AD 95-10-08 ACTIVE

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.

Final rule; request for comments

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, theowner/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 thereafterat 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 usedwhen 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.

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 componentfailure. 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 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 sufficientfederalism 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 tome 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 to read as follows:

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.

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.