Airworthiness Directives; Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B and 250-C Series Turboprop and Turboshaft Engines

[Federal Register Volume 70, Number 2 (Tuesday, January 4, 2005)]
[Rules and Regulations]
[Pages 261-265]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-14]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2004-18515; Directorate Identifier 2004-NE-12-AD; 
Amendment 39-13921; AD 2004-26-09]
RIN 2120-AA64


Airworthiness Directives; Rolls-Royce Corporation (formerly 
Allison Engine Company, Allison Gas Turbine Division, and Detroit 
Diesel Allison) 250-B and 250-C Series Turboprop and Turboshaft Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
Rolls-Royce Corporation (RRC) 250-B and 250-C series turboprop and 
turboshaft engines with certain part numbers (P/Ns) of compressor 
adaptor couplings manufactured by Alcor Engine Company (Alcor), EXTEX 
Ltd. (EXTEX), RRC, and Superior Air Parts (SAP) installed. This AD 
requires operators to remove from service affected compressor adaptor 
couplings. This AD results from nine reports of engine shutdown caused 
by coupling failure. We are issuing this AD to reduce the risk of 
failure of the compressor adaptor coupling and subsequent loss of all 
engine power.

DATES: This AD becomes effective February 8, 2005.

[[Page 262]]


ADDRESSES: You may examine the AD docket on the Internet at http://dms.dot.gov or in Room PL-401 on the plaza level of the Nassif 
Building, 400 Seventh Street, SW., Washington, DC.

FOR FURTHER INFORMATION CONTACT: Robert Baitoo, Aerospace Engineer, Los 
Angeles Aircraft Certification Office, FAA, Transport Airplane 
Directorate, 3960 Paramount Blvd., Lakewood, CA 90712-4137; telephone: 
(562) 627-5245, fax: (562) 627-5210, for questions about Alcor, EXTEX, 
or SAP compressor adaptor couplings; and John Tallarovic, Aerospace 
Engineer, Chicago Aircraft Certification Office, FAA, 2300 East Devon 
Avenue, Des Plaines, IL 60018-4696; telephone (847) 294-8180; fax (847) 
294-7834, for questions about RRC compressor adaptor couplings.

SUPPLEMENTARY INFORMATION: The FAA proposed to amend 14 CFR part 39 
with a proposed airworthiness directive (AD). The proposed AD applies 
to RRC 250-B and 250-C series turboprop and turboshaft engines with 
certain P/Ns of compressor adaptor couplings manufactured by Alcor, 
EXTEX, RRC, and SAP installed. We published the proposed AD in the 
Federal Register on July 1, 2004 (69 FR 39877). That action proposed to 
require operators to remove from service affected couplings. That 
proposal results from nine reports of engine shutdown caused by 
compressor adaptor coupling failure.

Examining the AD Docket

    You may examine the docket that contains the AD, any comments 
received, and any final disposition in person at the DMS Docket Offices 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The Docket Office (telephone (800) 647-5227) is located on 
the plaza level of the Department of Transportation Nassif Building at 
the street address stated in ADDRESSES. Comments will be available in 
the AD docket shortly after the DMS receives them.

Comments

    We provided the public the opportunity to participate in the 
development of this AD. We have considered the comments received.

Request To Change the Impeller-to-Coupling Target Fit Tolerance

    One commenter, RRC, requests that we change the fit between the 
compressor impeller and the coupling from 0.0000 to -0.0018 inch, to 
0.0000 to -0.0013 inch in the final rule. Based upon rig tests, RRC has 
changed their recommended fit between the impeller and coupling. We 
agree. We have changed paragraph (i)(4) and Table 3 of the final rule 
to reflect these new fit values.

Request To Clarify the Compliance Section

    The same commenter, RRC, requests the following wording changes to 
the AD to clarify the compliance section:
    Change Table 3 in the AD by deleting the column titled Impeller ID. 
There is no need to specify the impeller ID in Table 3. The key 
dimension is the fit between the impeller and the coupling and the 
column listing the impeller ID is unnecessary and only adds confusion.
    Change paragraph (h) from ``Remove RRC compressor adaptor 
couplings, P/Ns 23039791-1, -2, and -3 from service at next access but 
not later than March 1, 2012'' to ``Remove RRC compressor adaptor 
couplings, P/Ns 23039791-1, -2, and -3 from service next time the 
compressor rotor is disassembled for any reason but not later than 
March 1, 2012.'' This change more precisely defines the circumstances 
when the coupling must be replaced.
    Change paragraph (i)(1) from ``Machine the inside diameter (ID) to 
accept the next larger size outside diameter (OD) compressor adapter 
coupling'' to ``Select and measure pilot OD of a new larger dash size 
coupling.''
    Change paragraph (i)(4) from ``A fit of 0.0000 to -0.0018 inch must 
be achieved. No fretting is allowed on the impeller after machining'' 
to ``Machine inside diameter (ID) of impeller to achieve a fit of 0.000 
to -0.0013 inch. No fretting is allowed on the impeller after 
machining.''
    Add a paragraph under (i) that states ``A new coupling must never 
be installed into a worn impeller.'' These changes to paragraph (i) 
would clarify what should be done when the impeller and coupling are 
serviced.
    We agree with the intent of these requested changes and have 
incorporated them in the final rule. We have added paragraph (i)(10) 
that states the mating surfaces of the impeller and coupling must not 
have any fretting, and states, do not install a -1 coupling into a used 
impeller, to address the commenter's concerns to add a paragraph (i).

Request To Correct the Costs of Compliance

    One commenter requests that the economic evaluation be revised to 
better reflect the actual costs of the action. The commenter states 
that the FAA's economic impact estimate didn't consider engine and 
compressor removal, and shipping and out-of-service time if compliance 
doesn't coincide with a scheduled maintenance event.
    We do not agree. The costs are for replacing the coupling. We do 
not include any other costs.

Availability of Improved Couplings

    One commenter states that the improved couplings may not be 
available in sufficient quantities to support the proposed compliance 
schedule for the parts manufacturer approval (PMA) parts.
    We partially agree. The improved couplings may be unavailable in 
sufficient quantities to support the compliance schedule for the 
engines with EXTEX, SAP, and ALCOR PMA couplings. However, the 
compliance schedules are based primarily on our evaluation of field 
management plans developed by those PMA manufacturers.

Clarification of Field Management Responsibility

    EXTEX states that although it has agreed to include SAP couplings 
in the EXTEX service documents, for clarification, EXTEX requests we 
note that it is not responsible for the field management of the SAP 
produced couplings, nor is EXTEX responsible for any costs and 
liabilities associated with parts produced by SAP.
    We agree to note EXTEX's comment.

Request To Return Removed Couplings for Analysis

    One commenter requests that all removed, failed, cracked or fretted 
couplings of any part number should be returned to the manufacturer for 
analysis and reported to the FAA of any significant findings. This 
would help to gain more knowledge of the failure mode of couplings.
    We do not agree. We have a good understanding of the failure mode 
of the coupling and the marginal benefit of additional data does not 
justify the cost burden on the operators to return these couplings.

Request for Explanation of Compliance Time

    One commenter requests an explanation of the year 2012 compliance 
time for the RRC couplings. The commenter states there may be less 
attention given to this problem if there is a 7.5 year compliance 
period.
    We do not agree. As stated in the proposal, each manufacturer is 
responsible for their independent component design, design 
substantiation, component manufacture, and development of a field 
management plan for its fleet. An important element of the field 
management plans is the risk

[[Page 263]]

assessment. The varying outcomes of those independent risk assessments 
lead to differing compliance intervals. The compliance time for Rolls-
Royce couplings is not intended to convey the message that there is 
little risk. Operators are expected to use the compliance time to 
schedule the maintenance actions required by this AD.

Request To Add a Comment To Explain the Dimension Change for Press Fit 
and Add Requirement for Surface Finish

    One commenter requests we add a comment on how the press fit for 
the compressor adaptor coupling has changed, and requests we add a 
requirement for the correct surface finish for the impeller surface. 
The commenter states that the fit between the compressor adaptor 
coupling and the impeller is critical.
    We partially agree. We specified the change to the press fit for 
the compressor adaptor coupling in the compliance section of the final 
rule. Since the surface finish is specified in the Overhaul Manual, we 
will not include the surface finish of 40 microinches for the machined 
impeller in the final rule.

Costs of Compliance Could Be Mitigated

    One commenter states the costs of compliance could be mitigated by 
stating the costs occur over 7 years. The commenter gave no specific 
justification.
    We do not agree. The estimated costs of compliance for this AD 
already takes into account the 6,000 engines affected, without basing 
estimates over 7 years.

Request for Explanations

    One commenter requests that we explain the physical difference 
between the RRC P/N 23076559-1 and RRC P/N 23039791. The physical 
difference is that RRC P/N 23076559 has a coating that is more 
resistant to fretting compared to P/N 23039791.
    The commenter also asks why the -1 version of the P/N 23036559 
compressor adapter coupling is installed only when a new impeller is 
installed.
    The -1 coupling is the smallest size and will only fit correctly 
into a new impeller. As stated in the proposal, a used impeller must be 
machined before a new compressor adaptor coupling can be installed. 
This action is required to clean all fretting damage from the surface 
of the impeller that mates with the coupling. Once an impeller has been 
machined, a larger (-2 or -3) coupling is required.
    Also, the commenter requests to allow installation of a ``1 
coupling into a used impeller, if the fit is correct.
    We do not agree. A -1 coupling cannot be installed in a used 
impeller even if the fit is correct. The surface of a used impeller 
that mates to the coupling must be cleaned by machining. After 
machining, a larger coupling is required.

Conclusion

    We have carefully reviewed the available data, including the 
comments received, and determined that air safety and the public 
interest require adopting the AD with the changes described previously. 
We have determined that these changes will neither increase the 
economic burden on any operator nor increase the scope of the AD.

Costs of Compliance

    There are about 9,000 RRC 250-B and 250-C series turboprop and 
turboshaft engines of the affected design in the worldwide fleet. We 
estimate that 6,000 engines installed on helicopters and airplanes of 
U.S. registry will be affected by this AD. We also estimate that it 
would take about 3 work hours per engine to perform the actions when 
done at time of rotor disassembly, and that the average labor rate is 
$65 per work hour. Required parts will cost about $1,601 per engine. 
Based on these figures, we estimate the total cost of the AD to U.S. 
operators to be $10,776,000.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We have determined that this AD will not have federalism 
implications under Executive Order 13132. This AD will not have a 
substantial direct effect 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.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866;
    (2) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and
    (3) 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.
    We prepared a summary of the costs to comply with this AD and 
placed it in the AD Docket. You may get a copy of this summary at the 
address listed under ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the Federal Aviation Administration amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2004-26-09 Rolls-Royce Corporation (formerly Allison Engine Company, 
Allison Gas Turbine Division, and Detroit Diesel Allison): Amendment 
39-13921. Docket No. FAA-2004-18515; Directorate Identifier 2004-NE-
12-AD.

Effective Date

    (a) This airworthiness directive (AD) becomes effective February 
8, 2005.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Rolls-Royce Corporation (formerly Allison 
Engine Company, Allison Gas Turbine Division, and Detroit Diesel 
Allison) 250-B17, -B17B, -B17C, -B17D, -B17E, 250-C20, -C20B, -C20F, 
-C20J, -C20S, and -C20W series turboprop and turboshaft engines with 
the compressor adaptor couplings installed listed in the following 
Table 1:

[[Page 264]]



             Table 1.--Affected Compressor Adaptor Couplings
------------------------------------------------------------------------
           Manufacturer                     Affected part numbers
------------------------------------------------------------------------
Alcor Engine Company (Alcor)......  P/Ns 23039791AL.
                                    23039791AL-1/-2/-3.
EXTEX Ltd. (EXTEX)................  A23039791.
                                    E23039791.
                                    E23039791-1/-2/-3.
                                    EH23039791.
                                    EH23039791-1/-2/-3.
Rolls-Royce Corporation (RRC).....  23039791-1/-2/-3.
Superior Air Parts (SAP)..........  A23039791.
------------------------------------------------------------------------

    These engines are installed on, but not limited to, the aircraft 
in the following Table 2:

                      Table 2.--Applicable Aircraft
------------------------------------------------------------------------
                               Helicopters
-------------------------------------------------------------------------
Agusta Models.
A109, A109A, A109A II.
Bell Models.
206A, 207B, 206L.
Enstrom Models.
TH-28, 480, 480B.
Eurocopter France Models.
AS355E, AS355F, AS355F1, AS355F2.
Eurocopter Deutschland Models.
BO-105C, BO-105S.
MDHI Models.
369D, 369E, 369H, 369HM, 369HS, 369HE.
Schweizer Model 269D.
------------------------------------------------------------------------
                                Airplanes
------------------------------------------------------------------------
B-N Group Ltd. Model.
BN-2T.
------------------------------------------------------------------------

Unsafe Condition

    (d) This AD results from nine reports of engine shutdown caused 
by compressor adaptor coupling failure.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified unless the 
actions have already been done.

Alcor Compressor Adaptor Couplings

    (f) Remove Alcor compressor adaptor couplings, P/Ns 23039791AL, 
23039791AL-1, -2, and -3 from service as follows:
    (1) For couplings with 600 or more operating hours-since-new as 
of the effective date of this AD, or the operating hours are unknown 
and cannot be determined, remove couplings from service at next 
access but not to exceed 50 additional operating hours.
    (2) For couplings with fewer than 600 operating hours-since-new 
on the effective date of this AD, remove couplings from service at 
next access but not to exceed 649 operating hours-since-new.

EXTEX and SAP Compressor Adaptor Couplings

    (g) Remove EXTEX and SAP compressor adaptor couplings, P/Ns 
A23039791, E23039791, E23039791-1, -2, and -3, EH23039791, and 
EH23039791-1, -2, and -3, from service as follows:
    (1) For couplings with operating hours that are unknown and 
cannot be determined, remove couplings from service at next access 
but not to exceed 50 additional operating hours.
    (2) For couplings with 600 or more operating hours-since-new as 
of the effective date of this AD, remove couplings from service at 
next access but not to exceed 100 additional operating hours.
    (3) For couplings with fewer than 600 operating hours-since-new 
on the effective date of this AD, remove couplings from service at 
next access but not to exceed 150 additional operating hours.

RRC Compressor Adaptor Couplings

    (h) Remove RRC compressor adaptor couplings, P/Ns 23039791-1, -
2, and -3 from service next time the compressor rotor is 
disassembled for any reason, but not later than March 1, 2012.

Installation Requirements for Compressor Adaptor Couplings

    (i) Machine the compressor impeller as follows:
    (1) Select and measure the pilot outside diameter (OD) of a new 
larger dash size coupling.
    (2) For example, if a -1 coupling was removed, a -2 coupling 
must be installed.
    (3) If a -3 coupling is removed, a new impeller is required.
    (4) Machine the inside diameter (ID) of the compressor impeller 
to achieve a fit of 0.0000 to -0.0013 inch. No fretting is allowed 
on the impeller after machining.
    (5) Due to previous fretting, an impeller with a -1 coupling 
removed might have to be machined for a -3 coupling. Plating of the 
impeller ID is not allowed.
    (6) Fluorescent penetrant inspect the impeller.
    (7) Install a new compressor adaptor coupling, P/N 23076559-2 or 
-3; or
    (8) If a new impeller is installed, then install compressor 
adaptor coupling, P/N 23076559-1.
    (9) Heating of the impeller per the engine overhaul manual is 
required to install the coupling to achieve the target fit specified 
in the following Table 3:

                                    Table 3.--Impeller-to-Coupling Target Fit
----------------------------------------------------------------------------------------------------------------
              New adaptor                         Adaptor OD                       Fit  (interference)
----------------------------------------------------------------------------------------------------------------
(i) 23076559-1........................  0.9000 to 0.9008 inch.........  0.0000 to -0.0013 inch.
(ii) 23076559-2.......................  0.9020 to 0.9028 inch.........  0.0000 to -0.0013 inch.
(iii) 23076559-3......................  0.9040 to 0.9048 inch.........  0.0000 to -0.0013 inch.
----------------------------------------------------------------------------------------------------------------

    (10) The mating surfaces of the impeller and coupling must not 
have any fretting. Do not install a -1 coupling into a used 
impeller.

Definition

    (j) For the purposes of this AD, next access is defined as when 
the compressor module is separated from the engine and disassembled 
for any reason.

Alternative Methods of Compliance

    (k) The Manager, Los Angeles Aircraft Certification Office, has 
the authority to approve alternative methods of compliance for 
Alcor, EXTEX, and SAP adaptor couplings addressed in this AD if 
requested using the procedures found in 14 CFR 39.19. The Manager, 
Chicago Aircraft Certification Office, has the authority to approve 
alternative methods of compliance for RRC adaptor couplings 
addressed in this AD if requested using the procedures found in 14 
CFR 39.19.

Related Information

    (l) Alcor SLB No. 814-3-1, Revision C, dated April 28, 2004, 
EXTEX Alert Service Bulletin T-081, Revision B, dated May 4, 2004, 
and RRC CEB-A-1392 and CEB-A-

[[Page 265]]

1334, dated September 9, 2003, pertain to the subject of this AD.

    Issued in Burlington, Massachusetts, on December 23, 2004.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 05-14 Filed 1-3-05; 8:45 am]
BILLING CODE 4910-13-P

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