Airworthiness Directives; Allison Engine Company Model 250-C47B Turboshaft Engines

[Federal Register Volume 63, Number 89 (Friday, May 8, 1998)]
[Rules and Regulations]
[Pages 25389-25391]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-12063]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-ANE-40-AD; Amendment 39-10514; AD 98-10-03]
RIN 2120-AA64


Airworthiness Directives; Allison Engine Company Model 250-C47B 
Turboshaft Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: 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.

DATES: Effective May 26, 1998.

    The incorporation by reference of Allison Engine Company Alert 
Commercial Engine Bulletin (CEB) 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 Flight Manual BHT-407-FM-1, Revision 5, 
dated June 24, 1997, as listed in the regulations, was approved 
previously by the Director of the Federal Register as of December 3, 
1997 (62 FR 61438, November 18, 1997).
    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 as 
of May 26, 1998.
    Comments for inclusion in the Rules Docket must be received on or 
before July 7, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 97-ANE-40-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ad-
[email protected]''. Comments sent via the Internet must contain 
the docket number in the subject line.
    The service information referenced in this AD 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. This 
information may be examined at the FAA, New England Region, Office of 
the Regional Counsel, Burlington, MA; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Patricia Bonnen, Aerospace Engineer, 
Chicago Aircraft Certification Office, FAA, Small Airplane Directorate, 
2300 East Devon Ave., Des Plaines, IL 60018; telephone (847) 294-7134, 
fax (847) 294-7834.

SUPPLEMENTARY INFORMATION: 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 annunicated 
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

[[Page 25390]]

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.


Sec. 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:

98-10-03  Allison Engine Company: Amendment 39-10514. Docket 97-ANE-
40-AD. Supersedes AD 97-21-09, Amendment 39-10162.

    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 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 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 this 
AD, 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:

[[Page 25391]]



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          Document No.                      Pages                   Revision                     Date           
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Allison Engine Company Alert,     1-7.....................  Original................  October 15, 1996.         
 CEB-A-73-6010.                                                                                                 
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    Total pages: 7.                                                                                             
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BHTC Rotorcraft Flight Manual     Cover...................  5.......................  June 24, 1997.            
 BHT-407-FM-1.                                                                                                  
                                  NP......................  3.......................  July 30, 1996.            
                                  A,B.....................  5.......................  June 24, 1997.            
                                  C/D.....................  5.......................  June 24, 1997.            
                                  1-3.....................  5.......................  June 24, 1997.            
                                  1-4-1-7.................  4.......................  November 4, 1996.         
                                  1-8.....................  5.......................  June 24, 1997.            
                                  1-13....................  4.......................  November 4, 1996.         
                                  1-14....................  5.......................  June 24, 1997.            
                                  1-14A/14B...............  5.......................  June 24, 1997.            
                                  1-19/1-20...............  5.......................  June 24, 1997.            
                                  2-3.....................  5.......................  June 24, 1997.            
                                  2-4.....................  1.......................  March 8, 1996.            
                                  2-7-2-10................  5.......................  June 24, 1997.            
                                  2-13, 2-14..............  5.......................  June 24, 1997.            
                                  3-3-3-5.................  5.......................  June 24, 1997.            
                                  3-6.....................  2.......................  May 9, 1996.              
                                  3-7, 3-8................  5.......................  June 24, 1997.            
                                  3-15....................  5.......................  June 24, 1997.            
                                  3-16....................  2.......................  May 9, 1996.              
                                  3-17-3-22...............  5.......................  June 24, 1997.            
                                  4-5, 4-6................  5.......................  June 24, 1997.            
                                  4-9.....................  Original................  February 9, 1996.         
                                  4-10-4-12...............  5.......................  June 24, 1997.            
----------------------------------------------------------------------------------------------------------------
    Total pages: 40.                                                                                            
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Allison Engine Company Alert,     1-4.....................  1.......................  July 30, 1997.            
 CEB-A-73-6015.                                                                                                 
----------------------------------------------------------------------------------------------------------------
    Total pages: 4.                                                                                             
----------------------------------------------------------------------------------------------------------------
Allison Engine Company Alert,     1-4.....................  2.......................  October 31, 1997.         
 CEB-A-73-6015.                                                                                                 
----------------------------------------------------------------------------------------------------------------
    Total pages: 4.                                                                                             
----------------------------------------------------------------------------------------------------------------
Allison Engine Company Alert,     1-5.....................  1.......................  February 18, 1998.        
 CEB-A-73-6017.                                                                                                 
----------------------------------------------------------------------------------------------------------------
    Total pages: 5                                                                                              
----------------------------------------------------------------------------------------------------------------
Allison Engine Company Alert,     1-5.....................  2.......................  April 9, 1998.            
 CEB-A-73-6017.                                                                                                 
----------------------------------------------------------------------------------------------------------------
    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 May 26, 1998.
    (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 Executive Park, 
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.

    Issued in Burlington, Massachusetts, on April 29, 1998.
Thomas A. Boudreau,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 98-12063 Filed 5-7-98; 8:45 am]
BILLING CODE 4910-13-U

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