AD 97-16-02 ACTIVE

This amendment adopts a new airworthiness directive (AD) that is applicable to Robinson Helicopter Company (Robinson) Model R44 helicopters. This action requires inspections of the belt tension actuator switches (up-limit switches) for proper operation, and replacement if necessary; and replacement of a certain part-numbered clutch assembly. This amendment is prompted by six occurrences of prematurely worn sprag clutches. The actions specified in this AD are intended to prevent failure of the sprag clutch to lock in the driving direction, which would result in loss of power to the main rotor system and a subsequent forced landing; or failure of the sprag clutch to unlock in the overrunning direction, which, if combined with engine failure, would result in an inability to autorotate and a subsequent loss of control of the helicopter.

Final rule; request for comments

97-16-02 ROBINSON HELICOPTER COMPANY: Amendment 39-10092. Docket No. 97-SW- 19-AD.

Applicability: Model R44 helicopters, serial numbers 0001 through 0332, 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 (d) 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 sprag clutch to lock in the driving direction, which would result in loss of power to the main rotor system and a subsequent forced landing; or failure of the sprag clutch to unlock in the overrunning direction, which, if combined with engine failure, would result in an inability to autorotate and a subsequent loss of control of the helicopter, accomplish the following:

(a) Within 25 hours time-in-service (TIS) after the effective date of this AD, and thereafter, at intervals not to exceed 100 hours TIS, inspect both up-limit switches, part number (P/N) V3-1001, for proper operation in accordance with the Compliance Procedure in Robinson Helicopter Company R44 Service Bulletin SB-21, dated April 18, 1997. If the motor runs when the springs are depressed on one side, the switch on the OPPOSITE side is not functioning properly.

(b) If the inspections required by paragraph (a) of this AD indicate that either up-limit switch does not function properly, replace the up-limit switch with an airworthy up-limit switch in accordance with the Compliance Procedure contained in Robinson Helicopter Company R44 Service Bulletin SB-21, dated April 18, 1997.

(c) Within 50 hours TIS after the effective date of this AD, replace the clutch assembly, P/N C018-1, with a clutch assembly, P/N C018-2 or P/N C018-2A, in accordance with the Compliance Procedure contained in Robinson Helicopter Company R44 Service Bulletin SB-23, dated May 30, 1997.

(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Los Angeles Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment andthen send it to the Manager, Los Angeles Aircraft Certification Office.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles Aircraft Certification Office.

(e) 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.

(f) The inspections and replacements, if necessary, shall be done in accordance with Robinson Helicopter Company R44 Service Bulletin SB-21, dated April 18, 1997, and Robinson Helicopter Company R44 Service Bulletin SB-23, dated May 30, 1997. 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 Robinson Helicopter Company, 2901 Airport Drive, Torrance, California 90505, telephone (310) 539-0508, fax (310) 539-5198. Copies may be inspected at the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(g) This amendment becomes effective on August 18, 1997.

This amendment adopts a new Airworthiness Directive (AD), which is applicable to Robinson Model R44 helicopters and requires, within 25 hours time-in- service (TIS) after the effective date of this AD and thereafter at intervals not to exceed 100 hours TIS, an inspection of both up-limit switches, part number (P/N) V3-1001, for proper operation, and replacement of either switch, if necessary. Additionally, this AD requires, within 50 hours TIS after the effective date of this AD, replacement of the clutch assembly, P/N C018-1, with clutch assembly, P/N C018-2 or P/N C018-2A. This AD is prompted by six occurrences of prematurely worn sprag clutches. Five of those clutch assemblies' hours TIS ranged from 286.3 to 828.6 hours TIS. All of the clutch assemblies were making noise during the landings and/or shutdowns. One clutch assembly would not allow the main rotor to disengage from the engine during a practice autorotation. Excessive wear of the sprag crowns and chattering of the sprag races causes erratic operation of the clutch by preventing the sprags from rolling into or releasing from the locked position. A latent failure of one up-limit switch can exist undetected, eliminating the redundancy of the system. A failure of both up-limit switches while in the closed position will result in over- tensioning of the drive belts. The actions specified in this AD are intended to prevent failure of the sprag clutch to lock in the driving direction, which would result in loss of power to the main rotor system and a subsequent forced landing; or failure of the sprag clutch to unlock in the overrunning direction, which, if combined with engine failure, would result in an inability to autorotate and a subsequent loss of control of the helicopter.

The FAA has reviewed Robinson Helicopter Company R44 Service Bulletin SB-21, dated April 18, 1997, which describes procedures for removing the aft engine cowling and inspecting to verify that both up-limit switches function properly. If either up-limit switch does not function properly, the service bulletin refers the reader to the replacement procedures in the maintenance manual. The FAA has also reviewed Robinson Helicopter Company R44 Service Bulletin SB-23, dated May 30, 1997, which describes or refers to the appropriate procedures for replacing clutch assembly, P/N C018-1. The compliance times of this AD differ from those stated in the service bulletins. Robinson Helicopter Company R44 Service Bulletin SB-21 describes a one-time inspection within the next 10 hours TIS, or by April 30, 1997, whichever occurs first; this AD requires an initial inspection within 25 hours TIS after the effective date of this AD, and thereafter, repetitive inspections at intervals not to exceed 100 hours TIS. Robinson Helicopter Company R44 Service Bulletin SB-23 describes replacing the clutch assembly within the next 100 hours TIS, or by September 30, 1997, whichever occurs first;this AD requires replacing the clutch assembly within 50 hours TIS after the effective date of this AD, since the only indication of excessive sprag clutch wear is hard or rough engagement of the clutch, which may be difficult for a pilot to detect. The failure of the clutch assembly to allow the main rotor system to disengage from the engine in the event of an engine failure creates a significant unsafe condition in that this condition would result in an inability to autorotate.

Since an unsafe condition has been identified that is likely to exist or develop on other Robinson Model R44 helicopters of the same type design, this AD is being issued to prevent failure of the sprag clutch to lock in the driving direction, which will result in loss of power to the main rotor and a subsequent forced landing; or failure of the sprag clutch to unlock in the overrunning direction, which, if combined with engine failure, could result in catastrophic loss of the helicopter since the main rotor cannot be disengaged from the engine for autorotation.

This AD requires both initial and repetitive inspections of the up-limit switches, P/N V3-1001, to determine that they are functioning properly, and replacement of either up-limit switch, if necessary; and replacement of the clutch assembly, P/N C018-1 with clutch assembly, P/N C018-2 or P/N C018-2A. The actions are required to be accomplished in accordance with the compliance procedures contained in the service bulletins described previously.

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 rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 97-SW-19-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 USC 106(g), 40113, 44701.

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. 97-SW-19-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.
The service information referenced in this AD may be obtained from Robinson Helicopter Company, 2901 Airport Drive, Torrance, California 90505, telephone (310) 539-0508, fax (310) 539-5198. This information may be examined at the FAA, Office of the Assistant Chief Counsel, 2601Meacham Blvd., Room 663, Fort Worth, Texas 76137; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Ms. Elizabeth Bumann, Aerospace Engineer, FAA, Los Angeles Aircraft Certification Office, Propulsion Branch, 3960 Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5265, fax (562) 627-5210.