Lockheed's forgotten commercial gyroplanes

In the 1960s, Lockheed was busy with a variety of civil and military aircraft programs, namely the SR-71 Blackbird, A-12, C-141 Starlifter, C-5 Galaxy, F-104 Starfighter, C-130 Hercules, AH-56 Cheyenne and P-3 Orion. However, what has been seldom noticed is the company's flirtation with commercial gyroplane designs capable of intercity travel in that decade, and prior to the start of flight tests of the Cheyenne, it had investigated compound helicopter technology modifying one of the three prototypes of the XH-51 into a compound helicopter and flight testing it in his iteration in the 1964-1965. The impetus for Lockheed to took a serious look at the idea of a commercial gyroplane lay in forecasts that the bulk of a huge increase in the population would take place in urban areas by 1980, a recognition that the airports serving the main metropolitan areas of the US had to increase in size and move further from population centers to provide adequate space for long-distance travelers, and increased congestion on urban highways.

Left: Artwork of the Lockheed CL-879 gyroplane in flight
Right: Two-view drawing and specifications for the CL-879-8 from company documents.

The first Lockheed-California proposal for an intercity passenger gyroplane to be worked out, designated CL-879, was conceived in 1964. It featured seating capacity for 76-95 passengers and was intended for airport shuttling, intercity transport, and utility purposes. The CL-879-8 configuration was 102 feet (31 meters) long with a wingspan of 47 feet (14.32 meters), a height of 22 feet (6.7 meters), and a main rotor diameter of 94 feet (28.65 meters). Cruising speed was 287 mph (362 km/h), and operating range was to be 250 miles (402 km), while power would come from four 3,130 shp (2,302 kW) General Electric T64-GE-16 turboshafts housed in two paired underwing nacelles. In a confined area situation, the CL-879 would have a gross weight of 68,500 lb (31,071 kg) and a payload of 15,200 lb (6,895 kg), while gross weight and payload of the aircraft in a clear area situation were to be 79,800 lb (kg) and 19,000 lb (kg) respectively. Lockheed estimated that the CL-879 would be ready for airline service in the 1970s, and it suggested that the CL-879 itself could be optimized for cargo transport if a market demand for a short-haul commercial rotorcraft developed.

Artwork of the CL-1026 passenger compound helicopter 

Even as flight testing of its new AH-56 Cheyenne compound attack helicopter was underway, in 1967 Lockheed undertook design of the CL-1026 passenger derivative of the Cheyenne. Like the AH-56, the CL-1026 had a rigid main rotor, a four-blade anti-torque tail rotor, and a three-blade pusher propeller but was powered by two 3,435 shp (2,526 kW) Lycoming T55 turboshafts mounted side-by-side and had a deeper fuselage. It measured 60 feet 6.9 in (18.46 meters) long with a height of 15 feet 3 in (4.65 meters), a main rotor diameter of 51 feet 2.4 in (15.6 meters), a gross weight of 22,500 lb (10,206 kg) and seating for 30 passengers and three crewmembers. The CL-1026 would have a range of 225 miles (362 km/h) and a cruise speed of 230 mph (370 km/h), while it was primarily designed for intercity operations, it also could be convertible to cargo configuration in a matter of minutes.

Left: The Lockheed CL-1060 concept
Right: Artist's conception of the CL-1090 design

Although the earlier CL-879 project did not progress beyond the design phase, Lockheed capitalized on its work on the CL-879 to envisage two more large passenger gyroplane designs in 1967, the CL-1060 and CL-1090. These designs were powered by four turboshaft engines paired in two underwing nacelles and driving two propellers and a huge five-blade main rotor, and they had a crew of four. The CL-1060 proposal was 87 feet 6 in (26.67 meters) long with a wingspan of 49 feet 6 in (15.088 meters), a height of 15 feet 3 in (4.65 meters), and a main rotor diameter of 82 feet 6 in (meters), and it was intended to carry 60 passengers. The CL-1090, on the other hand, measured 124 feet 6 in (37.9 meters) in length and had a height of 30 feet 10.2 in (9.4 meters), a main rotor diameter of 102 feet (31 meters), a gross weight of 80,000 lb (36,287 kg), and seating for 95 passengers. 

Despite being pitched by Lockheed as commercial remedies to increasingly crowded US airports and congestion on urban highways, the CL-1026, CL-1060, and CL-1090 concepts, like the CL-879, did not progress to full-scale development, largely due to a lack of serious interest from commuter airlines.

For more on Lockheed's passenger gyroplane designs, see the following links:

https://www.secretprojects.co.uk/threads/various-lockheed-helicopter-projects.4153/

https://www.secretprojects.co.uk/threads/lockheed-ah-56-cheyenne-and-derivatives.941/

References:

Federal Aviation Administration, 1969. Heliport Design Guide. Washington, DC: Government Printing Office. (PDF) 

Francillon, R., 1987. Lockheed Aircraft Since 1913. Annapolis, MD: Naval Institute Press.