The Series 3.5 will also improve performance in ‘hot and high’ conditions. A key feature was the introduction of the T56 turboprop, first developed specifically for the C-130. At the time, the turboprop was a new application of turbine engines that used exhaust gases to turn a shafted propeller, which offered greater range at propeller-driven speeds compared to pure turbojets, which were faster but thirstier.  

As was the case on helicopters of that era, such as the UH-1 Huey, turboshafts produced much more power for their weight than piston engines. Lockheed would subsequently use the same engines and technology in the Lockheed L-188 Electra. That aircraft failed financially in its civilian configuration but was successfully adapted into the Lockheed P-3 Orion maritime patrol and submarine attack aircraft where the efficiency and endurance at high propeller speeds of turboprops excelled. 

Tom Bell, Rolls-Royce, President, Customer Business – Defense, said, “We look forward to carrying out flight tests to confirm what we have already demonstrated in the test cell – significant savings in fuel costs, improved reliability and performance. Rolls-Royce has invested to help the US Air Force and other operators around the world meet their goal of reducing fuel costs, while also extending the life of the C-130 fleet and potentially saving billions of dollars.”  

The Series 3.5 Engine Enhancement program is expected to enable the USAF to continue to operate its C-130H fleet until 2040, and a USAF analysis estimated its long-term savings from the Series 3.5 enhancements could reach $2 Billion.