AD 99-15-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Pratt & Whitney Division | PW4056 | Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines |
| engine | Pratt & Whitney Division | PW4152 | Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines |
| engine | Pratt & Whitney Division | PW4156A | Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines |
| engine | Pratt & Whitney Division | PW4164 | Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines |
| engine | Pratt & Whitney Division | PW4168 | Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines |
| engine | Pratt & Whitney Division | PW4460 | Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines |
Unsafe Condition
A change in cooling hole geometry on certain 4th stage low pressure turbine (LPT) disks inadvertently reduced cooling airflow and increased stress, risking uncontained disk failure and aircraft damage.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace affected 4th stage LPT disks before 7,500 cycles in service. Alternatively, restore original life limits by reoperating disks per specified service bulletins prior to specific cycle thresholds to incorporate slotted cooling holes.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Before further flight if beyond compliance cycles, or within specified cycle limits (4,500 to 7,000 CIS) depending on engine model.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Pratt & Whitney PW4056, PW4152, PW4156A, PW4164, PW4168, PW4460 engines with 4th stage LPT disks part number 50N924 and specific serial numbers listed in the AD.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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