[Federal Register Volume 59, Number 84 (Tuesday, May 3, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-10503]


[[Page Unknown]]

[Federal Register: May 3, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-ANE-11]

 

Airworthiness Directives; General Electric Company CF6 Series 
Turbofan Engines

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 General Electric Company 
(GE) CF6-45/-50/-80A series turbofan engines, that currently requires a 
one-time ultrasonic and eddy current inspection of the high pressure 
compressor rotor (HPCR) stage 3-9 spool for cracks. This action would 
retain the inspection requirements of the current AD, but would 
accelerate the inspection schedule, and introduce a repetitive 
inspection requirement. This proposal is prompted by a review of the 
inspection results to date, which indicate that the crack occurrence 
rate is higher than initially projected. The actions specified by the 
proposed AD are intended to prevent an uncontained HPCR stage 3-9 spool 
failure, which could result in damage to the aircraft.

DATES: Comments must be received by June 2, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 94-ANE-11, 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 General Electric Aircraft Engines, CF6 Distribution 
Clerk, room 132, 111 Merchant Street, Cincinnati, OH 45246. 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 J. 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 94-ANE-11.'' 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. 94-ANE-11, 12 New England Executive Park, 
Burlington, MA 01803-5299.

Discussion

    On October 25, 1991, the Federal Aviation Administration (FAA) 
issued airworthiness directive (AD) 91-20-01, Amendment 39-8035 (56 FR 
55230), to require a one-time ultrasonic and eddy current inspection of 
the high pressure compressor rotor (HPCR) stage 3-9 spool for cracks. 
That action was prompted by two reports of spools found cracked in 
service. That condition, if not corrected, could result in an 
uncontained HPCR stage 3-9 spool failure, which could result in damage 
to the aircraft.
    Since the issuance of that AD, the FAA has received reports of five 
additional spools found cracked in service. Investigation indicates 
that the cracks initiated in sub-surface origins in the stage 9 bore 
region of the spool. These cracks form from metallurgical anomalies 
that result from reduced forging work associated with the sixteen inch 
billet material used in the manufacture of certain HPCR stage 3-9 
spools.
    Based on the investigation findings, and the higher than projected 
crack occurrence rates, the FAA has determined that the inspection 
schedule in the current AD should be accelerated, and a repetitive 
inspection requirement be implemented.
    The FAA has reviewed and approved the technical contents of GE CF6-
50 Service Bulletin (SB) No. 72-1000, Revision 2, dated September 9, 
1993, and GE CF6-80A SB No. 72-583, Revision 4, dated September 15, 
1993, which describe procedures for the ultrasonic and eddy current 
inspection of the HPCR stage 3-9 spool.
    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 91-20-01, would retain the one-time 
ultrasonic and eddy current inspection of the HPCR stage 3-9 spool for 
cracks as required in the current AD, but would accelerate the 
inspection schedule, and introduce a repetitive ultrasonic and eddy 
current inspection requirement.
    There are approximately 462 GE CF6-45/-50/-80A series engines of 
the affected design in the worldwide fleet. The FAA estimates that 67 
engines installed in aircraft of U.S. registry would be affected by the 
proposed AD, that it would take approximately 584 work hours per engine 
to accomplish the proposed actions, and that the average labor rate is 
$55 per work hour. Required parts would cost approximately $127,412 per 
engine. Based on these figures, and assuming that 3 of the inspected 
spools will require replacement, the total cost impact of the proposed 
AD on U.S. operators is estimated to be $2,534,276.
    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 ``major rule'' under Executive Order 12291; 
(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 14 
CFR part 39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing Amendment 39-8035 (56 FR 
55230; October 25, 1991) and by adding a new airworthiness directive to 
read as follows:


General Electric Company: Docket No. 94-ANE-11. Supersedes AD 91-20-
01, Amendment 39-8035.

    Applicability: General Electric Company (GE) CF6-45/-50/-80A 
series turbofan engines installed on, but not limited to, Airbus 
A300 and A310 series, Boeing 747 and 767 series, and McDonnell 
Douglas DC-10 series aircraft.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent an uncontained high pressure compressor rotor (HPCR) 
stage 3-9 spool failure, which could result in damage to the 
aircraft, accomplish the following:
    (a) Eddy current and ultrasonic inspect GE CF6-45/-50 HPCR stage 
3-9 spools, Part Number (P/N) 9136M89G02, 9136M89G03, 9136M89G06, 
9136M89G08, 9253M85G01, 9253M85G02, 9273M14G01, and 9331M29G01, with 
serial numbers (S/N) listed in Table 2 of GE CF6-50 Service Bulletin 
(SB) No. 72-1000, Revision 2, dated September 9, 1993, as follows:
    (1) For spools that have not been previously inspected in 
accordance with GE CF6-50 SB No. 72-888, Original, Revision 1, 
Revision 2, Revision 3, or Revision 4, or GE CF6-50 SB No. 72-1000, 
Original, Revision 1, or Revision 2, inspect in accordance with 
paragraph 2.C of GE CF6-50 SB No. 72-1000, Revision 2, dated 
September 9, 1993, at the next engine shop visit, or by 30 days 
after the effective date of this AD, whichever occurs earlier.
    (2) For spools that have been inspected in accordance with GE 
CF6-50 SB No. 72-888, Original, Revision 1, or Revision 2, inspect 
in accordance with paragraph 2.D of GE CF6-50 SB No. 72-1000, 
Revision 2, dated September 9, 1993, at the next engine shop visit, 
or by December 31, 1994, whichever occurs earlier.
    (3) For spools that have been inspected in accordance with GE 
CF6-50 SB No. 72-888, Original, Revision 1, or Revision 2, and GE 
CF6-50 SB No. 72-1008, Original, inspect in accordance with 
paragraph 2.D of GE CF6-50 SB No. 72-1000, Revision 2, dated 
September 9, 1993, at the next piece-part exposure, or within 3,500 
cycles in service (CIS) since inspected in accordance with GE CF6-50 
SB No. 72-1008, Original, whichever occurs earlier.
    (4) For spools that have been inspected in accordance with GE 
CF6-50 SB No. 72-888, Revision 3, or Revision 4, or GE CF6-50 SB No. 
72-1000, Original, Revision 1, or Revision 2, inspect in accordance 
with paragraph 2.D of GE CF6-50 SB No. 72-1000, Revision 2, dated 
September 9, 1993, at the next piece-part exposure, or within 3,500 
CIS since inspected in accordance with, GE CF6-50 SB No. 72-888, 
Revision 3, or Revision 4, or GE CF6-50 SB No. 72-1000, Original, 
Revision 1, or Revision 2, whichever occurs earlier.
    (b) Thereafter, for spools that have been inspected in 
accordance with paragraph (a) of this AD, reinspect in accordance 
with paragraph 2.D of GE CF6-50 SB No. 72-1000, Revision 2, dated 
September 9, 1993, at intervals not to exceed 3,500 CIS since the 
last inspection.
    (c) Eddy current and ultrasonic inspect GE CF6-80A HPCR 3-9 
spool, P/N 9136M89G10, with S/N's listed in Table 2 of GE CF6-80A SB 
No. 72-583, Revision 4, dated September 15, 1993, as follows:
    (1) For spools that have not been previously inspected in 
accordance with GE CF6-80A SB No. 72-500, Original, Revision 1, 
Revision 2, Revision 3, or Revision 4, or GE CF6-80A SB No. 72-583, 
Original, Revision 1, Revision 2, Revision 3, or Revision 4, inspect 
in accordance with paragraph 2.C of GE CF6-80A SB No. 72-583, 
Revision 4, dated September 15, 1993, at the next engine shop visit, 
or by 30 days after the effective date of this AD, whichever occurs 
earlier.
    (2) For spools that have been previously inspected in accordance 
with GE CF6-80A SB No. 72-500, Revision 3, or Revision 4, or GE CF6-
80A SB No. 72-583, Original, Revision 1, Revision 2, Revision 3, or 
Revision 4, inspect in accordance with paragraph 2.D of GE CF6-80A 
SB No. 72-583, Revision 4, dated September 15, 1993, at the next 
piece-part exposure, or within 3,500 CIS since inspected in 
accordance with GE CF6-80A SB No. 72-500, Revision 3, or Revision 4, 
or GE CF6-80A SB No. 72-583, Original, Revision 1, Revision 2, 
Revision 3, or Revision 4, whichever occurs earlier.
    (d) Thereafter, for spools that have been inspected in 
accordance with paragraph (c) of this AD, reinspect in accordance 
with paragraph 2.D of GE CF6-80A SB No. 72-583, Revision 4, dated 
September 15, 1993, at intervals not to exceed 3,500 CIS since the 
last inspection.
    (e) Remove from service prior to further flight HPCR stage 3-9 
spools that meet or exceed the reject criteria established in 
Section 2.C and 2.D, as applicable, of GE CF6-50 SB No. 72-1000, 
Revision 2, dated September 9, 1993, and GE CF6-80A SB No. 72-583, 
Revision 4, dated September 15, 1993, as appropriate.
    (f) For the purpose of this AD, an engine shop visit is defined 
as the induction of an engine into a shop for maintenance involving 
the separation of any major flange.
    (g) For the purpose of this AD, piece-part exposure is defined 
as disassembly and removal of the stage 3-9 spool from the HPCR 
rotor.
    (h) An alternative method of compliance or adjustment of the 
compliance time, which provides an acceptable level of safety, may 
be used when 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 alternate 
methods of compliance with this airworthiness directive, if any, may 
be obtained from the Engine Certification Office.

    (i) Special flight permits may be issued, in accordance with 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 April 26, 1994.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 94-10503 Filed 5-2-94; 8:45 am]
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