# AD 68-12-06: Compressor Blades

- Type: Airworthiness directive
- Status: Current
- Products: Rolls-Royce 250-C10B (T63-A-5A), 250-C18, 250-C18A, 250-C18B, 250-C18C and 250-C19
- Effective: June 18, 1968
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-612
- Registered aircraft: 84 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/6551167848935F488625682700646615.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/68-12-06

## The airworthiness directive

68-12-06 ALLISON: Amdt. 39-612. Applies to Models 250-C18, 250-C18A, 250-C18B, 250-C18C, 250- C19 and 250-C10B engines. Before further flight of any aircraft equipped with one of the Allison model engines listed above, unless already accomplished, modify the sixth stage compressor blades in these engines in accordance with Allison Commercial Engine Bulletin No. 250 CEB-48, dated June 11, 1968, or any other method approved by the Chief, Engineering and Manufacturing Branch, Central Region. Further flight beyond the point where an aircraft equipped with one of these engines is grounded pursuant to this Airworthiness Directive, may be conducted only in accordance with Federal Aviation Regulation 21.197. This amendment becomes effective June 18, 1968.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E4CE](https://openairdocs.org/tcds/E4CE): Rolls-Royce Corporation; names 6 of 23 models: 250-C19, 250-C18, 250-C18A, 250-C18B, 250-C10B (T63-A-5A), 250-C18C

## 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: 84 (0 by airframe model, 84 by engine model)
- Makers: Bell 31, Hiller 15, Enstrom Helicopter 9, Cessna 7, Beech 6, Hughes 4, Siai-Marchetti 3, Ardoyno John W 1, Huizenga Mike 1, Maule 1

Models with the most aircraft:

- [Allison 250 series](https://openairdocs.org/engine/allison-250-series): 79 aircraft (engine model)
- [Allison 250-C18](https://openairdocs.org/engine/allison-250-c18): 2 aircraft (engine model)
- [Allison 250-C18B](https://openairdocs.org/engine/allison-250-c18b): 2 aircraft (engine model)
- [Rolls-Royce 250-C18](https://openairdocs.org/engine/rolls-royce-250-c18): 1 aircraft (engine model)

All 5 models: https://openairdocs.org/ad/68-12-06/models.md
Every aircraft: https://openairdocs.org/ad/68-12-06/aircraft.md

Its text cites no advisory circulars or STCs.

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