AD Amdt-39-9989

[Federal Register Volume 62, Number 77 (Tuesday, April 22, 1997)]
[Rules and Regulations]
[Pages 19483-19484]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 97-10357]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-ANE-44; Amendment 39-9989; AD 97-08-01]
RIN 2120-AA64


Airworthiness Directives; CFM International CFM56-3, -3B, and -3C 
Series Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to CFM International CFM56-3, -3B, -3C series turbofan 
engines, that requires a reduction of the low cycle fatigue (LCF) 
retirement lives for certain fan disks. This amendment is prompted by 
the results of a refined life analysis performed by the manufacturer 
which revealed minimum calculated LCF lives significantly lower than 
published LCF retirement lives. The actions specified by this AD are 
intended to prevent a LCF failure of the fan disk, which could result 
in an uncontained engine failure and damage to the aircraft.

DATES: Effective June 23, 1997.

FOR FURTHER INFORMATION CONTACT: Glorianne Messemer, Aerospace 
Engineer, Engine Certification Office, FAA, Engine and Propeller 
Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; 
telephone (617) 238-7132; fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to CFM International (CFMI) CFM56-3C 
series turbofan engines was published in the Federal Register on 
October 10, 1995 (60 FR 52636). That action proposed to require a 
reduction of the low cycle fatigue (LCF) retirement lives for certain 
fan disks.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    Two commenters state that the proposed rule should be revised to 
address the LCF retirement lives for engines that may have operated at 
several thrust ratings, including the CFM56-3 and -3B engine models, 
since the retirement lives are dependent on the thrust rating. The FAA 
concurs. The FAA has revised the Applicability paragraph and paragraphs 
(a), (b), and (c) of this final rule accordingly.
    Two commenters support the rule as proposed.
    In addition, the FAA has added the specific fan disk part numbers 
to the Applicability paragraph of this AD in order to more accurately 
define the population of engines to which this AD applies.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes

[[Page 19484]]

described previously. The FAA has determined that these changes will 
neither increase the economic burden on any operator nor increase the 
scope of the AD.
    The FAA estimates that 33 engines installed on aircraft of U.S. 
registry will be affected by this AD, and that it will not take any 
additional work hours per engine to accomplish the required actions. 
Assuming that the parts cost is proportional to the reduction of the 
LCF retirement lives, the required parts will cost approximately 
$17,275 per engine. Based on these figures, the total cost impact of 
the AD on U.S. operators is estimated to be $570,075.
    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.
    For the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it 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 USC 106(g), 40113, 44701.


Sec. 39.13  [AMENDED]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

97-08-01  CFM International: Amendment 39-9989. Docket 95-ANE-44.

    Applicability: CFM International (CFMI) CFM56-3, -3B, and -3C 
series turbofan engines with fan disks, Part Number (P/N) 335-014-
509-0 or 335-014-511-0, installed, that are currently operating at, 
or have previously operated at, the Category C thrust rating. These 
engines are installed on but not limited to Boeing 737 series 
aircraft.

    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 (g) 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 a low cycle fatigue (LCF) failure of the fan disk, 
which could result in an uncontained engine failure and damage to 
the aircraft, accomplish the following:
    (a) For CFM56-3C series engines operating at the Category C 
thrust rating on the effective date of this AD, remove the fan disk 
prior to accumulating a total Category C thrust rating life of 
20,100 cycles.
    (b) For CFM56-3B and -3C series engines operating at the 
Category B thrust rating on the effective date of this AD, but which 
have previously operated at the Category C thrust rating, 
recalculate the fan disk total cycles remaining at the Category B 
thrust rating using a Category C thrust rating life of 20,100 
cycles.

    Note 2: The current fan disk Category B thrust rating life is 
24,900 cycles, and is not affected by this AD.

    (c) For CFM56-3, -3B, and -3C series engines operating at the 
Category A thrust rating on the effective date of this AD, but which 
have previously operated at the Category C thrust rating, 
recalculate the fan disk total cycles remaining at the Category A 
thrust rating using a Category C thrust rating life of 20,100 
cycles.

    Note 3: The current fan disk Category A thrust rating life is 
30,000 cycles, and is not affected by this AD.

    (d) This action establishes the new Category C thrust rating LCF 
retirement life of 20,100 cycles listed in paragraphs (a), (b), and 
(c) of this AD. This retirement life is published in Chapter 05 of 
the CFM56-3 model series Engine Shop Manual, CFMI-TP.SM.5.
    (e) The Category A, B, and C thrust ratings listed in paragraphs 
(a), (b), and (c) of this AD are defined in Chapter 05 of the CFM56-
3 model series Engine Shop Manual, CFMI-TP.SM.5.
    (f) The method to recalculate the retirement life, as stated in 
paragraphs (b) and (c) of this AD is defined in Chapter 05 of the 
CFM56-3 model series Engine Shop Manual, CFMI-TP.SM.5.
    (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 4: 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.
    (i) This amendment becomes effective on June 23, 1997.

    Issued in Burlington, Massachusetts, on April 8, 1997.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 97-10357 Filed 4-21-97; 8:45 am]
BILLING CODE 4910-13-U