AD 2000-09-05

[Federal Register Volume 65, Number 88 (Friday, May 5, 2000)]
[Rules and Regulations]
[Pages 26121-26122]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 00-11177]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-46-AD; Amendment 39-11714; AD 2000-09-05]
RIN 2120-AA64


Airworthiness Directives; Allison Engine Company AE 3007 Series 
Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Allison Engine Company AE 3007 series turbofan 
engines. This AD would require removal of certain cone shafts from 
service before exceeding new cyclic life limits and replacement with 
serviceable parts. This amendment is prompted by additional testing and 
low cycle fatigue (LCF) life analysis that substantiate lower cyclic 
lives than originally determined. The actions specified by this AD are 
intended to prevent LCF failure of cone shafts, which could result in 
an uncontained engine failure and damage to the aircraft.

DATES: Effective date July 5, 2000.

ADDRESSES: This information may be examined at the Federal Aviation 
Administration (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, 
2300 East Devon Avenue, Des Plaines, IL 60018; telephone (847) 294-
8180, fax (847) 294-7834.

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 Allison Engine Company AE 3007A, 
AE 3007A1, AE 3007A1/1, AE 3007A1/2, AE 3007A1/3, AE 3007A1P, and AE 
3007C turbofan engines was published in the Federal Register on October 
12, 1999 (64 FR 55196). That action proposed to require the removal of 
certain cone shafts, P/Ns 23050728 and 23070729, from service prior to 
the accumulation of new cyclic life limits, depending on engine model.

Comments Received

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Increase Cone Shaft Life Limits for AE 3007A and AE 3007C Engines

    The manufacturer requests that the FAA increase the cone shaft life 
limits for the AE 3007A and AE 3007C engines from 7,500 cycles each to 
9,500 cycles and 14,500 cycles respectively. At the time the NPRM was 
issued, the cone shaft low cycle fatigue analysis for these engines was 
not available, and the FAA proposed lower, more conservative shaft life 
limits. The analysis has since been completed and the manufacturer 
requests that the life limits be increased.
    The FAA agrees. The methodology used to determine the lives for 
these engine models has been approved by the FAA and is consistent with 
that used to determine critical part lives for other engines already in 
service (AE 3007A1, AE 3007A1/1, and AE 3007A1/2). Therefore, the cone 
shaft life limits for the AE 3007A and AE3007C engines should be 
increased to 9,500 cycles for the AE 3007A engine and to 14,500 cycles 
for the AE 3007C engine. Accordingly, new paragraphs (a), (b), and (c) 
in the final rule are substituted for proposed paragraph (a), and the 
proposed paragraphs (b) through (g) become paragraphs (d) through (i) 
in the final rule.

Increase Cone Shaft Life Limits for AE 3007A1/3 and AE 3007A1P 
Engines

    One commenter requests that the FAA increase the cone shaft life 
limits for the AE 3007A1/3 and AE 3007A1P engines from 3,500 cycles and 
2,400 cycles, respectively, to 7,500 cycles each. The commenter 
suggests that the cone shaft life of the AE 3007A1/3 and AE 3007A1P 
engines should be increased to match those of the AE 3007A1, AE 3007A1/
1, and AE 3007A1/2 engines for two reasons:
    <bullet> The turbomachinery hardware is the same for all the engine 
models referenced above. The primary difference between the models is 
the engine control software.
    <bullet> A significant operational aspect of this group of engines 
is the ability to easily maintain fleet readiness by changing the 
engine model with an engine control software change.
    The FAA does not agree. When new data from tests or analysis 
suggests that component low cycle fatigue lives need to be reduced, 
different approaches may be taken, depending on the circumstances. If 
there are significant numbers of affected engines in the field (e.g. AE 
3007A, AE 3007A1, AE 3007A1/1, AE 3007A1/2, and AE 3007C models), a 
life management program is developed that allows the users some 
operational flexibility while maintaining an acceptable level of risk 
for the fleet. If there is a very small number of affected engines in 
the field, the FAA prefers a life management program structured on the 
lifing methodology intended for original certification of the engine 
design. For the AE 3007A1/3 and AE 3007A1P engines, therefore, the FAA 
has determined to use the original FAA approved lifing methodology.

Increase Cone Shaft Life Limits for AE 3007A3 Engines

    One commenter requests that the FAA increase the cone shaft life 
limits for the AE 3007A3 engines.
    The FAA does not agree. This engine model was not included in the 
NPRM and is beyond the scope of this AD.

Incorrect Model Designation

    The NPRM incorrectly specifies the AE 3007A1/P engine. This 
designation should read ``AE 3007A1P.'' This has been corrected in the 
final rule.

Conclusion

    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 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.

Economic Analysis

    There are approximately 598 engines of the affected design in the 
worldwide fleet. The FAA estimates that 364 engines installed on 
aircraft of U.S. registry will be affected by this AD, that it will 
take approximately 150 work hours per engine to accomplish the required 
actions, and that the average labor rate is $60 per work hour. Required 
parts will cost approximately $3,921 per engine. Based on these 
figures, the total cost impact of the AD on U.S. operators is estimated 
to be $4,703,244.

[[Page 26122]]

Regulatory Impact

    This rule does not have federalism implications, as defined in 
Executive Order 13132, because it does 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. Accordingly, 
the FAA has not consulted with state authorities prior to publication 
of this rule.
    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 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, 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 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

2000-09-05  Allison Engine Company: Amendment 39-11714; Docket 99-
NE-46-AD.

    Applicability: Allison Engine Company Models AE 3007A, AE 
3007A1, AE 3007A1/1, AE 3007A1/2, AE 3007A1/3, AE 3007A1P, and AE 
3007C turbofan engines, with cone shafts, part numbers (P/Ns) 
23050728 and 23070729, installed. These engines are installed on but 
not limited to EMBRAER EMB-135 and EMB-145 series and Cessna 750 
(Citation X) series airplanes.

    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 (h) 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 low cycle fatigue failure of cone shafts, which could 
result in an uncontained engine failure and damage to the aircraft, 
accomplish the following:

Removal From Service

    (a) For Allison Engine Company model AE 3007A engines, remove 
cone shafts from service prior to accumulating 9,500 cycles-since-
new (CSN) and replace with serviceable parts.
    (b) For Allison Engine Company model AE 3007C engines, remove 
cone shafts from service prior to accumulating 14,500 CSN and 
replace with serviceable parts.
    (c) For Allison Engine Company models AE 3007A1, AE 3007A1/1, 
and AE 3007A1/2 engines, remove cone shafts from service prior to 
accumulating 7,500 CSN and replace with serviceable parts.
    (d) For Allison Engine Company model AE 3007A1/3 engines, remove 
cone shafts from service prior to accumulating 3,500 CSN and replace 
with serviceable parts.
    (e) For Allison Engine Company model AE 3007A1P engines, remove 
cone shafts from service prior to accumulating 2,400 CSN and replace 
with serviceable parts.

New Life Limits

    (f) Paragraphs (a), (b), (c), (d) and (e) of this AD establish 
new, lower life limits for cone shafts, P/Ns 23050728 and 23070729.
    (g) Except for the provisions of paragraph (h) of this AD, no 
cone shafts, P/Ns 23050728 and 23070729, may remain in service 
exceeding the life limits established in paragraphs (a), (b), (c), 
(d) and (e) of this AD.

Alternative Method of Compliance

    (h) 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 (ACO). Operators shall submit their requests through an 
appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Chicago ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Chicago ACO.

Ferry Flights

    (i) No special flight permits will be issued.

Effective Date

    (j) This amendment becomes effective on July 5, 2000.


    Issued in Burlington, Massachusetts, on April 27, 2000.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 00-11177 Filed 5-4-00; 8:45 am]
BILLING CODE 4910-13-U