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Stinson L-1 Vigilant (Model 74) Liaison / Observation / Utility Aircraft


The Stinson L-1 Vigilant provided a much-needed Short Take-Off and Landing capability for American and British forces of World War 2.

 Updated: 6/12/2016; Authored By Staff Writer; Content ¬©www.MilitaryFactory.com

The massive American military of World War 2 (1939-1945) fielded various "Light Observation and Liaison" aircraft during the years-long conflict. One entry became the Stinson L-1 "Vigilant" of which 324 were completed. A first-flight was had on July 15th, 1940 and service introduction arrived in 1941. The system went on to be used by both the United States Army Air Corps (USAAC) and the British Royal Air Force (RAF). Design of the aircraft is attributed to A.P. Fontaine with all manufacture stemming from the Stinson Aircraft Corporation.

Observation and Liaison aircraft in military service provide improved communication for ground forces by giving a much-needed "eye in the sky". These aircraft are typically constructed as light as possible with few creature comforts for the crew and allow for basic performance while being very rarely armed. A high-wing monoplane fit is also typical as this generates inherent lift and allows the already light aircraft to loiter on station for longer periods of time when compared to traditional aircraft. It also allows these aircraft to operate from short, little-prepared airfields or rough terrain. A Short Take-Off and Landing (STOL) feature became common to such aircraft.

Prompted by the impressive showing of a German Fieseler "Storch" liaison aircraft at the Cleveland Air Races, the USAAC pushed forth a requirement in 1938 for a similar-minded aircraft. Nearly a dozen concerns threw their hats into the ring but Stinson was able to convince USAAC authorities of the merits of their proposed lightweight platform. The aircraft became known internally as the "Model 74" and carried the usual traits - a high-wing monoplane, fixed undercarriage, limited internal space, a nose-mounted engine, and traditionally-arranged tail unit. Internally, the aircraft's construction was largely of steel tubing while its skin consisted of fabric and some light metal.




The prototype was taken on by the Army for evaluation as the "YO-49" and managed a first-flight on July 15th, 1940 (American had yet to officially enter the war). Power was from a Lycoming engine which drove a two-bladed constant speed propeller at the nose. Satisfied with their new little aeroplane, the YO-49 graduated into the O-49 "Vigilant" through a 142-strong initial production batch. Then followed 182 examples of the O-49A standard which brought along an increased (13 inches) fuselage. The O-49B was a modified air ambulance with fewer than five converted for the role.

In 1942, the line was redesignated under the more familiar "L-1". The L-1 was the original O-49 while the O-49A and O-49B became the L-1A and L-1B respectively. The L-1C were additional air ambulance types modified from the L-1A stock and 113 conversions to this standard followed. The L-1D became a training glider tug (mothership) aircraft and as many as twenty were converted for the role. The L-1E became another air ambulance (based on the L-1 form) but these were given special equipment to operate as amphibians for water rescues. Seven conversions followed. The L-1F was similar and built up from the L-1A production stock - five conversions were seen. CQ-2 marked L-1A conversions by the United States Navy (USN) for service as target control aircraft. Few were procured.

Under Lend-Lease, the Vigilant was adopted by the RAF and arrived in the Vigilant Mk I (L-1) and Vigilant Mk II (L-1A) offerings.

Beyond its typical over-battlefield roles, the L-1 was pressed into other non-direct-combat roles - artillery spotting, light transport, special forces/mission support. Many saw modification in-the-field to fulfill even more non-official roles as needed. The series saw wartime service until the end of the conflict in 1945 and soldiered on for a time longer. Before the cessation of hostilities, the L-1 was already being challenged by entries from Piper (L-4 "Grasshopper") and by Stinson's own L-5 "Sentinel".



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Stinson L-1A Vigilant Technical Specifications



Service Year: 1941
Type: Liaison / Observation / Utility Aircraft
National Origin: United States
Manufacturer(s): Stinson - USA
Production Total: 324


Structural (Crew Space, Dimensions and Weights)



Operating Crew (Typical): 3
Overall Length: 34.25 feet (10.44 meters)
Overall Width: 50.85 feet (15.50 meters)
Overall Height: 10.17 feet (3.10 meters)

Weight (Empty): 2,668 lb (1,210 kg)
Weight (MTOW): 3,406 lb (1,545 kg)

Installed Power and Standard Day Performance



Propulsion: 1 x Lycoming R-680-9 radial piston engine developing 295 horsepower.

Maximum Speed: 121 mph (195 kph; 105 knots)
Maximum Range: 280 miles (450 km)
Service Ceiling: 12,795 feet (3,900 meters; 2.42 miles)
Rate-of-Climb: 410 feet-per-minute (125 m/min)

Armament / Mission Payload



None.

Global Operators / Customers



United Kingdom; United States

Model Variants (Including Prototypes)



L-1 "Vigilante" - Base Series Designation
Model 74 - Company model designation
YO-49 - U.S. Army evaluation designation
O-49 Vigilant - Initial production models; 142 built
O-49A Vigilant - Extended fuselages; 182 examples completed.
O-49B Vigilant - Air ambulance model; up to four converted.
L-1A Vigilant - 1942 redesignation of O-49A models
L-1B Vigilant - Redesignation of O-49B models
L-1C Vigilant - Air ambulance based on L-1A
L-1D Vigilant - Training glider tug based on L-1A
L-1E Vigilant - Amphibious Air Ambulance based on L-1
L-1F Vigilant - Amphibious Air Ambulance based on L-1A
Vigilant Mk I - RAF designation for L-1 models
Vigilant Mk II - RAF designation for L-1A models
CQ-2 Vigilant - USN target control aircraft variant