The Pratt & Whitney Canada JT15D is a small turbofan engine built by Pratt & Whitney Canada. It was introduced in 1971 at thrust, and has since undergone a series of upgrades to just over thrust in the latest versions. It is the primary powerplant for a wide variety of smaller jet aircraft, notably business jets. Design and development When it first ran in 1967 the JT15D was rare among turbofan engines in that it uses a centrifugal compressor as its high-pressure stage. About 70% of the air passing through the fan goes down the bypass duct. The JT15D-4 and later variants use a "booster" axial stage behind the fan which runs at the same speed as the fan and directs the remaining 30% of the air into the high-pressure compressor, after which it passes into a reverse-flow annular combustor. The hot gases flow through a high-pressure turbine that drives the centrifugal compressor, and a low-pressure turbine that drives the fan and booster. The engine was first run in August 1967 before being test flown on an Avro Canada CF-100 Canuck in an underslung external test pod. Variants JT15D-1The first model was introduced to power the Cessna Citation I, then known as the Fanjet 500. Deliveries started in 1972, and eventually on 1,417 -1s were delivered. JT15D-1A JT15D-1B JT15D-4Introduced in 1973, improving thrust to . The -4 was the primary engine for the Cessna Citation II, and went on to find use on the Mitsubishi Diamond 1A, Aerospatiale Corvette and SIAI-Marchetti S.211. Eventually 2,195 engines of the -4 series were delivered. JT15D-4A JT15D-4B JT15D-4C JT15D-4D JT15D-5 Certified in 1983. The first versions delivered and were used on the Beechjet 400A and Cessna T-47A. Several minor versions were introduced, the -5A for the Cessna Citation V, while the -5B powered the Beechcraft T-1A Jayhawk, the -5C the DASA Ranger 2000 and S-211A. JT15D-5A JT15D-5B JT15D-5C JT15D-5D Certified in 1993, increased thrust again, this time to . The -5D is used on the Cessna UC-35A and Cessna Citation Ultra. JT15D-5F Applications Aérospatiale Corvette Alenia Aermacchi M-311 Boeing Bird of Prey Beechcraft Beechjet 400 Cessna Citation I Cessna Citation II Cessna Citation V/Ultra EADS Barracuda Hawker 400 Honda MH02 Mitsubishi MU-300 Diamond Northrop Grumman X-47A Pegasus Raytheon T-1 Jayhawk Rockwell Ranger 2000 Scaled Composites 401 Scaled Composites ARES SIAI-Marchetti S.211/Aermacchi S-211 Sport Jet II Stratos 716X Specifications (JT15D-5D) References Notes Bibliography Gunston, Bill.