[Federal Register Volume 61, Number 54 (Tuesday, March 19, 1996)]
[Rules and Regulations]
[Pages 11129-11131]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-6421]



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[[Page 11130]]


DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-SW-27-AD; Amendment 39-9540; AD 96-06-03]


Airworthiness Directives; The Enstrom Helicopter Corporation 
Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, and 280FX 
Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to The Enstrom Helicopter Corporation (Enstrom) Model 
F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, and 280FX 
helicopters, that currently requires initial and repetitive inspections 
of a certain main rotor transmission clutch assembly (clutch assembly) 
for bearing roughness, noise, lock-up, or improper oil level and, if 
necessary, replacement of the clutch assembly. The existing AD also 
requires replacement of the clutch assembly at certain time-in-service 
intervals. This amendment requires the same inspections and 
replacements as required by the existing AD, but would provide for 
installation of an additional approved replacement part number and 
provide a reference to three additional manufacturer service documents. 
This amendment is prompted by the approval of an additional replacement 
clutch assembly; the manufacturer's issuance of additional service 
information, and the need to correct a service information letter's 
number. The actions specified by this AD are intended to prevent 
failure of the clutch assembly, loss of control of the main rotor 
system, and subsequent loss of control of the helicopter.

EFFECTIVE DATE: April 23, 1996.

ADDRESSES: 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 Blvd., Room 663, Fort Worth, Texas.

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 (847) 294-7136, fax (847) 294-7834.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding AD 89-04-09, 
Amendment 39-6138 (54 FR 6391, February 10, 1989), which is applicable 
to Enstrom Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, 
and 280FX helicopters, was published in the Federal Register on 
September 13, 1994 (59 FR 46944). That action proposed to require 
initial and repetitive inspections of certain clutch assemblies for 
bearing roughness, noise, lock-up, or improper oil levels and, if 
necessary, immediate replacement of the clutch assembly. Owner/operator 
checks were proposed after engine start and rotor engagement to verify 
proper operation of the clutch assembly, and after each engine 
shutdown, while the main rotor is still turning down, to check for 
abnormal noise (such as a clicking or racheting sound) from the upper 
pulley that houses the clutch assembly. Those proposed owner/operator 
checks do not require the use of tools, precision measuring equipment, 
training, pilot logbook endorsements, or the use of technical data not 
contained in the AD. Additionally, those owner/operator checks are 
considered part of the normal pilot ``Before Takeoff'' and ``After 
Landing'' checks and were allowed by the existing AD. Those owner/
operator checks are additional measures to ensure, between 25 hours TIS 
inspections, that sufficient lubricants are maintained in the clutch 
assembly and not lost through a leaking seal. Those checks may be 
performed by an owner/operator holding at least a private pilot 
certificate and must be entered into the aircraft records showing 
compliance with this AD in accordance with sections 43.11 and 
91.417(a)(2)(v) of the Federal Aviation Regulations. The action also 
proposed to require replacement of the clutch assembly at certain TIS 
intervals.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. No comments were received on the 
proposal or the FAA's determination of the cost to the public. The FAA 
has determined that air safety and the public interest require the 
adoption of the rule as proposed, except for editorial changes revising 
paragraph (a)(3) of the AD to clarify the aircraft records entries, and 
adding explanatory Note 1, relating to the scope of the applicability 
statement when modifications, alterations, or repairs have been made in 
the area subject to the requirements of the AD. Additionally, the FAA 
has revised the proposed estimated average labor rate from $55 per work 
hour to an estimated average labor rate of $60 per work hour in the 
preamble portion of this final rule. This revision will increase the 
estimated total cost impact of the AD from $471,420 to $473,040 if only 
overhauled clutch assemblies are installed, and from $1,718,820 to 
$1,720,440 if only zero-time clutch assemblies are used. The FAA has 
determined that these changes will neither increase the economic burden 
on any operator nor increase the scope of the AD.
    The FAA estimates that 162 helicopters of U.S. registry will be 
affected by this AD, that it will take approximately 2 work hours per 
helicopter to accomplish the required actions, and that the average 
labor rate is $60 per work hour. Required parts will cost approximately 
$2,800 to overhaul or $10,500 for a zero-time clutch assembly per 
helicopter. Based on these figures, the total cost impact of the AD on 
U.S. operators is estimated to be from $473,040 if only overhauled 
clutch assemblies are installed, to $1,720,440 if only zero-time clutch 
assemblies are installed.
    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, 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

[[Page 11131]]
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 USC 106(g), 40113, 44701.


Sec. 39.13   [Amended]

    2. Section 39.13 is amended by removing Amendment 39-6138 (54 FR 
6391, February 10, 1989), and by adding a new airworthiness directive 
(AD), Amendment 39-9540, to read as follows:

AD 96-06-03 The Enstrom Helicopter Corporation: Amendment 39-9540. 
Docket No. 93-SW-27-AD. Supersedes AD 89-04-09, Amendment 39-6138.

    Applicability: Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 
280C, 280F, and 280FX helicopters, certificated in any category.

    Note 1: This AD applies to each helicopter 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 helicopters that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must use the authority 
provided in paragraph (e) to request approval from the FAA. This 
approval may address either no action, if the current configuration 
eliminates the unsafe condition, or different actions necessary to 
address the unsafe condition described in this AD. Such a request 
should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any helicopter from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the main rotor transmission clutch 
assembly (clutch assembly), loss of control of the main rotor 
system, and subsequent loss of control of the helicopter accomplish 
the following:
    (a) For Model F-28, F-28A, F-28C, F-28C-2, 280, and 280C 
helicopters, with clutch assembly part number (P/N) 28-13401-1 
(Formsprag CL 40526-1 through -7) installed, perform the following:
    (1) Before the first flight of each day, before takeoff, gently 
close the throttle, splitting the tachometer needles to verify 
proper operation of the clutch assembly. If the tachometer needles 
do not split, before further flight, inspect the clutch assembly in 
accordance with paragraph (a)(4).
    (2) At the conclusion of the last flight of each day, after 
engine shutdown, while the main rotor is still running down, listen 
for any abnormal noise (such as a clicking or racheting sound) from 
the area of the upper pulley that houses the clutch assembly. If any 
abnormal noise is heard from the clutch assembly, inspect the clutch 
assembly in accordance with paragraph (a)(4).
    (3) The operational checks required by paragraphs (a)(1) and 
(a)(2) may be performed by an owner/operator holding at least a 
private pilot certificate and must be entered into the aircraft 
records showing compliance with paragraphs (a)(1) and (a)(2) of this 
AD in accordance with 14 CFR 43.11 and 91.417(a)(2)(v).
    (4) If any irregularities are noted while performing the 
procedures required by paragraph (1) or (2), inspect the clutch 
assembly to determine if it is locked-up, or if the upper pulley 
will rotate. Rotate it in both directions while feeling for any 
bearing roughness and listening for any bearing noise. The upper 
pulley should free-wheel if rotated in a clockwise direction and 
engage if rotated in a counterclockwise direction.
    (5) Within the next 25 hours time-in-service (TIS) after the 
effective date of this airworthiness directive (AD), make an entry 
in the aircraft log book documenting the clutch assembly part 
number, the number of hours TIS, and the date.
    (6) Within the next 25 hours TIS after the effective date of 
this AD, and thereafter at intervals not to exceed 100 hours TIS, 
inspect the clutch assembly for proper oil level in accordance with 
the appropriate maintenance manual. If there has been less than a 
complete loss of oil, replenish the oil and service the clutch 
assembly in accordance with the applicable maintenance manual.

    Note 2: The Enstrom Helicopter Corporation (Enstrom) Service 
Information Letter No. 0079A, dated February 14, 1980, provides 
specific information regarding clutch lubrication.

    (7) If there has been a complete oil loss, or lock-up, noise, or 
roughness are detected from the clutch assembly as a result of the 
inspections required by paragraphs (a) (4) or (a) (6) of this AD, 
before further flight, replace the clutch assembly, P/N 28-13401-1 
(Formsprag CL 40526-1 through -7), with an airworthy clutch 
assembly, P/N 28-13401-2 (Formsprag CL 40526-8) or P/N 28-13401-4 
(Formsprag CL 40526-10).
    (8) For a clutch assembly, P/N 28-13401-1 (Formsprag CL 40526-1 
through -7), that has 1,175 or more hours TIS on the effective date 
of this AD, within the next 25 hours TIS, replace the clutch 
assembly with an airworthy clutch assembly, P/N 28-13401-2 
(Formsprag CL 40526-8) or P/N 28-13401-4 (Formsprag CL 40526-10).
    (9) For a clutch assembly, P/N 28-13401-1 (Formsprag CL 40526-1 
through-7), that has less than 1,175 hours TIS on the effective date 
of this AD, replace the clutch assembly with an airworthy clutch 
assembly, P/N 28-13401-2 (Formsprag CL 40526-8) or P/N 28-13401-4 
(Formsprag CL 40526-10), prior to the clutch assembly accumulating 
1,200 hours TIS.

    Note 3: The clutch service information published in The Enstrom 
Helicopter Corporation (Enstrom) Service Note No. 0027, dated 
December 9, 1975; Enstrom Service Information Letter No. 0084, dated 
December 19, 1978; Enstrom Service Information Letter No. 0079A, 
dated February 14, 1980; Service Information Letter No. 0088, 
Revision A, dated August 6, 1980, Enstrom Service Directive Bulletin 
No. 0068, Revision A, dated July 9, 1990; and Enstrom Service 
Directive Bulletin No. 0069, Revision A, dated July 9, 1990; 
pertains to this AD.

    (b) For Model F-28F, 280F, and 280FX helicopters, accomplish the 
following:
    (1) Within the next 25 hours TIS after the effective date of 
this AD, determine the part number of the clutch assembly.
    (2) If a clutch assembly, P/N 28-13401-1 (Formsprag CL 40526-1 
through -7), is found, before further flight, replace it with an 
airworthy clutch assembly, P/N 28-13401-2 (Formsprag CL 40526-8) or 
P/N 28-13401-4 (Formsprag CL 40526-10). The clutch assembly, P/N 28-
13401-1 (Formsprag CL 40526-1 through -7), is not approved for use 
on Enstrom Model F-28F, 280F, or 280FX helicopters.
    (c) Installation of a clutch assembly, P/N 28-13401-2 (Formsprag 
CL 40526-8) or P/N 28-13401-4 (Formsprag CL 40526-10), on Model F-
28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, and 280FX 
helicopters constitutes a terminating action for the requirements of 
this AD.
    (d) This AD establishes a retirement life of 1,200 hours TIS for 
the clutch assembly, P/N 28-13401-1 (Formsprag CL 40526-1 through -
7). However, for clutch assemblies with 1,175 or more hours TIS on 
the effective date of this AD, those clutch assemblies need not be 
retired until on or before the accumulation of an additional 25 
hours TIS.
    (e) 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 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Chicago Aircraft Certification Office.

    (f) 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 helicopter to a location where 
the requirements of this AD can be accomplished.
    (g) This amendment becomes effective on April 23, 1996.

    Issued in Fort Worth, Texas, on March 11, 1996.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 96-6421 Filed 3-18-96; 8:45 am]
BILLING CODE 4910-13-U