AD 2000-20-02

This amendment adopts a new airworthiness directive (AD) that is applicable to General Electric Company (GE) CF6-50 series turbofan engines. This action requires inspection of the low pressure turbine nozzle lock assemblies, and replacement of the borescope plug with a new design plug. This amendment is prompted by three uncontained engine failures. The actions specified in this AD are intended to detect loose or missing LPT nozzle lock assembly studs that could lead to failure of the locks and subsequent uncontained failure of the engine.

Final rule; request for comments.

2000-20-02 General Electric Company: Amendment 39-11913. Docket 2000-NE-38-AD.

Applicability

This airworthiness directive (AD) is applicable to General Electric Company (GE) CF6-50 series turbofan engines. These engines are installed on, but not limited to, Airbus Industries A300, Boeing Airplane Company 747, and McDonnell Douglas Corporation DC10 airplanes.

Note 1: This 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

Compliance with this AD is required as indicated, unless already done.

To detect loose or missing LPT nozzle lock assembly studs that could lead to failure of the locks and subsequent uncontained failure of the engine, do the following:

Initial Inspection of Stage 2 LPT Nozzle Lock Assemblies

(a) Visually inspect the stage 2 LPT nozzle lock assemblies for loose or missing studs within the following times after the effective date of this AD. Information about on-wing visual inspections may be found in the appropriate aircraft maintenance manual (AMM).

Time on lock assembly
Inspect within the earlier of
(1) 5,500 or fewer hours time-since-new (TSN) on the effective date of this AD.
500 hours time-in-service (TIS) or 60 days after the
effective date of this AD.
(2) Greater than 5,500 hours TSN on the effective date of this AD, or if TSNis not known.
250 hours TIS or 30 days after the effective date of this
AD.

(b) If any stage 2 LPT nozzle lock assembly stud is loose or missing, replace all of the stage 2 LPT nozzle lock assemblies with new nozzle lock assemblies before further flight.

Repetitive Inspection of Stage 2 LPT Nozzle Lock Assemblies

(c) Thereafter, visually inspect the stage 2 LPT nozzle lock assemblies for loose or missing studs within the following times-since-last-inspection (TSLI). Information about on-wing visual inspections may be found in the appropriate AMM.

Time on lock assembly
Repetitive inspection
(1) 5,500 or fewer hours TSN.
500 hours TSLI.
(2) Greater than 5,500 hours TSN or if TSN is not known.
250 hours TSLI.

(d) If any stage 2 LPT nozzle lock assembly stud is loose or missing, replace all of the stage 2 LPT nozzle lock assemblies with new nozzle lock assemblies before further flight.

Replacement of Borescope Plug

(e) On engines with lock assemblies that have the following times on the effective date of this AD, remove the existing stage 2 LPT nozzle borescope plug, part number P/N 9022M63G13, and install borescope plug P/N 2083M99P01, or a plug with the alternate P/N's 305-381-303-0 or 2110M79P01, in accordance with the Accomplishment Instructions 3.A through 3.B.(7) of GE alert service bulletin (ASB) CF6-50 72-A1196, dated September 15, 2000.

Time on lock assembly
Install borescope plug within the earlier of
(1) 5,500 or fewer hours TSN on the effective date of this AD.
500 hours TIS or 60 days after the effective date of
this AD.
(2) Greater than 5,500 hours TSN on the effective date of this AD.
250 hours TIS or 30 days after the effective date of this AD.

(f) Do not install borescope plug P/N 9022M63G13 in the borescope inspection port for the stage 2 LPT nozzle after the plug has been replaced in accordance with paragraph (e) of this AD.

Inspection for Buckling and Cracks

(g) For engines on which the borescope plug has been replaced in accordance with paragraph (e) of this AD, visually inspect the LPT stator case assembly around the stage 2 LPT borescope inspection port boss each time the lock assemblies are inspected, as specified in paragraph (c) of this AD, for evidence of buckling or cracks. If buckling or cracks are found, replace the LPT stator case assembly before further flight with a serviceable case.

Alternative Methods of Inspection

(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, Engine Certification Office (ECO). Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

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

(i) 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.

Documents That Have Been Incorporated By Reference

(j) The borescope plug replacement must be done in accordance with GE ASB DF6-50 72 A1196, dated September 15, 2000. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained 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. Copies may be inspected at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

Effective Date

(k) This amendment becomes effective on October 17, 2000.

On April 25, 2000, a DC10-30 experienced an uncontained engine failure during takeoff. Ground inspection found uncontainment of the low pressure turbine (LPT) case, airplane damage, and ingestion damage to the other two engines. An investigation revealed that the failure of stage 2 LPT nozzle lock assemblies made of Waspalloy material resulted in the uncontained failure of all stage 2 nozzle segments.

Since that time, there have been two more uncontained engine failures, on September 5, 2000, and September 7, 2000, that have been attributed to the failure of Waspalloy stage 2 LPT nozzle lock assembly studs.

Before these three events, there had been two uncontained failures of stage 2 LPT nozzle lock assemblies made of Rene 41 material. One failure was in April 1991 which was contained within the cowl with no damage to the airplane, and one in 1996 that also penetrated the cowl and resulted in minor damage to the airplane.

There was also oneunscheduled engine removal (UER) for broken Rene 41 nozzle lock assembly studs in 1997 and two UER's for broken Waspalloy assemblies; one in January 1999, and one in December 1999.

Loose or missing LPT nozzle lock assembly studs could lead to failure of the locks and subsequent uncontained failure of the engine.

Manufacturer's Service Information

The FAA has reviewed and approved the technical contents of GE Alert Service Bulletin (ASB) CF6-50 72-A1196, dated September 15, 2000, that describes procedures for replacing the existing stage 2 LPT nozzle borescope plug, part number (P/N) 9022M63G13, with borescope plug P/N 2083M99P01. This new plug provides an additional antirotation feature for the nozzle segments in the event of failure of the nozzle locks.

Interim Action Requirements of This AD

Since an unsafe condition has been identified that is likely to exist or develop on other GE CF6-50 series turbofan engines of the same type design, this AD is being issuedas an interim action to detect loose or missing LPT nozzle lock assembly studs that could lead to failure of the lock assemblies, and subsequent uncontained failure of the engine. This AD requires:

Initial and repetitive inspections of the lock assemblies for loose or missing studs.
Replacement of all of the stage 2 LPT lock assemblies with new assemblies before further flight if a loose or missing stud is found.
Installation of borescope plug P/N 2083M99P01. This new borescope plug is designed to prevent rotation of the stage 2 LPT nozzle if the nozzle lock assemblies fail.
Inspection of the area surrounding the borescope plug for evidence of buckling or cracks whenever the nozzle lock studs are inspected.
Replacement of the LPT stator case assembly with a serviceable part before further flight if any buckling or cracks are found.

The borescope plug must be replaced as specified in ASB CF6-50 72-A1196.

Immediate Adoption of This AD

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited

Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this 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 under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluatingthe effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD 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 2000-NE-38-AD." The postcard will be date stamped and returned to the commenter.

Regulatory Impact

This proposed rule does not have federalism implications, as defined in Executive Order No. 13132, because it wouldnot 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 proposed rule.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location providedunder 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 Title 14 of the Code of Federal 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. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: