
[Federal Register: July 23, 2008 (Volume 73, Number 142)]
[Proposed Rules]               
[Page 42725-42727]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr23jy08-15]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-0419; Directorate Identifier 2007-NE-52-AD]
RIN 2120-AA64

 
Airworthiness Directives; General Electric Company CF34-1A, -3A, 
-3A1, -3A2, -3B, and -3B1 Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for General Electric Company (GE) CF34-1A, -3A, -3A1, -3A2, -3B, and -
3B1 turbofan engines with high-pressure (HP) rotor 4-step air balance 
piston stationary seals (4-step seals), part numbers 4923T54G01, 
6019T90G03, 6037T99G01, 6037T99G02, and 6037T99G03, installed. This 
proposed AD would require removing the 4-step seals and incorporating 
an 8-step seal at

[[Page 42726]]

the next piece-part exposure. This proposed AD results from the 
investigation of an airplane accident. Both engines experienced high-
altitude flameouts. Rotation of the HP rotors was not maintained during 
descent and the engines could not be restarted. We are proposing this 
AD to prevent the inability to restart both engines after flameout due 
to excessive friction of the 4-step seal, which could result in 
subsequent forced landing of the airplane.

DATES: We must receive any comments on this proposed AD by September 
22, 2008.

ADDRESSES: Use one of the following addresses to comment on this 
proposed AD.
     Federal eRulemaking Portal: Go to http://
www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: Docket Management Facility, U.S. Department of 
Transportation, 1200 New Jersey Avenue, SE., West Building Ground 
Floor, Room W12-140, Washington, DC 20590-0001.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
     Fax: (202) 493-2251.
    You can get the service information identified in this proposed AD 
from General Electric Company via Lockheed Martin Technology Services, 
10525 Chester Road, Suite C, Cincinnati, Ohio 45215, telephone (513) 
672-8400, fax (513) 672-8422.

FOR FURTHER INFORMATION CONTACT: Kenneth Steeves, Aerospace Engineer, 
Engine Certification Office, Engine and Propeller Directorate, FAA, 12 
New England Executive Park, Burlington, MA 01803; e-mail: 
kenneth.steeves@faa.gov; telephone: (781) 238-7765; fax: (781) 238-
7199.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    We invite you to send us any written relevant data, views, or 
arguments regarding this proposal. Send your comments to an address 
listed under ADDRESSES. Include ``Docket No. FAA-2007-0419; Directorate 
Identifier 2007-NE-52-AD'' in the subject line of your comments. We 
specifically invite comments on the overall regulatory, economic, 
environmental, and energy aspects of the proposed AD. We will consider 
all comments received by the closing date and may amend the proposed AD 
in light of those comments.
    We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact 
with FAA personnel concerning this proposed AD. Using the search 
function of the Web site, anyone can find and read the comments in any 
of our dockets. This includes, if provided, the name of the individual 
who sent the comment (or signed the comment on behalf of an 
association, business, labor union, etc.). You may review the DOT's 
complete Privacy Act Statement in the Federal Register published on 
April 11, 2000 (65 FR 19477-78).

Examining the AD Docket

    You may examine the AD docket on the Internet at http: //
www.regulations.gov; or in person at the Docket Operations office 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Operations office (telephone (800) 647-5527) is 
the same as the Mail address provided in the ADDRESSES section. 
Comments will be available in the AD docket shortly after receipt.

Discussion

    In October 2004, a Bombardier CL600-2B19 Regional Jet airplane 
experienced high-altitude flameouts of both engines while on a ferry 
flight. After flameout, when the airplane was descending, sufficient 
airspeed was not maintained to ensure rotation of the HP rotors and 
they stopped rotating. During repeated unsuccessful engine restart 
attempts on both engines, the HP rotors did not obtain sufficient 
rotational speeds for the engines to restart. The airplane eventually 
crashed while attempting to glide to an airport, and the crew was 
fatally injured. When these engines experience a high-altitude 
flameout, the engines are immediately subjected to rapid cooling due to 
the extremely cold air flowing around and through them. The static seal 
parts cool more rapidly than the rotors, and shrink until they contact 
the rotating seal surfaces. If the speed of the airplane is not 
sufficient to maintain windmill rotation of the HP rotors, the rotors 
will stop rotating and could lock if sufficient friction develops 
between the rotating and static air balance piston seal surfaces. This 
condition, if not corrected, could result in the inability to restart 
the engines and the subsequent forced landing of the airplane. 
Investigation by GE determined that under certain conditions, the 
existing 4-step seals used in CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 
turbofan engines can come into contact with the rotating seal surfaces 
and create friction. In a worse case, this friction could cause locking 
of the HP rotors, called ``rotor lock''. GE is introducing 8-step seals 
for all CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 turbofan engines. The 
8-step seals will reduce potential drag in the rotor system and enhance 
the windmilling capabilities of HP rotors. This will ultimately reduce 
the possibility of the HP rotor locking after a high-altitude flameout 
when HP rotor rotation is not maintained during descent.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other products 
of this same type design. We are proposing this AD, which would require 
removing the 4-step seal at next piece-part exposure and incorporating 
an 8-step seal, either by modifying the existing 4-step seal to an 8-
step seal or by replacing it with an 8-step seal.

Costs of Compliance

    We estimate that this proposed AD would affect 2,722 CF34-1A, -3A, 
-3A1, -3A2, -3B, and -3B1 turbofan engines installed on airplanes of 
U.S. registry. We also estimate that this proposed AD will not impose 
any additional labor or material costs as most of the seals will 
require replacement when they are removed from the engine during 
scheduled engine overhaul. For those few seals that can be reworked, we 
estimate that it would take about 5 work-hours per engine to perform 
the proposed seal modification, and that the average labor rate is $80 
per work-hour. Based on these figures, we estimate the total cost of 
the proposed AD to U.S. operators to be $108,800.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
subtitle VII, part A, subpart III, section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations

[[Page 42727]]

for practices, methods, and procedures the Administrator finds 
necessary for safety in air commerce. This regulation is within the 
scope of that authority because it addresses an unsafe condition that 
is likely to exist or develop on products identified in this rulemaking 
action.

Regulatory Findings

    We have determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would 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.
    For the reasons discussed above, I certify that the proposed AD:
    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. Would not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD. You may get a copy of this summary at the 
address listed under ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Under the authority delegated to me by the Administrator, the 
Federal Aviation Administration proposes to amend 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. The FAA amends Sec.  39.13 by adding the following new 
airworthiness directive:

General Electric Company: Docket No. FAA-2007-0419; Directorate 
Identifier 2007-NE-52-AD.

Comments Due Date

    (a) The Federal Aviation Administration (FAA) must receive 
comments on this airworthiness directive (AD) action by September 
22, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to General Electric Company (GE) CF34-1A, -
3A, -3A1, -3A2, -3B, and -3B1 turbofan engines, with high-pressure 
(HP) rotor 4-step air balance piston stationary seals (4-step 
seals), part numbers (P/Ns) 4923T54G01, 6019T90G03, 6037T99G01, 
6037T99G02, and 6037T99G03, installed. These engines are installed 
on, but not limited to, Bombardier, Inc. airplane models CL-600-
2A12, -2B16, and -2B19.

Unsafe Condition

    (d) This AD results from the investigation of an airplane 
accident. Both engines experienced high-altitude flameouts. Rotation 
of the HP rotors was not maintained during descent and the engines 
could not be restarted. We are issuing this AD to prevent the 
inability to restart both engines after flameout due to excessive 
friction of the 4-step seal, which could result in subsequent forced 
landing of the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed at the next piece-part exposure after the effective 
date of this AD, unless the actions have already been done.
    (f) Remove the 4-step seals, P/Ns 4923T54G01, 6019T90G03, 
6037T99G01, 6037T99G02, and 6037T99G03.
    (g) Incorporate an 8-step seal, either by modifying the existing 
4-step seal to an 8-step seal, or by replacing it with an 8-step 
seal.
    (h) Information on modifying the seal and part number 
configuration charts, can be found in GE Service Bulletin (SB) No. 
CF34-AL S/B 72-0238, dated July 27, 2007 (CL-600-2B19), and SB No. 
CF34-BJ S/B 72-0217, dated July 27, 2007 (CL-600-2A12 and CL-600-
2B16).

Definition

    (i) For the purposes of this AD, piece-part exposure means when 
the 4-step seal is removed from the combustion module in accordance 
with the disassembly instructions in the engine manufacturer's, or 
other FAA-approved engine manual.

Alternative Methods of Compliance

    (j) The Manager, Engine Certification Office, has the authority 
to approve alternative methods of compliance for this AD if 
requested using the procedures found in 14 CFR 39.19.

Related Information

    (k) Contact Kenneth Steeves, Aerospace Engineer, Engine 
Certification Office, Engine and Propeller Directorate, FAA, 12 New 
England Executive Park, Burlington, MA 01803; e-mail: 
keneth.steeves@faa.gov; telephone: (781) 238-7765, fax: (781) 238-
7199; for more information about this AD.

    Issued in Burlington, Massachusetts, on July 16, 2008.
Marc Bouthillier,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. E8-16884 Filed 7-22-08; 8:45 am]

BILLING CODE 4910-13-P
