AD 98-14-08

98-14-08 ROBINSON HELICOPTER COMPANY: Docket No. 98-SW-30-AD.

Applicability: Model R22 helicopters, with forward 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 thisAD. 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 the 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 2-4threads 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 thisAD, 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) Priority Letter AD 98-14-08, issued June 25, 1998, becomes effective upon receipt.

98-14-08 Robinson Helicopter

This Priority Letter Airworthiness Directive (AD) is prompted by a recent accident in which the forward flexplate (flexplate), part number (P/N) A947-1, failed, causing loss of the main rotor drive and rupture of the fuel tank. Prompted by three similar accidents involving failure of the flexplate, the FAA previously issued priority letter AD 94-11-01 on May 18, 1994, and subsequently issued AD 95-06-07 on March 20, 1995, which required an initial dye-penetrant inspection and repetitive visual inspections of the flexplate at intervals not to exceed 50 hours time-in-service (TIS), after accumulating 500 hours TIS or 2 years service life, whichever occurred first. AD 95-06-07 also exempted flexplate, P/N A947-1 E, and subsequent FAA-approved revisions, from the requirements of that AD, and provided that installation of flexplate, A947-1E or a subsequent FAA-approved revision to that P/N constituted a terminating action for the requirements of that AD.Since the issuance of AD 95-06-07, the FAA has determined that the repetitive inspections required by that AD do not correct the unsafe condition and should be eliminated, and that flexplate, P/N A947-1 A through D, or P/N A193-1, should be replaced with flexplate, P/N A947-1 E or F. 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.

The FAA has reviewed Robinson Helicopter Company R22 Service Bulletin SB-75, dated November 22, 1994, which describes procedures for removing the flexplate, P/N A947-1, Rev A thru D, or P/N A193-1, and replacing it with a flexplate, P/N A947-1, Rev E or later.

Since an unsafe condition has been identified that is likely to exist or develop on other Robinson Model R22 helicopters of the same type design, this AD requires, within 25 hours TIS or 15 calendar days, whichever occurs first, replacing the flexplate, P/N A193-1 or A947-1 A through D, with a flexplate, P/N A947-1 E or F.

This rule is issued under 49 U.S.C. Section 44701 pursuant to the authority delegated to me by the Administrator, and is effective immediately upon receipt of this priority letter.