AD 96-06-03

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.

Final rule

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 flightof 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 roughnessare 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; Enstrom 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.

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 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.

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: