of eight CH-47Cs; deliveries of the type began in 1974. Receiving the Canadian designation "CH-147", these were fitted with a power hoist above the crew door; other changes included a flight engineer station in the rear cabin: operators referred to the configuration as the "Super C". The CH-47C was used widely during the Vietnam War, eventually replacing the older Piasecki H-21 Shawnee in the combat assault support role. CH-47D The CH-47D shares the same airframe as earlier models, the main difference being the adoption of more powerful engines. Early CH-47Ds were originally powered by two T55-L-712 engines, the most common engine is the later T55-GA-714A. With its triple-hook cargo system, the CH-47D can carry heavy payloads internally and up to (such as containers) externally. It was first introduced into service in 1979. In air assault operations, it often serves as the principal mover of the 155 mm M198 howitzer, accompanying 30 rounds of ammunition, and an 11-man crew. The CH-47D also has advanced avionics, such as the Global Positioning System. Nearly all US Army CH-47D were conversions from previous A, B, and C models, a total of 472 being converted. The last U.S. Army CH-47D built was delivered to the U.S. Army Reserve, located at Fort Hood, Texas, in 2002. The Netherlands acquired all seven of the Canadian Forces' surviving CH-147Cs and upgraded them to CH-47D standard. Six more new-build CH-47Ds were delivered in 1995 for a total of 13. The Dutch CH-47Ds feature a number of improvements over U.S. Army CH-47Ds, including a long nose for Bendix weather radar, a "glass cockpit", and improved T55-L-714 engines. As of 2011, the Netherlands shall upgrade 11 of these which will be updated to the CH-47F standard at a later date. As of 2011, Singapore has 18 CH-47D/SDs, which includes twelve "Super D" Chinooks, in service. In 2008, Canada purchased 6 CH-47Ds from the U.S. for the Canadian Helicopter Force Afghanistan for $252 million. With 1 CH-47D lost to an accident, the remaining five were sold in 2011 after the end of Canada's mission in Afghanistan and replaced with seven CH-147Fs. MH-47D The MH-47D variant was developed for special forces operations and has inflight refueling capability, a fast rope-rappelling system, and other upgrades. The MH-47D was used by U.S. Army 160th Special Operations Aviation Regiment. Twelve MH-47D helicopters were produced. Six were conversions from CH-47A models and six were conversions from CH-47C