SANDRA HOYT COLLECTION
No. 5752. Lockheed 10-A Electra (NC14900 c/n 1015) Northwest Airlines
Source unknown

Lockheed 10-A Electra

06/30/2010. Upon acquiring in June 1932 the assets of the Lockheed Aircraft Corporation, a subsidiary of the defunct Detroit Aircraft Corporation, Robert Gross and his fellow investors planned to have the reorganized firm build a ten-seat, all-metal transport designed by its president Lloyd Carlton Stearman. However, before the construction of this single-engined aircraft could proceed, the new Lockheed management team agreed with the conclusions of Robert Gross' informal market study and decided to develop a twin-engined airliner.

The wisdom of this decision was confirmed within the next two years when the new Lockheed found itself competing against the slightly larger Boeing 247 and Douglas DC-l/DC-2, also twin-engined metal aircraft, and when from October 1934 single-engined transports operating in the United States were forbidden to carry passengers on scheduled services at night or over terrain unsuitable for emergency landings.

Continuing with the aircraft model numbering and naming systems of its immediate forebearer, the new Lockheed Aircraft Corporation designated the twin-engined aircraft Model 10 and named it Electra after the lost Pleiad in the cluster of stars in the constellation Taurus, thus continuing the company's policy of naming their aircraft after stars. Its design was undertaken by Hall Hibbard assisted by Richard Von Hake and, to a lesser extent by Lloyd Stearman.

The configuration evolved from the preliminary design work was for a cantilever low-wing monoplane, with a heavy truss passing through and over the cabin floor to join the wing spars. It had accommodation for a crew of two and ten passengers (five seats on each side of the central aisle, aft of the cockpit). Its two Pratt & Whitney Wasp Junior radials were to be enclosed in NACA cowlings and, to obtain a reasonable landing speed in spite of the relatively high wing loading, split flaps were to be installed on the wing trailing edge.

All these features were carried on to the final design and production aircraft; but three other initial design characteristics-single vertical tail surfaces, wing-to-fuselage fillets, and forward raked windshield-were not retained, the first two having been identified as likely to cause problems by Clarence 'Kelly' Johnson, then working as an assistant to Professor Edward Stalker, the University of Michigan aerodynamicist who had been entrusted with testing of a Model 10 model in the university's wind tunnel.

Although Johnson's report was not fully endorsed by Stalker, he was invited to join Hall Hibbard's staff and, for his first assignment with Lockheed, was asked to redesign the tail surfaces. After wind-tunnel testing of additional end-plate fins near the end of the tail plane, Johnson adopted a twin fin and rudder design-for long thereafter a Lockheed 'trademark' - and this was incorporated in the prototype during its construction.

The prototype, Registered X233Y (c/n 1001), however, initially retained the wing fillets and forward-raked windshield, and was completed in this form during February 1934. On the 23rd of that month the Electra prototype was taken by Marshall Beadle on its maiden flight from the company's airstrip at Burbank. It was powered by a pair of Wasp Junior SB engines rated at 450 hp for takeoff, 450 hp at 3,500 ft (1,067 m) and 400 hp at 5,000 ft (1,524 m), and driving two-blade variable-pitch propellers.

Initial trials confirmed Kelly Johnson's second recommendation and the wing fillets were soon removed. Another change introduced during that period was the replacement of the original windshield with a shallow unit blending with the nose of the aircraft, but it was not satisfactory and had to be replaced with more conventional V-panes; this final configuration was introduced on the line during the construction of the fifth Electra and was retrofitted on at least two aircraft by Northwest Airlines' maintenance personnel.

With these improvements, performance and handling characteristics gave complete satisfaction and the Electra completed its preliminary CAA airworthiness trials at Mines Field, Los Angeles, in the spring of 1934. Unfortunately, when returning to the company's airstrip in Burbank, the aircraft experienced an undercarriage malfunction. After dumping most of its fuel and the lead ballast used in the CAA's full-weight tests, the Electra was taken by Marshall Headle to the Union Air Terminal where a successful one-wheel landing was made. Damage was slight and, after repair and the offending undercarriage shaft replaced, the aircraft was awarded its Approved Type Certificate on 11 August, 1934.

The prototype was followed by 147 production Electras and the XC-35, delivered between August 4, 1934, and July 18, 1941, in four commercial and five military versions:

Model 10-A: Model 10-A: Ten-seat airliner powered by two 450 hp Pratt & Whitney R-985-SB Wasp Junior engines, 100 produced. The aircraft were delivered to fourteen airlines, to private customers, and to the Venezuelan Government, with the last Model 10-A being delivered to LAN-Chile. They were normally fitted with variable-pitch two-blade propellers, but later some aircraft received constant-speed units. Goodrich de-icing boots were also available as options.

The pictured aircraft became impressed as a C-36A, s/n 42-57213, on May 12, 1944 it was returned to Northwest and the registration NC14900 was reinstated. Subsequently it was transferred to the Força Aérea Brasileira, s/n 1002. After being struck off charge it came on the Brazil registry as PP-VAR, eventually returning to the USA, initially registered as N2067A.

By 1997 it was registered NX72GT and was used by Linda Finch to fly the planned around-the-world flight on which Amelia Earhart disappeared on July 2, 1937. Finch left Oakland International Airport at Oakland, California, USA, on March 17, returning on May 28, 1997. During the 73 days Finch covered about 26,000 mls (41,843 km), stopping at 36 way-points in 18 countries.

Model 10-B: Ten-seat airliner powered by two 440 hp Wright R-975-E3 Whirlwind engines, 18 produced.

Model 10-C: Ten-seat airliner powered by two 450 hp Pratt & Whitney
R-985-SC1 Wasp Junior engines, 8 produced. Pan American Airways expressed an early interest in the Electra but requested that Lockheed modify it to use the Wasp as the airline had a surplus of these engines. Upon receiving Lockheed's agreement to redesign and obtain certification of the Model 10-C with its specified engines, Pan American became the second customer for the Electra.

Eventually all eight Model 10-Cs produced were acquired by this carrier for its Alaska Division, and its subsidiaries, Aerovias Centrales and Cubana. The first (c/n 1004, X14257, later NC14257) was the fourth Electra to be built and was delivered in September 1934; the last Model 10-C delivery was made to Aerovias Centrales eight months later.

Model 10-D: Projected military development; none built.

Model 10-E: Airline and private transport powered by two 600 hp Pratt & Whitney R-1340-S3H1s Wasp engines, 15 produced.

XR2O-1: Model 10-A staff transport for the Secretary of the Navy powered by two 450 hp Pratt & Whitney R-985-48 Wasp Junior engines, 1 produced.

XR3O-1: Model 10-B multi-purpose transport powered by two 440 hp Wright R-975-E3 Whirlwind engines, 1 produced for the USCG, c/n 1053 s/n 383, later V151. The aircraft had a convertible interior arrangement providing for rapid change from command transport to ambulance, and was often used as staff transport for the Secretary of the Treasury.

After WW II, it was sold to a private owner and was modified to the Wasp S3H1 powered Model 10-E standard. In this configuration it became one of the last Electras to be used as an airliner, while operated by Provincetown-Boston Airline, registered as N233PB.

On August 27, 1967, after a power-loss, the 31-year old veteran was finally ditched in Massachusetts Bay near a beach close to Humarock, Massachusetts, some 25 mls (40 km) south-east of Boston. The pilot and thirteen passengers escaped serious injuries.

XC-35: Military research vehicle for pressurized-cabin and high-altitude operations powered by two 550 hp turbo supercharged Pratt & Whitney
XR-1340-43 engines, 1 produced.

Y1C-36: Model 10-A military multi-purpose transport powered by two 450 hp Pratt & Whitney R-985-13 engines, 3 produced for the USAAC (c/n 1071, 1073 and 1074, serial 37-65 to 37-67). The first Y1C-36 was damaged beyond repair in February 1938, fifteen months after its delivery. The other two, by then redesignated C-36-LOs, were transferred to the Força Aérea Brasileira (Brazilian AF) during the war. Both crashed during the early 1950s after going onto the Brazilian civil register.

Y1C-37: Model 10-A military multi-purpose transport powered by two 450 hp Pratt & Whitney R-985-13 engines, 1 produced for the National Guard Bureau USAAC (c/n 1104, serial 37-376). Ordered by the War Department shortly after the three Y1C-36s, the aircraft was used as a staff transport assigned to its Chief, the Y1C-37 was the first multi-engined aircraft. First redesignated
C-37, it became an UC-37-LO in January 1943. After the war this aircraft was sold and in January 1947 it crashed in Honduras.

Early into WW II the USAAF impressed 27 Electras, surviving aircraft were returned to the civil register beginning in 1944:

C-36A: Civil Model 10-A with serials 42-32535, 42-38341 to 42-38344,
42-56638 to 42-56641, 42-57213 to 42-57216, 42-57505 and 42-68362. Powered by two 450 hp Pratt & Whitney R-985-13 engines, these 15 aircraft were redesignated UC-36A-LOs in the utility transport category in January 1943.

C-36B: Civil Model 10-B with serials 42-32533, 42-32534, 42-38289, 42-38296 and 42-38304. These 5 aircraft with 600 hp Pratt & Whitney R-1340-49 Wasp engines were redesignated UC-36B-LOs in January 1943.

C-36C: Civil Model 10-B with serials 42-38345, and 42-57217 to 42-57222. These 7 aircraft with 440 hp Wright R-975-13 Whirlwind engines were redesignated UC-36C-LOs in January 1943.


Created October 15, 2006