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

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-SW-25-AD; Amendment 39-8943; AD 94-13-03]

Airworthiness Directives: The Enstrom Helicopter Corporation

Model F-28C, F-28C-2, F-28F, 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 Model F-28C, F-28C-

2, F-28F, 280C, 280F, and 280FX series helicopters. This action

requires a visual inspection for cracks in the tail rotor spindle; a

repetitive dye penetrant inspection for cracks; and removal and

replacement of the tail rotor spindle upon reaching 1,200 hours' time-

in-service (TIS). This amendment is prompted by five reports of cracked

tail rotor spindles. The actions specified in this AD are intended to

prevent failure of the tail rotor spindle, loss of directional control,

and subsequent loss of control of the helicopter.

DATES: Effective August 12, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of August 12, 1994.

Comments for inclusion in the Rules Docket must be received on or

before September 26, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Rules Docket No. 93-SW-25-AD, 2601 Meacham Boulevard, Room 663, Fort

Worth, Texas 76137-4298.

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, 2300 East

Devon Avenue, Room 202, Des Plaines, Illinois 60018, telephone (708)

294-7136, fax (708) 294-7834.

SUPPLEMENTARY INFORMATION: This amendment adopts a new airworthiness

directive that is applicable to The Enstrom Helicopter Corporation

(Enstrom) Model F-28C, F-28C-2, F-28F, 280C, 280F, and 280FX series

helicopters equipped with tail rotor spindle (spindle), part number (P/

N) 28-150064-11 or 28-150064-13. The manufacturer advises that there

have been five reports of cracked spindles that had time-in-service

(TIS) ranging from 282 to 3,449 hours. Three of the five defects were

found during a visual preflight inspection. One of the reported

incidents resulted in an emergency landing due to a tail rotor

imbalance and the resultant high vibrations as a result of the cracked

spindle. Based on an analysis and evaluation of the data, the FAA has

determined that an unsafe condition exists in the spindle. This

condition, if not corrected, could result in failure of the spindle,

loss of directional control, and subsequent loss of control of the

helicopter.

The FAA has reviewed and approved The Enstrom Helicopter

Corporation Service Directive Bulletin (SDB) No. 0077, Revision B,

dated November 16, 1992, that describes procedures for performing a

visual inspection of the area around the spindle teeter bearing bores

for cracks prior to the next flight and prior to each subsequent

flight, and if cracks are found, removal and replacement of the spindle

with an airworthy spindle; continuing the visual inspection before each

flight and performing a dye penetrant inspection of the spindle for

cracks within the next five hours' TIS; securing the spindle bearing

caps with safety wire following the dye penetrant inspection; and

removing and replacing spindles with 1,200 hours' or more total TIS.

Since an unsafe condition has been identified that is likely to

exist or develop on other Enstrom Model F-28C, F-28C-2, F-28F, 280C,

280F, and 280FX series helicopters of the same type design, this AD is

being issued to prevent failure of the spindle, loss of directional

control, and subsequent loss of control of the helicopter. Before

further flight, this AD requires a visual inspection of the spindle,

part number (P/N) 28-150064-11 or 28-150064-13, for cracks in

accordance with paragraph 5.2 of SDB 0077, Revision B, dated November

16, 1992. A dye penetrant inspection is required whenever track and

balance procedures are required more than once within a 5 hours' TIS

period. Additionally, within the next 25 hours' TIS and thereafter, at

intervals not to exceed 25 hours' TIS, this AD requires an inspection

of the spindle for cracks (without removing the tail rotor from the

helicopter) using a visual and dye penetrant inspection in accordance

with paragraph 5.3 of SDB 0077, Revision B, dated November 16, 1992.

Also, this AD requires replacement of spindles with cracks or

scratches, nicks, or surface discontinuities that are in excess of

certain specified tolerances, or, if the spindle is not required to be

replaced, returning the helicopter to service in accordance with

paragraph 5.4 of SDB 0077, Revision B, dated November 16, 1992.

Replacing a spindle, P/N 28-150064-11 or 28-150064-13, is also required

within the next 100 hours' TIS, or on or before reaching 1,200 hours'

TIS, whichever occurs later. Installing a spindle, P/N 28-150074-11,

constitutes terminating action for the requirements of this AD. Since

the unsafe condition requires an immediate inspection to ensure safety

of the fleet, this AD needs to be adopted immediately, without prior

public comment. The compliance requirements of this AD and take

precedence over those stated in the Service Directive Bulletin, except

where specifically referenced in this AD.

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 notice must submit a self-addressed,

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

to Docket Number 93-SW-25-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 94-13-03 The Enstrom Helicopter Corporation: Amendment 39-8943.

Docket Number 93-SW-25-AD.

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

280FX series helicopters, equipped with tail rotor spindle

(spindle), part number (P/N) 28-150064-11 or 28-150064-13,

certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the spindle, loss of directional control

and subsequent loss of control of the helicopter, accomplish the

following:

(a) Before further flight, visually inspect the spindle for

cracks using a 5-power or higher magnifying glass in accordance with

paragraph 5.2 of The Enstrom Helicopter Corporation Service

Directive Bulletin (SDB) No. 0077, Revision B, dated November 16,

1992.

(b) Before further flight, whenever tail rotor (T/R) vibrations

occur that cannot be corrected with track and balance procedures or

track and balance procedures are required more than once within a 5

hours' TIS period, inspect the spindle teetering bearing bores for

cracks using a dye penetrant method in accordance with paragraph 5.3

of SDB 0077, Revision B, dated November 16, 1992.

(c) Within the next 25 hours' time-in-service (TIS) after the

effective date of this airworthiness directive (AD) and thereafter

at intervals not to exceed 25 hours' TIS from the last inspection,

without removing the tail rotor from the helicopter, inspect the

spindle teetering bearing bores for cracks using a dye penetrant

inspection and visually inspect for scratches, nicks, or surface

discontinuities in accordance with paragraph 5.3 of SDB 0077,

Revision B, dated November 16, 1992.

(d) If neither a crack nor any scratches, nicks, or surface

discontinuities are found that exceed the tolerances specified in

paragraph 5.3.4 and 5.3.5 of SDB 0077, Revision B, dated November

16, 1992, during the inspections required by paragraphs (a), (b), or

(c) of this AD, return the helicopter to service in accordance with

the procedures contained in paragraph 5.3.5 of the SDB 0077,

Revision B, dated November 16, 1992, and the applicable maintenance

manual.

(e) If a crack is found, or scratches, nicks, or surface

discontinuities are found that exceed the tolerances specified in

paragraph 5.3.4 and 5.3.5 of SDB 0077, Revision B, dated November

16, 1992, remove the spindle before further flight and install an

airworthy spindle in accordance with the provisions of the

appropriate maintenance manual.

(f) Within the next 100 hours' TIS or, on or before reaching

1,200 hours' TIS, whichever occurs later, remove spindle, P/N 28-

150064-11 or 28-150064-13, from service and replace it with an

airworthy spindle in accordance with the appropriate maintenance

manual.

(g) Installation of a spindle, P/N 28-150074-11, constitutes

terminating action for the requirements of this AD.

(h) 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.

(i) Except for the inspection required by paragraphs (a) and (b)

of this AD, 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 other requirements of this AD can be accomplished.

(j) The inspections shall be done in accordance with The Enstrom

Helicopter Corporation Service Directive Bulletin No. 0077, Revision

B, 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 Boulevard, Room

663, Fort Worth, Texas; or at the Office of the Federal Register,

800 North Capitol Street, NW., suite 700, Washington, DC.

(k) This amendment becomes effective on August 12, 1994.

Issued in Fort Worth, Texas, on June 14, 1994.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 94-17867 Filed 7-27-94; 8:45 am]

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