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L-5 Sentinel
L-5futureshox.jpg
Role Liaison aircraft
Manufacturer Stinson Aircraft Company
First flight 28 June 1941
Primary users United States Army Air Forces,
United States Army Ground Forces
United States Marine Corps
Royal Air Force
Produced 1942–1945
Number built 3,590
Developed from Stinson Model 75B

The Stinson L-5 Sentinel is a World War II-era liaison aircraft used by the United States Army Air Forces, U.S. Army Ground Forces, U.S. Marine Corps and the British Royal Air Force. It was produced by the Stinson Division of the Vultee Aircraft Company (Consolidated-Vultee from mid-1943). Along with the Stinson L-1 Vigilant, the L-5 was the only other American liaison aircraft that was exclusively built for military use and had no civilian counterpart.

Design and development

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. Stylish, economical, spin resistant and easy to fly, the plane became an instant success with aircraft owners and flight schools across the United States and by the end of 1939 Stinson was building three per day. In 1940 the Model 105 was upgraded to an 80-horsepower Continental engine and with other small improvements this was marketed as the Model 10.[1]

Stinson HW-75 (Model 105)
Stinson HW-75 (Model 105)

Stinson became a subsidiary of the Vultee Aircraft Corporation in August 1940. Under Vultee management, an improved version was fitted with a four-cylinder 90 hp Franklin engine for the 1941 model year and the type became known as the Model 10A. 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 100 hp 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, 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. [a]

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.[1]

Adopted by the Army Air Forces as their standard liaison aircraft, replacing the larger and more costly L-1 Vigilant, the primary purpose of the L-5 was short range officer transport, courier work and artillery spotting. The fuselage was reconfigured in January 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.[1]

In addition to the previously listed uses, L-5's were employed in many diverse roles such as 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 enemy targets.[1]

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.[1]

Construction

The fuselage was constructed using arc-welded 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 through L-5E were powered by a six-cylinder 185 horsepower (138 kW) Lycoming O-435-1 engine. The L-5G used a 190 hp Lycoming O-435-11.

Operational history

Capable of operating from short unimproved airstrips, the L-5 "Sentinel" delivered personnel, intelligence and supplies to the front line. On return flights, wounded soldiers were often evacuated to rear area field hospitals for medical treatment. L-5s were primarily flown by the Army Air Forces liaison squadrons consisting of 32 planes each. One of these squadrons was attached to field army headquarters deployed overseas and an additional squadron was assigned to each Army Group headquarters. They saw action in Western Europe, Italy, the Philippines, New Guinea, and the China-Burma-India theater. In the hands of the U.S. Marine Corps artillery observation squadrons they were widely used during the Pacific Island campaigns of 1944 and 1945. The L-5 was used by generals and other high-ranking officers for short-range transportation.

An unusual use of the Sentinel was launch and recovery from a land-based overhead cable system designed by Lt. James Brodie that could be quickly set up in a large clearing that was otherwise unsuitable for a runway. The cable was strung between two tall masts and a braked carriage snagged an arresting hook attached to the top of the airplane. After successful tests of the "runway on a rope" in Oklahoma, it was demonstrated to the British in India who declined to adopt it. However, the unorthodox "Rube Goldberg" Brodie landing system was installed aboard the Naval vessel City of Dalhart. Staff Sergeant R. A. Gregory made ten good successful launches and recoveries with a Stinson L-5.[2] During the Battle of Okinawa, L-5s operated from an LST equipped with the "Brodie System".[3]

UN liaison service in Greece during the Greek Civil War
UN liaison service in Greece during the Greek Civil War

The Navy and Marine version of the L-5 through L-5E were designated OY-1, and all these aircraft had 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. A further two dozen or so OY-1's were converted to OY-2's in 1948 and 1949. The British Royal Air Force (RAF) procured 40 L-5s and 60 L-5Bs in 1944 and designated them Sentinel Is and Sentinel IIs respectively. These aircraft were used exclusively in the India-Burma theater of operations by SEAC communications and medical evacuation units.

After World War II, the L-5 was used in the continental United States, Hawaii and Alaska by the Civil Air Patrol for search and rescue work. They were also employed by state law enforcement, forestry and Fish & Wildlife departments. Many other countries also received L-5s after the war. The largest quantities were sold to Italy, the Republic of the Philippines, and India. A few went to Pakistan after the partition of India in 1948, and a small number were used by the Japan Defense Force. Others were also sold to Korea, China, Thailand, Mexico, Venezuela, and Brazil.

Variants

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

O-62
Original designation for the first contract for 275 aircraft but this was changed to L-5 before any of these planes were delivered.
L-5
Observation model used for artillery spotting and liaison work; 1,538 delivered, 82 transferred to the USMC as OY-1.
L-5A
Cancelled variant of L-5 with 24V electrical system. 688 examples falsely reported in 1944 by Jane's All the World's Aircraft to have been built.
L-5B
729 delivered. Ambulance versions with large hatch to permit loading of a stretcher or cargo; twin-float capability; 60 transferred to RAF as Sentinel Mk II. 42 delivered to USMC as OY-1.
L-5C
200 delivered. Same as L-5B but equipped with a vertical mount behind the rear seat for a K-20 aerial reconnaissance cameras. 39 delivered to USMC as OY-1.
L-5D
Not adopted. No prototype built.
L-5E
500 delivered. Same as L-5C but fitted with manually drooping ailerons for better low-speed handling; 45 transferred to USMC as OY-1.
L-5E-1
250 Delivered. Included larger wheels and tires and heavy duty brakes for better off-field performance. 82 transferred to USMC as OY-1.
L-5G
Similar to L-5E-1 but with a 24 volt electrical system and SCR-622 radio package. Powered by 190-hp (142-kW) Lycoming 0-435-11 engine with improved cylinders and carburetor. 115 were built by end of the war and the contract for 785 others was cancelled. 18 delivered to USMC as OY-2.
XL-5F
One modified L-5B used to develop the 24-volt system used on the L-5G. Re-surfaced in 1948 powered by a geared Lycoming G0-435 piston engine and equipped with a NASA-designed 5-bladed propeller and large exhaust system mounted in ambulance bay. Used for "quiet airplane" development and tests.
L-5B with "Quiet Flight" modifications at Langley
L-5B with "Quiet Flight" modifications at Langley
U-19A
L-5s still in service and redesignated U-19A by the USAF in 1962.
U-19B
Single L-5G redesignated U-19B in 1962. Used as a glider tug at the United States Air Force Academy and equipped with a Lycoming R-680 radial engine.
OY-1
288 L-5 through L-5E-1 transferred to the United States Marine Corps and United States Navy.
OY-2
18 transfers of L-5G 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.
L-5/235
Civilian variant developed in Italy for glider towing, powered by Lycoming O-540-B, 235 hp (175 kW).
Clevenger
Approximately 20 L-5's converted to crop dusters by Clevenger Aerial Applicators of Salinas, CA. Equipped with Continental 220 hp radial engines, larger main and tail wheels, and fitted with lower wings and interplane struts to create a biplane. Operated at up to 3,800# gross weight in the Restricted category.

Operators

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

Surviving aircraft

OY-1 on display at the Travis AFB Heritage Center
OY-1 on display at the Travis AFB Heritage Center
L-5E on display at the Museum of Aviation
L-5E on display at the Museum of Aviation

Today there are about 300 known examples left worldwide and less than half are in flying condition.[9] A group called the Sentinel Owners and Pilots Association is dedicated to the preservation and enjoyment of this aircraft type.[10]

Australia

Airworthy
OY-1

United States

Airworthy
OY-1
OY-2
L-5
On Display
OY-1
L-5
Under Restoration or in Storage

Netherlands

Airworthy
L-5

Specifications (L-5)

3-view line drawing of the Stinson L-13

Data from Stinson L-5 Sentinel[48]

General characteristics

Performance

See also

Related development

Aircraft of comparable role, configuration, and era

Related lists

References

Footnotes

  1. ^ Six stock Stinson Model 10's evaluated by the military as YO-54's in 1940 were unrelated to the development of the L-5.[1]

Notes

  1. ^ a b c d e f Sentinel Owners & Pilots Association, Stinson L-5 History Page
  2. ^ "Bax Seat: Hanging Out With the Brodies". Flying Magazine. Los Angeles: CBS Magazines. 112 (12): 96. December 1985. Retrieved 2 September 2019.
  3. ^ "L-5 Used in Pacific With Brodie System YouTube
  4. ^ Bridgman 1951, p. 11a.
  5. ^ "Indonesian aviation 1945-1950." Archived 14 December 2005 at the Wayback Machine adf-serials.com. Retrieved: 20 March 2021.
  6. ^ aeroflight
  7. ^ Bridgman 1951, p. 16a.
  8. ^ Bridgman 1951, p. 20a.
  9. ^ a b c d e f g h Gray, James (Summer 2014). "L-5 Newsletter" (PDF). Sentinel Owners & Pilots Association. Archived from the original (PDF) on 21 May 2016. Retrieved 7 August 2022.
  10. ^ "[Home Page]". Sentinel Owners & Pilots Association. Retrieved 6 December 2016.
  11. ^ Flypast Magazine, July 2007, Key Publishing Ltd.
  12. ^ "Aircraft Register [VH-NOY]". Australian Government Civil Aviation Safety Authority. Retrieved 6 December 2016.
  13. ^ "OY-1 Stinson/42-15060." Commemorative Air Force. Retrieved: 11 February 2020.
  14. ^ "FAA Registry: N9315H." faa.gov Retrieved: 11 February 2020.
  15. ^ a b "CAF Liaison/Observation". Commemorative Air Force. Retrieved 11 February 2020.
  16. ^ "FAA REGISTRY [N5138B]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 18 May 2017.
  17. ^ "Stinson L-5". DFW Wing. Archived from the original on 13 March 2017. Retrieved 18 May 2017.
  18. ^ "FAA REGISTRY [N57789]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 18 May 2017.
  19. ^ "FAA REGISTRY [N63777]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 18 May 2017.
  20. ^ "Stinson L-5 Sentinel". Commemorative Air Force Minnesota Wing. Retrieved 17 December 2016.
  21. ^ "FAA REGISTRY [N68591]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 18 May 2017.
  22. ^ "Our Stinson L-5 Sentinel". Capital Wing of the Commemorative Air Force. Retrieved 18 May 2017.
  23. ^ "FAA REGISTRY [N1156V]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 18 May 2017.
  24. ^ "Stinson L-5 Sentinel/44-17543." aerialvisuals.ca Retrieved: 13 February 2020.
  25. ^ "FAA Registry: N3706C."[permanent dead link] faa.gov Retrieved: 13 February 2020.
  26. ^ "Stinson L-5 Sentinel/44-17588." Military Aviation Museum. Retrieved: 13 February 2020.
  27. ^ "FAA Registry: N57WT."[permanent dead link] faa.gov Retrieved: 13 February 2020.
  28. ^ "Aircraft". Central California Valley Squadron. Retrieved 18 May 2017.
  29. ^ "FAA REGISTRY [N5625V]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 18 May 2017.
  30. ^ "Stinson L-5E Sentinel". Estrella Warbirds Museum. Retrieved 7 August 2022.
  31. ^ "FAA Registry [N45CV]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 7 August 2022.
  32. ^ "Indoor Exhibits – Humanitarian Missions". Travis Air Force Base Heritage Center. Travis Heritage Center. Archived from the original on 13 February 2020. Retrieved 13 February 2020.
  33. ^ "L-5E "Sentinel"". Museum of Aviation. Retrieved 7 August 2022.
  34. ^ "Stinson L-5 Sentinel". Smithsonian National Air and Space Museum. Retrieved 6 December 2016.
  35. ^ "Aircraft Listing". Flying Leathernecks. ((cite web)): Missing or empty |url= (help)
  36. ^ "L-5 Sentinel". March Field Air Museum. March Field Air Museum. Retrieved 6 December 2016.
  37. ^ "OY-1 SENTINEL". National Naval Aviation Museum. Naval Aviation Museum Foundation. Retrieved 6 December 2016.
  38. ^ "Airframe Dossier – Stinson OY-1 Sentinel, s/n 60465 USMC, c/n 76-0385, c/r N57598". Aerial Visuals. AerialVisuals.ca. Retrieved 6 December 2016.
  39. ^ "Stinson L-5 Sentinel". National Museum of the US Air Force. 17 April 2015. Retrieved 6 December 2016.
  40. ^ "Our Collection". Vintage Flying Museum. Retrieved 6 December 2016.
  41. ^ "Airframe Dossier – Stinson L-5E Sentinel, s/n 44-17925 USAAF, c/n 76-3199, c/r N1135V". Aerial Visuals. AerialVisuals.ca. Retrieved 6 December 2016.
  42. ^ "1944 Stinson L-5B-1VW Sentinel – PH-PBB". EAA. EAA. Retrieved 6 December 2016.
  43. ^ "South Dakota Air and Space Museum". www.sdairandspacemuseum.com. Retrieved 22 June 2019.
  44. ^ "1943 Stinson L-5 Sentinel". Air Group One. Air Group One CAF. Retrieved 18 May 2017.
  45. ^ "STINSON SENTINEL" (PDF). 27 June 2013. Retrieved 18 May 2017.
  46. ^ "FAA REGISTRY [N59AF]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 18 May 2017.
  47. ^ "1944 Stinson L-5B-VW Sentinel – N9658H". DDA. DDA. Archived from the original on 10 December 2017. Retrieved 9 December 2017.
  48. ^ "Stinson L-5 Sentinel". March Field Air Museum. Archived from the original on 15 September 2000. Retrieved 19 November 2020.
  49. ^ Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.

Bibliography