[Federal Register Volume 59, Number 168 (Wednesday, August 31, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-20589]


[[Page Unknown]]

[Federal Register: August 31, 1994]


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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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