Airworthiness Directives; Bell Helicopter Textron, Inc. Model 412, 412EP and 412CF Helicopters

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-SW-55-AD; Amendment 39-11419; AD 99-23-23]

RIN 2120-AA64

Airworthiness Directives; Bell Helicopter Textron, Inc. Model

412, 412EP and 412CF Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD)

applicable to Bell Helicopter Textron, Inc. (BHTI) Model 412, 412EP,

and 412CF helicopters. This action requires inspecting and measuring

the thickness of certain main rotor yoke assemblies. This AD also

requires adding 500 hours time-in-service (TIS) to the total time for

main rotor yoke assemblies that measure below 0.478-inch thickness and

noting the measurement and added TIS on the component history card or

equivalent record. This amendment is prompted by a report of an

emergency landing due to severe main rotor vibration on a BHTI Model

412 helicopter. Subsequent fatigue analysis indicates that the main

rotor yoke assembly (yoke) does not have the anticipated service life

when manufactured below 0.478-inch thickness. The actions specified in

this AD are intended to prevent a fatigue failure of the yoke, loss of

a main rotor blade, and subsequent loss of control of the helicopter.

DATES: Effective December 1, 1999.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of December 1, 1999.

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

before January 18, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Office of the Regional Counsel, Southwest Region,

Attention: Rules Docket No. 99-SW-55-AD, 2601 Meacham Blvd., Room 663,

Fort Worth, Texas 76137.

The service information referenced in this AD may be obtained from

Bell Helicopter Textron, Inc., P.O. Box 482, Fort Worth, Texas 76101,

telephone (817) 280-3391, fax (817) 280-6466. This information may be

examined at the FAA, Office of the Regional Counsel, Southwest Region,

2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137; or at the Office

of the Federal Register, 800 North Capitol Street, NW., suite 700,

Washington, DC.

FOR FURTHER INFORMATION CONTACT: Michael Kohner, FAA, Rotorcraft

Directorate, Rotorcraft Certification Office, 2601 Meacham Blvd., Fort

Worth, Texas 76137, telephone (817) 222-5447, fax (817) 222-5783.

SUPPLEMENTARY INFORMATION: This amendment adopts a new AD applicable to

BHTI Model 412, 412EP, and 412CF helicopters. This action requires

inspecting and measuring each yoke, part number (P/N) 412-010-101-123

or -127, installed on Model 412 and 412EP helicopters, serial numbers

(S/N) 33001 through 33213, 34001 through 34036, and 36001 through

36204; and on Model 412CF helicopters, S/N 46400 through 46499. If a

yoke measures less than 0.478-inch thickness, this AD requires adding

500 hours TIS to the total time for the component and noting the

measurement and the increase in hours TIS on the component history card

or equivalent record. This amendment is prompted by a report of an

emergency landing due to severe main rotor vibration on a BHTI Model

412 helicopter. Subsequent fatigue analysis indicates that a yoke does

not have the anticipated service life when manufactured to less than a

0.478-inch thickness. This condition, if not corrected could result in

a fatigue failure of the yoke, loss of a main rotor blade, and

subsequent loss of control of the helicopter.

The FAA has reviewed BHTI Service Bulletins 412-98-93 and 412CF-98-

5, both dated March 2, 1998 (ASB), which describe procedures for

inspecting and measuring certain yokes and imposing a flight-hour

penalty of 500 hours TIS for yokes measuring less than 0.478-inch

thickness.

Since an unsafe condition has been identified that is likely to

exist or develop on other BHTI Model 412, 412EP, and 412CF helicopters

of the same type design, this AD is being issued to prevent a fatigue

failure of a yoke, loss of a main rotor blade, and subsequent loss of

control of the helicopter. This AD requires inspecting and measuring

each yoke, P/N 412-010-101-123 and -127, for thickness. The AD also

requires noting on the component history card or equivalent record the

thickness measurement and adding 500 hours TIS to the total time of any

yoke that measures under 0.478-inch thickness. The actions are required

to be accomplished in accordance with the applicable ASB described

previously. The short compliance time involved is required because the

previously described critical unsafe condition can adversely affect the

controllability of the helicopter. Therefore, to prevent a fatigue

failure of the yoke, 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 149 helicopters will be affected by this AD,

that it will take approximately 8 work hours to accomplish the

measurement of the yoke thickness and to annotate the history card or

equivalent component record, and that the average labor rate is $60 per

work hour. Based on these figures, the total cost impact of the AD on

U.S. operators is estimated to be $71,520.

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

[[Page 62106]]

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. 99-SW-55.'' 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, Incorporation by

reference, 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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding a new airworthiness directive

to read as follows:

AD 99-23-23 Bell Helicopter Textron, Inc. Amendment 39-11419. Docket

No. 99-SW-55-AD.

Applicability: Model 412 or 412EP helicopters, serial numbers

(S/N) 33001 through 33213, 34001 through 34036, and 36001 through

36204, or Model 412CF helicopter, S/N 46400 through 46499, with main

rotor yoke assembly (yoke), part number 412-010-101-123 or -127,

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

otherwise 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 request approval for an

alternative method of compliance in accordance with paragraph (b) of

this AD. The request should include an assessment of the effect of

the modification, alteration, or repair on the unsafe condition

addressed by this AD; and, if the unsafe condition has not been

eliminated, the request should include specific proposed actions to

address it.

Compliance: Required within 10 hours time-in-service (TIS) for a

yoke with 4,500 or more hours TIS or required within 90 days for a

yoke with less than 4,500 hours TIS but prior to the accumulation of

4,500 hours TIS, unless accomplished previously.

To prevent a fatigue failure of a yoke, loss of a main rotor

blade, and subsequent loss of control of the helicopter, accomplish

the following:

(a) Inspect and measure each yoke in accordance with the

Accomplishment Instructions, paragraphs 1 through 6, of Bell

Helicopter Textron, Inc. (BHTI), Alert Service Bulletin (ASB) 412-

98-93, applicable to the Model 412 and 412EP helicopters, or BHTI

ASB 412CF-98-5, applicable to the Model 412CF helicopters, both

dated March 2, 1998. If any measurement for a yoke is less than

0.478-inch thickness, add 500 hours to the TIS indicated on the

component history card or equivalent record.

(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, Rotorcraft Certification Office,

FAA, Rotorcraft Directorate. Operators shall submit their requests

through an FAA Principal Maintenance Inspector, who may concur or

comment and then send it to the Manager, Rotorcraft Certification

Office.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Rotorcraft Certification Office.

(c) Special flight permits may be issued in accordance with

Secs. 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) The inspection shall be done in accordance with Bell

Helicopter Textron, Inc. Alert Service Bulletins 412-98-93 or 412CF-

98-5, both dated March 2, 1998, as applicable. This incorportion by

reference was approved by the Director of the Federal Register in

accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be

obtained from Bell Helicopter Textron, Inc., P.O. Box 482, Fort

Worth, Texas 76101, telephone (817) 280-3391, fax (817) 280-6466.

Copies may be inspected at the FAA, Office of the Regional Counsel,

Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas;

or at the Office of the Federal Register, 800 North Capitol Street,

NW., suite 700, Washington, DC.

(e) This amendment becomes effective on December 1, 1999.

Issued in Fort Worth, Texas, on November 4, 1999.

Henry A. Armstrong,

Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 99-29612 Filed 11-15-99; 8:45 am]

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