AD 97-25-09

This amendment adopts a new airworthiness directive (AD) that is applicable to Allison Engine Company Model 250-C40B turboshaft engines. This action requires installation of a placard requiring pilots to record torque level and time in service operating above 86% engine torque until the defective parts have been replaced, no later than December 31, 2000, or when certain maintenance actions are accomplished, or when certain operational restrictions are exceeded, whichever occurs earliest. This amendment is prompted by a report from Allison Engine Company of a manufacturing defect in certain helical power takeoff gearshaft assemblies, identified by serial numbers. The actions specified in this AD are intended to prevent fatigue failure of the helical power takeoff gearshaft assembly, which could result in a loss of engine power and inflight engine shutdown.

Final rule; request for comments.

97-25-09 Allison Engine Company: Amendment 39-10233. Docket 97-ANE-31-AD.
Applicability: Allison Engine Company Model 250-C40B turboshaft engines, with engines, gearboxes, and gears identified by serial number (S/N) in Allison Alert Commercial Engine Bulletin (CEB) No. A-72-5009, dated May 21, 1997. The 250-C40B engine is installed on and limited to the twin-engine Bell Helicopter Textron 430 series helicopters.
Note 1: This airworthiness directive (AD) applies to each engine 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 engines 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 (g) 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 as indicated, unless accomplished previously.
To prevent fatigue failure of the helical power takeoff gearshaft assembly, which could result in a loss of engine power and inflight engine shutdown, accomplish the following for part number (P/N) 23056617, identified by S/N in Allison Alert CEB No. A-72-5009, dated May 21, 1997:
(a) Prior to further flight, install the following placard on the instrument panel in clear view of the pilot, "RECORD TORQUE AND TIME ABOVE 86% ENGINE TORQUE." The placard shall be manufactured of a material that cannot be easily defaced or erased, and the lettering shall be block-style and at least 1/8 inches in height. Additionally, the color and lettering must contrast with the background (color of placard material) such that it is legible.
(b)Remove from service affected helical power takeoff gearshaft assemblies, P/N 23056617, and replace with serviceable parts, in accordance with Allison Alert CEB No. A-72-5009, dated May 21, 1997, when the first of the following conditions exists:
(1) At the time of turbine overhaul; or
(2) During gearbox disassembly for any reason; or
(3) If any of the operational restrictions listed in paragraph (c) of this AD are exceeded; or
(4) No later than December 31, 2000.
(c) After the effective date of this AD, observe the following operational restrictions at all times, until paragraph (b) of this AD is complied with by installing serviceable helical power takeoff gearshaft assemblies:
(1) Total operational time accumulated on the suspect helical power takeoff gearshaft assemblies may not exceed 1,750 hours time in service (TIS). Engines are to be operated in the torque sharing mode only.
(2) Operation of the engine at power between 86% torque and 93% torque is limited to one hour prior to reaching 1,750 hours TIS.
(3) Operation of the engine above 93% torque will require replacement of the helical power takeoff gearshaft assemblies. Any previously recorded time (Electronic Control Unit (ECU), Integrated Instrument Display System (IIDS) or Log Book) must be accounted for. Operators will be allowed four hours of operation at torque levels less than 86% torque to ferry the aircraft to a maintenance facility for replacement of the assembly unless any of the following have been exceeded:
(i) Operation of the engine between 93% torque and 105% torque for more than six minutes requires replacement of the assembly before further flight.
(ii) Operation of the engine between 105% torque and 110% torque for more than ninety seconds requires replacement of the assembly before further flight.
(d) Revise the limitations section of the FAA-approved Rotorcraft Flight Manual (RFM) by inserting a copy of this AD. Thereafter, except as provided in paragraph (g) of this AD, no alternative limitations may be approved for affected helical power takeoff gearshaft assemblies, P/N 23056617.
(e) After replacing parts in accordance with paragraph (b) of this AD, remove the placard and the AD required by paragraphs (a) and (d) of this AD.
(f) For the purposes of this AD, a serviceable helical power takeoff gearshaft assembly is one not identified by S/N in Allison Alert CEB No. A-72-5009, dated May 21, 1997.
(g) 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, Chicago Aircraft Certification Office. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Chicago Aircraft Certification Office.
Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, ifany, may be obtained from the Chicago Aircraft Certification Office.
(h) 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) and paragraph (c)(3) of this AD to operate the aircraft to a location where the requirements of this AD can be accomplished.
(i) The actions required by this AD shall be done in accordance with the following Allison Alert CEB:

Document No.
Pages
Date
A-72-5009
1-5
May 21, 1997
Total pages: 5.

This incorporation 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 Allison Engine Company, P.O. Box 420, Speed Code U-15, Indianapolis, IN 46206-0420; telephone: (317) 230-6674. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(j) This amendment becomes effective on December 23, 1997.

The Federal Aviation Administration (FAA) received a report from Allison Engine Company of a manufacturing defect discovered in certain helical power takeoff gearshaft assemblies, part number (P/N) 23056617, installed on Model 250-C40B turboshaft engines. The manufacturing defect was discovered while measuring the depth of the case hardening of the gear. The manufacturing defect was caused by excessive removal of case hardened material from the gear during manufacturing. This condition, if not corrected, could result in fatigue failure of the helical power takeoff gearshaft assembly, which could result in a loss of engine power and inflight engine shutdown.
The FAA has reviewed and approved the technical contents of Allison Alert Commercial Engine Bulletin (CEB) No. A-72-5009, dated May 21, 1997, that lists by serial number (S/N) 49 affected engines, gearboxes, and gears. This CEB also describes procedures for replacement of affected helical power takeoff gearshaft assemblies with serviceable parts.
Since an unsafe condition has been identified that is likely to exist or develop on other engines of the same type design, this AD is being issued to prevent a loss of engine power and inflight engine shutdown. This AD requires installation of a placard requiring pilots to record torque and time in service operating above 86% engine torque until replacement of defective helical power takeoff gearshaft assemblies with serviceable parts, and then the placard can be removed. The compliance times were determined based upon an analysis of the effect of gearbox assembly torque loading on component life. The actions are required to be accomplished in accordance with the CEB described previously.
The operational limitations imposed by this AD have been coordinated with the Rotorcraft Directorate.
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior publiccomment 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-ANE-31-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 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. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: