The Vigilant was designed in response to a 1938United States Army Air Corps design competition for a two-seat light observation aircraft. After the German-manufacturedFieseler Storch was demonstrated at the 4th International Air Meet in Zurich, Switzerland in 1937, the Air Corps Material Division at Wright Field initiated a feasibility study for the creation of a similar aircraft. The development program was approved in January 1938, design and performance specifications were determined in April 1938, and a Circular Proposal for a formal design competition was released to manufacturers in August 1938, just twelve days before a Storch was demonstrated at the Cleveland Air Races by German aviator Emil Kropf.[2] Stinson (later a division ofVultee), won the $1.5 million contract over 11 competitors, including theBellanca YO-50 andRyan YO-51 Dragonfly.[3]
Stinson won the $1.5 million contract with an initial order for 100 aircraft. Eleven competing designs included theBellanca YO-50 andRyan YO-51 Dragonfly that were each runners-up and garnered 3-plane contracts for further evaluation.[4] The Stinson Model 74 was a radial-engined, high-wing monoplane with large trailing-edge slotted flaps and full-span leading-edge automatic slats for low-speed, high-lift, short-field performance. The Model 74 prototype was given the Army designationYO-49 for evaluation, with the first flight by test pilot Al Schramm on 15 July 1940.[3]
The aircraft was built of chrome-molybdenum steel tubing and covered with doped cotton fabric; the engine cowling and the fuselage, forward of the wing, was fully enclosed in aluminum. Control surfaces and theempennage were fabric-coveredstainless steel. The Lycoming power plant was hand-cranked with an inertial starter and was fitted with aHamilton Standardconstant speed propeller. At least 12 ambulance conversions were fitted withEdo 49-4000 floats (4,000-pounddisplacement)[5] for amphibious landings and takeoffs.[3]
The Vigilant could maintain stable, level flight at 31 miles per hour and in a 20 mph breeze it was capable of stopping in less than its own length. Given an adequate headwind, it gave the illusion of "hovering" and sometimes surprised onlookers by drifting backward. Under calm conditions the L-1 could land and take off again inside a 200 foot diameter circle, and landing over a 50-foot obstacle it could stop on dry sod within 300 feet with a ground roll of approximately 100 feet.[4]
1941 L-1, Reserve Grand Champion, AirVenture 2016Ex-USAAC O-49 Vigilant in the Weeks Museum at Tamiami, Florida, in 1989 wearing RAF-style markings
The Stinson Vigilant was used in diverse roles such as towing training gliders, artillery spotting, liaison, emergency rescue, transporting supplies and special espionage flights.[6] Another contract was later awarded for theO-49A which had a slightly longer fuselage and other equipment changes. In April 1942 the aircraft were redesignated theL-1 andL-1A (liaison).Up to 17 L-1 and 96 L-1A aircraft were allocated to the BritishRoyal Air Force under theLend-Lease Act, with varying numbers given for aircraft actually delivered (seeVariants, below). The RAF designated the aircraft theVigilant Mk I andVigilant Mk II respectively. GeneralHarry Crerar, Commander of the First Canadian Army in Europe during World War II, maintained a Vigilant for his personal use.
Aircraft were modified for a variety of roles including as an ambulance aircraft. No further production orders were placed as the aircraft was superseded by procurement of vast numbers of both the militarized Piper J-3 Cub, theL-4 Grasshopper (in addition toAeronca's andTaylorcraft's similar conversions), and Stinson's ownL-5 Sentinel, itself produced in nearly 4,000 examples; were all generically classified as "puddle-jumper" aircraft.
^Memo, Adjutant General to Chief of the Air Corps, Jan. 11, 1938, Development Program Approved. Telegram, Chief of Air Corps to Wright Field, Revised Aircraft Specifications Approved Apr. 26, 1938, and Wright Field Contracting Officer, Circular Proposal 39-2 Released, August 23, 1938. All in NARA Wright Field Development Program Files, ARC-6545367.
Adcock, Al.US Liaison Aircraft in action (Aircraft in Action: No. 195). Carrollton, Texas: Squadron/Signal Publications, 2005.ISBN978-0897474870.
Donald, David (ed.).American Warplanes of World War II. London: Aerospace Publishing, 1995.ISBN1-874023-72-7.
Eden, Paul and Soph Moeng (eds.).The Complete Encyclopedia of World Aircraft. London: Amber Books Ltd., 2002.ISBN0-7607-3432-1
Gray, James H.L-5 History Blog #17 (2021), and notes from the Wright Field Liaison Program papers at the National Archives. www.sentinelclub.org.[not specific enough to verify]
Merriam, Ray (ed.).World War II Journal #15: U.S. Military Aircraft of World War II. Bennington, Vermont, USA: Merriam Press, 2002.ISBN1-57638-167-6.
Ogden, Bob.Aviation Museums and Collections of North America. Tonbridge, Kent, UK: Air-Britain (Historians ) Ltd, 2007.ISBN0-85130-385-4.
The Illustrated Encyclopedia of Aircraft (Part Work 1982–1985). London: Orbis Publishing, 1985.
