AD 94-13-03 ACTIVE

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.

Final rule; request for comments

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.

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 andapproved 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 servicein 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 modifythe 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 implicationsto 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.

39.13 - [AMENDED]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows:

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.

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.