Sikorsky S-60

The Sikorsky S-60 helicopter, a prototype "flying crane", was derived from the S-56 in 1958. Proving to be underpowered, the development of the S-60 led to the larger, turbine-engined Sikorsky CH-54 Tarhe military transport helicopter, and its civil S-64 Skycrane variant, which were already on the drawing board by the time the sole example of the S-60 crashed on 3 April 1961.