Airworthiness Directives; Fokker Model F-28 Mark 0100 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-148-AD; Amendment 39-8871; AD 94-07-13]

Airworthiness Directives; Fokker Model F-28 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 Fokker Model F-28 Mark 0100 series airplanes, that

requires inspection, necessary repair, and modification of the engine

mount shear shelf webs. This amendment is prompted by reports of

interference between the engine mount shear shelf web and the fixed

cowl mid and aft hooks, which caused fatigue cracks to occur in the

web. The actions specified by this AD are intended to prevent fatigue

cracking and other damage to the structure of the shear shelf web,

which subsequently could lead to loss of the engine mounting structure.

DATES: Effective May 16, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of May 16, 1994.

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: Mark Quam, Aerospace Engineer,

Standardization Branch, ANM-113, FAA, Transport Airplane Directorate,

1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (206)

227-2145; fax (206) 227-1320.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to Fokker Model F-28 Mark 0100 series airplanes was

published in the Federal Register on October 21, 1993 (58 FR 54312).

That action proposed to require inspection, necessary repair, and

modification of the engine mount shear shelf webs.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the proposal.

Two commenters request that proposed paragraph (a)(1) be deleted

from the rule. That paragraph proposed to require that a detailed

visual inspection be conducted to detect cracking or other damage of

the engine mount shear shelf webs around the areas of the fixed cowl

aft- and mid-hook centerlines. These commenters contend that, since the

modification required by paragraph (a)(2) reinforces the web and

eliminates the interference problems, the inspection of this area

should not be required to be accomplished. The FAA concurs. Since the

interference problem that prompted this AD action has been found only

in the area that is to be modified, and since the modification will

prevent the interference problem and remove any evidence of damage, the

FAA has determined that the proposed inspection is not necessary.

Further, if an operator has already performed the proposed

modification, the FAA finds that it would be an undue burden to require

that the operator disassemble the modified area to accomplish an

inspection of it. Additionally, the manufacturer and the one affected

U.S. operator have advised the FAA that inspection of this area at

intervals of 1,000 flight hours is already specified in the

manufacturer's recommended maintenance program. In light of all of

these factors, the FAA has revised the final rule to delete the

requirement to inspect the subject area.

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 change previously

described. The FAA has determined that this change will neither

increase the economic burden on any operator nor increase the scope of

the AD.

The FAA estimates that 20 airplanes of U.S. registry will be

affected by this AD, that it will take approximately 120 work hours per

airplane to accomplish the required actions, and that the average labor

rate is $55 per work hour. Required parts will cost approximately

$2,390 per airplane. Based on these figures, the total cost impact of

the AD on U.S. operators is estimated to be $179,800, or $8,990 per

airplane.

The total 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. However, the

FAA has been advised that all 20 affected U.S.-registered airplanes

have been modified in accordance with the requirements of the AD as of

December 1993. Therefore, there currently is no economic cost impact of

this rule on U.S. operators.

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 14 CFR part

39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-07-13 Fokker: Amendment 39-8871. Docket 93-NM-148-AD.

Applicability: Model F-28 Mark 0100 series airplanes; having

serial numbers 11244 to 11308 inclusive, 11310, 11312, 11313, 11314,

11316, 11321, 11328, and 11329; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent fatigue cracking and other damage to the engine mount

shear shelf web, which subsequently could lead to loss of the engine

mounting structure, accomplish the following:

(a) Prior to the accumulation of 12,000 total flight hours or

within 90 days after the effective date of this AD, whichever occurs

later, modify (reinforce) the engine mount shear shelf webs in

accordance with Part 1 or Part 2, as applicable, of the

Accomplishment Instructions of Fokker Service Bulletin SBF100-71-

012, dated February 7, 1992.

(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, FAA,

Transport Airplane Directorate, 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: 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

Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the

airplane to a location where the requirements of this AD can be

accomplished.

(d) The modification shall be done in accordance with Fokker

Service Bulletin SBF100-71-012, dated February 7, 1992. 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.

(e) This amendment becomes effective on May 16, 1994.

Issued in Renton, Washington, on March 30, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-8056 Filed 4-13-94; 8:45 am]

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