The Lockheed C-69 Constellation was a four-engined, propeller-driven military transport aircraft developed during World War II. It was co-developed with the Lockheed Constellation airliner.
It first flew in 1943, and production of the 22 constructed was shared between the United States Army Air Forces (15) and commercial carriers. Most of the C-69 aircraft built were later converted into civilian airliners under the designation Lockheed L-049 Constellation.[1]
Design and development
Following the Attack on Pearl Harbor and the United States entering World War II, the assembly lines at the Lockheed were taken over by the American government for the war effort. Along with the assembly lines, the Lockheed L-049 Constellation airliner was also requisitioned and redesignated C-69 and was to be used as an equipment and personnel transport by the United States Army Air Forces (USAAF). In February 1942, the 80 L-049/L-149 Constellations ordered by Transcontinental & Western Air and Pan American World Airways were also requisitioned. The 50 L-049s both airlines had on order were to be redesignated C-69 and C-69A, respectively, and used as troop transport aircraft. The 30 L-149 aircraft Pan Am had on order were replaced by the similar model L-349 (difference being the cargo door on the upper left hand side of the aircraft and the ability to carry cargo) and designated C-69B. Another 180 C-69B aircraft were ordered increasing the figure to 210. Due to the direction the war was heading during summer 1942, the need for a large troop transport capable of crossing the Atlantic Ocean or Pacific Ocean (by flying from island to island) became more important. This would help avoid the risks the convoys in the Atlantic were facing due to U-boat attacks. The Douglas C-54 Skymaster planned for these roles wasn't completely capable. So on September 29, 1942, the United States Department of War signed contract W535 AC-26610. With this contract, the nine L-049 aircraft under construction for TWA were purchased and 150 more C-69A and C-69B aircraft were ordered along with C-69C (L-549) and C-69D VIP transport versions. In reality, only one C-69C was produced out of all these planned variants.
The prototype XC-69, registered NX25600, c. 1943.
Around the same time the decision regarding contract W535 AC-26610 was made, the prototype XC-69 was completed and rolled out in December 1942. The aircraft was painted in olive green and grey camouflage colors and the civilian registration NX25600 along with Lockheed's logo being painted on the nose of the aircraft for promotional reasons; construction of the aircraft at Lockheed's Engineering Experimental Shop had been kept a secret. However, problems developed with the aircraft's powerplant, the Wright R-3350 Duplex-Cyclone. A consideration to replace the R-3350 engines with Pratt & Whitney R-2800 had been taken up. This led to a new version designated XC-69E, but the project was eventually abandoned.
The sole C-69C after civilianization for BOAC as an L049E at London Heathrow in 1954
On January 9, 1943, after the last inspections had been carried out by the USAAF and Lockheed, the XC-69 finally took to the skies. For the occasion, Lockheed had borrowed the Boeing Aircraft Company's chief test pilot, Edmund Allen. Allen was one of a small number of pilots to have experience with the R-3350 and was the test pilot for the Boeing B-29 Superfortress bomber, the role for which the R-3350 was originally developed. Lockheed test pilot Milo Burcham, who was known for flying the prototype Lockheed P-38 Lightning, acted as co-pilot during the flight. Both Allen and Burcham traded control of the aircraft during the entire experience. Both designers, Kelly Johnson and R.L. Thoren were also present on the flight (the latter acting as the flight engineer). The aircraft landed at Muroc Dry Lake (presently Edwards Air Force Base) and conducted four successful take-offs and landings. Burcham flew the XC-69 back to Burbank in 31 minutes. In total, the XC-69 performed six separate flights all adding up to 129 minutes. Two aircraft, a Boeing B-17 Flying Fortress and a Lockheed L-18 Lodestar acted as photo chase aircraft. After the experience Allen commented, "This machine works so well that you don't need me anymore!" Allen returned to Boeing. A seventh flight took place on January 18. This time, the landing gear doors were placed on the aircraft so the gear could be retracted (this was not done earlier to avoid any landing gear failure). On July 28, 1943, the XC-69 was symbolically handed over to the USAAF at Las Vegas, Nevada and given a military serial number 43-10309. Later that same day, the XC-69 returned to Lockheed for further testing. The C-69 was able to attain a higher maximum speed than the Japanese Mitsubishi A6M Zero fighter.[2]
Major problems, however, surfaced with the R-3350 powerplant that powered the C-69, when an XB-29 test aircraft crashed into a Boeing factory. The accident killed 14 factory workers, Edmund Allen, and the rest of Allen's test crew. The cause was due to one of the aircraft's R-3350 engines catching fire and burning through the wing of the aircraft causing it to fail and dooming the XB-29. All aircraft fitted with the R-3350, including the C-69, were grounded until the investigation of the engine's failure was concluded. The conclusion led to a recommendation to replace the existing carburetors with more reliable ones. With that, testing resumed after June 18, 1943. A fuel leakage problem was discovered with the C-69 and wasn't solved until April 1944 when a new method of sealing the fuel tanks surfaced. More overheating, fire and other troubles continued with the R-3350 engines. This happened to the point where Lockheed started to doubt the abilities of the engine's manufacturer, Curtiss-Wright. Lockheed suggested to the USAAF that the C-69's engines be replaced by more reliable R-2800 radial engines. Instead, the USAAF ceased production of the R-3350 until the troubles that plagued the engines were solved. This caused the development of the C-69 to slow down and furthermore, the C-69 was not declared a priority. Lockheed continued to focus on building combat aircraft while the C-54 Skymaster, the C-69's competitor was already flying and officially ordered.
The second production C-69 had first flown in August 1943. Lockheed had hoped to produce four C-69 aircraft by the end of 1943, but due to the low importance of the C-69 to the USAAF, this didn't occur. On April 16, 1944, Howard Hughes, one of the key people in the Constellation's development, and owner of TWA, flew the aircraft from Burbank to Washington D.C. in less than seven hours at 346mph (557km/h) at 65% engine power on a publicity stunt. This was done on the condition that the aircraft be delivered to the USAAF when it got to Washington. The aircraft was painted in full TWA livery while still retaining its military serial number. Also present on the flight was TWA president Jack Frye (who flew the first part of the journey and later handed the controls over to Hughes), and actress Ava Gardner, who was Hughes' girlfriend at the time. The other C-69 aircraft were used for different trials such as the seventh C-69 being flown to Fairbanks, Alaska for testing in Arctic conditions. During one flight, the XC-69 arrived at Wright Field and picked up famous aviator Orville Wright, on what would be his last flight in an aircraft. Wright was allowed to control the aircraft momentarily during the flight. He even commented that the wingspan was greater than that of his first flight. The third C-69 was sent on a flight between New York City and Paris on August 14, 1945 which showed its capability to cross the Atlantic. The test flight took less than 15 hours and was flown by a TWA crew.
Unfortunately for Lockheed, the C-69 became less important to the war effort as time progressed, especially since the tide of the war had turned in favor of the Allies. Only a small number of C-69 aircraft would see service in the last year of the war. Even so, Lockheed was able to conduct tests at the expense of the government to solve problems with the aircraft's design. Although the problems with the R-3350 were being solved, the B-29 had priority for the engines over the C-69. Even with all the effort put forth by Lockheed, the USAAF favored the C-54 Skymaster over the C-69. At the end of the war, only 22 C-69s were produced (seven of which were never delivered). Except for the C-69C, all other C-69s were declared surplus and sold on the civilian market between 1946 and 1947. These would later be converted by Lockheed into L-049 passenger aircraft for airline usage. The prototype XC-69 was converted into the sole XC-69E, which tested the possibility of using the R-2800 in place of the R-3350. This never happened. The XC-69E was later sold to the Hughes Tool Company, only to be bought back by Lockheed who converted it into the prototype L-1049 Super Constellation. In modern times, only one former C-69 is still in existence today. That C-69 currently resides at the Pima Air and Space Museum, and is painted in full TWA livery.
The Lockheed Constellation ("Connie") is a propeller-driven, four-engined airliner built by Lockheed Corporation starting in 1943. The Constellation series was the first pressurized-cabin civil airliner series to go into widespread use. Its pressurized cabin enabled commercial passengers to fly well above most bad weather for the first time, thus significantly improving the general safety and ease of air travel.
The Wright R-3350 Duplex-Cyclone is an American twin-row, supercharged, air-cooled, radial aircraft engine with 18 cylinders displacing nearly 3,350 cubic inches (54.9 L). Power ranged from 2,200 to 3,700 hp, depending on model. Developed before World War II, the R-3350's design required a long time to mature, and was still experiencing problems with reliability when used to power the Boeing B-29 Superfortress.
The Douglas DC-6 is a piston-powered airliner and cargo aircraft built by the Douglas Aircraft Company from 1946 to 1958. Originally intended as a military transport near the end of World War II, Douglas reworked it after the war to compete with the Lockheed Constellation in the long-range commercial transport market. Douglas built over 700, and many still fly in cargo, military, and wildfire control roles.
The Douglas DC-7 is an American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. A derivative of the DC-6, it was the last major piston engine-powered transport made by Douglas, being developed shortly after the earliest jet airliner—the de Havilland Comet—entered service and only a few years before the jet-powered Douglas DC-8 first flew in 1958. Larger numbers of both DC-7B and DC-7C variants were also built.
The Boeing C-97 Stratofreighter was a long-range heavy military cargo aircraft developed from the B-29 and B-50 bombers. Design work began in 1942, the first of three prototype XC-97s flew on 9 November 1944 and the first of six service-test YC-97s flew on 11 March 1947. All nine were based on the 24ST alloy structure and Wright R-3350 engines of the B-29, but with a larger-diameter fuselage upper lobe and they had the B-29 vertical tail with the gunner's position blanked off. The first of three heavily revised YC-97A incorporating the re-engineered wing, taller vertical tail and larger Pratt & Whitney R-4360 engines of the B-50 bomber, flew on 28 January 1948 and was the basis of the subsequent sole YC-97B, all production C-97s, KC-97s and civilian Stratocruiser aircraft. Between 1944 and 1958, 888 C-97s in several versions were built, 811 being KC-97 tankers. C-97s served in the Berlin Airlift, the Korean War, and the Vietnam War. Some aircraft served as flying command posts for the Strategic Air Command, while others were modified for use in Aerospace Rescue and Recovery Squadrons (ARRS).
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The Boeing Model 307 Stratoliner is an American stressed-skin four-engine low-wing tailwheel monoplane airliner derived from the B-17 Flying Fortress bomber, which entered commercial service in July 1940. It was the first airliner in revenue service with a pressurized cabin, which with supercharged engines, allowed it to cruise above the weather. As such it represented a major advance over contemporaries, with a cruising speed of 220 mph (350 km/h) at 20,000 ft (6,100 m) compared to the Douglas DC-3's 160 mph (260 km/h), at 8,000 ft (2,400 m) then in service. When it entered commercial service it had a crew of five to six, including two pilots, a flight engineer, two flight attendants and an optional navigator, and had a capacity for 33 passengers, which later modifications increased, first to 38, and eventually to 60.
The Pratt & Whitney T34 was an American axial flow turboprop engine designed and built by Pratt & Whitney. Its only major application was on the Douglas C-133 Cargomaster.
The Lockheed Model 44 Excalibur was a proposed American airliner designed by Lockheed. The Model 44 was the first four-engined design from the company, a low-wing monoplane with a retractable tricycle landing gear. Originally fitted with twin fins, the design ended up with three fins. It was to be powered by four 1,200 hp (890 kW) Pratt & Whitney Twin Wasp radial engines. Pan American Airways was close to ordering the Excalibur when Lockheed abandoned the project to devote its resources into developing the Model 49 Constellation that had been ordered by Trans World Airlines.
The Lockheed C-121 Constellation is a military transport version of the Lockheed Constellation. A total of 332 aircraft were constructed for both the United States Air Force and United States Navy for various purposes. Numerous airborne early warning versions were also constructed. The C-121 later saw service with smaller civilian operators until 1993.
The Lockheed L-1649 Starliner was the last model of the Lockheed Constellation line of airliners. Powered by four Wright R-3350 TurboCompound engines, it was built at Lockheed's Burbank, California plant from 1956 to 1958.
The Lockheed L-1049 Super Constellation is an American aircraft, a member of the Lockheed Constellation aircraft line. The aircraft was colloquially referred to as the Super Connie.
The Lockheed L-049 Constellation was the first model of the Lockheed Constellation aircraft line. It entered service as the C-69 military transport aircraft during World War II for the United States Army Air Forces and was the first civilian version after the war. When production ended in 1946 it was replaced by the improved L-649 and L-749 Constellation.
The Lockheed L-649 Constellation was the first real civilian version of the Lockheed Constellation line, as the Lockheed L-049 Constellation was a simple redesign from the military Lockheed C-69 Constellation. The L-649 was planned to be the new standard version of the Constellation, but the L-749 Constellation, a co-jointly produced improved derivative, was chosen over the L-649 by most airlines. Most of the few L-649 aircraft built were delivered and operated by Eastern Air Lines.
The Lockheed L-749 Constellation is the first Lockheed Constellation to regularly cross the Atlantic Ocean non-stop. Although similar in appearance to the L-649 before it, the L-749 had a larger fuel capacity, strengthened landing gear, and eventually weather radar.
The Lockheed L-1249 Super Constellation was a turboprop-powered version of the Lockheed Constellation aircraft family. Built in 1954 and 1955, the aircraft were used as prototypes for possible future military transport aircraft for both the United States Air Force and United States Navy. Both aircraft saw very short lives and the airframes were later used to build L-1049 Super Constellations.
References
Citations
↑ Breffort, Dominique. Lockheed Constellation: from Excalibur to Starliner Civilian and Military Variants. Paris: Histoire and Collecions, 2006. Print. ISBN2-915239-62-2. p. 11 to p. 17.
Breffort, Dominique (2006). "Lockheed Constellation: from Excalibur to Starliner Civilian and Military Variants". Histoire and Collecions. Paris: Print. ISBN2-915239-62-2.
Lockheed Constellation Survivors – A website that explains information and whereabouts of surviving Constellations of all variants, including the last surviving C-69 Constellation.
1 Not assigned •2 Assigned to multiple types •3 Unconfirmed
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