Unbuilt McDonnell Douglas jumbo jets, part 1: the D-916C, D-918, D-950, D-952, and D-956

Today, there are two gigantic passenger/freight aircraft flying in our skies, the Boeing 747 first flown in 1969 and the larger double-deck Airbus A380 built early in this century, and these airliners have come to be colloquially known as the "jumbo jets" (the A380 is more popularly nicknamed "superjumbo" given its larger wingspan and greater seating capacity). However, what many people don't know is that once upon a time, in the late 1960s and again in the early 1990s, Douglas and later McDonnell Douglas worked out design studies for jumbo jets similar to or rivaling the Boeing 747 in size, seating capacity, and wingspan. Since Douglas tinkered with very large airliner proposals in the mid-1960s before it merged with McDonnell in 1967 to form McDonnell Douglas, and the aerospace industry in Long Beach returned to double-deck airliner design in the early 1990s, I'm covering the history of jumbo jet design in Long Beach in two parts, with this blog post dedicated to proposals for a 747- and A380-type airliner envisaged by Douglas in the 1960s. 

Artwork of the Douglas D-918 double-deck airliner, which was derived from the losing D-916 submission for the CX-HLS competition. 

In early 1965, Douglas began tinkering with design studies for an airliner comparable to the Boeing 747 when it proposed a commercial derivative of the losing D-916 strategic airlifter design for the CX-HLS (Cargo Experimental - Heavy Logistics System) competition, known as D-916C by the company. Like the D-916, the D-916C had shoulder-mounted wings and the cockpit situated at the top in a flight deck that formed a hump similar to that of the 747. The airliner variant of the D-916C had a seating capacity for 616 passengers, with 219 seated on the first deck, 300 passengers seated in a full upper deck, and 96 people (36 seats in a private compartment and 60 seats in the siesta balcony) seated in the partial upper deck at the level of the cockpit, and its lower deck could also carry 16,000 cubic feet (453 cubic meters) of cargo. When configured as a commercial freighter, the D-916C could carry 30,720 cubic feet (870 cubic meters) of freight within the two full decks. Douglas simultaneously conceived another similarly-sized twin-deck airliner project with shoulder-mounted wings, the D-918, which had a seating capacity for 900 passengers on two full decks and a partial upper deck at the level of the cockpit.

Left: Three-view drawing of the Douglas D-950-30
Right: Three-view drawing of the Douglas D-952-30

In the second half of 1965 the D-916C and D-918 projects faded away as Douglas envisaged a pair of twin-deck four-engine airliner projects, internally called D-950 and D-952, which were powered by four 40,000 lb (177.9 kN) thrust General Electric CF6 or Pratt & Whitney JTF-14E turbofans. Both airliner proposals retained the double-bubble cross-section of the D-916C and D-918, and the D-950 had a wingspan of 167 feet 6 in (51.04 meters) and a range of 6,000 miles (9,656 km), while the D-952 was to have a wingspan of 206 feet 9 in (63 meters). Three iterations of the D-950 were considered, the 376-seat D-950-10 with a length of 180 feet 4 in (55 meters), the 457-seat D-950-30 with a length of 194 feet 4 in (58 metes), and the 524-seat D-950-50 having a fuselage 206 feet 4 in (62.89 meters) long, and they had a maximum takeoff weight of 275,000 lb (124,738 lb). As a freighter, the D-950 was to carry two side-by-side 88 x 125 inch pallets on the main deck, and single pallets on the upper deck. The D-952 had a more voluminous cross-section of both decks, which had higher cabin ceilings, and two variants of the D-952 were studied, the 458-seat D-952-10 with a length of 182 feet (55.47 meters) and a range of 4,000 miles (6,437 kg), and the 563-seat D-952-30 measuring 212 feet (64.61 meters) long and having an operating range of either 3,500 miles (5,632 km) with a 150,000 lb (68,039 kg) payload or 2,150 miles (3,460 kg) when carrying a 300,000 lb (136,077 kg) payload. Work on the D-950 project was shelved by the time that the Boeing 747 program was launched after Pan Am ordered for 25 aircraft on April 13, 1966, but Douglas continued development of the D-952 on a low-key basis, tentatively eyeing a first flight of 1972 and service entry in 1975 for the D-952, eventually abandoning all work on the D-952 after market researchers concluded that a very large jet airliner was not yet viable given that the Boeing 707 and Douglas DC-8 could occupy most of long-haul routes for which the D-952 had been designed. 

Artwork of the Douglas D-956-13 double-deck airliner project in flight with the writing "Douglas DC-10" on the fuselage. 

Even before the D-950 and D-952 were axed, Douglas worked out one more project in late 1965 for a double-deck airliner/commercial freighter, designated D-956, steadfast in its opinion that airfreight growth was central to the future of large transport aircraft. Like the D-950 and D-952, the D-956 had low-mounted wings but differed in having a wider fuselage and a wingspan of 191 feet (58.21 meters), and three different fuselage lengths were investigated for this aircraft along with two engine options, the General Electric TF39 and Pratt & Whitney JT9D turbofans, which generated 41,000 lb (182.38 kN) of thrust. The baseline TF39-powered D-956-13 and JT9D-powered D-956-23 airliner proposals along with the baseline D-956-13F and D-956-23F freighter designs were 180 feet (54.86 meters) long, and the D-956-13 and -15 could carry 400 passengers over a distance of 6,000 miles (10,460 km), while the D-956-13F and -15F were to haul 215,000 lb (97,522 kg) of freight over a range of 2,775 miles (4,466 km) or 200,000 lb (90,718 kg) of freight in a typical transatlantic flight over a distance of 3,500 miles (5,632 km). Four stretched D-956 proposals were conceived, the TF39-powered D-956-14 and JT9D-powered D-956-24 with a length of 200 feet (61 meters), a seating capacity for 500 passengers, and a range of 5,100 miles (8,208 km), and the even bigger 602-seat D-956-15 (with TF39s) and D-956-25 (with JT9Ds) with a length of 220 feet (67 meters) and an operating range of 3,500 miles (5,632 km). One D-956 design study was proposed with a length of 260 feet (79 meters) and a single deck fuselage accommodating 585 passengers, but was quickly shelved because it had less fuel efficiency than the double-deck D-956 designs. The D-956-15 and -25 iterations were selected for further development because Douglas considered the seat-mile operating costs of those designs to be 30 percent cheaper than that of the DC-8-61. However, the D-956 did not proceed beyond the design phase because Douglas in May 1966 turned its attention to design of a twin-engine successor to the Boeing 727 in response to an American Airlines requirement issued in April for a twin-engine airliner with 250 seats and capable of operating from 7,000 foot (2,134 meter) runways.

References:

Endres, Gunter, 1998. McDonnell Douglas DC-10. St. Paul, MN: MBI Publishing. 

Waddington, T., 2000. McDonnell Douglas DC-10. Miami, FL: World Transport Press.