Airworthiness Directives; Fokker Model F28 Mark 1000 Through 4000 Series Airplanes

[Federal Register Volume 63, Number 55 (Monday, March 23, 1998)]
[Rules and Regulations]
[Pages 13775-13776]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-7093]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-176-AD; Amendment 39-10412; AD 98-06-33]
RIN 2120-AA64


Airworthiness Directives; Fokker Model F28 Mark 1000 Through 4000 
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 1000 through 4000 series 
airplanes, that requires 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 amendment 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 this 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: Effective April 27, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 27, 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 1000 
through 4000 series airplanes was published in the Federal Register on 
June 10, 1997 (62 FR 31536). That action proposed to 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.

Comments

    Interested persons were afforded an opportunity to participate in 
the making of this amendment. Due consideration has been given to the 
comments received.

Request to Shorten Compliance Time

    One commenter supports the proposed AD, but believes the compliance 
period should be less than 12 months. In addition, the commenter 
believes that, in the event the proposed compliance time cannot be 
changed, it would be beneficial to advise pilots operating the affected 
airplanes to be particularly cautious about landing with a crab angle. 
The commenter notes that since the proposed AD fails to define what is 
meant by ``significant crab angle,'' pilots are uncertain as to whether 
the crab angle they choose to use is above or below the safe threshold.
    The FAA does not concur with the commenter's request to shorten the 
compliance time. The primary concern in developing the proposed 
compliance time was the degree of urgency of the unsafe condition. 
Other practical considerations were also taken into account. Those 
include the availability of the required parts and the time needed for 
the majority of the affected operators to install the required 
modification within a time interval coinciding with normal scheduled 
maintenance. In addition, the proposed compliance time is consistent 
with the parallel document issued by the airworthiness authority of the 
state of design of the airplane, Dutch airworthiness directive 94-
095(A), dated July 15, 1995, and with the manufacturer's 
recommendations. A compliance time of 12 months is, therefore, adopted 
as proposed.
    The incident that precipitated this AD action, the collapse of a 
main landing gear on a similar Fokker Model F28 Mark 0100 airplane, 
occurred due to touchdown at a relatively large ``crab'' angle. 
Following subsequent investigation, it was concluded that a failure of 
this nature could only occur under extreme inward side-load conditions 
that are rarely encountered in service. Currently, no crab angle 
limitations have been established for the affected airplanes. Because 
of considerations other than structural integrity of the main landing 
gear, there are, however, existing limitations concerning landing in 
cross winds. The FAA concludes that, since normal cross wind landing 
technique involves adjusting the airplane heading at touchdown as 
necessary to reduce or eliminate the crab angle, no further limitation 
or cautionary information is needed in this regard.

Request to Withdraw the Proposal

    The Air Transport Association (ATA) of America, on behalf of one of 
its members, states that its member does not object to the proposed AD, 
but believes that it is unnecessary. According to the commenter, the 
changes that would be required were accomplished during production of 
each of its affected airplanes.
    The FAA infers from these remarks that the commenter requests the 
proposed AD be withdrawn. The FAA does not concur with this request. 
Since this AD states that compliance is ``required as indicated, unless 
accomplished previously,'' no further action would be required for any 
airplane that already incorporates the required change. Nevertheless, 
the AD must be issued because there may be other airplanes of these 
models in service in this country or imported into this country that 
have not incorporated the required change.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air

[[Page 13776]]

safety and the public interest require the adoption of the rule as 
proposed.

Cost Impact

    The FAA estimates that 37 Fokker Model F28 Mark 1000 through 4000 
series airplanes of U.S. registry will be affected by this AD, that it 
will take approximately 4 work hours per airplane to accomplish the 
required actions, and that the average labor rate is $60 per work hour. 
Required parts will cost approximately $3,554 per airplane. Based on 
these figures, the cost impact of the 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 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 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:

98-06-33  Fokker: Amendment 39-10412. 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 
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, 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the International Branch, ANM-116.

    (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.
    (d) The actions shall be done in accordance with Fokker Service 
Bulletin F28/32-123, Revision 1, dated June 30, 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 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 3: The subject of this AD is addressed in Dutch 
airworthiness directive BLA 94-095 (A), dated July 15, 1994.

    (e) This amendment becomes effective on April 27, 1998.

    Issued in Renton, Washington, on March 12, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-7093 Filed 3-20-98; 8:45 am]
BILLING CODE 4910-13-P

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