AD 98-06-33

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AD Number:
98-06-33
Document Type:
AD Final Rules
Docket Number:
96-NM-176-AD
Subject Heading:
Airworthiness Directives; Fokker Model F28 Mark 1000 through 4000 Series Airplanes
Subject:
Hydraulic Hose Of UP-Port Actuator Of MLG
Status:
Current
Citation:
Federal Register: March 23, 1998 (Volume 63, Number 55)
Citation Publish Date:
03/23/1998
Effective Date:
04/27/1998
Make:
Model:
F.28 Mark 1000 | F.28 Mark 2000 | F.28 Mark 3000 | F.28 Mark 4000
Product Type:
Aircraft
Product Subtype:
Large Airplane
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39 [63 FR 13775 NO. 55 03/23/98]
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 98-06-33
CITATION:   [Federal Register: March 23, 1998 (Volume 63, Number 55)]

PAGE NUMBER:   [Page 13775]

DOCKET NUMBER:   96-NM-176-AD

AMENDMENT:   39-10412

AD NUMBER:   98-06-33

SUBJECT HEADING:   Airworthiness Directives; Fokker Model F28 Mark 1000 through 4000 Series Airplanes

ACTION:   Final rule

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 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.

§ 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive:

REGULATORY TEXT:  
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.


FOOTER: