AD 95-06-07

This amendment supersedes an existing airworthiness directive (AD), applicable to Robinson Helicopter Company (RHC) Model R22 helicopters, that currently requires an initial dye penetrant inspection of the main rotor drive forward flexplate (flexplate), and repetitive visual inspections of certain installed flexplates. This amendment is prompted by three accidents reported by the airworthiness authority of Australia involving failure of the flexplate, located between the main rotor gearbox and clutch assembly. The actions specified by this AD are intended to prevent failure of the flexplate, failure of the main rotor drive system, and subsequent loss of control of the helicopter.

Final rule; request for comments.

95-06-07 ROBINSON HELICOPTER COMPANY: Amendment 39-9177. Docket Number 94-SW-22-AD. Supersedes Priority Letter AD 94-11-01, issued May 18, 1994.

Applicability: Model R22 helicopters, with forward flexplate (flexplate), part number (P/N) A947-1 with bonded washers, or P/N A193-1 without bonded washers, installed, certificated in any category. Flexplate, P/N A947-1E and subsequent FAA-approved revisions to P/N A947-1, is exempt from the requirements of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the flexplate, failure of the main rotor drive, and subsequent loss of control of the helicopter, accomplish the following:

(a) Within the next 25 hours time-in-service (TIS) after the effective date of this airworthiness directive (AD), accomplish the following:

(1) With the clutch disengaged, support the forward end of the clutch shaft, P/N A166-1, remove the flexplate, and record the shim locations for useduring reinstallation.

(i) Replace any flexplate that does not have eight bonded washers (two per arm) with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1.

(ii) For those flexplates that have eight bonded washers (two per arm), comply with the following:

(2) Remove all coating down to bare metal from the outer edges of the flexplate to approximately 0.125 inches inward, but in no case within 0.50 inches of the bonded washers, using Scotch Brite or 600 grit sand paper. Do not use a chemical paint stripper since it may adversely affect the adhesive that bonds the washers to the flexplate.

(3) Inspect the outer edges of the flexplate for cracks, avoiding the bonded washers, using a dye penetrant inspection method in accordance with Appendix I of this AD. If the dye penetrant contacts the bonded washers, remove the solution from the bonded washers within 1 minute since longer exposure may adversely affect the adhesive.(i) If a crack is found, replace the flexplate with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1.

(ii) If no crack is found, paint the bare edge area of the flexplate with an even coat of zinc-chromate or epoxy primer. Do not paint the bare metal surface of the bonded washers.

(4) Reinstall the flexplate and ensure sheave and clutch shaft angle are properly aligned in accordance with the applicable maintenance manual.

(b) For those helicopters with flexplates that have less than 2 years or 450 hours TIS, accomplish the following prior to or upon reaching 2 years or 500 hours TIS, and thereafter at intervals not to exceed 50 hours TIS from the last inspection; for those helicopters with flexplates that have 2 years or more or 450 hours or more TIS, accomplish the following at intervals not to exceed 50 hours TIS from the last inspection. (If the flexplate TIS cannot be determined through a review of the maintenance records, then use the helicopter TIS as the TIS of the flexplate).

(1) Remove the flexplate in accordance with the applicable maintenance manual.

(2) Clean the flexplate using a solvent (e.g., methyl-ethyl ketone or naphtha).

(3) Inspect the flexplate for nicks, cracks, or corrosion using a 10-power or higher magnifying glass, paying close attention to the edges of the flexplate.

(i) If a crack is found, replace the flexplate with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1, in accordance with the applicable maintenance manual.

(ii) If a nick or corrosion is found, repair the flexplate in accordance with the applicable maintenance manual.

(iii) Paint any bare edges of the flexplate with an even coat of zinc-chromate or epoxy primer. Do not paint the bare metal surface of the bonded washers.

(iv) If any nick or corrosion cannot be repaired within the rework limits specified in the applicable maintenance manual, replace the flexplate with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1, in accordance with the applicable maintenance manual.

(4) Reinstall the flexplate and ensure sheave and clutch shaft are properly aligned in accordance with the applicable maintenance manual.

NOTE 1: Robinson Helicopter Company R22 Maintenance Manual, Change 14, dated March 14, 1994, pertains to this AD.

(c) If a crack, nick, or corrosion is found on the flexplate as a result of the inspections required by this AD, report a description of the crack, nick, or corrosion, the total TIS, and the operating conditions to the Manager, Propulsion Branch, Los Angeles Aircraft Certification Office, FAA. Reporting requirements have been approved by the Office of Management and Budget and assigned control number 2120-0056.

(d) Installation of a flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1, constitutes terminating actionfor the requirements of this AD.

(e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when 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 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.

(f) 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.

(g) This amendment becomes effective on April 4, 1995.

APPENDIX I

DYE PENETRANTS
Several dye penetrant typeinspection kits are now available that will reveal the presence of surface cracks or defects and subsurface flaws that extend to the surface of the part being inspected. These penetrant type inspection methods are considered acceptable, provided the part being inspected has been thoroughly cleaned, all areas are readily accessible for viewing, and the manufacturer's recommendations as to the method of application are closely followed.

a. Cleaning. An inspection is initiated by first cleaning the surface to be inspected of dirt, loose scale, oil, and grease. Precleaning may usually be accomplished by vapor degreasing or with volatile cleaners. Use a volatile cleaner as it will evaporate from the defects before applying the penetrant dye. Sand blasting is not as desirable a cleaning method, since surface indications may be obscured. It is not necessary to remove anodic films from parts to be inspected, since the dye readily penetrates such films. Special procedures for removing the excess dye should be followed.

b. Application of Penetrant. The penetrant is applied by brushing, spraying, or by dipping and allowing to stand for a minimum of 2 minutes. Dwell time may be extended up to 15 minutes, depending upon the temperature of the part and fineness of the defect or surface condition. Parts being inspected should be dry and heated to at least 70* F, but not over 130* F. Very small indications require increased penetration periods.

c. Removal of Dye Penetrant. Surplus penetrant is usually removed by application of a special cleaner or remover, or by washing with plain water and allowing the part to dry. Water rinse may also be used in conjunction with the remover, subject to the manufacturer's recommendations.

d. Application of Developer. A light and even coat of developer is applied by spraying, brushing, or dipping. When dipping, avoid excess accumulation. Penetrant that has penetrated into cracks or other openings in the surface of the material will be drawn out by the developer resulting in a bright red indication. Some idea of the size of the defect may be obtained after experience by watching the size and rate of growth of the indication.

On May 18, 1994, the FAA issued Priority Letter AD 94-11-01, applicable to RHC Model R22 helicopters, to require an initial dye penetrant inspection of the flexplate on all RHC Model R22 helicopters, and repetitive visual inspections of flexplates that have been in service for 2 or more years or 500 or more hours time-in-service (TIS). That action was prompted by three accidents reported by the airworthiness authority of Australia involving failure of the flexplate. In one accident, the flexplate fractured during normal cruise flight releasing several fragments, some of which punctured the fuel tank. A metallurgical report issued by the airworthiness authority of Australia suggests that the failures resulted from fatigue cracking that initiated at areas of intergranular pitting corrosion on the edge of the flexplates. The FAA has determined that any crack, nick, or corrosion in the flexplate creates an unsafe condition and should be corrected. That condition, if not corrected, could result in failure of the flexplate, failure of the main rotor drive system, and subsequent loss of control of the helicopter.

Since the issuance of that AD, the FAA has received information indicating that flexplates, part number (P/N) A193-1 without bonded washers, and P/N A947-1 with bonded washers, may have been subjected to paint overspray at Robinson Helicopter Company when they were painting hardware adjacent to the flexplate. Damage to flexplate edges with paint overspray could result in corrosion due to the retention of contaminants under the paint. Robinson Helicopter Company has revised their inspection procedures to ensure that subsequently-produced flexplates are not subject to the paint overspray. This corrective procedure was implemented with the production of flexplate, P/N A947-1E. In addition, flexplate, P/N A947-1E is stronger and more resistant to corrosion damage than the previously-designed flexplates. Therefore, the initialdye penetrant inspection for cracks and repetitive visual inspections for nicks, cracks, or corrosion may be terminated upon installation of this improved flexplate or a subsequent FAA-approved revision to P/N A947-1E.

The reference to the flexplate's TIS in paragraph (b) of the Priority Letter AD has been clarified to require that the repetitive visual inspections in paragraph (d) of the AD be conducted upon reaching 2 years or 500 hours TIS on the flexplate. If the flexplate TIS cannot be determined through a review of the log book, the helicopter TIS must be used to determine the TIS of the flexplate.

Paragraph (c) has been revised to delete the reference to the repetitive visual inspections for flexplates used to replace those that were determined to have cracks as a result of the inspection of paragraph (a) of the Priority Letter AD. This deletion changes the lettering of the subsequent paragraphs. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Since an unsafe condition has been identified that is likely to exist or develop on other Robinson Helicopter Company Model R-22 helicopters of the same type design, this AD supersedes Priority Letter AD 94-11-01, to require a one-time dye penetrant inspection of the flexplate, P/N A193-1 without bonded washers and P/N A947-1 with bonded washers, for cracks within the next 25 hours TIS, and replacement if a crack is found. Additionally, for flexplates that have been in service for 2 or more years or 450 or more hours TIS, repetitive visual inspections of the flexplate for nicks, cracks, or corrosion are required at intervals not to exceed 50 hours TIS. This AD also provides for repair of the flexplate if a nick or corrosion is found, or replacement if a crack is found. The flexplate connects the gearbox and the clutch shaft, and failure of the flexplate could lead to failure of the driveshaft and loss of power to the rotor system. Due to the critical need for the flexplate to ensure the continued safe flight of the affected helicopters, this rule must be issued immediately to correct an unsafe condition in aircraft.

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 Number 94-SW-22-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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [AMENDED]
2. Section 39.13 is amended by adding a new airworthiness directive (AD), Amendment 39-9177, to read as follows: