[Federal Register Volume 62, Number 111 (Tuesday, June 10, 1997)]
[Proposed Rules]
[Pages 31536-31538]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-15061]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-176-AD]
RIN 2120-AA64


Airworthiness Directives; Fokker Model F28 Mark 1000 Through 4000 
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 1000 
through 4000 series airplanes. This proposal would require replacing 
certain flexible hydraulic hoses that connect to the UP-port of the 
actuator of each main landing gear (MLG) with certain new flexible 
hoses that have built-in restrictor check-valves. This proposal is 
prompted by results of tests, which indicate that, for airplanes on 
which restrictor check-valves are not installed, sudden movement of the 
actuator of the MLG, which could occur under extreme inward sideload 
conditions (such as touching down at a large crab angle), may 
pressurize the downlock-actuator and lift the MLG toggle-links. The 
actions specified by the proposed AD are intended to prevent such 
pressurization of the downlock-actuator and consequent lifting of the 
toggle-links, which could result in collapse of the MLG and reduced 
controllability of the airplane during landing.

DATES: Comments must be received by July 21, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-176-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 Aircraft USA, Inc., 1199 North Fairfax Street, 
Alexandria, Virginia 22314. 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 (425) 
227-2141; fax (425) 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-176-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-176-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On August 5, 1996, the FAA issued AD 96-16-05, amendment 39-9706, 
(61 FR 40510, August 5, 1996), applicable to certain Fokker Model F28 
Mark 1000, 2000, 3000, and 4000 series airplanes, and Model F28 Mark 
0100 series airplanes. That AD currently requires repetitive pre-load 
adjustments of the downlock-actuator of the main landing gear (MLG), 
and also provides for optional terminating action for the repetitive 
adjustments. These actions were prompted by a report indicating that, 
upon landing, the MLG of a Model F28 Mark 0100 series airplane 
collapsed as a result of the lock toggle-links being pulled out of the 
over-center position by the downlock-actuator, which was due to the 
relative movement of the upper and lower side-stay members. The 
requirements of that AD are intended to prevent collapse of the MLG, 
which could adversely affect the controllability of the airplane during 
landing.
    Prior to the issuance of AD 96-16-05, the Rijksluchtvaartdienst 
(RLD), which is the airworthiness authority for the Netherlands, 
notified the FAA that additional mandatory actions are necessary on 
certain Fokker Model F28 Mark 1000 through 4000 series airplanes to 
correct this unsafe condition because these earlier airplane models do 
not have restrictor check-valves. The RLD advises that Fokker has 
conducted additional tests of the actuator of the MLG. The results of 
these tests revealed that, in addition to pre-load adjustments of the 
downlock-actuator of the MLG (as required by AD 96-16-05), installation 
of a restrictor check-valve is necessary to address the identified 
unsafe condition.
    If restrictor check-valves are not installed, sudden movement of 
the actuator of the MLG could pressurize the downlock-actuator and lift 
the

[[Page 31537]]

toggle-links of the MLG. This situation could occur under extreme side 
load conditions, such as touching down at relatively large crab angles, 
and could result in collapse of the MLG and reduced controllability of 
the airplane during landing.
    Because Fokker Model F28 Mark 0100 series airplanes are equipped 
with a restrictor check-valve, they are not subject to the requirements 
of this proposed AD.

Explanation of Relevant Service Information

    Fokker has issued Service Bulletin F28/32-123, Revision 1, dated 
June 30, 1994, which describes procedures for replacing certain 
flexible hydraulic hoses that connect to the UP-port of the actuator of 
the MLG with new flexible hoses that have built-in restrictor check-
valves. The RLD classified this service bulletin as mandatory and 
issued Dutch airworthiness directive BLA 94-095 (A), dated July 15, 
1994, in order to assure the continued airworthiness of these airplanes 
in the Netherlands.

FAA's Conclusions

    These airplane models are manufactured in the Netherlands and are 
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 replacing certain 
flexible hydraulic hoses that connect to the UP-port of the actuator of 
the MLG with certain new flexible hoses that have built-in restrictor 
check-valves. These actions would be required to be accomplished in 
accordance with the service bulletin described previously.

Cost Impact

    The FAA estimates that 37 Fokker Model F28 Mark 1000 through 4000 
series airplanes of U.S. registry would be affected by this proposed 
AD, that it would take approximately 4 work hours per airplane to 
accomplish the proposed actions, and that the average labor rate is $60 
per work hour. Required parts would cost approximately $3,554 per 
airplane. Based on these figures, the cost impact of the proposed AD on 
U.S. operators is estimated to be $140,378, or $3,794 per airplane.
    The cost impact figure discussed above is 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.


Sec. 39.13  [Amended]

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

Fokker: Docket 96-NM-176-AD.

    Applicability: Fokker Model F28 Mark 1000 through 4000 series 
airplanes, equipped with flexible hydraulic hoses, part number (P/N) 
A71462-401; certificated in any category.

    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 (b) 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 pressurization of the downlock-actuator during 
extreme inward sideload conditions (such as touching down at a large 
crab angle) and consequent lifting of the toggle-links of the main 
landing gear (MLG), which could result in the collapse of the MLG 
and reduced controllability of the airplane during landing, 
accomplish the following:
    (a) Within 12 months after the effective date of this AD, 
replace the flexible hydraulic hoses, P/N A71462-401, that connect 
to the UP-port of the actuator of the MLG with new flexible hoses, 
P/N 97867-1, that have built-in restrictor check-valves, in 
accordance with Fokker Service Bulletin F28/32-123, Revision 1, 
dated June 30, 1994.
    (b) 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 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.

    (c) 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.


[[Page 31538]]


    Issued in Renton, Washington, on June 4, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-15061 Filed 6-9-97; 8:45 am]
BILLING CODE 4910-13-U