# AD 79-18-13: Third Stage Turbine Wheel

- Type: Airworthiness directive
- Status: Current
- Products: Rolls-Royce 250-C28B and 250-C28C
- Effective: September 6, 1979
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-3548
- Registered aircraft: 130 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/44F6CE0D4E57503D86256827006975FA.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/79-18-13

## The airworthiness directive

79-18-13 DETROIT DIESEL ALLISON: Amendment 39-3548. Applies to all Model 250-C28B and 250-C28C Series engines equipped with third stage turbine wheel P/Ns 6898553 or 6898773 installed in, but not limited to Bell 206L-1 rotorcraft certificated in all categories. Compliance required as indicated unless previously accomplished. A. For turbine wheels with less than 300 hours total time in service, compliance is required before reaching 325 hours total time in service. B. For turbine wheels with more than 300 hours total time in service, compliance is required within 25 hours time in service. To preclude engine power loss due to possible turbine blade failure, remove above listed third stage turbine wheels from service. This amendment becomes effective September 6, 1979, as to all persons except those to whom it was made immediately effective by the airmail letter dated July 19, 1979, which contained this amendment.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E1GL](https://openairdocs.org/tcds/E1GL): Rolls-Royce Corporation; names 2 of 23 models: 250-C28C, 250-C28B

## 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: 130 (0 by airframe model, 130 by engine model)
- Makers: Bell Helicopter Textron 45, Bell 29, Hiller 15, Enstrom Helicopter 9, Cessna 7, Beech 6, Eurocopter/Canada 3, Siai-Marchetti 3, Messerschmitt-Bolkow-Blohm 2, Ardoyno John W 1

Models with the most aircraft:

- [Allison 250 series](https://openairdocs.org/engine/allison-250-series): 79 aircraft (engine model)
- [Allison 250-C28 series](https://openairdocs.org/engine/allison-250-c28-series): 43 aircraft (engine model)
- [Allison 250-C28B](https://openairdocs.org/engine/allison-250-c28b): 5 aircraft (engine model)
- [Rolls-Royce 250-C28B](https://openairdocs.org/engine/rolls-royce-250-c28b): 3 aircraft (engine model)

All 5 models: https://openairdocs.org/ad/79-18-13/models.md
Every aircraft: https://openairdocs.org/ad/79-18-13/aircraft.md

Its text cites no advisory circulars or STCs.

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