The Lockheed C-69 Constellation was developed as a civil airline, but all early production was taken over by the USAAF after the US entry into the Second World War.
Lockheed began working on a new civil airline in 1938. The original Model 44 Excalibur would have been able to carry 21 passengers at a top speed of 241mph. The company took this to Pan American, who wanted a larger aircraft, and the Model 44 eventually evolved into a 40 passenger aircraft capable of 300mph. However in 1939 Howard Hughes of TWA approached Lockheed to discuss the possibility of them producing a pressurized aircraft capable of non-stop flight across the continental US, with a speed of over 250mph at 20,000ft and a payload of 6,000lb. Lockheed dropped the Model 44 and replaced it with the Model 49 Excalibur A, soon to be renamed the Constellation.
The Model 49 was a four engined low winged monoplane. The fuselage had a circular cross section and could be pressured at 8,000ft at up to 20,000ft. It had nose wheel landing gear, and a three rudder tail. Fuel tanks were built into the wings, which had Fowler flaps. It could carry 44 passengers in rows of four, two on each side of a centre aisle, or 20 passengers in the sleeper version. Two versions were proposed - the Model 049-16-01 with Pratt & Whitney Double Wasp engines or the Model 49-99-01 with Wright Double Cyclone engines. Both versions had an estimated top speed of 360mph and would cruise at 20,000ft.
Early in 1940 Howard Hughes's TWA placed an order for nine Constellations, later increased to forty aircraft. Pan American ordered forty aircraft and another four were sold, for a total of 84 initial orders.
Work on these first aircraft was underway when American entered the Second World War, and all construction of civil aircraft was cancelled. On 20 September 1942 Lockheed were given permission to complete the first nine aircraft from the TWA order as the C-69-LO. On 29 September 1942 an order was placed for 180 aircraft with full military equipment, and eventually 313 C-69s were ordered. However only fifteen C-69s were actually delivered, including the prototype.
The first prototype, with four 2,200hp Wright R-3350-35s made its maiden flight on 9 January 1943, with Eddie Allen, (the Boeing test pilot) and Milo Burcham (P-38 Lightning test pilot) sharing the piloting duties. Each flew three times during the day, and the aircraft then went to the USAAF base at Muruc Dry Lake (Edwards Airforce Base). This aircraft was officially accepted by the USAAF in July 1943 but then went back to Lockheed for more tests. On 17 April 1944 it was flown back to the Air Force with Howard Hughes himself at the controls. After more test it was converted into the XC-69E, with 2,100hp Pratt & Whitney R-2800-83 engines. It was then sold to Hughes Aircraft, but in the 1950s was bought back by Lockheed and used as the prototype for the Super Constellation.
Those C-69s that were delivered in 1944-45 entered service with the Air Transport Command, where they performed well. The type's first transatlantic flight came in August 1945, when one reached Paris from New York in 14 hours 12 minutes. However after the war the Air Force decided to standardize on the Douglas C-54 and twelve of the fifteen C-69s were sold as surplus.
After the war Lockheed decided to finish the many incomplete C-69s on their production lines as a civil airliner, the Model 059 Constellation. The first of these aircraft entered civil service on 6 February 1946, and gave Lockheed time to develop the improved Model L-649, which made its maiden flight on 19 October 1946. This was followed by the L-749 of 1947, which carried more fuel and was designed as an intercontinental airliner. This was ordered in small numbers by the USAAF as the C-121.
This was the designation given to the original nine TWA aircraft when taken over by the USAAF and to five aircraft from the military order. They were all powered by four 2,200hp eighteen cylinder Wright R-3350-35 engines. They had 44 seats on the starboard side of the cabin and four folding benches on the port side and two toilets. Most were quickly sold off as surplus, but the few that were still in USAF service in 1948 became the ZC-69-LO.
The C-69A would have been a 100 seat troop transport, with R-3350 engines and rifle firing ports in the windows, a rather odd feature. None were built.
C-69B-LO (Model 349)
The C-69B was a design for a long range troop transport with more fuel capacity, but none were built and the contract was cancelled on VJ-Day.
The C-69C-1-LO was the final aircraft to be accepted, and was a VIP transport version with 42 seats. It would have become the Presidential aircraft if Tom Dewey had won the 1948 election, but after his defeat was sold as surplus.
Engines: Four Wright R-3350-35
Power: 2,200hp each
Crew: 7 to 9
Wing span: 123ft
Length: 95ft 1in
Height: 18ft 8in
Empty weight: 55,350lb
Loaded weight: 86,500lb
Cruising speed: 275mph
Maximum payload: 15,250lb/ 60 passengers