AD 94-22-09 ACTIVE

This amendment supersedes an existing airworthiness directive (AD), applicable to Bell Helicopter Textron, Inc. restricted category military Model UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and TH-1L helicopters, that currently requires an inspection before the first flight of each day of certain tail rotor drive shafts and the tail rotor drive shaft hanger bearings (bearings) for grease leakage, security, overheat conditions, binding, or roughness until the bearings are replaced. This amendment requires the same inspection of the bearings, but also requires replacement of the affected bearings within the next 100 hours time-in-service and extends the requirements of this AD to the Model UH-1P and TH-1F helicopters that were recently type certificated. This amendment is prompted by an accident involving a bearing failure, and by the certification of two additional affected helicopter models. The actions specified by this AD are intended to prevent failure of the bearing, failure of the tail rotor drive shaft, and subsequent loss of control of the helicopter.

Final rule; request for comments

94-22-09 CALIFORNIA DEPARTMENT OF FORESTRY; GARLICK HELICOPTERS; HAWKINS AND POWERS AVIATION, INC.; HERCULES; INTERNATIONAL HELICOPTERS, INC.; OFFSHORE CONSTRUCTION; OREGON HELICOPTERS; PILOT PERSONNEL INTERNATIONAL, INC.; SMITH HELICOPTERS; SOUTHERN AERO CORPORATION; SOUTHWEST FLORIDA AVIATION; WEST COAST FABRICATIONS; and WESTERN INTERNATIONAL AVIATION INC. : Amendment 39-9058. Docket Number 93-SW-08-AD. Supersedes Priority Letter AD 92-03-14, Docket No. 91-ASW-32.

Applicability: Bell Helicopter Textron, Inc.-manufactured Model UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, TH-1F, and TH-1L helicopters, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of a tail rotor (T/R) drive shaft hanger bearing (bearing), failure of the T/R drive shaft, and subsequent loss of control of the helicopter, accomplish the following:

(a) Before further flight, after the effective date of this AD, determine the serial number (S/N) etched on the seal area of the bearing, part number (P/N) 204-040-623-005. If the bearing has a S/N with a prefix of T or N, accomplish the inspection specified in paragraph (b) until the affected bearing is replaced in accordance with paragraph (d) of this AD.

NOTE: Bearings with a S/N prefix of NC are not required to comply with this AD.

(b) Before the first flight of each day, until the affected bearings are replaced in accordance with paragraph (d) of this AD, accomplish the following inspections of the T/R drive shaft and bearings:

(1) Visually inspect the bearings for grease leakage that continues for more than 10 hours time-in-service after installation of a zero-time bearing.

(2) Visually inspect the T/R drive shaft and the bearings and housing for security and damage.

(3) Visually inspect the bearings for an overheat condition and inspect overheat indicator stripes for discoloration.

(4) Rotate the T/R drive shaft by hand while feeling the bearing housing for bearing binding or roughness.

(c) Before further flight, replace any bearings that exhibit signs of continued grease leakage, overheating, binding, roughness, or are otherwise unairworthy, and secure any insecure bearings and housings in accordance with the applicable maintenance, repair, and overhaul manuals.

(d) Within the next 100 hours time-in-service after the effective date of this AD, remove from further service any bearing, P/N 204-040-623-005, that has a S/N with a prefix of T or N, and replace with a bearing, P/N 204-040-623-005, that has a S/N without a prefix of T or N. Remove and replace the bearings in accordance with the procedures in the applicable Bell Helicopter Textron, Inc. maintenance, repair and overhaul manuals.

(e) Installation of bearings containing a prefix other than T or N constitutes terminating action for the requirements of this AD.

(f) 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: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Certification Office.

(g) 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.(h) This amendment becomes effective on November 22, 1994.

On February 5, 1992, the FAA issued Priority Letter (PL) AD 92-03-14, applicable to Bell Helicopter Textron, Inc. (BHTI)-manufactured Model UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and TH-1L helicopters, to require an inspection before the first flight of each day of certain tail rotor (T/R) drive shafts and T/R drive shaft hanger bearings (bearings) for grease leakage, security, overheat conditions, binding, or roughness until the affected bearings are replaced. That action was prompted by an accident involving a BHTI Model 412 helicopter that experienced a bearing failure. Inspections performed as part of the accident investigation found metal particles from the manufacturing process in the bearings. Contaminated bearings can seize and stop rotating, causing the spline coupling shaft to rotate inside the bearing and overheat. That condition, if not corrected, could result in failure of the bearing, failure of the T/R drive shaft, and subsequent loss ofcontrol of the helicopter.

Since the issuance of that AD, the FAA has determined that the affected bearings need to be replaced within the next 100 hours time-in-service in lieu of continued inspections before the first flight of each day as required by the PL AD. In addition, Type Certificate No. H12NM was issued March 30, 1993, to Western International Aviation, Inc. for Model UH-1F, UH-1P, and TH-1F helicopters that use the same bearings. Therefore, this AD should be applicable to these model helicopters. Also, some editorial changes were made to the AD.

Since an unsafe condition has been identified that is likely to exist or develop on other helicopters of the same type design, this AD supersedes PL AD 92-03-14 to require the same inspection of the affected bearings, but also to require replacement of the affected bearings within the next 100 hours time-in-service. Due to the critical need to ensure the integrity of the bearings that maintain control of the T/R drive shaft through which power is provided to the T/R system, to comply with the requirements of this AD before the first flight of each day, and to start the required inspections on the additionally-affected model helicopters, this rule must be issued immediately to correct an unsafe condition in the affected helicopters.

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 93-SW-08-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 anemergency 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.

39.13 - [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive (AD), Amendment 39-9058, to read as follows:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Assistant Chief Counsel, Attention: Rules Docket No. 93-SW-08-AD, 2601 Meacham Boulevard, Room 663, Fort Worth, Texas 76137.

Mr. Uday Garadi, Aerospace Engineer, Rotorcraft Certification Office, FAA, Rotorcraft Directorate, 2601 Meacham Boulevard, Fort Worth, Texas 76137, telephone (817) 222-5157, fax (817) 222-5959.