[Federal Register Volume 62, Number 9 (Tuesday, January 14, 1997)]
[Proposed Rules]
[Pages 1866-1868]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-883]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-185-AD]
RIN 2120-AA64


Airworthiness Directives; Fokker Model F28 Mark 0100 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Fokker Model F28 Mark 0100 
series airplanes. This proposal would require repetitive inspections of 
certain flanges and finger strips at rib 5.0 of the vertical stabilizer 
to detect fatigue cracking, and repairs, if necessary. It also would 
require modifications that would strengthen the torsion box at rib 5.0 
and prevent fatigue cracking; one of these modifications would be 
terminating action for the repetitive inspections. This proposal is 
prompted by reports indicating that, during full-scale fatigue testing, 
cracking has been found on the vertical stabilizer of the test article. 
The actions specified by the proposed AD are intended to detect and 
prevent fatigue cracking in the subject area, which, if not corrected, 
could reduce the structural integrity of the vertical stabilizer.

DATES: Comments must be received by February 24, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-185-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule 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 FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington.

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:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-185-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 96-NM-185-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The Rijksluchtvaartdienst (RLD), which is the airworthiness 
authority for the Netherlands, has notified the FAA that an unsafe 
condition may exist on certain Fokker Model F28 Mark 0100 series 
airplanes. The RLD advises that it has received reports indicating that 
cracks have been found on the vertical stabilizer during the 
manufacturer's full-scale fatigue tests on the Fokker Model F28 Mark 
0100 test article. These fatigue cracks were detected at the bolt holes 
of the right-hand flange of the torsion box, and in the finger strip on 
the left-hand flange at rib 5.0 of the vertical stabilizer.
    The RLD also advises that it has received reports indicating that 
subsequent full-scale fatigue tests have detected additional cracks in 
rib 5.0 of the vertical stabilizer after a stiffener had been added to 
the torsion box in accordance with Fokker Service Bulletin SBF100-55-
018. Although this modification was performed to strengthen this area 
against fatigue cracking, investigation has shown that the stiffener 
produces a too-rapid change in the structural strength of the torsion 
box, which may lead to fatigue cracking in an adjacent area.
    Fatigue cracking in the subject area, if not prevented, could 
reduce structural integrity of the vertical stabilizer.

Explanation of Relevant Service Information

    Fokker has issued Service Bulletin SBF100-55-019, Revision 1, dated 
May 19, 1993, which describes procedures for conducting repetitive eddy 
current inspections of the flanges and finger strips at rib 5.0 of the 
vertical stabilizers to detect fatigue cracking, and repair, if 
necessary.
    Fokker also has issued Service Bulletin SBF100-55-018, Revision 1, 
dated December 27, 1993, which describes procedures for modifying the 
torsion box at rib 5.0 of the vertical stabilizer by installing 
stiffening to the rib web and flanges for added strength. This service 
bulletin also describes procedures for a pre-modification eddy current 
inspection of the vertical stabilizer to detect cracking, and repair, 
if necessary, in accordance with Fokker Service Bulletin SBF100-55-019. 
Accomplishment of this modification eliminates the need for repetitive 
inspections to detect fatigue cracking.
    Additionally, Fokker has issued Service Bulletin SBF100-55-023, 
dated January 3, 1995, which describes procedures for another 
modification to strengthen rib 5.0 of the vertical stabilizer. This 
modification, which entails the cold expansion of holes in the torsion 
box at rib 5.0, is intended to prevent additional fatigue cracking that 
could be caused by the earlier installation of the torsion box 
stiffener.
    The RLD classified these service bulletins as mandatory and issued 
Netherlands airworthiness directives (BLA) 93-069 (A), dated June 1, 
1993, and BLA 1995-017 (A), dated February 28, 1995, in order to assure 
the continued airworthiness of these airplanes in the Netherlands.

[[Page 1867]]

FAA's Conclusions

    This airplane model is manufactured in the Netherlands and is type 
certificated for operation in the United States under the provisions of 
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and 
the applicable bilateral airworthiness agreement. Pursuant to this 
bilateral airworthiness agreement, the RLD has kept the FAA informed of 
the situation described above. The FAA has examined the findings of the 
RLD, reviewed all available information, and determined that AD action 
is necessary for products of this type design that are certificated for 
operation in the United States.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design registered 
in the United States, the proposed AD would require repetitive eddy 
current inspections to detect fatigue cracking of the left-hand and 
right-hand flanges and finger strips at rib 5.0 of the vertical 
stabilizer, and repair, if necessary.
    The proposed AD also would require modification of rib 5.0 by the 
installation of a stiffener to the torsion box; this modification would 
be preceded by an eddy current inspection to detect fatigue cracking, 
and repair, if necessary. Accomplishment of this modification would 
terminate the requirement for repetitive eddy current inspections.
    In addition, the proposed AD would require another modification of 
rib 5.0 by cold-expanding certain bolt holes on the torsion box.
    These actions would be required to be accomplished in accordance 
with the applicable service bulletins described previously.

Differences Between the Proposed Rule and the Service Bulletins

    If any cracking is detected during an eddy current inspection of 
the left-hand and right-hand flanges and finger strips at rib 5.0 of 
the vertical stabilizer, the proposed rule would require that the 
Manager, Standardization Branch, ANM-113, FAA, Transport Airplane 
Directorate approve the method of repair. The applicable Fokker service 
bulletins do not provide instructions for repair, but recommend that 
Fokker be contacted prior to repairing fatigue cracks at rib 5.0.

Other Related Rulemaking Actions

    The FAA has issued AD 91-18-15, amendment 39-8018 (56 FR 43548, 
September 3, 1991), which requires reinforcement of the left-hand and 
right-hand flanges of rib 5.0 of the vertical stabilizer by the 
installation of reinforcing finger clips, in accordance with Fokker 
Service Bulletin F100-55-014, dated November 29, 1990. That AD was 
prompted by reports of cracking in the flange of the torsion box at the 
junction of rib 5.0 and intermediate spar I; it is applicable to Fokker 
Model F28 Mark 0100 series airplanes having serial numbers 11244 
through 11335.
    The reinforcement required by AD 91-18-15 is to be installed prior 
to the accumulation of 6,000 total landings on the airplane, or within 
100 days after October 8, 1991 (the effective date of that AD), 
whichever is later. Under the proposed AD, however, this modification 
would not have to be installed if the addition of steel reinforcement 
to the torsion box [as specified in proposed paragraph (b)(2)] is 
accomplished before an airplane has accumulated 6,000 total landings.

Cost Impact

    The FAA estimates that 122 Fokker Model F28 Mark 0100 series 
airplanes of U.S. registry would be affected by this proposed AD.
    Approximately 77 airplanes would be required to conduct repetitive 
inspections of the left-hand and right-hand flanges and finger strips 
at rib 5.0 of the vertical stabilizer. It would take approximately 10 
work hours per airplane to accomplish each proposed inspection. The 
average labor rate is $60 per work hour. Based on these figures, the 
cost impact of the proposed inspection requirement on U.S. operators of 
these airplanes is estimated to be $46,200, or $600 per airplane, per 
inspection.
    Approximately 77 airplanes also would be required to accomplish the 
proposed installation of steel reinforcement in the torsion box at rib 
5.0 of the vertical stabilizer. It would take approximately 170 work 
hours per airplane to accomplish this modification (including a pre-
modification inspection). The average labor rate is $60 per work hour. 
Required parts would cost approximately $27,000. Based on these 
figures, the cost impact of this proposed action on U.S. operators of 
these airplanes is estimated to be $2,864,400, or $37,200 per airplane.
    Approximately 122 airplanes would be required to accomplish the 
proposed cold expansion of holes in the torsion box at rib 5.0 of the 
vertical stabilizer. It would take approximately 17 work hours per 
airplane to accomplish this modification, or approximately 8 work hours 
per airplane if this proposed action is done at the same time as the 
proposed installation of steel reinforcement. The average labor rate is 
$60 per work hour. Required parts would cost approximately $206. Based 
on these figures, the cost impact of this proposed action on U.S. 
operators of these airplanes is estimated to be between $83,692 and 
$149,572, or between $686 and $1,226 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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.

[[Page 1868]]

Sec. 39.13  [Amended]

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

Fokker: Docket 96-NM-185-AD.

    Applicability: Model F28 Mark 0100 series airplanes having the 
serial numbers specified in Table 1 of this AD; certificated in any 
category.

        Table 1.--Serial Numbers of Airplanes Subject to This AD        
                                                                        
                                                                        
                                                                         
11244 through 11460, inclusive                                          
11463 through 11469, inclusive                                          
11471                                                                   
11474 through 11483, inclusive                                          
11489 through 11491, inclusive                                          
11497 through 11499, inclusive                                          
11501                                                                   
11502                                                                   
11504                                                                   
11506                                                                   
11507                                                                   
11512 through 11515, inclusive                                          
11517                                                                   
11520                                                                   
                                                                        

    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 not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To detect and prevent fatigue cracking in the vertical 
stabilizer, which consequently could reduce its structural 
integrity, accomplish the following:
    (a) For airplanes having serial numbers 11244 through 11419, 
inclusive, and 11421: Except as provided by paragraph (c) of this 
AD, prior to the accumulation of 8,500 total landings or within 30 
days after the effective date of this AD, whichever occurs later, 
perform an eddy current inspection to detect fatigue cracking in the 
left-hand and right-hand flanges and finger strips at rib 5.0 of the 
vertical stabilizer, in accordance with Fokker Service Bulletin 
SBF100-55-019, Revision 1, dated May 19, 1993.
    (1) If no cracking is detected, repeat this inspection 
thereafter at intervals not to exceed 2,000 landings until the 
requirements of paragraph (b) of this AD are accomplished.
    (2) If any cracking is detected, prior to further flight, repair 
in accordance with a method approved by the Manager, Standardization 
Branch, ANM-113, FAA, Transport Airplane Directorate.
    (b) For airplanes with serial numbers 11244 through 11419, 
inclusive, and 11421, accomplish the requirements of both paragraphs 
(b)(1) and (b)(2) of this AD:
    (1) Except as provided by paragraph (c) of this AD, prior to the 
accumulation of 13,500 total landings, or within 6 months after the 
effective date of this AD, whichever occurs later, perform an eddy 
current inspection to detect fatigue cracking in the left-hand and 
right-hand flanges and finger strips at rib 5.0 of the vertical 
stabilizer, in accordance with Part 1 of the Accomplishment 
Instructions of Fokker Service Bulletin SBF100-55-018, Revision 1, 
dated December 27, 1993.
    (i) If no cracking is detected, prior to further flight, 
accomplish the requirements of paragraph (b)(2) of this AD.
    (ii) If any cracking is detected, prior to further flight, 
repair in accordance with a method approved by the Manager, 
Standardization Branch, ANM-113, and accomplish the requirements of 
paragraph (b)(2) of this AD.
    (2) After accomplishing the requirements of paragraph (b)(1) of 
this AD, modify rib 5.0 of the vertical stabilizer by installing new 
stiffening, in accordance with Part 2 of the Accomplishment 
Instructions of Fokker Service Bulletin SBF100-55-018, Revision 1, 
dated December 27, 1993. Accomplishment of this modification 
constitutes terminating action for the repetitive inspections 
required by paragraph (a) of this AD.
    (c) The following exceptions apply with regard to the 
requirements of paragraphs (a) and (b) of this AD:
    (1) Accomplishment of the inspection specified in paragraph (a) 
and (b)(1) of this AD is not required if the modification specified 
in paragraph (b)(2) is accomplished prior to the accumulation of 
7,300 total landings on the airplane.
    (2) Compliance with AD 91-18-15, amendment 39-8018, is not 
required if the requirements of paragraph (b)(2) of this AD are 
accomplished prior to the accumulation of 6,000 total landings on 
the airplane.
    (d) For all airplanes: At the applicable times specified in 
paragraph (d)(1) or (d)(2), modify the Hi-lok bolt holes at rib 5.0 
of the vertical stabilizer by cold expansion, in accordance with 
Fokker Service Bulletin SBF100-55-023, dated January 3, 1995.
    (1) For airplanes that have been modified in accordance with the 
requirements of paragraph (b) of this AD prior to the effective date 
of this AD: Modify prior to the accumulation of either 10,000 
landings after in-service modification, or 10,000 landings after 
delivery with factory modification, as applicable; or within 30 days 
after the effective date of this AD, whichever occurs later.
    (2) For all other airplanes: Modify concurrent with 
accomplishing the requirements of paragraph (b) of 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, Standardization Branch, ANM-113. 
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 2: 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 
Secs. 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.

    Issued in Renton, Washington, on January 8, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-883 Filed 1-13-97; 8:45 am]
BILLING CODE 4910-13-U