The Hughes XH-17 "Flying Crane" was the first helicopter project for the helicopter division of Hughes Aircraft Company. The XH-17, which had a two-bladed main rotor system with a diameter of 134 feet, still holds the world record for flying with the largest rotor system. It was capable of flying at a gross weight of more than 50,000 pounds (23,000 kg), but proved too inefficient and cumbersome to be mass-produced beyond the prototype unit.
The Agusta A.115 was a prototype helicopter flown in 1961 in Italy. It was essentially a Bell 47J-3 with an unclad, tubular tail boom, and powered by a Turbomeca Astazou II turboshaft engine. No production ensued.
The Agusta A.101 was a large prototype transport helicopter developed in Italy during the 1960s. Despite prospective orders from the Italian armed forces, no buyers emerged and the project was abandoned in 1971.
The Agusta A.104 Helicar was an Italian prototype light commercial helicopter first flown in December 1960.
The Agusta AB.102 was an Italian helicopter produced in small numbers in the early 1960s. The aircraft was based on the mechanical components of a Bell 48 that Agusta incorporated into an all-new, streamlined fuselage. The first flight was on 3 February 1959 and the prototype was exhibited at that year's Paris Air Show in faux military colours. Only two production examples were built, operated by Elivie in a regular air service between Turin and Milan from 1961. However, the advent of turbine-powered helicopters in the 1960s soon rendered the AB.102 obsolete.
The Fairey FB-1 Gyrodyne is an experimental British rotorcraft that used single lifting rotor and a tractor propeller mounted on the tip of the starboard stub wing to provide both propulsion and anti-torque reaction.
The Bölkow Bo 103 was an ultralight experimental helicopter flown in West Germany in 1961. It was designed for reconnaissance and command-control purposes and constructed by Bölkow Entwicklungen KG as part of a research order by the German Federal Ministry of Defense.
The Doman LZ-5 was a utility helicopter developed in the United States in the early 1950s by Doman Helicopters Inc. of Danbury, Connecticut. Despite the procurement of international manufacturing agreements, no series production of the aircraft ever occurred, and only three prototypes were built. Two of these were purchased by the United States Army as the YH-31, but eventually becoming VH-31.
The Cierva CR Twin was a five-seat utility helicopter that first flew in the UK in 1969. It was a joint development between Cierva Autogiro Company and Rotorcraft now a subsidiary of Cierva, based on the dynamic systems of the latter company's Grasshopper design. A new, highly streamlined pod-and-boom fuselage was married to the Grasshopper's coaxial rotor system, and the new aircraft registered G-AWRP first flew on 18 August 1969.
The Fiat Model 7002 was a 1960s Italian general-purpose helicopter with a tip jet driven rotor built by Fiat Aviazione. Only one aircraft was built.
The Gyrodyne RON Rotorcycle was a tiny, single-seat helicopter designed under contract for the United States Navy. in the mid-1950s. It later was redesigned for a U.S. Marine Corps requirement for a small personal helicopter that would fulfill a number of roles, including observation, liaison, small unit tactical maneuvers, and which could be dropped to downed airmen behind enemy lines to facilitate their escape.
The HTM Skytrac was a light utility helicopter developed in Germany in the 1960s and 70s. A later four-seat version was known as the Skyrider. Despite achieving certification from the German aviation authorities and firm orders from customers, the Skytrac was never produced in series.
The Kamov Ka-126 is a Soviet light utility helicopter with co-axial rotors. Evolved from Ka-26 with engine pods removed from stub wings, fitted with one TVO-100 turboshaft engine positioned on top of fuselage, modified rotor blades, new fuel system.
The Kellett XR-8 was a helicopter built in the United States during World War II. It was a two-seat machine intended to demonstrate the feasibility of a twin-rotor system and, while it accomplished this, it also demonstrated a number of problems that prevented further development of this particular design.
The McDonnell XHJH Whirlaway, aka McDonnell Model 65, was a 1940s American experimental transverse-rotor helicopter designed and built by McDonnell Aircraft Corporation for the United States Navy and was the largest helicopter at the time, as well as the first successful twin-engined twin-rotor helicopter in the world.
The Spitfire Mark II, later given the name Tigershark, was a utility helicopter built in the United States in the late 1970s and intended for series production. It was a further evolution of the Spitfire Mark I design, a turbine-powered conversion of the Enstrom F-28. Although airframe changes on the Mark I had been minimal, the Mark II had a substantially redesigned fuselage that rearranged the F-28's 2+2 seating to move the pilot's seat forward in the nose by itself and add a bench seat for three passengers abreast behind it. The leftmost seat on the bench could be fitted with dual controls. The fuselage was lengthened, and the powerplant installation was mounted well to the rear. The Mark II still used the dynamic components of the F-28, plus some of its airframe.
The Transcendental Model 1-G was an experimental American tiltrotor prototype of the 1950s. It was a single-seat aircraft powered by a single piston engine, and was the first tiltrotor to fly. A single example was built, which was destroyed in a crash in 1955.
The SNCAC NC.2001 Abeille was a single engine, twin intermeshing rotor helicopter designed and built in France in the late 1940s. Three were completed but only one flew, development ending when SNCAC was closed.
The Doman LZ-4 was an American eight-seat helicopter designed and developed by Doman Helicopters of Danbury, Connecticut.
The Gyrodyne GCA-2 was a general-purpose helicopter built by the Gyrodyne Company of America in the late 1940s.
