[Federal Register Volume 63, Number 109 (Monday, June 8, 1998)]
[Proposed Rules]
[Pages 31138-31140]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-15087]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-23-AD]
RIN 2120-AA64


Airworthiness Directives; Allison Engine Company 250-B and 250-C 
Series Turboshaft Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Allison Engine Company 
250-B and 250-C series turboshaft engines. This proposal would require 
replacing existing beryllium copper main fuel control (MFC) bellows 
assemblies with Inconel 718 stainless steel welded MFC bellows 
assemblies. This proposal is prompted by reports of leaking MFC bellows 
assemblies resulting in an uncommanded minimum fuel flow condition, 
loss of engine fuel flow control and subsequent forced landing. The 
actions specified by the proposed AD are intended to prevent MFC 
bellows assembly leakage, which can result in an uncommanded minimum 
fuel flow condition and subsequent loss of engine fuel flow control.

DATES: Comments must be received by August 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. 98-ANE-23-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``<a href="/cdn-cgi/l/email-protection#7d44501c19507718131a1413180d0f120d3d1b1c1c53191209531a120b">9-ad-
<span class="__cf_email__" data-cfemail="187d767f71767d686a7768587e7979367c776c367f776e">[email protected]</span></a>''. Comments sent via the Internet must contain 
the docket number in the subject line. Comments may be inspected at 
this location between 8:00 a.m. and 4:30 p.m., Monday through Friday, 
except Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Allison Engine Company, P.O. Box 420, Speed Code U-15, 
Indianapolis, IN 46206-0420, telephone (317) 230-6674. This information 
may be examined at the FAA, New England Region, Office of the Regional 
Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: John Tallarovic, Aerospace Engineer, 
Chicago Aircraft Certification Office, FAA, Small Airplane Directorate, 
2350 E. Devon Avenue, Room 323, Des Plaines, IL 60018; telephone (847) 
294-8180, fax (847) 294-7834.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments

[[Page 31139]]

submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-ANE-23-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, New England Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 98-ANE-23-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    The Federal Aviation Administration (FAA) has received reports of 
inflight engine shutdowns due to main fuel control (MFC) beryllium 
copper bellows assembly leakage on Allison Engine Company engines. This 
same design is used on Allison Engine Company 250-B15, 250-B17, 250-
B17F, 250-C18, 250-C20, 250-C20R, 250-C28, and 250-C30 series 
turboshaft engines. The investigation revealed that the MFC bellows 
assemblies leaked due to corrosion. This AD requires the replacement of 
existing beryllium copper MFC bellows assemblies with Inconel 718 
stainless steel welded MFC bellows assemblies, a material that is less 
susceptible to corrosion. The compliance schedule balanced the need to 
remove the highest risk bellows assemblies first with the ability to 
manufacture replacement parts at the required rate. This condition, if 
not corrected, could result in MFC bellows assembly leakage, which can 
result in an uncommanded minimum fuel flow condition and subsequent 
loss of engine fuel flow control.
    The FAA has reviewed and approved the technical contents of Allison 
Commercial Engine Bulletins (CEBs) No. CEB-A-282 (250-C18 series), No. 
CEB-A-1329 (250-C20 series), No. CEB-A-73-2053 (250-C28 series), No. 
CEB-A-73-3068 (250-C30 series), No. CEB-A-73-4029 (250-C20R series), 
No. TP CEB-A-158 (250-B15G series), No. TP CEB-A-1286 (250-B17 series), 
and TP CEB-A-73-2014 (250-B17F series), all Revision 2, all dated April 
15, 1998, that describe procedures for replacing existing beryllium 
copper MFC bellows assemblies with Inconel 718 stainless steel welded 
MFC bellows assemblies.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require replacing the existing beryllium copper MFC 
bellows assemblies at the next repair or overhaul of the MFC bellows 
assembly, or, since corrosion was a factor, by the calendar end-dates 
specified, whichever occurs first. The actions would be required to be 
accomplished in accordance with the CEBs described previously.
    The FAA estimates that 2,500 engines installed on aircraft of U.S. 
registry would be affected by this proposed AD, that it would take no 
additional work hours per engine to accomplish the proposed actions at 
regularly scheduled overhaul, and required parts would cost 
approximately $1,495 per engine. Based on these figures, the total cost 
impact of the proposed AD on U.S. operators is estimated to be 
$3,737,500.
    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 adding the following new 
airworthiness directive:

Allison Engine Company: Docket No. 98-ANE-23-AD.

    Applicability: Allison Engine Company 250-B15, 250-B17, 250-
B17F, 250-C18, 250-C20, 250-C20R, 250-C28, and 250-C30 series 
turboshaft engines, installed on but not limited to Bell Models 206, 
230, 406; Enstrom Model TH28/480; and Boeing Models 500, 520N, 530F 
rotorcraft.

    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 (c) 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 main fuel control (MFC) bellows assembly leakage, 
which can result in an uncommanded minimum fuel flow condition and 
subsequent loss of engine fuel flow control, accomplish the 
following:
    (a) Replace existing beryllium copper MFC bellows assemblies, 
part numbers (P/Ns) 2523722, 2539647, 2540539, 2540767, and 2542526, 
with Inconel 718 stainless steel welded MFC bellows assemblies, P/N 
2543598, in accordance with the applicable Allison Commercial Engine 
Bulletins (CEBs) referenced in paragraph (b) of this AD, at the 
earlier of the following:
    (1) The next time after the effective date of this AD the MFC is 
being repaired or overhauled; or
    (2) The following populations of MFCs, as applicable
    (i) All MFCs listed by P/Ns in Tables 1 and 2 of the Allison 
CEBs referenced in paragraph (b) of this AD by March 31, 1999; or
    (ii) All MFCs listed by P/Ns in Table 3 of the Allison CEBs 
referenced in paragraph (b) of this AD by August 31, 1999.
    (iii) All MFCs listed by P/Ns in Tables 4 and 5 of the Allison 
CEBs referenced in paragraph (b) of this AD by October 31, 1999.
    (b) Perform the replacement of MFC bellows assemblies required 
by paragraph (a) of this AD in accordance with the applicable 
Allison CEB from among the following:
    (1) CEB-A-282 Revision 2, dated April 15, 1998 (250-C18 series), 
or
    (2) CEB-A-1329 Revision 2, dated April 15, 1998(250-C20 series), 
or
    (3) CEB-A-73-2053 Revision 2, dated April 15, 1998(250-C28 
series), or
    (4) CEB-A-73-3068 Revision 2, dated April 15, 1998(250-C30 
series), or,
    (5) CEB-A-73-4029 Revision 2, dated April 15, 1998(250-C20R 
series), or

[[Page 31140]]

    (6) TP (Turboprop) CEB-A-158 Revision 2, dated April 15, 1998 
(250-B15G series), or
    (7) TP CEB-A-1286 Revision 2, dated April 15, 1998 (250-B17 
series), or
    (8) TP CEB-A-73-2014 Revision 2, dated April 15, 1998 (250-B17F 
series).
    (c) 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 request 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.

    (d) Special flight permits may be issued in accordance with 
Secs. 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.

    Issued in Burlington, Massachusetts, on May 29, 1998.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 98-15087 Filed 6-5-98; 8:45 am]
BILLING CODE 4910-13-P


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