# AD 2012-02-07: LPT rotor stage 3 disks - Type: Airworthiness directive - Status: Historical - Products: General Electric CF6-45A, CF6-45A2, CF6-50A, CF6-50C, CF6-50C1, CF6-50C2, CF6-50C2B, CF6-50C2D, CF6-50CA, CF6-50E, CF6-50E1, CF6-50E2 and 1 more - Effective: March 6, 2012 - Published: January 31, 2012, 77 FR 4650–4653 - Issued: January 20, 2012 - Issued as: Final rule - Supersedes: [AD 2011-02-07](https://openairdocs.org/ad/2011-02-07), [AD 2011-18-01](https://openairdocs.org/ad/2011-18-01) - Superseded by: [AD 2023-04-11](https://openairdocs.org/ad/2023-04-11) - Product type: Engine - Amendment: 39-16930 - Docket: FAA-2010-0068 (https://www.regulations.gov/docket/FAA-2010-0068) - Project: 2010-NE-05-AD - Registered aircraft: 21 may be affected, by airframe or engine model (OpenAirDocs) - Official PDF: https://openairdocs.org/files/sha256/33/3e/333e8ca86b583e0dadefc3514cc8816aaa703dfabf95dacc1e79f872c32fedcf (from https://www.govinfo.gov/content/pkg/FR-2012-01-31/pdf/2012-1953.pdf) - Federal Register: https://www.federalregister.gov/documents/2012/01/31/2012-1953/airworthiness-directives-general-electric-company-turbofan-engines - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/5F4B4DDF471D288C86257996004E81D3.0001 - DRS record last changed: November 21, 2025 - Page: https://openairdocs.org/ad/2012-02-07 ## Summary We are superseding two existing airworthiness directives (ADs) for General Electric Company (GE) CF6-45 and CF6-50 series turbofan engines with certain low-pressure turbine (LPT) rotor stage 3 disks installed. The existing ADs currently require inspections of high-pressure turbine (HPT) and LPT rotors, engine checks, and vibration surveys. This new AD retains the requirements of the two ADs being superseded, adds an optional LPT rotor stage 3 disk removal after a failed HPT blade borescope inspection (BSI) or a failed engine core vibration survey, establishes a new lower life limit for the affected LPT rotor stage 3 disks, and requires removing these disks from service at times determined by a drawdown plan. This AD was prompted by the determination that a new lower life limit for the LPT rotor stage 3 disks is necessary. We are issuing this AD to prevent critical life-limited rotating engine part failure, which could result in an uncontained engine failure and damage to the airplane. ## The airworthiness directive 1. The authority citation for part 39 continues to read as follows: ## Rule preamble ### Dates This AD is effective March 6, 2012. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of February 22, 2011 (76 FR 6323, February 4, 2011). ### Addresses For service information identified in this AD, contact General Electric Company, GE-Aviation, Room 285, 1 Neumann Way, Cincinnati, OH 45215, phone: (513) 552-3272; email: geae.aoc@ge.com. You may review copies of the referenced service information at the FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA. For information on the availability of this material at the FAA, call (781) 238-7125. ### For further information contact Tomasz Rakowski, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; phone: (781) 238-7735; fax: (781) 238-7199; email: tomasz.rakowski@faa.gov. ### Discussion We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2011-02-07, Amendment 39-16580 (76 FR 6323, February 4, 2011) and AD 2011-18-01, Amendment 39-16783 (76 FR 52213, August 22, 2011). Those ADs apply to the specified products. The NPRM published in the Federal Register on October 19, 2011 (76 FR 64844). That NPRM proposed to retain the requirements of AD 2011-02-07 and AD 2011-18-01, except that reporting to the FAA would no longer be required and there would be an optional LPT rotor stage 3 disk removal after a failed HPT blade BSI or a failed engine core vibration survey. That NPRM also proposed to establish a new lower life limit for the LPT rotor stage 3 disk part numbers listed in Table 1 of the proposed AD, and proposed to require removing these disks from service at times determined by a drawdown plan. ### Comments We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the proposal and the FAA's response to each comment. ### Support for the NPRM as Written One commenter, The Boeing Company, supports the NPRM (76 FR 64844, October 19, 2011) as written. ### Request To Allow Credit for Vibration Surveys Performed in a Test Cell One commenter, MTU Maintenance Hannover GmbH, requested that we add a paragraph that allows credit for performing vibration surveys in a test cell, as meeting the AD vibration survey requirements. We agree. We added paragraph (k)(8) to the AD, which states “Vibration surveys carried out in an engine test cell as part of an engine manual performance run fulfill the vibration survey requirements of paragraphs (k)(2) through (k)(3) of this AD.” ### Request To Add a Requirement for Raw Exhaust Gas Temperature (EGT) Trend Data Point Exceedance One commenter, Evergreen International Airlines, requested that we add a requirement that two consecutive raw EGT trend data point exceedances must be confirmed by a corresponding shift of other engine parameters to trigger the HPT blade BSI. We partially agree. We agree that EGT system error should not force a BSI of turbine blades. But we disagree with troubleshooting the EGT raw data points once the EGT system error was ruled out. We added paragraph (o)(4) to the AD to state that, for the purposes of this AD, a raw EGT trend data point above the smoothed average is a confirmed temperature reading over the rolling average of EGT readings that is not a result of EGT system error. We also rearranged the wording in paragraph (iv) in Table 2 of the AD for clarification. ### Correction to Engine Model CF6-50-E2D Since we issued the NPRM (76 FR 67844, October 19, 2011), we discovered that, in applicability paragraph (c), engine model CF6-50-E2D was incorrect. We corrected it to read CF6-50E2B in the AD. ### Conclusion We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these minor changes: • Are consistent with the intent that was proposed in the NPRM (76 FR 64844, October 19, 2011) for correcting the unsafe condition; and • Do not add any additional burden upon the public than was already proposed in the NPRM. We also determined that these changes will not increase the economic burden on any operator or increase the scope of the AD. ### Costs of Compliance We estimate that this AD will affect 387 CF6-45 and CF6-50 series turbofan engines installed on airplanes of U.S. registry. We also estimate that it will take about 8 work-hours to perform the HPT blade inspection, 6 work-hours to perform a vibration survey, 4 work-hours to perform an ultrasonic inspection, 2 work-hours to perform an EGT resistance check, 1 work-hour to perform an EGT thermocouple inspection, and 7 work-hours to clean and perform an fluorescent-penetrant inspection of the LPT rotor stage 3 disk for each engine. The average labor rate is $85 per work-hour. The cost estimate for the work just described was covered in the two ADs we are superseding. For this AD, we estimate that a replacement LPT rotor stage 3 disk prorated part cost is $75,000. Based on these figures, we estimate the total cost of this AD to U.S. operators to be $29,025,000. ### 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 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 AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD: (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), (3) Will not affect intrastate aviation in Alaska, and (4) 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. ### Adoption of the Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS E23EA](https://openairdocs.org/tcds/E23EA): General Electric Company; names 13 of 18 models: CF6-50E1, CF6-50CA, CF6-50A, CF6-50E, CF6-50C2D, CF6-50C1, CF6-50E2B, CF6-50C2… ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 21 (0 by airframe model, 21 by engine model) - Makers: Mcdonnell Douglas 17, Mcdonnell-Douglas 2, Boeing 1, Bombardier 1 Models with the most aircraft: - [GE CF6-50C2](https://openairdocs.org/engine/ge-cf6-50c2): 10 aircraft (engine model) - [GE CF6-50 series](https://openairdocs.org/engine/ge-cf6-50-series): 9 aircraft (engine model) - [GE CF6-45A2](https://openairdocs.org/engine/ge-cf6-45a2): 1 aircraft (engine model) - [GE CF6-50C](https://openairdocs.org/engine/ge-cf6-50c): 1 aircraft (engine model) All 4 models: https://openairdocs.org/ad/2012-02-07/models.md Every aircraft: https://openairdocs.org/ad/2012-02-07/aircraft.md ## Related documents - [AD 2011-02-07](https://openairdocs.org/ad/2011-02-07) (historical): Rotor · General Electric CF6-45A, CF6-45A2, CF6-50A and 9 more. Effective Feb 22, 2011. Replaced by this AD - [AD 2011-18-01](https://openairdocs.org/ad/2011-18-01) (historical): LPT rotor stage 3 disks · General Electric CF6-45A, CF6-45A2, CF6-50A and 9 more. Effective Sep 26, 2011. Replaced by this AD - [AD 2023-04-11](https://openairdocs.org/ad/2023-04-11): Turbine Section · General Electric CF6-45A, CF6-45A2, CF6-50A and 10 more. Effective Apr 28, 2023. Supersedes this AD No proposed rule in this release led to it. Its text cites no advisory circulars or STCs. ## NTSB investigations that cite this AD (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB ENG09IA004](https://openairdocs.org/ntsb/ENG09IA004), Mar 26, 2009: Mcdonnell-Douglas DC-10-30 (N526MD), Bogota, Colombia, incident, minor damage. Probable cause: Failure of the low pressure turbine stage 3 disk due to a design that is vulnerable to high pressure turbine unbalance-induced synchronous vibration that cannot be detected in flight, and the… --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.