The designations JO, R2O and R3O were assigned to two different aircraft. The JOs were Lockheed Model 12-A Electra Juniors; the R2O was a Model 10-A Electra; and contrary to standard practice, the two R3Os were a Model 10-B Electra and a Model 12-A Electra Junior.
In 1932, the Lockheed Aircraft Corporation of Burbank, California began planning for a ten-seat, all-metal, single-engined transport. Fortunately for Lockheed, the design was changed to a twin-engined transport because in October 1934, the Civil Aeronautics Administration (CAA) banned the transportation of passengers on scheduled services at night or over terrain unsuitable for emergency landings in single-engine airliners. The new aircraft was designated the Model 10 and named the Electra. The Electra was a twin-engined, twin-tailed, low-wing monoplane with retractable landing gear; the main landing gear retracted into the engine nacelles but the tail wheel did not retract. The aircraft could accommodate ten passengers in five rows plus a pilot and copilot and was intended for use by the short-haul, medium capacity airlines. The Electra had the same cruising speed as the Douglas DC-2 [R2D in U.S. Navy (USN) service, q.v.], and offered a high degree of comfort but its seat-mile cost was higher than the DC-2 and its limited capacity of ten passengers meant that its use was limited to smaller airlines. The Model 10's first flight was on 23 February 1934.
A total of 148 Electras, in four versions, were delivered between 4 August 1934 and 18 July 1941. The production consisted of 101 Model 10-As, 18 Model 10-Bs, eight Model 10-Cs and 15 Model 10-Es for civilian use; the difference between the four versions was the engines installed. The USN ordered a Model 10-A, designated XR2O-1 for its own use and a Model 10-B, designated XR3O-1, for use by the U.S. Coast Guard (USCG). The U.S. Army Air Corps (USAAC), which was superseded by the U.S. Army Air Forces (USAAF) on 20 June 1941, ordered one modified Model 10-E as the XC-35, a unique research aircraft; three Model 10-As designated Y1C-36's; and a Model 10-A designated Y1C-37 for the National Guard Bureau. After the U.S. entered World War II in December 1941; the USAAF impressed 15 Model 10-As, designating them C-36A-LOs; five Model 10-Es designated C-36B-LOs; and seven Model 10-Bs designated C-36C-LOs. All were redesignated UC-36's in January 1943..
The first operator of the Model 10 was Northwest Airlines which began flying them in August 1934. Other U.S. airlines that operated the Electra included the Alaska Division of Pan American World Airways, Braniff Airways, Chicago & Southern Airlines, Delta Air Lines, Hanford Tri-State, Mid-Continent Airlines, and National Airlines. Non-U.S. airlines operating the Model 10 included airlines in Australia (Ansett and MacRobertson Miller), Brazil (Panair do Brasil), Canada (Trans-Canada Airlines), Guinea (Guinea Airways), Mexico (Aerovias Centrales), the Netherlands (KLM), New Zealand (Union Airways), Poland (LOT), Romania (LARES), the UK (British Airways), Venezuela (LAV) and Yugoslavia (Aeroput).
One of the most famous Electras was the Model 10-E Special purchased by the Purdue Research Foundation of Purdue University for Amelia Earhart and registered NR16020. On 20 May 1937, Earhart and her navigator Fred Noonan departed Oakland, California for an west-to-east around-the-world flight. The aircraft disappeared on 2 July 1937 while en route from Lae, New Guinea (06-45S 147-00E) to Howland Island (00-48N 176-38W) and her disappearance has become one of the great aviation mysteries.
In 1935, Lockheed had identified a need for a scaled down aircraft for use by feeder airlines and the business aircraft market. Using the same engines as the Model 10, the new Model 12, named the Electra Junior, made its first flight on 27 June 1936. The Electra Junior had the same physical configuration as the Model 10 Electra but could only accommodate six passengers in three rows plus a pilot and copilot. Because it used the same engines as the Model 10, it had an even more lively performance than it predecessor. A total of 130 Model 12's were built but they had limited success with U.S. feeder airlines with only six of the 90 Model 12-As purchased by them. The USN purchased seven aircraft and designated them JOs and impressed one in 1941 as the R3O-2. The USAAC purchased three C-40's, t-40As and a C-40B and impressed another ten during World War II as C-40Cs. Private owners in the U.S. accounted for 39 Electra Jrs and U.S. non-military government agencies purchased another 25. All were redesignated UC-40's in January 1943. Other military users included Argentina (two), Brazil (eight) and the Dutch East Indies (37).
The seven JOs, the XR2O and the R3O-2 were all powered by the same engines, two 450 hp (335.6 kW) Pratt & Whitney R-985-48 nine-cylinder, single row, air-cooled, radial engines driving two-bladed Hamilton Standard variable-pitch propellers. The XR3O-1 was powered by a Wright engine as described below.
JO-1: One 5-passenger Model 12-A Electra Junior for the USN..
JO-2: Five 6-passenger Model 12-A Electra Juniors for the USN and U.S. Marine Corps (USMC).
XJO-3: One Model 12-A Electra Junior with a fixed tricycle landing gear and an arrester tail hook for the USN.
XR2O-1: One Model 10-A Electra for the USN.
XR3O-1: One Model 10-B Electra for the USCG with two 440 hp (328.1 kW) Wright R-975-E3 nine-cylinder, single row, air-cooled, radial engines driving two-bladed Hamilton Standard variable-pitch propellers. This aircraft could be rapidly reconfigured from a staff transport to an ambulance.
R3O-2: One civil Model 12-A Electra Junior, originally purchased by Sky Kraft Corporation, impressed (drafted) by the USN.
The single JO-1 was delivered on 9 August 1937 for the use of the U.S. Naval Attache in Rio de Janeiro, Brazil and was still in use in December 1941.
The JO-2's were used as staff transport aircraft; two went to the USN and three were transferred to the USMC. The first aircraft was delivered on 8 September 1937. The two USN aircraft were based at Naval Air Station (NAS) Anacostia, District of Columbia. Two of the three USMC aircraft were assigned to Marine Utility Squadron ONE (VMJ-1) (redesignated VMJ-152 on 1 July 1941) at Marine Corps Air Station (MCAS) Quantico, Virginia; and VMJ-2 (redesignated VMJ-252 on 1 July 1941) at NAS San Diego, California. One of the VMJ-1 JO=92s was assigned for use by Headquarters, USMC. In early 1941, VMJ-2 moved to MCAS Ewa, Territory of Hawaii with the JO-2 and it was destroyed on the ground during the Japanese attack on 7 December 1941.
The XJO-3, delivered to the USN on 15 October 1938, was an experimental aircraft intended to test the feasibility of using (1) twin-engined aircraft and (2) aircraft with a tricycle landing gear on an aircraft carrier. On 30 August 1939, the XJO-3 made eleven landings and takeoffs from the USS Lexington (CV-2) off the coast of California demonstrating the basic adaptability of this type of aircraft to carrier operations. By 1941, the XJO-3 had been converted to an airborne radar test aircraft. Between 1 August and 16 October 1941, an AI-10 microwave radar set with a Plan Position Indicator (PPI) scope developed by the Radiation Laboratory of the Massachusetts Institute of Technology (MIT) had been installed. Operating from Boston Airport, Massachusetts, the aircraft flew test missions where surface vessels were detected at ranges up to 40 miles (64 km) and radar-guided approaches against simulated enemy aircraft were achieved at ranges up to 3.5 miles (5.6 km). Operational radars which were developed from this equipment were capable of searching a circular area and included the ASG radar set for K-type airships (blimps) and the AN/APS-2 radar set for patrol aircraft. On 31 December 1941, this aircraft was based at NAS Norfolk, Virginia.
The XR2O-1 was ordered in 1935 and delivered to the USN on 19 February 1936 as a VIP transport for the Secretary of the Navy until being replaced in that role by an R5O-1, q.v. Through 1941, the fuselage was painted dark blue. The aircraft was based at NAS Anacostia, District of Columbia throughout World War II until being disposed of after the war.
The XR3O-1 was ordered in 1935 and delivered to the USCG on 9 April 1936 as a VIP transport for the Secretary of the Treasury. (The USCG was part of the Treasury Department until being transferred to the jurisdiction of the USN on 1 November 1941.) This aircraft was replaced as the VIP aircraft by an XR5O-1, q.v., in 1940 and was then assigned to various Coast Guard Air Stations (CGAS=92s) during World War II, e.g., CGAS Cape May, New Jersey and CGAS Biloxi, Mississippi. Disposed of after the war, this aircraft was operated by several U.S. commercial airlines. By 1967, this aircraft was being operated by Provincetown-Boston Airline and on 27 August 1967, it came to an end after being ditched on a beach in Massachusetts Bay.
The R3O-2 had been impressed on 16 August 1941 for the use of the U.S. Naval Attache in London, England. In 1944, it was transferred to the USMC and was subsequently sold to a private owner in the United Kingdom after the war and registered G-AGTL.
JO & R3O-2: 49 feet 6 inches (15.09 meters)
R2O & R3O-1: 55 feet (16.76 meters)
JO & R3O-2: 36 feet 4 inches (11.07 meters)
R2O & R3O-1: 38 feet 7 inches (11.76 meters)
JO & R3O-2: 9 feet 9 inches (2.97 meters)
R2O & R3O-1: 10 feet 1 inch (3.07 meters)
JO & R3O-2 square feet (32.70 square meters)
R2O & R3O-1: 484.5 square feet (45.01 square meters)
JO & R3O-2: 5,765 pounds (2,615 kg)
R2O: 6,454 pounds (2,927 kg)
R3O-1: 6,203 pounds (2,814 kg)
JO & R3O-2: 8,650 pounds (3,924 kg)
R2O & R3O-1: 10,300 pounds (4,672 kg)
JO & R3O-2: 225 mph at 5,000 feet (362.1 km/h at 1,524 meters)
R2O & R3O-1: 202 mph at 5,000 feet (325.1 km/h at 1,524 meters)
JO & R3O-2: 213 mph (342.8 km/h)
R2O & R3O-1: 190 mph (305.8 km/h)
Initial Rate of Climb
JO & R3O-2: 1,400 feet (426.7 meters) per minute at sea level
R2O & R3O-1: 1,140 feet (347.5 meters) per minute at sea level
JO & R3O-2: 22,900 feet (6,980 meters)
R2O: 19,400 feet (5,913 meters)
R3O-1: 21,450 feet (6.538 meters)
JO & R3O-2: 800 miles (1,287 km)
R2O & R3O-1: 810 miles (1,304 km)