[Federal Register Volume 64, Number 158 (Tuesday, August 17, 1999)]
[Proposed Rules]
[Pages 44667-44670]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-21331]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-07-AD]
RIN 2120-AA64


Airworthiness Directives; Allison Engine Company AE 3007A and AE 
3007C Series Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This proposal would require revisions to the Airworthiness 
Limitations Section of the Allison Engine Company AE 3007A and AE 3007C 
Engine Manuals to include required enhanced inspection of selected 
critical life-limited parts at each piece-part exposure. This proposal 
would also require an air carrier's approved continuous airworthiness 
maintenance program to incorporate these inspection procedures. Air 
carriers with an approved continuous airworthiness maintenance program

[[Page 44668]]

would be allowed to either maintain the records showing the current 
status of the inspections using the record keeping system specified in 
the air carrier's maintenance manual, or establish an acceptable 
alternate method of record keeping. This proposal is prompted by an FAA 
study of in-service events involving uncontained failures of critical 
rotating engine parts that indicated the need for improved inspections. 
The improved inspections are needed to identify those critical rotating 
parts with conditions, which if allowed to continue in service, could 
result in uncontained failures. The actions specified by this proposed 
AD are intended to prevent critical life-limited rotating engine part 
failure, which could result in an uncontained engine failure and damage 
to the airplane.

DATES: Comments must be received by September 16, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 99-NE-07-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ane-
[email protected]''. Comments sent via the Internet must contain the 
docket number in the subject line. Comments may be inspected at this 
location between 8:00 a.m. and 4:30 p.m., Monday through Friday, except 
Federal holidays.

FOR FURTHER INFORMATION CONTACT: Chung-Der Young, Aerospace Engineer 
Chicago Aircraft Certification Office, FAA, Small Airplane Directorate, 
2300 East Devon Avenue, Des Plaines, IL 60018; telephone (847) 294-
7309, fax (847) 294-7834.

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 99-NE-07-AD.'' 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 Regional Counsel, 
Attention: Rules Docket No. 99-NE-07-AD, 12 New England Executive Park, 
Burlington, MA 01803-5299.

Discussion

    A recent FAA study analyzing 15 years of accident data for 
transport category airplanes identified several failure mode root 
causes that can result in serious safety hazards to transport category 
airplanes. This study identified uncontained failure of critical life-
limited rotating engine parts as the leading engine-related safety 
hazard to airplanes. Uncontained engine failures have resulted from 
undetected cracks in rotating parts that initiated and propagated to 
failure. Cracks can originate from causes such as unintended excessive 
stress from the original design, or they may initiate from stresses 
induced from material flaws, handling damage, or damage from machining 
operations. The failure of rotating parts can present a significant 
safety hazard to the airplanes by release of high energy fragments that 
could injure passengers or crew by penetration of the cabin, damage 
flight control surfaces, sever flammable fluid lines, or otherwise 
compromise the airworthiness of the airplane.
    Accordingly, the FAA has developed an intervention strategy to 
significantly reduce uncontained engine failures. This intervention 
strategy was developed after consultation with industry and will be 
used as a model for future initiatives. This intervention strategy is 
to conduct enhanced, nondestructive inspections of fan disks which 
could most likely result in a safety hazard to the airplane in the 
event of a disk fracture. The FAA is also considering the need for 
additional rule making. Future ADs may be issued introducing additional 
intervention strategies to further reduce or eliminate uncontained 
engine failures.
    Properly focused enhanced inspections require identification of the 
parts whose failure presents the highest safety hazard to the airplane, 
identifying the most critical features to inspect on these parts, and 
utilizing inspection procedures and techniques that improve crack 
detection. The FAA, with close cooperation of the engine manufacturers, 
has completed a detailed analysis that identifies the most safety 
significant parts and features, and the most appropriate inspection 
methods.
    Critical life-limited high-energy rotating parts are currently 
subject to some form of recommended crack inspection when exposed 
during engine maintenance or disassembly. As a result of this AD, the 
inspections currently recommended by the manufacturer will become 
mandatory for those parts listed in the compliance section.
    Furthermore, the FAA intends that additional mandatory enhanced 
inspections resulting from this AD serve as an adjunct to the existing 
inspections. The FAA has determined that the enhanced inspections will 
significantly improve the probability of crack detection while the 
parts are disassembled during maintenance. All mandatory inspections 
must be conducted in accordance with detailed inspection procedures 
prescribed in the manufacturer's Engine Manuals.
    Additionally, this AD allows for air carriers operating under the 
provisions of 14 CFR part 121 with an FAA-approved continuous 
airworthiness maintenance program, and entities with whom those air 
carriers make arrangements to perform this maintenance, to verify 
performance of the enhanced inspections by retaining the maintenance 
records that include the inspections resulting from this AD, provided 
that the records include the date and signature of the person 
performing the maintenance action. These records must be retained with 
the maintenance records of the part, engine module, or engine until the 
task is repeated. This will establish a method of record preservation 
and retrieval typical to those in existing continuous airworthiness 
maintenance programs. Instructions must be included in an air carrier's 
maintenance manual providing procedures on how this record preservation 
and retrieval system will be implemented and integrated into the air 
carrier's record keeping system.
    This proposal would require, within the next 30 days after the 
effective date of this AD, revisions to the

[[Page 44669]]

Airworthiness Limitations Section in the Allison Engine Company AE 
3007A and AE 3007C Engine Manuals, and, for air carriers, the approved 
continuous airworthiness maintenance program. Allison Engine Company, 
the manufacturer of AE 3007A and AE 3007C series turbofan engines, used 
on 14 CFR part 25 airplanes, has provided the FAA with a detailed 
proposal that identifies and prioritizes the critical life-limited 
rotating engine parts with the highest potential to hazard the airplane 
in the event of failure, along with instructions for enhanced, focused 
inspection methods. The enhanced inspections resulting from this AD 
will be conducted at piece-part opportunity, as defined below in the 
compliance section, rather than specific time inspection intervals.
    The FAA estimates that 450 engines installed on airplanes of U.S. 
registry would be affected by this proposed AD, that it would take 
approximately 1 work hour per engine to accomplish the proposed 
actions. The average labor rate is $60 per work hour. Based on these 
figures, the total cost impact of the proposed AD on U.S. operators is 
estimated to be $27,000.
    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), 40113, 44701.


Sec. 39.13  [Amended]

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

Allison Engine Company: Docket 99-NE-07-AD.

    Applicability: Allison Engine Company AE 3007A, A1/1, A1/2, 
A1and AE 3007C series turbofan engines, installed on but not limited 
to EMBRAER EMB-145 series and Cessna 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 (c) 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 critical life-limited rotating engine part failure, 
which could result in an uncontained engine failure and damage to 
the airplane, accomplish the following:
    (a) Within the next 30 days after the effective date of this AD, 
revise the Airworthiness Limitations Section of the Allison Engine 
Company AE 3007A and AE 3007C Engine Manuals, and for air carrier 
operations revise the approved continuous airworthiness maintenance 
program, by adding the following:

``Mandatory Inspections

    (1) Perform inspections of the following parts at each piece-part 
opportunity in accordance with the instructions provided in the 
applicable manual provisions:

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          Part nomenclature               Part No. (P/N)               Inspect per engine manual chapter
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Wheel, Fan..........................  All...................  72-21-21 (Task 72-21-21-200-801)
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    (2) For the purposes of these mandatory inspections, piece-part 
opportunity means:
    (i) The part is completely disassembled when done in accordance 
with the disassembly instructions in the engine manufacturer's Heavy 
Maintenance Manual; and
    (ii) The part has accumulated more than 100 cycles in service 
since the last piece-part opportunity inspection, provided that the 
part was not damaged or related to the cause for its removal from 
the engine.''
    (b) Except as provided in paragraph (c) of this AD, and 
notwithstanding contrary provisions in Sec. 43.16 of the Federal 
Aviation Regulations (14 CFR 43.16), these mandatory inspections 
shall be performed only in accordance with the Airworthiness 
Limitations Section of the Allison Engine Company AE 3007A and AE 
3007C Engine Manuals.
    (c) 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 Engine Certification Office. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector (PMI), who may add comments and then send it 
to the Engine Certification Office.

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

    (d) Special flight permits may be issued in accordance with 
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
21.197 and 21.199) to operate the airplane to a location where the 
requirements of this AD can be accomplished.
    (e) FAA-certificated air carriers that have an approved 
continuous airworthiness maintenance program in accordance with the 
record keeping requirement of Sec. 121.369(c) of the Federal 
Aviation Regulations [14 CFR 121.369(c)] of this chapter must 
maintain records of the mandatory inspections that result from 
revising the Airworthiness Limitations Section and the air carrier's 
continuous airworthiness program. Alternately, certificated air 
carriers may establish an approved system of record retention that 
provides a method for preservation and retrieval of the maintenance 
records that include the inspections resulting

[[Page 44670]]

from this AD, and include the policy and procedures for implementing 
this alternate method in the air carrier's maintenance manual 
required by Sec. 121.369(c) of the Federal Aviation Regulations [14 
CFR 121.369(c)]; however, the alternate system must be accepted by 
the appropriate PMI and require the maintenance records be 
maintained either indefinitely or until the work is repeated. 
Records of the piece-part inspections are not required under 
Sec. 121.380(a)(2)(vi) of the Federal Aviation Regulations [14 CFR 
121.380(a)(2)(vi)]. All other Operators must maintain the records of 
mandatory inspections required by the applicable regulations 
governing their operations.

    Note 3: The requirements of this AD have been met when the 
engine manual changes are made and air carriers have modified their 
continuous airworthiness maintenance plans to reflect the 
requirements in the Engine Manuals.

    Issued in Burlington, Massachusetts, on August 9, 1999.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-21331 Filed 8-16-99; 8:45 am]
BILLING CODE 4910-13-U