AD 98-10-03

This amendment supersedes an existing airworthiness directive (AD) 97-21-09, applicable to Allison Engine Company Model 250-C47B turboshaft engines, that currently requires replacing the engine main electrical harness assembly with an improved assembly, installing a new hydromechanical unit (HMU) and electronic control unit (ECU), removing the placard notifying the pilot that the overspeed protection system is disabled, and revising the Bell Helicopter Textron, A Division of Textron Canada Ltd. (BHTC), Model 407 Rotorcraft Flight Manual (RFM). This amendment continues the requirements of the current AD, but adds the requirement to install ECUs with improved resistance to corrosion. This amendment is prompted by reports of ECUs with annunciated hard faults due to corrosion on internal connectors. The actions specified by this AD are intended to prevent uncommanded inflight engine shutdowns, which can result in autorotation, forced landing, and possible loss of the helicopter.

Final rule; request for comments.

98-10-03 Allison Engine Company: Amendment 39-10514. Docket 97-ANE-40-AD. Supersedes AD 97-21-09, Amendment 39-10162 which superseded 96-24-09, amdt 39-9834 which superseded Priority Letter 96-21-12.

Applicability: Allison Engine Company Model 250-C47B turboshaft engines, installed on but not limited to Bell Helicopter Textron, A Division of Textron Canada Ltd. (BHTC) Model 407 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 (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair onthe 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 uncommanded inflight engine shutdowns, which can result in autorotation, forced landing, and possible loss of the helicopter, accomplish the following:

(a) Prior to further flight, replace the engine main electrical harness assembly, part number (P/N) 23062796, with an improved assembly, P/N 23065805, in accordance with Allison Engine Company Alert Commercial Engine Bulletin (CEB) CEB-A-73-6010, dated October 15, 1996.

(b) Prior to May 20, 1998, install a new hydromechanical control unit (HMU) and electronic control unit (ECU) in accordance with Allison Engine Company Alert CEB-A-73-6015, Revision 1, dated July 30, 1997, or Revision 2, dated October 31, 1997.

(c) After completing the requirements of paragraph (b) of thisAD, and prior to further flight:

(1) Remove the "OVRSPD SYSTEM INOP" placard required by paragraph (d) of AD 96-24-09, and

(2) Revise the FAA-approved Rotorcraft Flight Manual (RFM) by removing the pages added by paragraph (f) of AD 96-24-09, and incorporate BHTC RFM BHT-407-FM-1, Revision 5, dated June 24, 1997.

(d) Within 45 days after the effective date of this AD, install a corrosion resistant electronic control unit (ECU) in accordance with Allison Engine Company Alert CEB-A-73-6017, Revision 1, dated February 18, 1998, or Revision 2, dated April 9, 1998. Installation of a corrosion resistant ECU in accordance with this paragraph will satisfy the requirement in paragraph (b) of this AD to install a new ECU.

(e) 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, if any, may be obtained from the Chicago Aircraft 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 aircraft to a location where the requirements of this AD can be accomplished.

(g) The actions required by this AD shall be done in accordance with the following service documents:

Document No.
Pages
Revision
Date
Allison Engine Company Alert CEB-A-73-6010
1-7
Original
October 15, 1996
Total Pages: 7.

BHTC Rotorcraft Flight Manual BHT-407-FM-1
Cover
NP
A,B
C/D
1-3
1-4
1-7, 1-8
1-13
1-14
1-14A/14B
1-19/1-20
2-3
2-4
2-7 -2-10 2-13,2-14
3-3 - 3-5
3-6
3-7,3-8
3-15
3-16
3-17 - 3-22
4-5, 4-6
4-9
4-10 - 4-12
5
3
5
5
5
4
5
4
5
5
5
5
1
5
5
5
2
5
5
2
5
5
Original
5
June 24, 1997
July 30, 1996
June 24, 1997
June 24, 1997
June 24, 1997
November 4, 1996
June 24, 1997
November 4, 1996
June 24, 1997
June 24, 1997
June 24, 1997
June 24, 1997
March 8, 1996
June 24, 1997
June 24, 1997
June 24, 1997
May 9, 1996
June 24, 1997
June 24, 1997
May 9, 1996
June 24, 1997
June 24, 1997
February 9, 1996
June 24, 1997
Total pages: 40

Allison Engine Company Alert CEB-A-73-6015
1-4
1
July 30, 1997
Total Pages: 4

Allison Engine Company Alert CEB-A-73-6015
1-4
2
October 31, 1997
Total pages: 4.

Allison Engine Company Alert CEB-A-73-6017
1-5
1
February 18, 1998
Total pages: 5.

Allison Engine Company Alert CEB-A-73-6017
1-5
2
April 9, 1998
Total pages: 5.

(h) The incorporation by reference of Allison Engine Company Alert CEB-A-73-6010, dated October 15, 1996, CEB A-73-6015, Revision 1, dated July 30, 1997, and Revision 2, dated October 31, 1997, and BHTC RFM BHT-407-FM-1, Revision 5, dated June 24, 1997, was approved previously by the Director of the Federal Register as of December 3, 1997 (62 FR 61438, November 18, 1997).

(i) The incorporation by reference of Allison Engine Company Alert CEB-A-73-6017, Revision 1, dated February 18, 1998, and Revision 2, dated April 9, 1998, is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 as of [Insert date 15 days after date of publication in the Federal Register].

(j) Copies of these service documents may be obtained from Allison Engine Company, P.O. Box 420, Speed Code P-40A, Indianapolis, IN 46206-0420; telephone (317) 230-2720, fax (317) 230-3381. Copies may be inspected at the FAA, New England Region, Office of the Regional Counsel, 12 New England ExecutivePark, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(k) This amendment becomes effective on May 26, 1998.

On November 10, 1997, the Federal Aviation Administration (FAA) issued airworthiness directive (AD) 97-21-09, Amendment 39-10162 (62 FR 61438, November 18, 1997), to require replacing the engine main electrical harness assembly with an improved assembly, installing a new hydromechanical unit (HMU) and electronic control unit (ECU), removing the placard notifying the pilot that the overspeed protection system is disabled, and revising the Bell Helicopter Textron, A Division of Textron Canada Ltd. (BHTC) Model 407 Rotorcraft Flight Manual (RFM). That action was prompted by development of overspeed protection system modifications to reactivate the overspeed solenoid (which had been disabled in accordance with AD 96-24-09 to prevent engine shutdown due to zero fuel flow when tripped) in conjunction with raising the power turbine overspeed trip point and revising the overspeed system to default to a minimum fuel flow in the event of its activation. That condition, if not corrected, could result in uncommanded inflight engine shutdowns, which can result in autorotation, forced landing, and possible loss of the helicopter.

Since the issuance of that AD, the FAA received reports of two BHTC 407 rotorcraft involved in incidents where there was an annunciated hard fault with the ECU. In each case, the result was a failed fixed event in which the pilot transitioned to manual mode without incident. The hard faults have been attributed to corrosion on internal connectors. Subsequent to the incidents, the manufacturer conducted an initial investigation on returned ECUs and found two additional units with corrosion on internal connectors.

The FAA has reviewed and approved the technical contents of Allison Engine Company Alert CEB-A-73-6017, Revision 1, dated February 18, 1998, and Revision 2, dated April 9, 1998, that describes procedures for installing ECUs with improved resistance to corrosion.

Since an unsafe condition has been identified that is likely to exist or develop on other engines of this same type design, this AD supersedes AD 97-21-09 and continues to require replacement of the engine main electrical harness assembly with an improved assembly, and, after replacing the ECU and HMU, removing the "OVRSPD SYSTEM INOP" placard required by paragraph (d) of AD 96-24-09, revising the BHTC Model 407 RFM. These actions are now required prior to further flight, if not already accomplished. In addition, this AD adds a requirement to install an ECU with improved resistance to corrosion within 45 days after the effective date of this AD, based upon the need to protect the affected engines against effects of corrosion. Installation of the improved, corrosion resistant ECU will meet the requirement to install a new ECU. The requirements of paragraph (c) of this AD have been coordinated with the Rotorcraft Directorate. The actions are required to be accomplished in accordance with the service documents described previously.

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 notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-ANE-40-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 removing Amendment 39-10162, (62 FR 61438, November 18, 1997), and by adding a new airworthiness directive, Amendment 39-10514, to read as follows: