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

SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to The Endstrom Helicopter

Corporation Model F-28A, F-28C, 280, and 280C series helicopters, that

currently requires an initial and repetitive visual inspections of the

upper swashplate bearings for corrosion, and replacement of defective

upper swashplate bearings with airworthy bearings. This action would

require that the visual inspections apply to both the upper and lower

swashplate bearings (bearings); expand the applicability to those

affected helicopters manufactured prior to January 1, 1981; establish a

retirement life of 1,200 hours' time-in-service for certain bearings;

and provide a corrected upper swashplate bearing part number. This

proposal is prompted by the necessity to require visual inspection so

the lower swashplate bearings; expand the applicability to include the

Model F-28C-2 helicopter; establish a retirement life for certain

bearings; and correct the upper swashplate bearing part number from the

existing AD. The actions specified by the proposed AD are intended to

prevent failure of the bearings and subsequent loss of control of the

helicopter.

DATES: Comments must be received by September 6, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Rules Docket No. 93-SW-26-Ad, 2601 Meacham Blvd., Room 663, Fort Worth,

Texas 76137. 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

Meachum 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 (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-26-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-26-Ad, 2601 Meacham Blvd., Room 663, Fort Worth, Texas

76137.

Discussion

On March 19, 1976, the FAA issued AD 76-01-11, Amendment 39-2560,

(41 FR 13906, April 1, 1976), to require an initial and repetitive

visual inspection of the upper swashplate bearing, part number (P/N)

Z993L13XR3B, for corrosion, and replacement of corroded upper

swashplate bearings. That action was prompted by three reports of upper

swashplate bearing failures that were attributed to corrosion. These

failures occurred between 205 and 586 hours' time-in-service (TIS). In

two of these incidents, the probable cause of the upper swashplate

bearing failures was corrosion of the balls and race due to water

impregnating the housing after the loss of lubricant. This led to a

spalling interaction between the balls and race, resulting in upper

swashplate bearing failure. After reviewing the data, the FAA has

determined that corrosion of either upper or lower bearings (bearings)

could create an unsafe condition. These conditions, if not corrected,

could result in failure of the bearings and subsequent loss of control

of the helicopter.

Since the issuance of that AD, improved and modified bearings have

been approved by the FAA for these model helicopters. Additionally, the

manufacturer has issued The Enstrom Helicopter Corporation Service

Information Letter (SIL) No. 0110, Revision B, dated March 18, 1993,

that extends the previous visual inspections to include the Model F-

28C-2 helicopters. The SIL describes an approved swashplate

modification and indicates that the SIL should only apply to those

affected helicopters manufactured prior to January 1, 1981. In

addition, a swashplate modification that would constitute terminating

action for the requirements of this AD has been approved.

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 76-06-11 to require visual inspections

of the lower swashplate bearings; expand the applicability to the Model

F-28C-2 helicopter; establish a retirement life of 1,200 hours' time-

in-service for certain upper and lower swashplate bearings; and correct

the upper swashplate bearing part number in the existing AD. This

proposed AD would also provide an optional terminating action from the

requirements of this AD and limit the applicability of the AD

requirements to those affected model helicopters manufactured prior to

January 1, 1981.

The FAA estimates that 660 helicopters of U.S. registry would be

affected by this proposed AD, that it would take approximately 5 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 $1,400 per helicopter. Based on these figures, the total

cost impact of the proposed AD on U.S. operators is estimated to be

$1,105,500.

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 39-2560 (41 FR

13906, April 1, 1976), and by adding a new airworthiness directive

(AD), to read as follows:

The Enstrom Helicopter Corporation: Docket No. 93-SW-26-AD.

Supersedes AD 76-06-11, Amendment 39-2560.

Applicability: Model F-28A, F-28C, F-28C-2, 280, and 280C

helicopters, manufactured prior to January 1, 1981, certificated in

any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the upper and lower swashplate bearings

(bearings) and subsequent loss of control of the helicopter,

accomplish the following:

(a) Within the next 10 hours' time-in-service (TIS) after the

effective date of this AD, and thereafter at intervals not to exceed

100 hours' TIS since the last inspection, perform a visual

inspection of the upper swashplate bearing, P/N Z993L13X3B, bearing

number SKF 6013-RS, or ECD013-13, and lower swashplate bearing, P/N

5201SBKZZ-ABEC, or ECD009-11, for corrosion as follows:

(1) Lower the swashplate to lowest position with the collective

control.

(2) Remove the plastic bearing seal using a blunt scribe.

(3) Using an inspection mirror, visually inspect the bearings

for grease lubricant and any evidence of corrosion. Rotate the

bearings and housing to reposition balls and race for complete

inspection. For bearings found free of corrosion or defects, repack

them with Exxon ANDOK-B grease or any MIL-G-18709A grease, and

reinstall them in accordance with the applicable maintenance manual.

(b) Replace any unairworthy bearing with an airworthy bearing in

accordance with the applicable maintenance manual.

(c) Before further flight, after the effective date of this AD,

remove all upper and lower swashplate bearings having 1,200 hours'

or more TIS, and replace them with airworthy bearings. For bearings

with less than 1,200 hours' TIS on the effective date of this AD,

replace the bearings on or before attaining 1,200 hours' TIS.

(d) The owner may elect to install revised upper swashplate

bearing housing, P/N 28-16108-2, and lower swashplate bearing

housing, P/N 28-16361-1, that are equipped with grease fittings and

integral bearing shields as described in The Enstrom Helicopter

Corporation Service Information Letter No. 0110, Revision B, dated

March 18, 1993. This would constitute terminating action for the

requirements of this AD.

(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

Secs. 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 June 27, 1994.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 94-16273 Filed 7-5-94; 8:45 am]

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