Airworthiness Directives: McDonnell Douglas Helicopter Company and Hughes Helicopters, Inc. Model 369 and OH-6A Series Helicopters

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-SW-05-AD]

Airworthiness Directives: McDonnell Douglas Helicopter Company

and Hughes Helicopters, Inc. Model 369 and OH-6A Series Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to McDonnell Douglas

Helicopter Company and Hughes Helicopters, Inc. Model 369 and OH-6A

series helicopters equipped with certain main rotor (M/R) blade

assemblies or certain M/R hub lead-lag assemblies, that currently

requires repetitive inspections and checks for cracks. This action

would require the same inspections as the superseded AD, but would

eliminate pilot checks, expand the areas of inspection, and require the

application of slippage marks on each M/R blade root fitting lug and

related bushings to detect movement. This proposal is prompted by

additional reports of cracks in the M/R blade root fittings, lugs, and

adjacent blade skin, and movement of the root fitting bushings. The

actions specified by the proposed AD are intended to prevent failure of

a M/R blade assembly or a M/R hub lead-lag link assembly, loss of a M/R

blade, and subsequent loss of control of the helicopter.

DATES: Comments must be received by September 6, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Rules Docket No. 94-SW-05-AD, 2601 Meacham Blvd., Room 663, Fort Worth,

Texas 76137-4298. Comments may be inspected at this location between

9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal

holidays.

The service information referenced in the proposed rule may be

obtained from McDonnell Douglas Helicopter Company, Technical

Publications, Bldg 530/B111, 5000 E. McDowell Road, Mesa, Arizona

85205-9797. This information may be examined at the FAA, Office of the

Assistant Chief Counsel, 2601 Meacham Blvd., Room 663, Fort Worth,

Texas.

FOR FURTHER INFORMATION CONTACT: Mr. Brent Bandley, Aerospace Engineer,

Airframe Branch, ANM-123L, Northwest Mountain Region, Los Angeles

Aircraft Certification Office, 3229 E. Spring Street, Long Beach,

California 90806-2425, telephone (310) 988-5237, fax (310) 988-5210.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed 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 above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals contained in this notice may be changed in

light of the comments received.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket Number 94-SW-05-AD.'' The postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, Office of the Assistant Chief Counsel, Attention: Rules

Docket No. 94-SW-05-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas

76137-4298.

Discussion

On August 8, 1991, the FAA issued AD 91-17-04, Amendment 39-8003

(56 FR 42230, August 27, 1991), to require initial and repetitive

inspections and checks of certain main rotor (M/R) blade assemblies and

M/R hub lead-lag link assemblies for fatigue cracks and for loose

bushings in the M/R blade lead-lag link lugs (lead-lag lugs). That

action was prompted by two incidents involving a cracked M/R blade root

fitting lug (root fitting lug). Bushing movement in the M/R blade lead-

lag link lugs may have caused fatigue cracks in the lead lag link

assemblies. The lead lag link assembly attaches to the M/R blade. Any

cracks in the lead lag link assembly, the M/R blade, the MR blade root

fitting, or any movement of the bushing, could create an unsafe

condition. That condition, if not corrected, could result in failure of

a M/R blade assembly or a M/R hub lead-lag link assembly, loss of a M/R

blade, and subsequent loss of control of the helicopter.

Since the issuance of that AD, additional incidents of cracks in

the M/R blade root fitting (root fitting), and M/R blade skin have been

reported. Additionally, the manufacturer has discovered that in some M/

R blade assemblies, the M/R blade root fitting bushing (bushing) can

loosen and contribute to fretting-induced fatigue cracking in the root

fitting lug. The root fittings and M/R blade skins are parts of the M/R

blade assembly. Therefore, McDonnell Douglas Helicopter Company issued

a revised Service Information Notice No. HN-211.4, DN-51.6, EN-42.4,

and FN-31.4 (SIN), dated January 27, 1993, that requested operators

mark each root fitting lug and bushing with a slippage mark and

thereafter inspect for slippage on each root fitting lug and bushing.

The revised SIN, dated January 27, 1993, includes the M/R blade

assembly and M/R hub lead-lag link assembly inspections contained in

the preceding versions of the SIN, dated August 5, 1991.

Since an unsafe condition has been identified that is likely to

exist or develop on other products of this same type design, the

proposed AD would supersede AD 91-17-04 to require application of a

slippage mark on each root fitting lug and bushing within 25 hours'

time-in-service (TIS). In addition, this proposal would require, within

25 hours' TIS after the effective date of this AD and thereafter at

intervals not to exceed 100 hours' TIS, that the M/R blade assembly be

removed and that the root fittings, root fitting lugs, lead-lag lugs,

the M/R blade skin, and the doublers adjacent to the root fitting be

inspected for cracks. This AD proposal also requires that the bushings

be inspected for looseness and slippage, and that slippage marks be

applied if not already present. Visual inspections of the exposed M/R

blade skin, root fittings, root fitting lugs, and lead-lag lugs for

cracks and inspection of the bushing slippage marks for movement are

also required at intervals not to exceed 25 hours' TIS. The FAA no

longer allows pilots to perform checks such as those contained in AD

91-17-04, paragraph (b). Therefore, a pilot would not be permitted to

perform any of the proposed inspections in this AD.

The FAA estimates that 1,000 helicopters of U.S. registry would be

affected by this proposed AD, that it would take approximately 22 work

hours per helicopter to accomplish the proposed actions, and that the

average labor rate is $55 per work hour. Based on these figures, the

total cost impact of the proposed AD on U.S. operators is estimated to

be Sec. 1,210,000.

The regulations proposed herein would 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

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

regulation (1) Is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, will not have a significant economic impact,

positive or negative, on a substantial number of small entities under

the criteria of the Regulatory Flexibility Act. A copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend

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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing Amendment 39-8003 (56 FR

42230, August 27, 1991), and by adding a new airworthiness directive

(AD), to read as follows:

Mcdonnell Douglas Helicopter Company and Hughes Helicopters, Inc.:

Docket No. 94-SW-05-AD. Supersedes AD 91-17-04, Amendment 39-8003.

Applicability: Model 369 and OH-6A series helicopters,

certificated in any category, equipped with any of the following

parts: (1) Main rotor blade assembly (blade assembly), part number

(P/N) 369A1100-BSC, -501, -503, -505, -601, or -603; 369D21100-BSC,

-503, -505, -507, -509, -511, -513, or -515; 369D21102-BSC or -501;

or

(2) Main rotor hub lead-lag link assembly (lead-lag link

assembly), P/N 369A1203-BSC, -3, or -11; 369H1203-BSC, -11, -21, or

-31.

Compliance: Required as indicated, unless accomplished

previously.

To prevent the failure of a main rotor blade assembly or a main

rotor hub lead-lag link assembly, loss of a main rotor blade, and

subsequent loss of control of the helicopter, accomplish the

following:

(a) Within 25 hours' time-in-service (TIS) after the effective

date of this AD, and thereafter at intervals not to exceed 100

hours' TIS from the last inspection, remove each blade assembly from

the helicopter and accomplish the following:

(1) Inspect the attachment lugs of the main rotor (M/R) blade

root fittings (root fittings) and the M/R lead-lag links (links) for

cracks and the lug bushings (bushings) for looseness. Conduct the

inspections in accordance with paragraph (b) of Part I of McDonnell

Douglas Helicopter Company Service Information Notice HN-211.4, DN-

51.6, EN-42.4, FN-31.4 (SIN), dated January 27, 1993.

(2) Visually inspect for cracks--

(i) The root fittings around the blade attachment lugs, and

(ii) The M/R blade doubler and blade skin adjacent to the root

fittings.

(3) Mark the root fittings and bushings with slippage marks in

accordance with paragraph (e) of Part I of the SIN, dated January

27, 1993, if the slippage marks are degraded or missing.

(4) Replace any M/R blades or links found to be cracked or to

have loose bushings with airworthy parts before further flight.

(b) Within 25 hours' TIS after compliance with the requirements

of paragraph (a) of this AD, and thereafter at intervals not to

exceed 25 hours' TIS from the last inspection, accomplish the

following without removing the M/R blade:

(1) Visually inspect the root fittings and links for cracks or

loose bushings in accordance with Part II of the SIN, dated January

27, 1993.

(2) Replace any M/R blades or links found to be cracked or to

have loose bushings with airworthy parts before further flight.

(c) 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: 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.

(d) 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.

Issued in Fort Worth, Texas, on June 14, 1994.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 94-17797 Filed 7-20-94; 8:45 am]

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