[Federal Register Volume 63, Number 54 (Friday, March 20, 1998)]
[Rules and Regulations]
[Pages 13502-13505]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-6948]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-193-AD; Amendment 39-10404; AD 98-06-26]
RIN 2120-AA64


Airworthiness Directives; Fokker Model F28 Mark 0100 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: 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.

DATES: Effective April 24, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 24, 1998.

ADDRESSES: The service information referenced in this AD may be 
obtained from Fokker Services B.V., Technical Support Department, P.O. 
Box 75047, 1117 ZN Schiphol Airport, the Netherlands. This information 
may be examined at the Federal Aviation Administration (FAA), Transport 
Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, 
Washington; or at the Office of the Federal Register, 800 North Capitol 
Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Norman B. Martenson, Manager, 
International Branch, ANM-116, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2110; fax (425) 227-1149.

SUPPLEMENTARY INFORMATION: 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 structural elements similarly rely on a well-defined 
inspection program to maintain safety by ensuring that fatigue

[[Page 13503]]

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. The ATA'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

[[Page 13504]]

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 impact of 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 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.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

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 first accomplishment 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

[[Page 13505]]

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) of this 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:

----------------------------------------------------------------------------------------------------------------
                                                   Revision level shown on                                      
 Service bulletin referenced and date   Page No.             page                    Date shown on page         
----------------------------------------------------------------------------------------------------------------
Fokker SBF100-32-079, Revision 1,             1-3   1.....................  October 4, 1993.                    
 October 4, 1993.                               4  Original...............  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.                     
Dowty Aerospace F100-32-63, Revision          1-3  2......................  September 23, 1993.                 
 2, September 23, 1993.                         4  Original...............  July 29, 1993.                      
Appendix A...........................         1-2  Original...............  July 29, 1993                       
Appendix B...........................           1  2......................  September 23, 1993.                 
Dowty Aerospace F100-32-64, Revision          1-6  1......................  February 18, 1994.                  
 1, February 18, 1994.                                                                                          
Appendix A...........................         1-2  Original...............  September 23, 1993.                 
Appendix B...........................           1  Original...............  September 23, 1993.                 
Appendix C...........................           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.

    Issued in Renton, Washington, on March 11, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-6948 Filed 3-19-98; 8:45 am]
BILLING CODE 4910-13-U