CH-53 Sea Stallion, CH-53E Super Stallion heavy lift helikopters (1964, 1974)
The R-6/Hoverfly II was developed to improve on the successful Sikorsky R-4. In order to enhance performance, a completely new streamlined fuselage was designed and the boom carrying the tail rotor was lengthened and straightened. The main rotor and transmission system of the R-4 were retained. Sikorsky allotted their Model 49 designation to the new design. Later, dynamically-balanced modifications to the rotor were carried out by Doman Helicopters Inc. The new aircraft could attain 100 mph (160 km/h) compared with 82 mph (132 km/h) by the earlier design.
The first R-6s were delivered to the United States Army Air Forces (USAAF) in late 1944 and some were transferred to the United States Navy (USN). It was initially intended to pass 150 R-6s to the Royal Air Force (RAF), but delays caused by the switch of production from Sikorsky’s factory at Stratford, Connecticut to Nash-Kelvinator at Detroit Michigan meant that only 27 R-6As were actually delivered to the RAF as the Hoverfly II. Fifteen of these were passed on to the Royal Navy’s Fleet Air Arm (FAA).
An air force, also known in some countries as an aerospace force or air army, is in the broadest sense, the national military branch that primarily conducts aerial warfare.