[Federal Register Volume 60, Number 199 (Monday, October 16, 1995)]
[Proposed Rules]
[Pages 53550-53552]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-25568]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-ANE-47]


Airworthiness Directives; CFM International Model CFM56-3C-1 and 
CFM56-3B-2 Turbofan Engines Installed on Boeing 737-400 Aircraft

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This notice proposes the supersedure of an existing 
airworthiness directive (AD), applicable to all CFM International 
(CFMI) CFM56-3C-1 and certain CFM56-3B-2 engines, that currently 
requires the removal from service of certain fan disk and fan blade 
hardware, and limits the use of CFM56-3C-1 thrust levels. This action 
would require removal of additional fan blade hardware, require an 
Airplane Flight Manual (AFM) revision to impose thrust level 
limitations for airplanes equipped with affected engines, and require 
the installation of redesigned fan blades as a terminating action to 
the thrust level limitations of this AD. The current AD requirements 
for certain CFM56-3B-2 engines are unchanged and carried over into the 
proposed AD. This proposal is prompted by the availability of 
redesigned fan blades that are not subject to the thrust level 
limitations, and the need to clarify the AD requirements by deleting 
references to specific AFM's. The actions specified by the proposed AD 
are intended to prevent a fan blade failure that can result in complete 
loss of engine power.

DATES: Comments must be received by December 15, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 95-ANE-47, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may be inspected at 
this location between 8 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 Boeing Commercial Airplanes, Publications Department, 
P.O. Box 3707, Seattle, WA 98124-2207; and CFM International, Technical 
Publications Department, 1 Neumann Way, Cincinnati, OH 45215. This 
information may be examined at the FAA, New England Region, Office of 
the Assistant Chief Counsel, 12 New England Executive Park, Burlington, 
MA.

FOR FURTHER INFORMATION CONTACT: Robert Ganley, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (617) 
238-7138, fax (617) 238-7199.

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 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 95-ANE-47.'' 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 Assistant Chief Counsel, 
Attention: Rules Docket No. 95-ANE-47, 12 New England Executive Park, 
Burlington, MA 01803-5299.

Discussion

    On December 1, 1989, the Federal Aviation Administration (FAA) 
issued airworthiness directive (AD) 89-13-51, Amendment 39-6425 (55 FR 
1401, January 16, 1990), to require that all CFM International CFM56-
3C-1 and certain CFM56-3B-2 model turbofan engines have their fan blade 
and fan disk hardware removed from service prior to further flight and 
replaced with serviceable hardware. That AD also requires that all 
aircraft with CFM56-3C-1 model turbofan engines must be modified to 
operate at or below CFM56-3B-2 thrust levels if using auto-throttle. In 
addition, that AD provides for the use of CFM56-3C-1 thrust levels 
within a limited operating envelope and with certain operational 
restrictions. That action was prompted by several fan blade high cycle 
fatigue failures, and one occurrence of fan disk cracking in the 
dovetail post area while operating at CFM56-3C-1 thrust levels. That 
condition, if not corrected, could result in a fan blade failure that 
can result in complete loss of engine power.
    Since the issuance of that AD, the FAA has determined that two 
additional fan blades, Part Numbers (P/N) 9527M99P10 and 9527M99P11, 
have the same design configuration as the fan blades restricted in the 
current AD and therefore also require thrust level limitations.
    In addition, since the issuance of AD 89-13-51 a new fan blade 
design has been introduced that has reduced vibratory stress levels. 
This new fan blade design and current fan disks in which these blades 
are installed would not be subject to the thrust level limitations of 
the current AD. The new fan blades will only be required on CFM56-3C-1 
model turbofan engines. Installation of redesigned fan blades prior to 
June 30, 1996, would constitute 

[[Page 53551]]
a terminating action to the required thrust level limitations. The 
manufacturer has informed the FAA that at least 97% of the CFM56-3C-1 
model turbofan engines have already incorporated the new fan blade 
design. The June 30, 1996, date would allow any engines that are in the 
process of incorporating the new fan blade design time to comply.
    Finally, this proposal deletes references to specific Airplane 
Flight Manuals (AFM's), states the required CFM56-3C-1 operational 
restrictions in an Appendix to the AD, and requires that these 
restrictions be added to certain Boeing 737-400 AFM's. This change is 
being made to clarify the AD requirements since the AFM references in 
the current AD may be interpreted to only apply to a limited number of 
airplanes. The requirements of this AD have been reviewed by the 
Transport Airplane Directorate.
    The FAA has reviewed and approved the technical contents of Boeing 
Service Bulletin (SB) No. 737-71-1203, Revision 10, dated July 21, 
1994, that describes procedures for airplane modifications that limit 
engine thrust at or below CFM56-3B-2 levels when using auto-throttle; 
and CFM International CFM56-3/-3B/-3C SB No. 72-543, Revision 4, dated 
July 29, 1992, that provides instructions for installation of 
redesigned fan blades that have reduced vibratory stress levels.
    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 supersede AD 89-13-51 to require removal of 
additional fan blade hardware, require an AFM revision to impose thrust 
level limitations for airplanes equipped with affected engines, and 
require the installation of redesigned fan blades as a terminating 
action to the thrust level limitations of this AD. The current AD 
requirements for certain CFM56-3B-2 engines are unchanged and carried 
over into the proposed AD.
    There are approximately 289 CFMI CFM56-3C-1 and CFM56-3B-2 series 
engines of the affected design in the worldwide fleet. The FAA has been 
advised by the manufacturer that there are no engines on U.S. 
registered aircraft that would be affected by this AD. Therefore, there 
is no associated cost impact on U.S. operators as a result of this AD.
    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), 40101, 40113, 44701.


Sec. 39.13   [Amended]

    2. Section 39.13 is amended by removing Amendment 39-6425 (55 FR 
1401, January 16, 1990) and by adding the following new airworthiness 
directive (AD):

CFM International: Docket No. 95-ANE-47. Supersedes AD 89-13-51, 
Amendment 39-6425.

    Applicability: CFM International (CFMI) CFM56-3B-2 and CFM56-3C-
1 model turbofan engines installed on but not limited to Boeing 737-
400 series aircraft.

    Note: 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 use the 
authority provided in paragraph (g) to request approval from the 
Federal Aviation Administration (FAA). This approval may address 
either no action, if the current configuration eliminates the unsafe 
condition, or different actions necessary to address the unsafe 
condition described in this AD. Such a request should include an 
assessment of the effect of the changed configuration on the unsafe 
condition addressed by this AD. In no case does the presence of any 
modification, alteration, or repair remove any engine from the 
applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent fan blade failure that may result in complete loss of 
power, accomplish the following:
    (a) For CFM56-3C-1 model turbofan engines:
    (1) Prior to further flight, remove from service stage 1 fan 
disk Part Number (P/N) 335-014-511-0 that have operated at 
unrestricted CFM56-3C-1 thrust levels with fan blade P/N's 
9527M99P08, 9527M99P09, 9527M99P10, 9527M99P11, or 1285M39P01 and 
replace with a serviceable fan disk.
    (2) Prior to further flight, remove from service stage 1 fan 
blade P/N's 9527M99P08, 9527M99P09, 9527M99P10, 9527M99P11, and 
1285M39P01 that have operated at unrestricted CFM56-3C-1 thrust 
levels and replace with a serviceable fan blade.
    (b) For CFM56-3C-1 model turbofan engines equipped with fan 
blade P/N's 9527M99P08, 9527M99P09, 9527M99P10, 9527M99P11, or 
1285M39P01:
    (1) Prior to further flight, for aircraft that have not already 
complied with any of the revision levels 3 through 10 of Boeing 
Service Bulletin (SB) No. 737-71-1203, incorporate the provisions of 
Boeing SB No. 737-71-1203, Revision 10, dated July 21, 1994, as 
described in item III titled, ``Accomplishment Instructions'', part 
V, ``Airplane Wiring Modification for Operation at 22,000 Pounds 
Thrust Levels with two CFM56-3C-1 Engines Installed.''
    (2) Prior to further flight, revise the engine limitations 
section of the Boeing 737-400 series Airplane Flight Manuals (AFM) 
by adding the operational restrictions contained in Appendix I. This 
may be accomplished by inserting a copy of Appendix I of this AD in 
the AFM.
    (3) Operate engines at or below CFM56-3B-2 thrust levels, or in 
accordance with the limitations contained in Appendix I of this AD.

Appendix I

Operational Restrictions Referenced in Paragraphs (b)(2) and (b)(3)

    (a) Use of fan speed (N1) values for take-off and maximum 
continuous thrust levels at CFM56-3C-1 (23.5K) thrust levels are 
restricted.
    (b) The following limitations must be observed for all CFM56-3C-
1 (23.5K) operations:
    (1) Airport pressure altitude must be 2,500 feet or less for 
take-off.
    (2) The auto-throttle must be OFF and the thrust must be set 
manually for take-off.
    (3) Both power management controls (PMC's) must be operative for 
airplane dispatch.
    (4) Maximum take-off thrust for CFM56-3C-1 (23.5K) rating must 
not be used above 

[[Page 53552]]
5,000 feet pressure altitude, or the 5 minute time limit, whichever 
occurs first.
    (5) Maximum continuous or maximum climb thrust for CFM56-3C-1 
(23.5K) rating must not be used above 10,000 feet pressure altitude.
    (6) LANDING.
    (i) For landing at destination airport or for less than maximum 
landing weight the CFM56-3B-2 (22K) go-around rating should be used.
    (ii) Go-around at CFM56-3C-1 (23.5K) rating should be used when 
returning to departure airport or diverting in an emergency 
situation providing airport pressure altitude is 2,500 feet or less 
and the landing weight is greater than maximum landing weight.

End of Appendix I

    (c) For CFM56-3C-1 model turbofan engines equipped with fan 
blade P/N's 9527M99P08, 9527M99P09, 9527M99P10, 9527M99P11, or 
1285M39P01, install fan blade P/N's 1590M21P01, 1663M24P01, 
1663M24P02, 1663M24P03, 7M99P08, 9527M99P09, 9527M99P10, 9527M99P11, 
or 1285M39P01, 1663M24P04, or 1663M24P05 in accordance with CFMI 
CFM56-3/-3B/-3C SB No. 72-543, Revision 4, dated July 29, 1992, 
prior to June 30, 1996. The installation of new fan blades in 
accordance with this paragraph constitutes terminating action to the 
thrust level limitations required by paragraph (b) of this AD.
    (d) For CFM56-3B-2 model turbofan engines, Serial Number (S/N) 
725101, 725102, 725103, 725104, 725105, 725107, 725108, 725141, and 
725142:
    (1) Prior to further flight, remove from service stage 1 fan 
disk P/N 335-014-511-0 that have operated at unrestricted CFM56-3C-1 
thrust levels with fan blade P/N's 9527M99P08, 9527M99P09, 
9527M99P10, 9527M99P11, or 1285M39P01 and replace with a serviceable 
fan disk.
    (2) Prior to further flight, remove from service stage 1 fan 
blade P/N's 9527M99P08, 9527M99P09, 9257M99P10, 9257M99P11, and 
1285M39P01 that have operated at unrestricted CFM56-3C-1 thrust 
levels and replace with a serviceable fan blade.

    Note: Ground running for maintenance purposes should be 
conducted in accordance with CFM56-3B-2 rating limitations.

    (e) Fan disk removal, fan blade removal, and airplane wiring 
modifications done in accordance with AD 89-13-51 satisfies the 
corresponding requirements of paragraphs (a), (b), and (d) of this 
AD.
    (f) For the purpose of this AD, unrestricted CFM56-3C-1 thrust 
levels include operation at either of the following:
    (1) More than CFM56-3B-2 maximum take-off thrust above 5,000 
feet pressure altitude.
    (2) More than CFM56-3B-2 maximum continuous or maximum climb 
thrust above 10,000 feet pressure altitude.
    (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, Engine Certification Office. The 
request should be forwarded through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Engine Certification Office.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Engine 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) to operate the aircraft to a location where 
the requirements of this AD can be accomplished.

    Issued in Burlington, Massachusetts, on October 2, 1995.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 95-25568 Filed 10-13-95; 8:45 am]
BILLING CODE 4910-13-U