Description

The Model 250 Series II turboshaft engines are of two-shaft modular design featuring four to six-stage axial and single-stage centrifugal compressors, a two-stage LP turbine, two-stage HP turbine with a hydromechanical fuel control system, and a gearbox with 6,000rpm output. Compressed air is routed to the aft end of the engine for combustion, with exhaust gases exiting upward from the middle of the engine. The larger Series IV family is identical in layout except for having one-stage centrifugal rather than a centrifugal/axial compressor. The latest Series IV turboshafts also feature a FADEC (Full Authority Digital Engine Control) system.

The highly successful family of Model 250 engines remains the industry-standard powerplant. More than 28,500 Model 250s have been delivered to date, with an estimated 16,000 engines currently in service.

Originally developed as the T63 to meet a US Army requirement for a 317shp turboshaft, the original Series I Model 250 has spawned an entire family of small turbine engines, including turboshafts, turboprops, industrial/marine starter-generators and disposable turbojet derivatives.

A program of continuous development has resulted in today's range of Series II and Series IV engines which power many of the world's most popular helicopters. Series II (Model 250-C20) turboshaft applications include the Bell 206B/TH-67, MDH MD500/520N and Eurocopter AS.355/BO 105. The recent introduction of the Model 250-C20R+ performance improvement package further enhanced the type's performance and economy.

The latest FADEC-equipped Model 250 Series IV turboshaft family (Model 250-C30/C40/C47) spans 650-715shp (815shp thermodynamic), and powers the Bell 407/430/206L and MDH MD530/600N. Engine upgrade programs are also under way for the US Army Bell OH-58D Kiowa Warrior and US Special Operations Command AH/MH-6 Mission Enhanced Little Bird (MELB) fleets.

Production improvement programs for the Model 250 have led to dramatic improvements in engine pass-off performance, with margins of up to 15 percent regularly recorded.

The long association of the Model 250 with unmanned aerial vehicle (UAV) applications was reinforced in February 2000 with the selection of the Northrop Grumman RQ-8A Fire Scout Vertical Take-off UAV (VTUAV) for a major US Navy/Marine Corps shipborne requirement. Based on the Model 250-C20W-powered Schweizer 330 helicopter, the Fire Scout is paving the way for a major new class of air systems. In addition to serving aboard the first flight of the U.S. Navy's Littoral Combat Ship (LCS), the Fire Scout VTUAV has also been selected to meet the U.S. Army's Class IV Future Combat Systems (FCS) UAV requirement.

Other recent applications include the Russian Kamov Ka-226, now in production for Gazpromavia and the Russia Ministry of Emergencies; and the PZL SW-4 light single.