection of this AD on U.S. operators is estimated to be $105,000, or $840 per airplane.

It will take approximately 66 work hours per airplane to accomplish the required terminating modifications, at an average labor rate of $60 per work hour. Required parts will cost approximately $865 per airplane. Based on these figures, the cost impact of the required terminating modification of this AD on U.S. operators is estimated to be $603,125, or $4,825 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.

Should an operator elect to accomplish the repetitive visual inspections that would be provided by this AD action, it would take approximately 14 work hours to accomplish each repetitive inspection, at an average labor rate of $60 per work hour. The FAA estimates that these inspections would be accomplished four times per year. Based on these figures, the cost impact of the repetitive inspections on U.S. operators is estimated to be $3,360 per airplane, per year.

Should an operator elect to accomplish the interim actions that would be provided by this AD action, it would take approximately 26 work hours for the rework, and 26 work hours per airplane for the brake unit replacement. It would take between 28 to 168 work hours per year for the sampling program, depending on the size of an operator's fleet. The average labor rate is $60 per work hour. The cost for required parts would be approximately $865 per airplane. Additionally, once these interim actions are accomplished, the cost impact of the terminating modifications discussed previously would be reduced by $2,400 per airplane.

Regulatory Impact
The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the nationalgovernment 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: