In 1939, Lockheed Aircraft Corporation decided to complete its family of high-speed twin-engine passenger aircraft with a new, larger capacity aircraft. This was prompted by a competitive battle with the Douglas company, which was successfully selling their Douglas DC-3 (DST) aircraft both in the USA and abroad. The new aircraft, named the Lockheed L-18 “Lodestar”, used many design elements from the previous Lockheed L-14 “Super Electra” design, including the wing almost entirely. However, the fuselage was new, longer and higher, accommodating 15-18 passengers, in further versions the number of passengers was increased to 26. In order to meet the requirements of potential customers a number of versions were developed with different engines of Pratt & Whitney (L-18-07, L-18-08, L-18-10, L-18-14) and Wright (L-18-40, L-18-50, L-18-56) with power from 490 hp to 650 hp. Three “Lodestar” prototypes were built as a result of the conversion of serial Lockheed L-14H aircraft. The first of them was flown on 21. September 1939. The first serial aircraft took to the air on 02. February, 1940.
The exploitation of the L-18 began in March 1940. However, the plane was not very popular in the USA, most of the airlines used the slower, but more capacious DC-3 planes. Only 43 planes (including the improved versions L-118 and L-218) were sold to various airlines, the largest number was purchased by Pan Am – 12 planes. A further 96 aircraft were sold abroad, including 38 to Great Britain and 29 to South Africa. They were also used in Brazil, Canada, France, the Dutch East Indies (today’s Indonesia), Norway and Venezuela.
In May 1941, the USAAF purchased one L-18-20 (under the designation C-56) and three L-18-14s (as C-57), followed by a further 10 C-57s. The C-57 were ordinary passenger aircraft used to transport staff officers. When the USA entered the Second World War, a number of Model 18 aircraft of various versions were purchased for military aviation. In 1941-1943 the large-scale production of aircraft for the transport aviation developed.
Versions built for USAAF:
– C-56- powered by 760 hp Wright R-1820 engines, 1 example was built,
– C-56A, C-56B, C-56C, C-56D, C-56E – versions powered by the engines Pratt & Whitney R-1690. 25 copies were built,
– C-57A – powered by the engines Pratt & Whitney R-1830. 1 example was built,
– C-57B – powered by Pratt & Whitney R-1830 engines. 7 examples were built,
– C-57C- variant C-60A powered by Pratt & Whitney R-1830-51 engines. 3 examples were built,
– C-57D – C-57A variant powered by Pratt & Whitney R-1830-92 engines. 1 built,
– C-59 (RAF Mk.IA)- a version powered by Pratt & Whitney R-1690 “Hornet” engines. 10 copies were built,
– C-60 (RAF Mk.II)- powered by Wright R-1820-87 engines. 36 examples were built,
– C-60A – powered by the engines Pratt & Whitney R-1830 “Twin Wasp”. 125 were built.
– XC-60B- a variant of the C-60A with an experimental anti-icing system. 1 example built,
– C-60C- project of a transport aircraft designed for transport of 21 soldiers, was not realized,
– C-66- powered by Wright R-1820-87 engines. 1 aircraft built, donated to Brazilian military aviation.
Versions built for the US Navy:
– XR5O-1- powered by Wright R-1820-40 engines with 895 kW. 1 example built,
– R5O-1- powered by Wright R -1820-97 engines with 895 kW. 3 examples were built, one was transferred to United States Coast Guard,
– R5O-2- powered by Pratt & Whitney R-1690-25 engines with power 634 kW. 1 ex. was built,
– R5O-3- powered by Pratt & Whitney R-1830-34A engines with 895 kW. Initially it was a VIP transport aircraft for 4 passengers. There were built 4 examples,
– R5O-4- powered by Wright R-1820-40 engines with power 895 kW. It was a staff transport plane for 7 passengers. There were 12 built,
– R5O-5- powered by Wright R-1820-40 engines with 895 kW. Similar to R5O-4 but with seats for 14 passengers. 14 examples were built,
– R5O-6- designation of 35 aircraft C-60A-5-LO which were transferred by USAAC to the US Navy (USMC), they took 18 soldiers on board.
In 1941-1943 the large-series production of the planes for the transport aviation was started. For USAAF there were built 10 ex. C-59, 30 ex. C-60 (15 of them were given to Great Britain) and 325 C-60A. C-60A. They had simplified equipment of passenger cabin and reinforced floor. The planes were unarmed, in the C-60 and C-60A versions there were openings in the cabin windows for fire from the airborne small arms. About 100 copies were delivered to the aviation of the United States Navy. In total 625 aircrafts of the Lockheed Model 18 family were built.
The transport aircrafts of Lockheed Model 18 family were used in the military aviation: Australia, Brazil, Dutch East Indies, Canada, New Zealand, Norway, South Africa, USA, UK.
On the basis of the aircraft Lockheed Model 18 Lodestar there was constructed a maritime patrol aircraft Ventura.