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

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-SW-27-AD]

Airworthiness Directives; The Enstrom Helicopter Corporation

Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, and 280FX

Series Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to The Enstrom Helicopter

Corporation Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F,

and 280FX series 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 current AD also requires replacement of the clutch

assembly at certain time-in-service intervals. This action would

require the same inspections and replacements as required by the

current AD, but would provide an additional approved replacement part

number and provide a reference to three additional manufacturer service

documents. The actions specified by the proposed 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.

DATES: Comments must be received by October 28, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Rules Docket No. 93-SW-27-AD, 2601 Meacham Blvd., Room 663, Fort Worth,

Texas 76137-4298. Comments may be inspected at this location between

9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal

holidays.

The service information referenced in the proposed rule 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 202, Des Plaines,

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

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed 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 above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals contained in this notice may be changed in

light of the comments received.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

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

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

to Docket Number 93-SW-27-AD.'' The postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, Office of the Assistant Chief Counsel, Attention: Rules

Docket No. 93-SW-27-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas

76137-4298.

Discussion

On January 23, 1989, the FAA issued AD 89-04-09, Amendment 39-6138

(54 FR 6391, February 10, 1989), to require initial and repetitive

inspections of certain main rotor transmission clutch assemblies for

bearing roughness, noise, lock-up, and improper oil levels. AD 89-04-09

also requires replacement of the main rotor transmission clutch

assembly (clutch assembly) when unairworthy, and establishes a 1,200

hours time-in-service retirement life on the clutch assembly. That

action was prompted by several failures of the clutch assembly. Based

on an analysis of the clutch assembly failure data, the FAA, in

conjunction with The Enstrom Helicopter Corporation and Formsprag, the

clutch assembly manufacturer, determined that the clutch assembly, P/N

28-13401-1 (Formsprag CL 40526-1 through -7), could not be safely

overhauled and returned to service. The FAA has determined that

premature failure of the clutch assembly due to a loss of lubricant

creates an unsafe condition. The requirements of that 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.

Since the issuance of that AD, the FAA has approved the use of

clutch assembly, part number (P/N) 28-13401-4 (Formsprag CL 40526-10),

in addition to the earlier clutch assembly, P/N 28-13401-2 (Formsprag

CL 40526-8) as replacement clutch assemblies. Additionally, subsequent

to the issuance of AD 89-04-09, The Enstrom Helicopter Corporation

(Enstrom) issued Service Directive Bulletin (SDB) No. 0069, Revision A,

dated July 9, 1990, that contains an overhaul time interval for clutch

assemblies, P/N 28-13401-2 (Formsprag CL 40526-8) and P/N 28-13401-4

(Formsprag CL 40526-10). Also, AD 89-04-09 referenced neither Enstrom

Service Information Letter (SIL) No. 0084, dated December 19, 1978,

pertaining to checking the run-out of the main rotor pinion shaft nor

Enstrom SDB No. 0068, dated May 8, 1986, subsequently reissued July 9,

1990, pertaining to the retirement life of the clutch assembly.

Finally, a note contained in AD 89-04-09 incorrectly referenced SIL

``0038A''; the reference should have been SIL ``No. 0088, Revision A,

dated August 6, 1980.''

Since an unsafe condition has been identified that is likely to

exist or develop on other products of this same type design, the

proposed AD would supersede AD 89-04-09 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 are

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. These 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, these owner/operator checks are considered part of

the normal pilot ``Before Takeoff'' and ``After Landing'' checks and

were allowed by the existing AD. These 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. These 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 proposed AD would also require replacement of

the clutch assembly at certain TIS intervals.

The FAA estimates that 162 helicopters of U.S. registry would be

affected by this proposed AD, that it would take approximately 2 work

hours per helicopter to accomplish the proposed actions, and that the

average labor rate is $55 per work hour. Required parts would 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 proposed AD on U.S. operators is estimated to be from $471,420,

if only overhauled clutch assemblies are installed, to $1,718,820, if

only zero-time clutch assemblies are used.

The regulations proposed herein would 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

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

regulation (1) is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, 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 copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend

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 removing Amendment 39-6138 (54 FR

6391, February 10, 1989), and by adding a new airworthiness directive

(AD), to read as follows:

The Enstrom Helicopter Corporation (Enstrom): 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 series helicopters, certificated in any

category.

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 series

helicopters, equipped with clutch assembly part number (P/N) 28-

13401-1 (Formsprag CL 40526-1 through-7) 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 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 Enstrom Helicopter Corporation

Service Information Letter No. 0079A, dated February 14, 1980.

(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 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: 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 series 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 series 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 series

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: 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.

Issued in Fort Worth, Texas, on September 6, 1994.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 94-22627 Filed 9-12-94; 8:45 am]

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