"Almost immediately after the R-4 was in production, the R-5 was being designed to provide a more substantial platform. It retained the forward cabin, predominantly Plexiglas, the three-bladed main rotor, and the anti-torque tail rotor was moved to the left side of the tail boom. The landing gear included a bent nose-wheel strut and a smaller rocker wheel under the rear of the cabin. Twenty-one R-5A helicopters were converted to R-5D's [sic]. This conversion included the addition of an external rescue hoist, an auxiliary fuel tank, and an increase in engine power from 450 HP to 600 HP. Modifications in the cabin allowed for a 2nd passenger. One of these conversions was responsible for the first documented military sea-air rescue."