Stinson L-5 Sentinel

L-5 Sentinel
Role Liaison / Observation / Light plane
Manufacturer Stinson
Produced 1942–1945
Number built over 3,896
Developed from Stinson YO-54

The Stinson L-5 Sentinel was a World War II era liaison aircraft used by all branches of the U.S. military and by the British Royal Air Force. Along with the Stinson L-1 Vigilant, the L-5 was the only other American liaison aircraft of World War II that was purpose-built for military use and had no civilian counterpart. All other military liaison airplanes adopted during World War II were lightly modified "off-the-shelf" civilian models.

Design and development

The origins of the L-5, affectionately known as the "Flying Jeep", can be traced to the prewar civilian Stinson HW-75. The 75 horsepower civilian high-wing design was built by the Stinson Aircraft Company at Wayne, Michigan and first flew in 1939. The HW-75 featured two seats up front side-by-side, and a third "jumpseat" in the rear on which a small passenger could sit sideways. The design was easy to fly. Shortly after the introduction of the HW-75, Stinson became a subsidiary of the Vultee Aircraft corporation. Under Vultee management, the HW-75 was equipped with an 80-horsepower four-cylinder engine for the 1940 model year and the HW-75 became known as the Model 105 "Voyager", touting its 105 mph cruise speed. Fitted with a four-cylinder 90 hp Franklin engine for the 1941 model year, the type became known as the Model 10A. In the postwar era, the fuselage of the Model 10A was enlarged to accommodate four seats, and the four-cylinder powerplant was replaced with a Franklin 150 hp six-cylinder engine. This conversion became the Stinson Model 108 Voyager and the only civilian aircraft commercially produced by Stinson after WWII.

Six examples of the Model 105 Voyager were equipped with 80 horsepower Continental O-170 engines and provided to the military for testing under the experimental designation YO-54. Evaluated by the Air Corps in 1940 for potential use as a low-cost short-range observation aircraft, it failed to meet performance requirements. The Voyager was then completely re-engineered by Stinson into a much stronger and more powerful tandem-seat airplane that met rigorous Army engineering handbook standards for the design of military aircraft. The prototype, designated as the Model V-76 by Vultee / Stinson was accepted by the military after accelerated service trials and entered into service in December 1942 as the Army O-62 ('O' for observation). The L-5 carried a pilot and observer in a tandem-seating configuration, which was preferred by the military for observation work.

In March 1943, with the creation of the liaison category of light observation aircraft (previous examples came from Taylorcraft Aircraft as the L-2, and from Aeronca as their L-3, along with the numerous Piper L-4) the designation for Stinson's new purpose-built military design was changed to the L-5. The primary purpose as a liaison aircraft was courier and communication work, artillery spotting and casualty evacuation. The fuselage of later models was redesigned so the aircraft could also be used as an air ambulance, or for cargo work. 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 aboard.

The L-5 series was manufactured between December 1942 and September 1945, during which time 3,590 of the unarmed two-seaters were built for the United States armed forces, making it the second most widely used light observation aircraft of the war behind the Piper L-4 Cub.

Construction

The fuselage was constructed using chrome-moly steel tubing covered with doped cotton fabric and 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 was powered by a six-cylinder 190 horsepower Lycoming O-435 engine.

Operational history

Capable of operating from short unimproved airstrips, the L-5 "Sentinel" delivered personnel, critical intelligence and needed supplies to the front line troops. On return flights, wounded soldiers were often evacuated to rear area field hospitals for medical treatment, boosting the morale of combat troops fighting in remote areas. L-5s were also used for aerial photography, controlling vehicle convoys, para-dropping food, medical supplies and ammunition, laying communication wire, distributing propaganda leaflets, spraying pesticide, transporting prisoners, and directing fighter-bombers to ground targets. The L-5 was also popular with Generals and other high-ranking officers for fast, efficient short-range transportation.

During the Battle of Okinawa, L-5s operated from an LST using the Brodie landing system which allowed a light aircraft to take off and land without a flat surface by snagging a wire hung between two booms. One of the L-5s that used the Brodie system off Okinawa is now on display in the Boeing Aviation Hangar facility of the Smithsonian's NASM's Udvar-Hazy Center annex at Dulles Airport just west of Washington, DC.[1] [2]

UN liaison service in Greece during the Greek Civil War

The USAAF, US Marines, and US Navy used this aircraft in the European, Pacific, and Far East theaters during World War II, and in Korea during the Korean War.

The Navy and Marine version of the L-5 through L-5E were designated OY-1, and all these aircraft has 12-volt electrical systems. The 24-volt L-5G became the OY-2. Neither the L-5G nor OY-2 saw combat during World War II because production did not begin until July, 1945, just weeks before the war ended, but they were used extensively during the Korean War. The British RAF procured 40 L-5s and 60 L-5Bs, and designated them Sentinel Is and Sentinel II's respectively. These aircraft were used exclusively in the India-Burma theater of operations.

After World War II, the L-5 was widely used by the Civil Air Patrol for search and rescue work. Many other countries also received L-5s after the war, particularly India which received 200. A number of these went to Pakistan after the partition of India in 1948. From 1950 in India, L-5s were used by flying clubs to teach civilian pilots until about 1973 when a lack of spares forces their retirement.

Variants

USMC OY-2 takes off from the USS Sicily, 1950

Five versions of the Sentinel were produced for the U.S. Army Air Force (USAAF); the L-5, L-5B, L-5C, L-5E and L-5G. There was no official L-5A variant as is often reported because the designation was intended for a version of the aircraft that was never built. Nonetheless, many people in and out of the military still refer to the standard "observer" version of the L-5 as an L-5A. Like the L-5A, the L-5D was a planned version that was not adopted. A single L-5F was an L-5B equipped with an experimental low-noise "stealth" propeller and exhaust system for research purposes. The L-5B through L-5G models were modified to carry a litter patient or light cargo, or a rear seat passenger sitting in the normal position. An L-5H version was on the drawing boards at Stinson when the war ended, and it never reached the prototype stage.

O-62
Observation, artillery spotting and liaison aircraft, powered by a Lycoming 0-435-1 piston engine; 275 built.
L-5
Observation, artillery spotting and liaison aircraft; 1,538 built, 79 transferred to USN/USMC as OY-1.
L-5A
Cancelled conversions of L-5 with 24V electrical system and 200 hp ranger engine.
L-5B
729 aircraft with rear fuselage hatch to permit loading of a stretcher or cargo; twin-float capability; 60 transferred to RAF as Sentinel Mk II, 40 transferred to USN/USMC as OY-1.
L-5C
200 L5-B were equipped K-20 reconnaissance cameras.
L-5D
Not adopted. No prototype built.
L-5E with "Quiet Flight" modifications at Langley
L-5E
750 STOL variants with larger tires and brakes and manually drooping ailerons allowing shorter takeoff and landing; 152 transferred to USN/USMC as OY-1. An L-5E-1 variant included larger wheels and tires and heavy duty brakes. Thirty L-5E's were later converted to 24 volt electrical systems and re-designated OY-2.
L-5G
Similar to L-5E but with a 24 volt electrical system and powered by 190-hp (142-kW) Lycoming 0-435-11 piston engine with improved cylinders and carburetor and fitted with controllable pitch propellers. 115 were built by end of the war and the contract for 785 others was cancelled. Final production model redesignated U-19B in 1962.
XL-5
One test and evaluation aircraft, powered by a Lycoming 0-435-2 piston engine.
U-19A
L-5 variants still in service redesignated U-19A by the USAF in 1962.
U-19B
L-5G redesignated U-19B in 1962. One used as a glider tug at the [United States Air Force Academy].
OY-1
306 L-5 and L-5Bs transferred to the United States Marine Corps and United States Navy.
OY-2
152 transfers of L-5E to USN/USMC; 30 OY-1 conversions to 24V electrical system.
Sentinel Mk I
40 L-5s supplied to the RAF under Lend-Lease.
Sentinel Mk II
60 L-5Bs supplied to the RAF under Lend-Lease.
L5/235
variant powered by Lycoming O-540-B, 235 hp, used for glider towing.

Aircraft markings

Standard camouflage as delivered from the factory was non-specular "Bulletin 41" medium gray #43 undersides with olive drab #41 above, broken around the edges of the wing and tail surfaces with medium green #41. Stars, or "stars and bars" were applied to both sides of the fuselage and on the upper left and lower right wingtips. The USAAF number appeared on both sides of the vertical stabilizer in either yellow or black. The USMC number appeared in smaller size in black only. Most aircraft were repainted silver during the post-World War II period. Some Marine Corps and Navy aircraft painted overall non-specular Sea Blue. A variety of unit identification markings including nose art were applied in the field. Interior surfaces were generally finished in yellow-green chromate primer and slightly darker ANA 611 "interior green". Instrument panels were "raw" phenolic sheet naturally matte black in color.

Operators

 Australia
 Greece
 Italy
 Japan
 South Korea
 Philippines
 Poland
 Republic of China
 People's Republic of China
 Thailand
 United Kingdom
 United States

Survivors

Today there are about 300 known examples left world wide and less than half are in flying condition. A restored, flying example of the OY-1 (L-5E) variant (VH-NOY) is located in Coolangatta, Australia. This example was built for the USAAF but was delivered directly to the US Navy instead, serving until 1949.[4] A group called the Sentinel Owners and Pilots Association[5] is dedicated to the preservation and enjoyment of this aircraft type.

Specifications (L-5)

Data from March Field Air Museum website[6]

General characteristics

Performance

Armament

none

See also

Related development
Aircraft of comparable role, configuration and era
Related lists

References

Notes

  1. ↑ "NASM - Collections - Objects - Stinson L-5 Sentinel". http://airandspace.si.edu. National Air & Space Museum. Retrieved December 9, 2015. The L-5 is one of the most important but overlooked aircraft of the Second World War. Versatile and durable, the L-5 flew a wide variety of missions: photo reconnaissance, resupply, evacuation of wounded, message courier, VIP transport, and artillery spotting. External link in |website= (help)
  2. ↑ "L-5 Used in Pacific With Brodie System YouTube
  3. ↑ aeroflight
  4. ↑ Flypast Magazine, July 2007, Key Publishing Ltd.
  5. ↑ "Sentinel club." sentinelclub.org. Retrieved: 23 February 2012.
  6. ↑ "Stinson L-5 Sentinel." March Field Air Museum. Retrieved: 8 December 2006.

Bibliography

External links

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