Pratt & Whitney Canada JT15D

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The 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. Over 6,000 JT15D's have been delivered since the 1970s, with over 30 million hours of operation.

Design and development

The JT15D is fairly unique among modern turbofans in that it uses a centrifugal compressor as its main high-pressure system. This was a common feature of early jet engines, but was quickly replaced by axial compressors in most roles due to its large frontal size. In the turbofan role most of the jet thrust is generated by the cold air blown past the engine, and the internal "jet" portion is quite small. In this role the high single-stage compression of the centrifugal design has advantages, and the main reason most small turbofans don't use them is that they are often developments of previous turbojet designs.

In the JT15D the fan blows about 70% of the air into the bypass duct, producing most of the overall thrust. On JT15D-4 models and above there is a small "booster" axial stage just behind the fan which is running at the same speed as the fan and directing the remaining...
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