Airworthiness Directives; The Enstrom Helicopter Corporation Model F-28A, F-28C, F-28C2, F-28F, 280, 280C, 280F, and 280FX Series Helicopters

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-SW-09-AD; Amendment 39-9010; AD 94-17-15]

Airworthiness Directives; The Enstrom Helicopter Corporation

Model F-28A, F-28C, F-28C2, F-28F, 280, 280C, 280F, and 280FX Series

Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that

is applicable to The Enstrom Helicopter Corporation (Enstrom) Model F-

28A, F-28C, F-28C2, F-28F, 280, 280C, 280F, and 280FX series

helicopters. This action requires initial and repetitive inspections

for delamination of the main rotor feathering elastomeric Lamiflex

bearing (Lamiflex bearing). This amendment is prompted by several

reported failures of the Lamiflex bearing. The actions specified in

this AD are intended to prevent failure of the Lamiflex bearing,

abnormal vibrations in the airframe and flight control system, and

subsequent loss of control of the helicopter.

DATES: Effective on September 15, 1994.

The incorporation by reference of certain publications listed in

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

of September 15, 1994.

Comments for inclusion in the Rules Docket must be received on or

before October 31, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Office of the Assistant Chief Counsel, Attention:

Rules Docket No. 94-SW-09-AD, 2601 Meacham Blvd., Room 663, Fort Worth,

Texas 76137.

The service information referenced in this AD may be obtained from

The Enstrom Helicopter Corporation, Twin County Airport, P.O. Box 490,

Menominee, Michigan 49858. This information may be examined at the FAA,

Office of the Assistant Chief Counsel, 2601 Meacham Boulevard, Room

663, Fort Worth, Texas; or at the Office of the Federal Register, 800

North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Mr. Joe McGarvey, Aerospace Engineer,

Chicago Aircraft Certification Office, Airframe Branch, FAA, Small

Airplane Directorate, 2300 East Devon Avenue, Room 232, Des Plaines,

Illinois 60018, telephone (708) 294-7136, fax (708) 294-7834.

SUPPLEMENTARY INFORMATION: This amendment adopts a new airworthiness

directive (AD) that is applicable to Enstrom Model F-28A, F-28C, F-

28C2, F-28F, 280, 280C, 280F, and 280FX series helicopters. Field

reports indicate that several failures of the main rotor feathering

elastomeric Lamiflex bearings (Lamiflex bearings), part numbers (P/N)

28-14320-12 or 28-14320-15, have occurred in which the Lamiflex

bearings have partially delaminated and extruded rubber and brass. This

delamination and extrusion caused a significant loss in flight control

system feedback dampening and resulted in a sudden increase in flight

control system feedback, rotorcraft vibration, and degradation in

flying qualities. Continued operation of the helicopters resulted in

complete delamination of the Lamiflex bearings. The exact cause of the

bearing delaminations is under investigation; however, both grease

contamination and main rotor overspeeds may have contributed to the

reported premature failures. The reported Lamiflex bearing

delaminations occurred between 200 and 400 hours' total time-in-service

(TIS). The Lamiflex bearing, located in the main rotor retention

system, allows the blades to change pitch, or angle of attack. Although

delamination and degradation of the Lamiflex bearing occurs slowly,

once complete delamination has occurred, flying conditions could

rapidly deteriorate. This condition, if not corrected, could result in

failure of the Lamiflex bearing, abnormal vibrations in the airframe

and flight control systems, and subsequent loss of control of the

helicopter.

The FAA has reviewed The Enstrom Helicopter Corporation Service

Directive Bulletin (SDB) No. 0081, Revision A, dated November 16, 1992,

which describes procedures for performing a visual inspection of the

Lamiflex bearing for delamination within the next 5 hours' TIS or

whenever: (1) There is a significant deterioration in ride quality

during flight; (2) a smooth rotor system suddenly loses track and/or

experiences difficulty in maintaining a smooth track; (3) a trimmable

aircraft becomes untrimmable, or develops high cyclic stick forces; or

(4) there is any sudden abnormal feedback from the cyclic or collective

controls, followed by a moderate to severe one-per-rev vibration. The

SDB also describes procedures for performing repetitive visual

inspections of the Lamiflex bearing for delamination at each 100 hours'

TIS or at the annual inspection, whichever occurs first. The FAA has

also reviewed Enstrom Helicopter Corporation Service Information Letter

(SIL) No. 0097, dated July 1, 1980, that provides information on

replacement of the Lamiflex bearing no later than 5 years from the date

of manufacture. Since 1975, the date of manufacture has been stamped or

etched on the end plate of each Lamiflex bearing to assist in complying

with the SIL.

Since an unsafe condition has been identified that is likely to

exist or develop on other Enstrom Model F-28A, F-28C, F-28C2, F-28F,

280, 280C, 280F, and 280FX series helicopters of the same type design,

this AD is being issued to prevent failure of the Lamiflex bearing,

abnormal vibrations in the airframe and flight control system, and

subsequent loss of control of the helicopter. This AD requires initial

and repetitive visual inspections of the Lamiflex bearing for

delamination within the next 5 hours' TIS; whenever main rotor tracking

and balancing procedures are required more than once within a 5 hours'

TIS period; or, whenever abnormal airframe or flight control system

vibrations exist; and, replacement with an airworthy part if

delamination is found. The AD also requires replacement of the Lamiflex

bearing not later than 5 years after the date of manufacture of the

Lamiflex bearing. The actions would be required to be accomplished in

accordance with the SDB described previously and the applicable

maintenance manual. Due to the critical need for the Lamiflex bearing

to ensure the continued safe flight of the affected helicopters, and

the necessary short compliance time that requires an inspection for

delamination of the Lamiflex bearing be conducted upon the occurrence

of specified conditions or within the next 5 hours' TIS, this rule must

be issued immediately to correct an unsafe condition in the affected

helicopters.

Since a situation exists that requires the immediate adoption of

this regulation, it is found that notice and opportunity for prior

public comment hereon are impracticable, and that good cause exists for

making this amendment effective in less than 30 days.

Comments Invited

Although this action is in the form of a final rule that involves

requirements affecting flight safety and, thus, was not preceded by

notice and an opportunity for public comment, comments are invited on

this rule. Interested persons are invited to comment on this rule by

submitting such written data, views, or arguments as they may desire.

Communications should identify the Rules Docket number and be submitted

in triplicate to the address specified under the caption ADDRESSES. All

communications received on or before the closing date for comments will

be considered, and this rule may be amended in light of the comments

received. Factual information that supports the commenter's ideas and

suggestions is extremely helpful in evaluating the effectiveness of the

AD action and determining whether additional rulemaking action would be

needed.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the rule that might

suggest a need to modify the 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 that

summarizes each FAA-public contact concerned with the substance of this

AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this rule must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket No. 94-SW-09-AD.'' The postcard will be date stamped and

returned to the commenter.

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.

The FAA has determined that this regulation is an emergency

regulation that must be issued immediately to correct an unsafe

condition in aircraft, and that it is not a ``significant regulatory

action'' under Executive Order 12866. It has been determined further

that this action involves an emergency regulation under DOT Regulatory

Policies and Procedures (44 FR 11034, February 26, 1979). If it is

determined that this emergency regulation otherwise would be

significant under DOT Regulatory Policies and Procedures, a final

regulatory evaluation will be prepared and placed in the Rules Docket.

A copy of it, if filed, 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. 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 a new airworthiness directive

to read as follows:

AD 94-17-15 The Enstrom Helicopter Corporation: Amendment 39-9010.

Docket No. 94-SW-09-AD.

Applicability: Model F-28A, F-28C, F-28C2, F-28F, 280, 280C,

280F, and 280FX series helicopters, equipped with main rotor

feathering elastomeric Lamiflex bearing (Lamiflex bearing), part

numbers (P/N) 28-14320-12 or 28-14320-15, certificated in any

category.

Compliance: Required as indicated, unless accomplished

previously. To prevent failure of the Lamiflex bearing, abnormal

vibrations in the airframe and flight control system, and subsequent

loss of control of the helicopter, accomplish the following:

(a) Within the next 5 hours' time-in-service (TIS) or whenever

main rotor tracking and balancing procedures are required more than

once in 5 hours' TIS, or abnormal airframe or flight control system

vibrations exist, remove and visually inspect the Lamiflex bearing

for evidence of delamination in accordance with the Inspection

Criteria of paragraph 5.2 in The Enstrom Helicopter Corporation

Service Directive Bulletin No. 0081, Revision A, dated November 16,

1992.

(b) Repeat the inspections of paragraph (a) at intervals not to

exceed 100 hours' TIS since the last inspection or during each

annual inspection, whichever occurs first.

(c) If Lamiflex bearing delamination is found during the

inspections required by paragraph (a) or (b) of this AD, replace the

Lamiflex bearing with an airworthy Lamiflex bearing before further

flight.

(d) If any Lamiflex bearing is found that has no date stamped or

etched on an end plate, remove and replace it with an airworthy

Lamiflex bearing before further flight.

(e) No later than 5 years from the date of manufacture of the

Lamiflex bearing, remove and replace the Lamiflex bearing with an

airworthy Lamiflex bearing.

(f) This AD establishes a retirement life of 5 years for the

Lamiflex bearing.

Note: The Enstrom Helicopter Corporation Service Information

Letter No. 0097, dated July 1, 1980, pertains to the replacement of

the Lamiflex bearing.

(g) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used when approved by the Manager, Chicago Aircraft Certification

Office, FAA. Operators shall submit their requests through an FAA

Principal Maintenance Inspector, who may concur or comment and then

send it to the Manager, Chicago Aircraft Certification Office.

Note: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Chicago Aircraft Certification Office.

(h) 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 helicopters that do not have

abnormal vibrations to a location where the requirements of this AD

can be accomplished.

(i) The inspection, removal, and replacement shall be done in

accordance with The Enstrom Helicopter Corporation Service Directive

Bulletin No. 0081, Revision A, dated November 16, 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 The Enstrom Helicopter Corporation,

Twin County Airport, P.O. Box 490, Menominee, Michigan 49858. Copies

may be inspected at the FAA, Office of the Assistant Chief Counsel,

2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of

the Federal Register, 800 North Capitol Street, NW., suite 700,

Washington, DC.

(j) This amendment becomes effective on Setpember 15, 1994.

Issued in Fort Worth, Texas, on August 17, 1994.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 94-20589 Filed 8-30-94; 8:45 am]

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