AD 85-25-56 R1
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | General Electric Company | CF6-45A | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-45A2 | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50A | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50C | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50C1 | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50C2 | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50C2B | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50C2D | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50CA | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
| engine | General Electric Company | CF6-50E | GENERAL ELECTRIC COMPANY Models CF6-50 and -45 Series Engines |
Unsafe Condition
Failure of the left hand side seventh stage low pressure turbine (LPT) cooling air manifold tube could result in an LPT overtemperature condition and subsequent LPT stage 1 disk rupture.
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Required Actions
Accomplish requirements of GE SB 75-55 paragraphs 2.A.1., 2.A.2., and 2.A. with FAA approved equivalents within 10 flight cycles. Then accomplish paragraph 2 of GE SB 75-55 within 60 calendar days. For engines already compliant with SB 75-54 or SB 75-46, accomplish paragraph 2 of SB 75-55 within 60 days. Replace cracked hardware before flight. Inspect tubes and hardware every 250 flight cycles. Replace or tighten worn hardware before flight.
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Compliance Time
Within 10 flight cycles after the effective date for initial actions, and within 60 calendar days for subsequent steps. Inspections required within the next 250 flight cycles and recurring every 250 flight cycles.
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Affected Aircraft
General Electric Company CF6-45A, CF6-45A2, CF6-50A, CF6-50C, CF6-50C1, CF6-50C2, CF6-50C2B, CF6-50C2D, CF6-50CA, and other CF6-50 and -45 series engines as listed.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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