Airworthiness Directives; Robinson Helicopter Company Model R22 Helicopters

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-SW-22-AD; Amendment 39-9177; AD 95-06-07]

Airworthiness Directives; Robinson Helicopter Company Model R22

Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: 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.

DATES: Effective April 4, 1995.

Comments for inclusion in the Rules Docket must be received on or

before May 19, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Office of the Assistant Chief Counsel, Attention:

Rules Docket No. 94-SW-22-AD, 2601 Meacham Boulevard, Room 663, Fort

Worth, Texas 76137-4298.

FOR FURTHER INFORMATION CONTACT: Ms. Elizabeth Bumann, Aerospace

Engineer, Los Angeles Aircraft Certification Office, Propulsion Branch,

FAA, 3960 Paramount Blvd., Lakewood, California 90712, telephone (310)

627-5265, fax (310) 627-5210.

SUPPLEMENTARY INFORMATION: 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

[[Page 14620]] 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 initial dye 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.

[[Page 14621]]

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding a new airworthiness

directive (AD), Amendment 39-9177, to read as follows:

AD 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 use during 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 action

for 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 type inspection 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 deg. F, but not over 130 deg. 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.

Issued in Fort Worth, Texas, on March 10, 1995.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 95-6684 Filed 3-17-95; 8:45 am]

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