[Federal Register Volume 62, Number 29 (Wednesday, February 12, 1997)]
[Rules and Regulations]
[Pages 6459-6461]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-2608]



[[Page 6459]]

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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-02-AD; Amendment 39-9915; AD 97-03-09]
RIN 2120-AA64


Airworthiness Directives; Fokker Model F28 Mark 0100 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Fokker Model F28 Mark 0100 series airplanes, that 
requires repetitive checks to detect backlash in the elevator 
mechanical control system, and various follow-on actions. This 
amendment also provides for an optional terminating action for the 
repetitive check requirements. This amendment is prompted by a report 
indicating that corrosion was found on the pivot bolts and bushings of 
the backlash remover lever mechanism on the elevator booster control 
unit (BCU) of a Model F28 Mark 0100 series airplane. The actions 
specified by this AD are intended to prevent such corrosion, which 
could result in backlash in the elevator controls and reduced elevator 
control authority in the manual mode.

DATES: Effective March 19, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 19, 1997.

ADDRESSES: The service information referenced in this AD may be 
obtained from Fokker Aircraft USA, Inc., 1199 North Fairfax Street, 
Alexandria, Virginia 22314. 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:
Tim Dulin, Aerospace Engineer, Standardization Branch, ANM-113, FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2141; fax (206) 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 in the Federal Register on March 17, 
1995 (60 FR 14395). That action proposed to require repetitive checks 
to detect backlash in the elevator mechanical control system, and 
various follow-on actions. That action also proposed an optional 
terminating action for the repetitive check requirements.
    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 Defer Release of Final Rule

    One commenter requests that the FAA defer the release of the final 
rule until a bolt replacement program can be developed to 
satisfactorily address the problems with corrosion. This commenter 
asserts that the proposed rule goes beyond what is needed to address 
the stated safety concern. Further, this commenter considers that, 
since both U.S. operators affected by this proposed rule already have 
instituted a maintenance program that includes applying corrosion 
inhibitor to the subject bolts, the FAA's interim safety objectives are 
being met. The commenter also notes that a similar problem of bolt 
corrosion occurred on the same system on a Fokker Model F28 series 
airplane, and the manufacturer simply recommended that a corrosion-
resistant bolt be installed. The commenter maintains that, if the 
proposed rule is adopted without change, then the FAA will be mandating 
a very complex inspection program at operators' ``B''-check intervals, 
with little thought to actually correcting the unsafe condition. If 
there is a simple, cost-effective terminating action that could be 
introduced--other than the replacement of the elevator booster control 
unit (BCU) with an improved unit--then it should be considered prior to 
going forward with this AD.
    The FAA does not concur with the commenter's request to delay the 
issuance of this AD until a ``bolt replacement program'' is developed, 
because such a ``program'' is already included in the AD as an optional 
terminating action. This AD provides for two optional actions, either 
of which could be accomplished in order to terminate the required 
repetitive inspections:
    1. modification of the affected BCU by replacing the currently 
installed bolts with improved bolts that are corrosion-resistant; or
    2. replacement of the currently installed BCU with a unit that 
already has the improved, corrosion-resistant bolts installed.
    The FAA has provided the terminating actions as optional to 
operators, since the accomplishment of either terminating action is far 
more complicated and time-consuming than performing the required 
repetitive operational checks and inspections. For example, because it 
is physically impossible to replace one of the affected bolts while the 
BCU is still installed on the airplane, in order to perform either 
terminating action, the BCU must be removed; this procedure in itself 
is more labor-intensive that performing the required checks and 
inspections. However, the FAA maintains that the accomplishment of 
either action provided for in this AD--repetitive checks/inspections or 
terminating action--will adequately address the unsafe condition 
presented by corrosion.
    The FAA cannot concur with the commenter's suggestion that the 
FAA's ``interim safety objectives are being met'' by operators' current 
practice of applying a corrosion inhibitor to the suspect bolts. The 
commenter provided no data to substantiate that the procedure will 
provide a level of safety equivalent to that provided by the actions 
required by this AD. However, under the provisions of paragraph (e) of 
the final rule, the FAA may approve requests for use of alternative 
methods of compliance if data are submitted to substantiate that such a 
method would provide an acceptable level of safety.

Request To Add ``Intermediate'' Step in Operational Check

    One commenter requests that the proposal be revised to include the 
``intermediate'' step of checking the position of the backlash remover 
lever, which is specified in the referenced Fokker Service Bulletin 
SBF100-27-052. This commenter notes that proposed paragraph (b), as 
written, would require an inspection of the elevator BCU backlash 
remover bolts for freedom of movement and corrosion if any backlash is 
detected during the operational check required by proposed paragraph 
(a). However, the referenced Fokker service bulletin specifies an 
intermediate step to inspect the position of the backlash remover to 
determine whether the bolt inspection is even necessary, or if 
troubleshooting for some other cause of the problem is necessary.
    The FAA concurs with the commenter's request. While this 
``intermediate'' step was not specified in the proposal, the FAA's 
intent was to require operators to accomplish all of the check and 
inspection procedures specified in Fokker Service Bulletin SBF100-27-
052. The final rule has been revised to indicate that operators are to 
perform this intermediate step to determine if the bolt inspection is

[[Page 6460]]

necessary, rather than immediately performing the bolt inspection in 
all cases. Since this addition to the final rule is relieving in nature 
(i.e., operators may not have to accomplish a more complicated 
inspection immediately, as was proposed), it will not increase the 
economic burden on any operator, nor will it increase the scope of the 
AD.

Request To Allow Deferment of BCU Replacement Requirement

    One commenter requests that the proposal be revised to include the 
option to defer the replacement of the elevator BCU prior to further 
flight if the backlash remover bolts are found to be frozen or 
corroded. The commenter states that the backlash remover bolts are 
neither torqued nor subjected to high shear loads; therefore, operators 
should not be required to remove the BCU prior to further flight, 
provided that the bolts can be freed and lubricated, and the backlash 
operational check is subsequently accomplished successfully. If removal 
and modification of the BCU (in accordance with Fokker Service Bulletin 
SBF100-27-061) could be deferred so that operators could schedule it 
during a regular maintenance interval, the amount of downtime and 
additional expenses could be minimized.
    The FAA concurs with the commenter's request. If the bolt having 
part number NAS6204C22D can be freed so that it rotates and slides 
freely, and is lubricated; and if the backlash operational check is 
subsequently accomplished and is successful; then the FAA agrees that 
the replacement of the elevator BCU can be deferred somewhat. The FAA 
considers an appropriate deferral interval to be 10 days. Paragraph (b) 
of the final rule has been revised to specify this deferral provision.
    However, for the bolt having part number NAS6204C13D, the FAA has 
determined that its replacement cannot be deferred if it does not 
rotate and slide freely, or if there are any signs of corrosion; under 
those conditions, that bolt must be replaced prior to further flight. 
The FAA considers this action both appropriate and warranted, since 
that bolt is readily accessible on the airplane.

Request To Add Optional Repetitive Inspections

    One commenter requests that the proposal be revised to include the 
option to conduct periodic inspections of the backlash remover 
mechanism and to apply corrosion preventative lubrication on the 
subject backlash remover bolts at 1,800-flight cycle intervals. The 
commenter requests that operators be permitted to accomplish these 
actions in lieu of the proposed operational checks to detect backlash. 
This commenter does not consider the proposed backlash check from the 
flight deck to be a good solution to the problem of corroded or frozen 
backlash remover lever bolts because:
    1. the check is subjective, since it requires a sense of feel that 
may vary from person to person; and
    2. the check procedures are ill-defined in the referenced Fokker 
Service Bulletin SBF100-27-052.
    In addition, this commenter states that the Fokker service bulletin 
does not provide any instructions that will prevent the existing bolts 
from corroding.
    This commenter, a U.S. operator, indicates that it already has 
implemented a program that includes periodic inspection and lubrication 
of the subject bolts at 1,800-flight cycle intervals; the commenter 
considers its program to be a more proactive approach to addressing the 
unsafe condition.
    The FAA does not concur with the commenter's request. In 
consultation with Fokker and the Netherlands airworthiness authority 
(RLD), the FAA has determined that the operational check is not 
``subjective,'' as suggested by the commenter: there will be a clear 
indication of backlash if the mechanism is stuck, and the referenced 
Fokker service bulletin provides objective standards of approximately 2 
inches of freeplay. In addition, the commenter has not provided any 
technical data to prove that inspection and lubrication of the bolts at 
1,800-flight cycle intervals will provide at least the same level of 
safety as that provided by the operational check at 500-flight cycle 
intervals. While an inspection and lubrication may help to prevent 
sticking of the mechanism, it may not provide the necessary safety 
margins. Paragraph (e) of the final rule, however, does provide for the 
use of alternative methods of compliance with the AD, provided that 
sufficient justification is presented to the FAA.
    Further, the FAA agrees that Fokker Service Bulletin SBF100-27-052 
does not provide instructions to prevent corrosion, other than 
inspection and lubrication of the bolts whenever backlash is detected 
during the operational check. However, this AD provides for two 
optional terminating actions for the checks: either modification of the 
existing BCU by replacing the currently-installed bolts with corrosion-
resistant bolts (as described in Fokker Service Bulletin SBF100-26-
061); or by replacement of the affected elevator BCU with a unit that 
already has corrosion-resistant bolts installed. Such replacement of 
the bolts positively addresses the problem of galvanic corrosion.

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 112 Fokker Model F28 Mark 0100 series 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 1 work hour per airplane to accomplish the required 
actions, and that the average labor rate is $60 per work hour. Required 
parts will be supplied by the manufacturer at no cost to the operators. 
Based on these figures, the cost impact of the AD on U.S. operators is 
estimated to be $6,720, or $60 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

[[Page 6461]]

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:

97-03-09 FOKKER: Amendment 39-9915. Docket 95-NM-02-AD.

    Applicability: Model F28 Mark 0100 series airplanes; equipped 
with Menasco Aerospace Elevator Booster Control Unit (BCU) having 
part number (P/N) 23400-3 or P/N 23400-5 with serial numbers MC-001 
through MC-288 inclusive; 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, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent backlash in the elevator controls and reduced 
elevator control authority in the manual mode, accomplish the 
following:
    (a) Within 500 flight cycles or 60 days after the effective date 
of this AD, whichever occurs first, perform an operational check to 
detect backlash in the elevator mechanical control system, in 
accordance with Part 1 of the Accomplishment Instructions of Fokker 
Service Bulletin SBF100-27-052, Revision 1, dated March 29, 1994. If 
no backlash is detected, repeat the check thereafter at intervals 
not to exceed 500 flight cycles or 60 days, whichever occurs first.
    (b) If any backlash of the elevator mechanical control system is 
detected during any operational check required by paragraph (a) of 
this AD, prior to further flight, perform an inspection to determine 
whether the backlash remover lever and pistons are in the proper 
position, in accordance with Part 2 (paragraph I.) of Fokker Service 
Bulletin SBF100-27-052, Revision 1, dated March 29, 1994.
    (1) If the backlash remover lever and pistons are in the proper 
position: Prior to further flight, perform appropriate trouble-
shooting procedures in accordance with the Airplane Maintenance 
Manual.
    (2) If the backlash remover lever and pistons are not in the 
proper position: Prior to further flight, perform an inspection to 
determine whether the elevator booster control unit (BCU) bolts, 
having part numbers (P/N) NAS6204C22D and P/N NAS6204C13D, rotate 
and slide freely; and to detect corrosion on the bolts of the 
backlash remover lever mechanism; in accordance with Part 2 
(paragraph J.) of the Accomplishment Instructions of Fokker Service 
Bulletin SBF100-27-052, Revision 1, dated March 29, 1994.
    (i) If no anomaly is detected, prior to further flight, perform 
appropriate trouble-shooting procedures in accordance with the 
Airplane Maintenance Manual.
    (ii) Except as provided by paragraph (b)(2)(iii) of this AD, if 
any anomaly is detected, prior to further flight, replace the 
elevator BCU or bolts, as applicable, with serviceable parts, in 
accordance with the service bulletin.
    (iii) If any anomaly is detected, replacement of the elevator 
BCU or the bolt having P/N NAS6204C22D, as applicable, may be 
deferred for a period of 10 days, provided that the three conditions 
specified below are met:
    (A) The bolt having P/N NAS6204C22D can be freed so that it 
rotates and slides freely; and
    (B) That bolt is lubricated subsequent to the inspection; and
    (C) An operational check, as specified in paragraph (a) of this 
AD, is accomplished subsequent to lubrication and is successful.

    Note 2: The deferral provision of paragraph (b)(2)(iii) of this 
AD does not apply to the bolt having P/N NAS6204C13D. Replacement of 
that part-numbered bolt, when necessary, cannot be deferred.

    (c) Terminating action for the repetitive check and inspection 
requirements of this AD consists of the accomplishment of the 
actions specified in either paragraph (c)(1) or (c)(2) of this AD:
    (1) Modification of the affected elevator BCU having P/N 23400-3 
or -5, in accordance with Fokker Service Bulletin SBF100-27-061, 
dated March 2, 1994; or
    (2) Replacement of any affected elevator BCU having P/N 23400-3 
or -5 with a unit having a serial number other than MC-001 through 
MC-288 inclusive, in accordance with the Airplane Maintenance 
Manual.
    (d) As of the effective date of this AD, no person shall install 
in any airplane a Menasco Aerospace BCU having P/N 23400-3 or P/N 
23400-5 with serial numbers MC-001 through MC-288, inclusive.
    (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, Standardization Branch, ANM-113, 
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, 
Standardization Branch, ANM-113.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (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 SBF100-27-052, Revision 1, dated March 29, 1994; and Fokker 
Service Bulletin SBF100-27-061, dated March 2, 1994. 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 Aircraft USA, Inc., 1199 
North Fairfax Street, Alexandria, Virginia 22314. 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.
    (h) This amendment becomes effective on March 19, 1997.

    Issued in Renton, Washington, on January 28, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-2608 Filed 2-11-97; 8:45 am]
BILLING CODE 4910-13-U