The origins of the
L-5 can be traced to the prewar civilian Stinson
HW-75. This 75 horsepower civilian high-wing design was built by the Stinson Aircraft Company at Wayne, Michigan and first flew in 1939. It was marketed as the
Model 105 and was first introduced to the public at the
New York World's Fair. The three-place HW-75 featured two side-by-side seats and a third
jumpseat in back on which a small passenger could sit facing sideways. Economical, spin resistant and easy to fly, the plane was popular with aircraft owners and flight schools and by the end of 1939 Stinson was building three per day. In 1940 the Model 105 was upgraded to an Continental engine and with other small improvements this was marketed as the
Model 10. Stinson became a subsidiary of the Vultee Aircraft Corporation in August 1940. Under Vultee management, an improved version was fitted with a four-cylinder Franklin engine for the 1941 model year and the type became known as the
Model 10A Voyager. In the postwar era, the fuselage of the Model 10A was lengthened to accommodate four passengers and the four-cylinder powerplant was replaced with a Franklin 150 hp six-cylinder engine. This conversion became the
Stinson Model 108 Voyager that was the only aircraft commercially produced by Stinson after WWII. During the summer of 1940, Stinson built an experimental tandem-seat version of the HW-75, equipping it with a Lycoming engine. This was known as the
Model 75B. Under Vultee management it was re-designated
V-75B. Soon increased to 125 horsepower for better performance, this became the Model
V-75C that was demonstrated to the military in August and September 1940. The
V-75C failed to meet military requirements for performance and durability, so the Stinson engineers went back to the drawing board and came up with a clean-sheet design that was similar in concept to the V-75C but was a far stronger, more powerful and completely new tandem-seat airplane that met rigorous Army-Navy engineering standards for the design of military aircraft. This was called the
Model 76 and was adopted as the
L-5. The experimental 175 hp
Model 76, dubbed "the Flying Jeep" by factory personnel, was first flown at the Stinson factory airport on June 23, 1941, by chief pilot Al Schramm. Accepted by the military after accelerated service trials were completed in September, the first contract for 275 planes was issued in January 1942. Originally designated
O-62 ('O' for observation), this was changed to
L-5 Sentinel ('L' for liaison) in April 1942, seven months before the first production airplanes were delivered. With minor changes, the six-cylinder Lycoming O-435 engine was upped to 185 horsepower, becoming the O-435-1 that powered all production Sentinel models through the L-5E-1. Adopted by the Army Air Forces as their standard liaison aircraft, replacing the larger and more costly L-1 Vigilant, the primary use of the L-5 was courier work, short range observation over friendly territory, and officer transport. The fuselage was reconfigured in June 1944 and the modified aircraft, designated as the
L-5B, could be used as an air ambulance or for light cargo transport. With a wider and deeper rear fuselage section and a large rear door that folded downward, a litter patient or 250 pounds of cargo could be quickly loaded. Later iterations of the cargo / ambulance version were the
L-5C with provisions for mounting a K-20 aerial camera, the
L-5E with drooping ailerons for better low-speed control, the
L-5E-1 with larger tires and heavy-duty brakes for better short and soft-field performance, and the final
L-5G with a 24-volt electrical system and 190 hp version of the Lycoming engine. Each was similar to the previous model except for the changes noted. In addition, L-5s were employed in roles such as artillery spotting, route reconnaissance, search & rescue, aerial photography, forward air control of fighter-bombers, laying communication wire, spraying pesticides, dropping para-cargo, dropping leaflets, and aerial broadcasting with loudspeakers. It also served as a test bed for radar tracking, firing aerial rockets, and airborne remote television. In uncommon instances, L-5 crews dropped grenades and fired wing-mounted bazookas at ground targets. The L-5 series was manufactured between November 1942 and September 1945 during which time 3,590 of the unarmed two-seaters were delivered for military service, making it the second most widely used light observation liaison aircraft of the war behind the Piper L-4 Cub.
Construction The fuselage was constructed using arc-welded chrome-moly steel tubing covered with doped cotton fabric while the wings and empennage were constructed of spruce and mahogany plywood box spars and plywood ribs and skins, also covered with fabric. The use of aluminum, which was in critically short supply and more urgently needed for other aircraft, was limited to the engine cowling, tail cone, framework for the ailerons, rudder and elevator and the landing gear fairings. The L-5 through L-5E were powered by a six-cylinder Lycoming O-435-1 engine. The L-5G used a 190 hp Lycoming O-435-11. == Operational history ==