A new "flat-riser" is the de Lackner DH-5 Aerocycle which has been developed for the U.S. Army from the 1955 DH-4 Heli-Vector. The DH-5 is powered by a 44-h.p. Mercury Mk. 55, which drives coaxially two three-blade main rotors each of 15 ft. diameter. Range is 50 miles at 75 m.p.h.