[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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