[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]
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