# AD 79-16-06: Accessory Drive Gearbox - Type: Airworthiness directive - Status: Current - Products: Rolls-Royce 250-C28, 250-C28B, 250-C28C, 250-C30, 250-C30G, 250-C30G/2, 250-C30M, 250-C30P, 250-C30R (T703-AD-700), 250-C30R/1 (T703-AD-700B), 250-C30R/3, 250-C30S and 1 more - Effective: January 11, 1980 - Superseded by: Nothing supersedes this AD - Product type: Engine - Amendment: 39-3650 - Registered aircraft: 625 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D1363EDDE698275686256E120055B151.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/79-16-06 ## The airworthiness directive 79-16-06 DETROIT DIESEL ALLISON: Amendment 39-3527 is further amended by Amendment 39- 3650. Applies to all Model 250-C28 and 250-C30 series engines equipped with generator idler gearshaft P/N 6898980, or 6898591, or 77 tooth spur idler gearshaft P/N 6898652 installed in, but not limited to Bell 206L-1 and Sikorsky S-76 rotorcraft certificated in all categories. Compliance required as indicated unless previously accomplished. To preclude engine power loss as a result of an accessory drive gearbox failure, remove the referenced gearshafts from service prior to reaching 9000 cycles if installed in a 250-C28 series engine and prior to reaching 2000 cycles if installed in a 250-C30 engine. For those gearshafts that are within 50 cycles of the appropriate limit on the effective date of this AD, compliance is required within 100 cycles. For the purpose of this AD, a cycle is defined as an attempted or completed start, or a motoring of the engine using the starter. The start counter is activated and accumulates the count of cycles only when the ignition circuit is energized. Therefore, cycles due to motoring with the starter (ignition circuit not energized) must be added to the cycle count. (Detroit Diesel Allison Commercial Engine Bulletins CEB 72-2003 for the 250-C28B and CEB 72-3003 for the 250-C30 also pertain to this subject.) Amendment 39-3527 became effective August 15, 1979. This amendment 39-3650 becomes effective January 11, 1980. ## 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 13 of 23 models: 250-C30, 250-C30R (T703-AD-700), 250-C30R/1 (T703-AD-700B), 250-C28, 250-C30U, 250-C30R/3, 250-C30S, 250-C30G… ## 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: 625 (0 by airframe model, 625 by engine model) - Makers: Bell 290, Bell Helicopter Textron Canada 106, Bell Helicopter Textron 69, MD Helicopters 69, Hiller 15, Mcdonnell Douglas Heli 14, Sikorsky 10, Enstrom Helicopter 9, Cessna 7, Beech 6 Models with the most aircraft: - [Allison 250-C30 series](https://openairdocs.org/engine/allison-250-c30-series): 224 aircraft (engine model) - [Rolls-Royce 250-C30P](https://openairdocs.org/engine/rolls-royce-250-c30p): 152 aircraft (engine model) - [Allison 250 series](https://openairdocs.org/engine/allison-250-series): 79 aircraft (engine model) - [Rolls-Royce 250-C30](https://openairdocs.org/engine/rolls-royce-250-c30): 76 aircraft (engine model) - [Allison 250-C28 series](https://openairdocs.org/engine/allison-250-c28-series): 43 aircraft (engine model) - [Allison 250-C30P](https://openairdocs.org/engine/allison-250-c30p): 25 aircraft (engine model) - [Allison 250-C30](https://openairdocs.org/engine/allison-250-c30): 5 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) - [Rolls-Royce 250-C30G](https://openairdocs.org/engine/rolls-royce-250-c30g): 3 aircraft (engine model) - [Rolls-Royce 250-C30G/2](https://openairdocs.org/engine/rolls-royce-250-c30g-2): 3 aircraft (engine model) - [Rolls-Royce 250-C30S](https://openairdocs.org/engine/rolls-royce-250-c30s): 2 aircraft (engine model) - [Allison 250-C30G/2](https://openairdocs.org/engine/allison-250-c30g-2): 1 aircraft (engine model) - [Rolls-Royce 250-C28](https://openairdocs.org/engine/rolls-royce-250-c28): 1 aircraft (engine model) - [Rolls-Royce 250-C30M](https://openairdocs.org/engine/rolls-royce-250-c30m): 1 aircraft (engine model) - [Rolls-Royce 250-C30R](https://openairdocs.org/engine/rolls-royce-250-c30r): 1 aircraft (engine model) - [Rolls-Royce 250-C30R/3](https://openairdocs.org/engine/rolls-royce-250-c30r-3): 1 aircraft (engine model) All 18 models: https://openairdocs.org/ad/79-16-06/models.md Every aircraft: https://openairdocs.org/ad/79-16-06/aircraft.md Its text cites no advisory circulars or STCs. --- 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.