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The Boeing L-15 Scout was an advanced liaison aircraft that used the same basic layout as the wartime ‘Grasshopper’ liaison aircraft, but in a much more radical form.
The L-15 was designed by the Wichita division of Boeing, which had originally been Stearman Aircraft. This company become part of Boeing’s parent company United Aircraft and Transport Corporation in 1929, and a Boeing subsidiary in 1934, when Boeing had to be separated from United. The L-15 used Stearman style serial numbers and was originally developed as the Wichita Model 200 before becoming the Boeing Model 451.
During the war the vast majority of American liaison aircraft had been military versions of civilian light aircraft, the most numerous of which was the Piper L-4. These aircraft all followed the same basic layout, being high winged monoplanes with a fixed undercarriage, fairly standard fuselages, capable of carrying two men in heavily glazed cockpits. They were all known as the ‘Grasshopper’ because of their ability to operate from small unimproved fields.
The L-4 followed a similar layout, with a heavily glazed cockpit, high wing and fixed undercarriage. However in other ways it was a much more advanced looking design. The main fuselage only contained the cockpit and a Lycoming engine, and ended with a fully glazed rear wall. The observer’s chair could rotate fully around so they were facing backwards, looking back through this wall of glass. A long thin boom connected the top of the cockpit to the tail, which had two downward mounted vertical control surfaces. There were thus very few obstructions to the view down or around the aircraft. Unlike the wartime Grasshoppers, which tended to be fabric covered, the L-15 was of all metal construction apart from fabric covers on the movable control surfaces. It had a fixed undercarriage which could also be replaced with twin floats to turn it into a seaplane. The main wheels were level with the leading edge of the wing, and the tail wheel was at the rear of the cockpit.
The aircraft’s most advance feature were its ‘flaperons’, a combination of flaps and ailerons. These were separated from the rear of the wing by a small gap, and could move from 10 degrees up to 40 degrees down. These greatly improved its STOL capabilities.
One of the most unusual features of the L-15 was that it could be dismantled and turned into trailer that could be towed on the aircraft’s own wheels. The wheels could rotate through 180 degrees on their struts, so the wheel was on the inside of the struts, thus reducing the width of the undercarriage to that of a normal vehicle, and allowing the dismantled aircraft to fit inside a C-97. The main wing was split in half, and mounted on either side of the fuselage, with the flaperons folded over to form a sort of roof. The tail was removed from the end of the boom and attached to one of the wings. The long boom jutted out forwards, but the height of the aircraft meant that there was enough space for a jeep to fit underneath it to tow the aircraft.
Work on the XL-15 began in July 1946, and the first prototype made its maiden flight on 13 July 1946. A second prototype was produced, which was used to test the floats.
The two prototypes were followed by ten YL-15 service test aircraft. These had slightly larger rudders but were otherwise identical to the prototypes. They had 1947 serial numbers but were built in 1948-49. They were tested by the Army, but not selected for production. The YL-15s were then given to the US Forest Service and the Department of the Interior and some ended up in private hands.
XL-15
Engine: Lycoming O-290-7
Power: 125hp
Crew: 2
Span: 40ft
Length: 25ft 3in
Height: 8ft 8.5in
Empty weight: 1,509lb
Gross weight: 2,050lb
Max speed: 112mph
Cruising speed: 101mph
Stall speed: 35mph
Climb Rate: 628ft/ min
Service ceiling: 16,400ft
Endurance: 2h 15m normal, 5hr 30m with auxiliary fuel tanks.