On April 5, 1999, the FAA issued AD 99-07-18, Amendment 39-11127 (64 FR 17964, April 13, 1999), to require inserting a Special Pilot Caution into the Rotorcraft Flight Manual (RFM) to alert pilots of the potential for the sprag clutch failing to overrun during autorotation maneuvers. The Special Pilot Caution was an interim measure until permanent corrective action was developed by the manufacturer. The FAA now believes that the affected sprag clutches need to be replaced within 30 days or 50 hours time-in-service (TIS), whichever occurs first. Since the sprag clutch is such a critical component of the rotor drive system, this AD requires replacing sprag clutch part number (P/N) C188-3, S/N 0003 through 0505, inclusive, with sprag clutch, P/N C188-3, S/N 0506 and higher. This amendment is prompted by several reports of clutch assemblies, including one from wreckage of an accident, with cracked or fractured sprag ends. The actions specified by this ADare intended to prevent a sprag clutch failure, loss of main rotor RPM during autorotation, and subsequent loss of control of the helicopter.
The FAA has reviewed RHC Service Bulletin SB-36, dated November 5, 1999, which describes replacing the sprag clutch, P/N C188-3, S/N 0453 through 0505, inclusive, with sprag clutch, P/N C188-3, S/N 0506 and subsequent. RHC Service Bulletin SB-32, dated March 22, 1999, affected this same P/N, S/N 0003 through 0452.
Since an unsafe condition has been identified that is likely to exist or develop on other Robinson R44 helicopters of the same type design, this AD is being issued to prevent a sprag clutch failure, loss of main rotor RPM during autorotation, and subsequent loss of control of the helicopter. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the controllability of the helicopter after an actual engine failure. Therefore, replacing sprag clutch, P/NC188-3, S/N 0003 through 0505, inclusive, with sprag clutch, P/N C188-3, S/N 0506 and higher, is required within 30 calendar days or 50 hours TIS after the effective date of this AD, whichever occurs first, and this AD must be issued immediately.
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.
The FAA estimates that 200 helicopters will be affected by this proposed AD, that it will take approximately 4 work hours to replace a sprag clutch, and that the average labor rate is $60 per work hour. Required parts will cost approximately $3,600 per helicopter. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $768,000.
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 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 theclosing 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-70-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, it is determined that this final rule does not have federalism implications under Executive Order 13132.
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, 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 (AD), to read as follows: