AD 99-02-02

This amendment supersedes an existing airworthiness directive (AD), applicable to RHC Model R22 helicopters, that currently requires an initial and repetitive inspections of the forward flexplate (flexplate) at specified time intervals. This amendment also supersedes an existing priority letter AD that requires, within 25 hours time-in-service (TIS) or 15 calendar days, whichever occurs first, replacing the flexplate with an airworthy flexplate. This amendment requires the same replacement as the priority letter AD. This amendment is prompted by an accident in which the flexplate failed, causing loss of main rotor drive and rupture of the fuel tank. The actions specified by this AD are intended to prevent failure of the flexplate, which could result in failure of the main rotor drive system and subsequent loss of control of the helicopter.

Final rule; request for comments

99-02-02 ROBINSON HELICOPTER COMPANY: Amendment 39-10991. Docket No. 98-SW-79-AD. Supersedes AD 95-06-07, Amendment 39-9177, Docket No. 94-SW-22-AD and Priority Letter AD 98-14-08, Docket No. 98-SW-30-AD.

Applicability: Model R22 helicopters, with forward flexplate (flexplate), part number (P/N) A947-1, A through D, or P/N A193-1, 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 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 (b) 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 within 25 hours time-in-service (TIS) or 15 calendar days, whichever occurs first, unless accomplished previously.

To prevent failure of the flexplate, which could result in failure of the main rotor drive system and subsequent loss of control of the helicopter, accomplish the following:

(a) Remove the flexplate and replace it with an airworthy flexplate, P/N A947-1 E or F, in accordance with following:

(1) With the clutch disengaged, support the forward end of the clutch shaft, P/N A166-1, and remove the forward flexplate, P/N A947-1 or A193-1, and the intermediate flexplate, P/N A947-2 or P/N A193-2. Record any shim locations for reinstallation.(2) Install a zero TIS forward flexplate, P/N A947-1 E or F, and any shims that were noted. Use washers, P/N AN960-516 or AN960-516L, under the nut so that 2-4 threads are exposed. Torque the fasteners.

(3) Inspect the sheave alignment.

(4) Inspect the clutch shaft, P/N A166-1, angle.

(5) Reinstall the intermediate flexplate and shim.

NOTE 2: Robinson R22 Maintenance Manual, Sections 1.320, 7.230, 7.240, and 7.330 pertain to paragraphs (a)(2), (a)(3), (a)(4), and (a)(5) of this AD, respectively.

NOTE 3: Robinson Helicopter Company R22 Service Bulletin SB-75, dated November 22, 1994, pertains to the subject of this AD.

(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 an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Los Angeles 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 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 February 1, 1999.

The FAA issued priority letter AD 94-11-01 on May 18, 1994 and AD 95-06-07 (60 FR 14619, March 20, 1995) on March 10, 1995. AD 95-06-07 superseded priority letter AD 94-11-01. Both AD's were prompted by three accidents involving failure of the flexplate. Both AD's also required an initial dye-penetrant inspection and repetitive visual inspections of the flexplate at intervals not to exceed 50 hours TIS, after accumulating 500 hours TIS or 2 years service life, whichever occurred first. AD 95-06-07 also exempted flexplate, part number (P/N) A947-1 E, and subsequent FAA-approved revisions, from the requirements of that AD, and provided that installation of flexplate, P/N A947-1 E or a subsequent FAA-approved revision to that P/N, constituted a terminating action for the requirements of that AD.

After the issuance of AD 95-06-07, another accident occurred in which the flexplate, P/N A947-1, failed, causing loss of the main rotor drive and ruptureof the fuel tank. Prompted by that accident, the FAA determined that the repetitive inspections required by AD 95-06-07 did not correct the unsafe condition. Therefore, the FAA issued priority letter AD 98-14-08 on June 25, 1998, which specifies procedures for replacing flexplate, P/N A193-1 or P/N A947-1 A through D, with flexplate, P/N A947-1 E or F. Also, the FAA intended that Priority Letter AD 98-14-08 (Docket 98-SW-33-AD) supersede AD 95-06-07 (Docket 94-SW-22-AD), but did not state that in Priority Letter AD 98-14-08. To eliminate any confusion, this AD supersedes Priority Letter AD 98-14-08 (Docket 98-SW-30-AD), and AD 95-06-07, Amendment 39-9177 (Docket 94-SW-22-AD). This action is intended to prevent failure of the flexplate, which could result in failure of the main rotor drive system and subsequent loss of control of the helicopter.

Since an unsafe condition has been identified that is likely to exist or develop on other RHC Model R22 helicopters of the same type design, this AD supersedes AD 95-06-07 and priority letter AD 98-14-08 to prevent failure of the flexplate, which could result in failure of the main rotor drive system 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. Therefore, replacing the flexplate with an airworthy flexplate is required within 25 hours TIS or 15 calendar days, 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 100 helicopters will be affected by this AD, that it will take approximately 1.5 work hours to replace the flexplate, and that the average laborrate is $60 per work hour. Required parts will cost approximately $536 per helicopter. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $62,600.
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. 98-SW-79-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, 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 removing Amendment 39-9177 (60 FR 14619, March 20, 1995), and by adding a new airworthiness directive (AD), Amendment 39-10991, to read as follows: