| Allison T56 variants | |
|---|---|
| |
| Allison T-56 on display at the National Naval Aviation Museum, Pensacola | |
| Type | Turboprop/turboshaft |
| National origin | United States |
| Manufacturer | Allison Engine Company Rolls-Royce Holdings |
| First run | 1950 |
The Allison T56 turboprop engine has been developed extensively throughout its production run, the many variants are described by the manufacturer as belonging to four main series groups.
Initial civil variants (Series I) were designed and produced by the Allison Engine Company as the 501-D and powered the Lockheed C-130 Hercules. Later variants (Series II, III, 3,5 and IV) gave increased performance through design refinements.
Further derivatives of the 501-D/T56 were produced as turboshafts for helicopters including a variant with a United States military aircraft engine designation of T701, which was developed for the canceled Boeing Vertol XCH-62 project.