AD 99-07-18 ACTIVE

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 99-07-18 which was sent previously to all known U.S. owners and operators of Robinson Helicopter Company (RHC) Model R44 helicopters by individual letters. This AD requires, before further flight, inserting a Special Pilot Caution into the Normal Procedures section of the Rotorcraft Flight Manual (RFM). This amendment is prompted by several reports of sprag clutch assemblies with cracked or fractured sprag ends. The sprag clutch failures, determined to be due to a change in the manufacturing process, could result in loss of main rotor revolutions-per-minute (RPM) during autorotations. The intent of this AD is to alert pilots of the potential for the sprag clutch failing to overrun during autorotation, loss of main rotor RPM, and subsequent loss of control of the helicopter.

Final rule; request for comments

99-07-18 ROBINSON HELICOPTER COMPANY: Amendment 39-11127. Docket No. 99-SW-25-AD.

Applicability: Model R44 helicopters, serial numbers (S/N) 0001 through 0541, 0543, 0556, and 0565, with sprag clutch, part number (P/N) C188-3, S/N's 0003 through 0452, installed, certificated in any category.

NOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise 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 request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the requestshould include specific proposed actions to address it.

Compliance: Required before further flight, unless accomplished previously.

To alert pilots of the potential for the sprag clutch failing to overrun during autorotation due to failure of the sprags within the sprag clutch assembly, and loss of main rotor revolutions-per-minute, accomplish the following:

(a) Insert either the Special Pilot Caution, revised March 22, 1999, which is contained in Robinson Helicopter Company R44 Service Bulletin SB-32, dated March 22, 1999, or the following Special Pilot Caution paragraphs, into the Normal Procedures section of the Rotorcraft Flight Manual, between pages P.4-8 and P.4-9:

SPECIAL PILOT CAUTION

Some sprags in overrunning clutches have been found cracked in service. A broken sprag could conceivably prevent the clutch from overrunning when entering autorotation. Until the clutch in this aircraft has been replaced, do not enter practice autorotations by rapidlyclosing or "chopping" the throttle. "Chopping" the throttle could result in a sudden loss of rotor RPM if the clutch failed to disengage.

Enter autorotation by first lowering collective and then rolling off just enough throttle to produce a small visible split between the rotor and engine tachometer needles. If the clutch fails to disengage, immediately complete a power recovery. Perform hovering autos only after checking the function of the overrunning sprag clutch prior to lift-off, then smoothly rolling off the throttle from a low hover with the skids no more than two feet above the ground.

Be sure to perform the sprag clutch check (split tach needles) before every flight, not just the first flight of the day.

(b) 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 a FAAPrincipal Maintenance Inspector, who may concur or comment and then 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.

(c) 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.

(d) This amendment becomes effective on April 28, 1999 to all persons except those persons to whom it was made immediately effective by Priority Letter AD 99-07-18, issued March 26, 1999, which contained the requirements of this amendment.

On March 26, 1999, the FAA issued Priority Letter AD 99-07-18, applicable to RHC Model R44 helicopters, which requires, before further flight, inserting a Special Pilot Caution into the Normal Procedures section of the RFM. That action was prompted by several reports of sprag clutch assemblies, including one from wreckage of an accident that occurred within the past year, with cracked or fractured sprag ends. The sprag clutch failures, determined to be due to a change in the manufacturing process, could result in loss of main rotor RPM during autorotations. The intent of that priority letter AD is to alert pilots of the potential for the sprag clutch failing to overrun during autorotation, loss of main rotor RPM, and subsequent loss of control of the helicopter.

The FAA has reviewed Robinson Helicopter Company R44 Service Bulletin SB-32, dated March 22, 1999, which describes procedures for checking whether sprag clutches with certain serial numbers are installed and replacing certain serial numbered sprag clutches, and inserting a Special Pilot Caution in the Normal Procedures section of the RFM.

Since the unsafe condition described is likely to exist or develop on other RHC Model R44 helicopters of the same type design, the FAA issued Priority Letter AD 99-07-18 to alert pilots of the potential for the sprag clutch failing to overrun during autorotation due to the failure of the sprags within the sprag clutch assembly and loss of main rotor RPM. The AD requires, before further flight, inserting a Special Pilot Caution into the Normal Procedures section of the RFM which primarily addresses autorotation maneuvers and a before every flight sprag clutch (split tach needles) check for proper function of the sprag clutch. Inserting the Special Pilot Caution is an interim action. The FAA will issue an AD to supersede this AD and require replacing the clutch assembly when parts become available from the manufacturer. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity of the helicopter. Therefore, inserting a Special Pilot Caution into the Normal Procedures section of the RFM is required before further flight, and this AD must be issued immediately.

Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on March 26, 1999, to all known U.S. owners and operators of RHC Model R44 helicopters. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective to all persons.

The FAA estimates that 200 helicopters of U.S. registry will be affected by this AD, that it will take approximately 0.5 work hour per helicopter to insert the caution into the RFM, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $6,000.

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 helpfulin 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. 99-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 locationprovided 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 U.S.C. 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 Regional
Counsel, Southwest Region, Attention: Rules Docket No. 99-SW-25-AD, 2601 Meacham Blvd., Room 663, Fort Worth,
Texas 76137.

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.