Stinson L-5 Sentinel
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|Role||Liaison / observation / light plane|
|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. It was produced by the Stinson Aircraft Company. 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.
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.
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.
After tests on land, the system was first tested in September 1943 for shipboard use with an installation on the motor ship City of Dalhart. Staff Sergeant R. A. Gregory made ten good takeoffs and hookups with a Stinson L-5 light plane. 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.
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 Royal Air Force (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 forced their retirement.
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.
- Observation, artillery spotting and liaison aircraft, powered by a Lycoming 0-435-1 piston engine; 275 built.
- Observation, artillery spotting and liaison aircraft; 1,538 built, 79 transferred to USN/USMC as OY-1.
- Cancelled conversions of L-5 with 24V electrical system and 200 hp ranger engine.
- 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.
- 200 L5-B were equipped K-20 reconnaissance cameras.
- Not adopted. No prototype built.
- 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.
- 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.
- One test and evaluation aircraft, powered by a Lycoming 0-435-2 piston engine.
- L-5 variants still in service redesignated U-19A by the USAF in 1962.
- L-5G redesignated U-19B in 1962. One used as a glider tug at the [United States Air Force Academy].
- 306 L-5 and L-5Bs transferred to the United States Marine Corps and United States Navy.
- 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.
- variant powered by Lycoming O-540-B, 235 hp, used for glider towing.
- Royal Australian Air Force – operated one L-5 Sentinel from 1944 to 1946, loaned from the USAAF.
- Polish Air Force – The fuselage of the sole L-5 used in Poland after 1945 is displayed at the Polish Aviation Museum.
- Civil Air Patrol
- United States Army Air Forces
- United States Air Force
- United States Marine Corps
- United States Navy
Today there are about 300 known examples left worldwide and less than half are in flying condition. A group called the Sentinel Owners and Pilots Association is dedicated to the preservation and enjoyment of this aircraft type.
- 03995 – OY-1 airworthy with Robert William Kemmis in Coolangatta, Queensland, Australia. This example was built for the USAAF but was delivered directly to the US Navy instead, serving until 1949.
- United States
- 03917 – OY-1 on static display at the Travis Air Force Base Heritage Center in Fairfield, California. It is painted as an L-5.
- 04013 – OY-2 airworthy with the Commemorative Air Force Ohio Valley Wing in Columbus, Ohio.
- 42-14798 – L-5 on static display at the Steven F. Udvar-Hazy Center of the National Air and Space Museum in Chantilly, Virginia. This airframe is the first production L-5 built and was donated to the museum on 5 June 1960.
- 42-14918 – L-5 on static display at the Flying Leatherneck Aviation Museum in San Diego, California.
- 42-14934 – L-5 under restoration to airworthy with the Commemorative Air Force Air Group One in El Cajon, California.
- 42-15046 – L-5 on static display at the March Field Air Museum in Riverside, California.
- 42-15060 – OY-1 airworthy with the Commemorative Air Force FloriBama Wing in Pensacola, Florida.
- c/n 76-272 – L-5 airworthy with the Commemorative Air Force Dallas Fort Worth Wing in Lancaster, Texas.
- 42-98144 or 42-98453 – L-5 on static display at the National Naval Aviation Museum in Pensacola, Florida.
- 42-98225 – L-5 on static display at the National Museum of the United States Air Force in Dayton, Ohio.
- 42-98285 – L-5 airworthy with the Commemorative Air Force Dew Line Squadron in Amarillo, Texas.
- 42-98667 – L-5 airworthy with the Commemorative Air Force Minnesota Wing in South St. Paul, Minnesota.
- 42-98758 or 42-990444 – L-5 airworthy with the Commemorative Air Force Capital Wing in Brandy Station, Virginia.
- 42-17588 – L-5E airworthy with the Fighter Factory/Military Aviation Museum in Pungo, VA
- 44-17590 – L-5E airworthy with the Commemorative Air Force Central California Valley Squadron in Modesto, California.
- 44-17925 – L-5E on static display at the Vintage Flying Museum in Fort Worth, Texas.
- 44-18010 – L-5E on static display at the EAA AirVenture Museum in Oshkosh, Wisconsin.
- L-5E on static display at the Museum of Aviation, Robins AFB
- 45-35046 – L-5G on static display at the South Dakota Air and Space Museum, Box Elder, South Dakota.
Data from March Field Air Museum website
- Crew: two (pilot and observer)
- Length: 24 ft 1 in (7.34m)
- Wingspan: 34ft 0 in (10.36m)
- Height: 7 ft 11 in (2.41m)
- Wing area: 155 ft2 (14.40m2)
- Empty weight: 1550 lb (702 kg)
- Useful load: lb (kg)
- Loaded weight: 2020 lb (916 kg)
- Max. takeoff weight: 2050 lb (929 kg)
- Powerplant: 1 × Lycoming O-435-1, 185hp (138kW)
- Never exceed speed: 145 knots (163 mph (262 km/h)(200 mph (322 km/h military, in dive))
- Stall speed: 38 knots (42 mph, 70 km/h)
- Range: 375 sm (603 km)
- Service ceiling: 15,800 ft (4,815.6m)
- Rate of climb: 900 ft/min at sea level (4.6 m/s)
- Wing loading: lb/ft2 (kg/m2)
- Power/mass: hp/lb (W/kg)
None (technically). Some aircraft had jury rigged, anti-tank rocket launchers (mainly bazookas) installed and used with success against ground targets in WWII.
Aircraft of comparable role, configuration and era
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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.
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- Morgała, Andrzej. Ex-USAAF aircraft 1945: Piper L-4 Grasshopper, Douglas C-47 Skytrain/Dakota, Cessna UC-78 Bobcat, Stinson L-5 Sentinel, Taylorcraft L-2A Grasshopper. Sandomierz: STRATUS, 2011.
|Wikimedia Commons has media related to Stinson L-5 Sentinel.|
- Sentinel Owners and Pilots Association (SOPA), an organization dedicated to restoring, flying, maintaining and increasing public awareness of the Stinson L-5.
- "America Reports On Aid To Allies etc." Universal Newsreel, 1942