|
|
The Lockheed C-140 was the designation given to a small number of Lockheed Jetstars that were ordered as cargo aircraft, after the original military requirement for the aircraft had been cancelled.
In the mid 1950s the USAF was still relying on a large fleet of transport aircraft that had been produced during the Second World War, and didn’t have the budget to fund the development of their replacements. In an attempt to get past this obstacle, the USAF produced two specifications, a small Utility Trainer Experimental (UTX) and a larger Utility Transport Experimental (UCX), and promised that when its budget improved it would purchase existing aircraft that matched these specifications.
The problem for the aircraft manufacturers was that they would have to fund the development of these aircraft themselves. North American decided to focus on the cheaper UTX, while McDonnell and Lockheed both picked the UCX. Work on the Lockheed CL-329 began at the start of 1957, with Kelly Johnson in charge. The resulting aircraft was a fairly small twin engined jet powered transport aircraft, capable of carrying 14 passengers or 5,000lb of cargo, The engines were mounted in pods on either side of the rear fuselage, in the configuration made famous on the Learjet. The main wings were low mounted and swept back, while the horizontal tail surfaces were mounted low on the vertical tail.
The project suffered from engine problems. A twin engine layout was preferred, but no American designed engines of the right power were available. As a result Lockheed selected the Bristol Orpheus, which was about to enter licensed production as the Wright TJ37. The prototypes used British built Orpheus 1/5 turbojets, each providing 4,850lb thrust. In the end this engine didn’t go into licensed production, forcing Lockheed to look for alternatives.
The first prototype made its maiden flight on 4 September 1957. However by this point the USAF’s budget had been cut, meaning that they were no longer interested in the UCX. The prototype CL-329 took part in a sales campaign in 1958, but this clashed with a recession that cut civilian aircraft orders. Despite these problems, in October 1958 Lockheed won a USAF crew trainer competition, and the Air Force announced that it intended to purchase the JetStar as the T-40A-LM. In November 1958 Lockheed decided to put the type into production as the JetStar. Soon afterwards the Air Force changed its mind, and ordered the cheaper North American NA-246 instead, as the T-39.
This blow was followed by loss of the Orpheus engines. Lockheed were forced to adopt a four engined configuration instead, with two engines in pods on each side of the rear fuselage. A series of engines were tested, and the Pratt & Whitney JT12A was eventually selected for the aircraft. During 1959 Lockheed began to receive orders for the type, including several private orders and one for twenty nine aircraft from the Canadian government.
The first firm US military order came in 1960, and was for five C-140A-LMs, which were to be used to calibrate military navigation aids. The Navy also ordered two CV-1s, although this order was later cancelled.
The aircraft was produced in a number of civil versions, starting with the JetStar 6. This was powered by four JT12A-6 or 6A engines, and normally carried ten passengers and two crew. The first production aircraft flew in 1960 and eighty were built. Next came the JetStar 8, which was powered by four 3,300lb thrust JT12A-8 turbojets, of which sixty-six were built. The JetStar 731 was the designation given to aircraft that had been modified to use turbofan engines by the AiResearch Aviation Company. The JetStar II was a Lockheed produced version that used the same turbofans as the JetStar 731. The last JetStar II was built in 1980, and a total of 204 were completed.
Military Versions
C-140A-LM
The first five military aircraft were designed to calibrate navigation aids. Deliveries began in September 1961, and they were used by the 1866th Flight Checking Flight of the Air Force Communications Service. They were powered by four 3,000lb Pratt & Whitney J60-P-5 engines, the military version of the A-6 turbojet. They remained in service for over twenty years.
C-140B-LM
This designation was given to five aircraft ordered as utility transports that could be converted between passenger and cargo configurations. This was the last version of the aircraft to be ordered by the USAF, but the first to enter service, with the first aircraft arriving in April 1961. Almost as soon as they entered service they were upgraded to the VC-140B standard.
VC-140B-LM
Six more transport aircraft were ordered as VIP transports, to be operated by the 1254th Air Transport Wing, Special Air Mission, based at Andrews Air Force Base. Eight VC-140Bs and C-140Bs were still in service in 1986, when they were replaced by the Gulfstream C-20A and Gates Learjet C-21A.
C-140C-LM
The C-140C was a designation given to the two UV-1s in September 1962.
UV-1
The US Navy ordered two JetStars for use as staff transports in 1960. The order was cancelled before the aircraft were delivered.
C-140B
Engines: Four Pratt & Whitney J60-P-5 turbojets
Power: 3,000lb each
Crew: 2
Wing span: 53ft 8in
Length: 60ft 5in
Height: 20ft 6in
Empty weight: 19,302lb
Loaded weight: 39,288lb
Maximum weight: 42,000lb
Maximum speed: 573mph at 36,000ft
Cruising speed: 507mph
Service ceiling: 38,000ft
Normal range: 2,220 miles
Maximum range: 2,345 miles