[Federal Register Volume 60, Number 91 (Thursday, May 11, 1995)]
[Rules and Regulations]
[Pages 25124-25125]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-11540]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-SW-03-AD; Amendment 39-9225; AD 95-10-08]


Airworthiness Directives; Bell Helicopter Textron, Inc.-
Manufactured Restricted Category Model UH-1A, UH-1B, UH-1E, UH-1F, UH-
1H, UH-1L, UH-1P, TH-1F, and TH-1L 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) that 
is applicable to Bell Helicopter Textron, Inc. (BHTI)-manufactured 
restricted category Model UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-
1P, TH-1F, and TH-1L helicopters. This action requires verification 
that the tail rotor control system is rigged in accordance with the 
applicable maintenance manual; a fluorescent penetrant inspection for 
cracks at the roots of the gear teeth on the pinion and gear of 
affected 42-degree tail rotor drive gearbox assemblies (42-degree 
gearboxes), and replacement of the 42-degree gearbox pinion or gear if 
cracks are found; and, creation of a component history card to track 
numbers of torque events. A torque event is defined as a takeoff or a 
lift (internal or external). This amendment is prompted by 14 accidents 
reported since 1979 in the United States and Canada related to failure 
of the 42-degree gearbox. The actions specified in this AD are intended 
to prevent failure of the 42-degree gearbox, loss of tail rotor 
control, and subsequent loss of control of the helicopter.

DATES: Effective May 26, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before July 10, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Assistant Chief Counsel, Attention: 
Rules Docket No. 95-SW-03-AD, 2601 Meacham Blvd., Room 663, Fort Worth, 
Texas 76137.

FOR FURTHER INFORMATION CONTACT: Mr. Uday Garadi, Aerospace Engineer, 
FAA, Rotorcraft Directorate, Rotorcraft Certification Office, 2601 
Meacham Blvd., Fort Worth, Texas 76137, telephone (817) 222-5157, fax 
(817) 222-5959.

SUPPLEMENTARY INFORMATION: This amendment adopts a new AD that is 
applicable to BHTI-manufactured restricted category Model UH-1A, UH-1B, 
UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, TH-1F, and TH-1L helicopters. There 
have been 14 accidents reported since 1979 in the United States and 
Canada, with the most recent accident occurring on August 31, 1994, 
related to failure of the 42-degree gearbox. In operation, these 
helicopters endure many more torque events than were originally 
anticipated during the certification and fatigue-life substantiation 
processes. This was confirmed by BHTI after bench test results 
indicated that gear life is reduced when the helicopter is subjected to 
repeated torque events. Obviously, operations at power and load levels 
outside the gross weight and/or external cargo hook weight limits 
specified in the flight manual (i.e., operations at power and load 
levels in excess of those allowed by the operating limitations) will 
accelerate drivetrain and/or structural component failure. The National 
Transportation Safety Board (NTSB) has investigated these accidents and 
issued a recommendation that operators should not exceed the 
limitations stated in the rotorcraft flight manual. Obviously, the FAA 
concurs with this recommendation. The 42-degree gearbox is an integral 
part of the tail rotor drivetrain. Failure of the 42-degree gearbox 
could lead to a complete loss of directional control. Due to the 
criticality of the drivetrain and structural components in maintaining 
control of the helicopter, and the short compliance time required, this 
AD is being issued immediately to correct an unsafe condition. This 
condition, if not corrected, could result in failure of the 42-degree 
gearbox, loss of tail rotor control, and subsequent loss of control of 
the helicopter.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other BHTI-manufactured restricted category Model 
UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, TH-1F, and TH-1L 
helicopters of the same type design, this AD is being issued to prevent 
failure of the 42-degree gearbox, loss of tail rotor control, and 
subsequent loss of control of the helicopter. This AD requires, before 
further flight, and thereafter, at intervals not to exceed 400 torque 
events, disassembly of the affected 42-degree gearbox, part number (P/
N) 204-040-003-023 or -037, a fluorescent penetrant inspection for 
cracks at the roots of the gear teeth on the pinion, P/N 204-040-500-
007 or -009, and gear, P/N 204-040-500-008 or -010, and replacement of 
any unairworthy pinions or gears as necessary. This AD also requires 
creation of a component history card to track the number of torque 
events.
    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 
[[Page 25125]] 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 No. 95-SW-03-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.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive 
to read as follows:

95-10-08 CALIFORNIA DEPARTMENT OF FORESTRY; ERICKSON AIR-CRANE CO.; 
GARLICK HELICOPTERS; HAWKINS AND POWERS AVIATION, INC.; 
INTERNATIONAL HELICOPTERS, INC.; SMITH HELICOPTERS; SOUTHWEST 
FLORIDA AVIATION; WEST COAST FABRICATIONS; WESTERN INTERNATIONAL 
AVIATION, INC.; WILLIAMS HELICOPTER TECHNOLOGY, INC.; AND, UNC 
HELICOPTERS: Amendment 39-9225. Docket No. 95-SW-03-AD.

    Applicability: Model UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, 
UH-1P, TH-1F, and TH-1L helicopters, with a 42-degree tail rotor 
drive gearbox assembly (42-degree gearbox), part number (P/N) 204-
040-003-023, or -037, installed, certificated in the restricted 
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 (e) 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 this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any helicopter from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the 42-degree gearbox, loss of tail rotor 
control, and subsequent loss of control of the helicopter, 
accomplish the following:
    (a) Before further flight, after the effective date of this AD, 
verify that the tail rotor control system is rigged in accordance 
with the applicable maintenance manual.
    (b) Before further flight, and thereafter at intervals not to 
exceed 400 torque events, disassemble the affected 42-degree gearbox 
and inspect for cracks at the roots of the gear teeth on the pinion, 
P/N 204-040-500-007 or -009, and gear, P/N 204-040-500-008 or -010, 
using a fluorescent penetrant inspection method in accordance with 
the applicable maintenance manual. Only post emulsified fluorescent 
penetrant inspection materials (Type I, Method B or D, Sensitivity 
Level 3 or greater) are approved for use. A torque event is defined 
as a takeoff or a lift (internal or external).
    (c) If any crack is found at the roots of the gear teeth on the 
pinion or gear, replace the pinion or gear with an airworthy pinion 
or gear in accordance with the applicable maintenance manual.
    (d) Create a component history card for the 42-degree gearbox. 
Record the number of torque events on a daily basis.
    (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, 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.

    (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 May 26, 1995.

    Issued in Fort Worth, Texas, on May 4, 1995.
Mark R. Schilling,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 95-11540 Filed 5-10-95; 8:45 am]
BILLING CODE 4910-13-P