Lockheed Constellation C-69

After the attack on Pearl Harbor brought the United States into the Second World War, the government took over Lockheed's assembly lines and, with them, the L-049 Constellation airliner, which was redesignated C-69 and assigned to the USAAF as a personnel and equipment transport. In February 1942 the 80 L-049/L-149s ordered by Transcontinental & Western Air (TWA) and Pan American were requisitioned. The 50 L-049s on order were to become C-69 and C-69A troop transports, while Pan Am's 30 L-149s were replaced by the closely related L-349, which added a cargo door on the upper left side, designated C-69B; a further 180 C-69Bs raised that figure to 210.

By the summer of 1942 the course of the war made a large troop transport able to cross the Atlantic or hop across the Pacific more pressing, as a way of avoiding convoys exposed to U-boat attack; the C-54 Skymaster planned for the role was not fully up to it. On 29 September 1942 the War Department signed contract W535 AC-26610, buying the nine L-049s under construction for TWA and ordering 150 more C-69As and C-69Bs together with the C-69C (L-549) and C-69D VIP versions. Of that whole plan, only one C-69C was ever built.

The XC-69 was rolled out of Lockheed's experimental shop in December 1942 in olive green and grey, carrying the civil registration NX25600 and the company logo on the nose for publicity; it had been built in secret. Problems with the Wright R-3350 Duplex-Cyclone led to a study of replacing it with the Pratt & Whitney R-2800, which produced the XC-69E designation but was eventually dropped.

For the first day of flying, on 9 January 1943, Lockheed borrowed Edmund Allen, Boeing's chief test pilot and one of the few pilots with R-3350 experience from the B-29 programme. Milo Burcham, who had flown the P-38 prototype, was co-pilot and the two shared the controls, with Kelly Johnson and R. L. Thoren, the latter as flight engineer, on board. The aircraft landed at Muroc Dry Lake, made four take-offs and landings and returned to Burbank in 31 minutes: six flights totalling 129 minutes, chased by a B-17 and a Lodestar as photo aircraft. Allen remarked that the machine worked so well it no longer needed him. The seventh flight, on 18 January, was the first with the gear doors fitted so the undercarriage could be retracted. On 28 July 1943 the XC-69 was symbolically handed over to the USAAF at Las Vegas with serial 43-10309, returning to Lockheed the same day for further testing.

The R-3350 was the programme's main burden. When an XB-29 crashed into a Boeing factory after one of those engines caught fire, Allen, his crew and 14 workers were killed, and every R-3350-powered aircraft, the C-69 included, was grounded until the investigation recommended more reliable carburettors. Testing resumed after 18 June 1943. A fuel leak then appeared that was not cured until April 1944, with a new way of sealing the tanks, and overheating and fires continued. Lockheed began to doubt Curtiss-Wright and proposed fitting the R-2800; the USAAF instead halted R-3350 production until it was fixed, the C-69 was not made a priority, and the company kept concentrating on combat aircraft while its rival, the C-54, was already flying and on firm order.

The second production C-69 flew in August 1943. Lockheed had hoped to finish four by the end of the year, but the USAAF's lack of interest prevented it. On Howard Hughes's famous dash to Washington the sources disagree on date and figure: the C-69 article gives 16 April 1944 at 557 km/h on 65 % power, while the Constellation article gives 17 April at an average of 533 km/h; the aircraft wore full TWA livery with its military serial and was delivered to the USAAF on arrival. Other C-69s were used for trials: the seventh was flown to Fairbanks, Alaska, for Arctic testing, and on 14 August 1945 the third crossed from New York to Paris in under 15 hours with a TWA crew, proving its transatlantic reach. On one flight that called at Wright Field, Orville Wright briefly took the controls on what would be his last flight.

With the war turning in the Allies' favour, the C-69 lost importance and only a few served in the final year of the conflict; the B-29 had priority for engines and the USAAF favoured the C-54. The figures do not agree between sources and are given here as published. The Wikipedia article on the C-69 gives 22 built (seven never delivered), with 15 for the USAAF, and its variants table lists 1 XC-69, 16 C-69-1-LO, 4 C-69-5-LO and 1 C-69C-1-LO; its own list of versions, however, says 13 C-69 troop transports were completed and seven more under construction were converted to L-049s on the line. The list of Constellation variants also says 22 C-69s, while Lockheed Martin writes that only 13 Constellations were built during the war. The USAAF cancelled the rest of the order in 1945 and Lockheed was asked to focus on the P-38.

Apart from the C-69C, all C-69s were declared surplus and sold on the civil market between 1946 and 1947, and Lockheed converted them into L-049 passenger aircraft. The sole C-69C, later ZC-69C-1, was civilianised as an L-049E for Britain's BOAC. The prototype, turned into the only XC-69E to test the R-2800 without that change ever reaching production, was sold to the Hughes Tool Company; Lockheed bought it back, stretched it and made it the prototype of the L-1049 Super Constellation. Some aircraft stayed in USAF service into the 1960s, carrying military personnel in Military Air Transport Service colours. Today a single former C-69 survives: 42-94549, one of TWA's first Constellations, displayed as N90831 in TWA livery at the Pima Air & Space Museum in Tucson, Arizona.