Climbing over the narrow, wing-root walkway and stepping on to the cushioned seat of the tandem, two-place, blue and yellow fabric-covered open-cockpit Boeing PT-17 Stearman registered N55171 in Stow, Massachusetts, I lowered myself into position with the aid of the two upper wing trailing edge hand grips and fastened the olive-green waist and shoulder harnesses. Donning era-prerequisite goggles and helmet, I surveyed the fully duplicated instrumentation before me and prepared myself both for an aerial sightseeing fight of Massachusetts and a brief, although temporary, return to World War II primary flight training skies.
The Boeing PT-17 Stearman had its origins in a self-financed design project intended for military training purposes. Just beginning to see a flicker of light at the end of Great Depression’s tunnel and hitherto only surviving by manufacturing parts and components for other aircraft, primarily those for the Boeing B247 twin-engined airliner, the Stearman Aircraft Company believed that its future could only be secured with a military design.
Investing its own funds in 1933, it modified a Model 6 Cloudboy, an earlier Lloyd Stearman aircraft, by introducing a new, circular fuselage cross-section similar to that used by the Model 80, another Stearman design, providing only lower-wing ailerons, incorporating a cantilever undercarriage, and mounting a new tail with adjustable trims on the trailing edge of its elevators. Designated Model 70, it had first flown from Wichita, Kansas, on January 1, 1934 powered by a nine-cylinder, 210-hp, Lycoming R-680 radial engine, proving rugged, reliable, and well-suited to rigorous training regiments with the ability to tolerate the aerobatic maneuvers to which fledgling pilots often subjected it. Although it exhibited excellent handling characteristics during its demonstration flights to the Army Air Corps and the United States Navy in Dayton, Anacostia, and Pensacola, its almost docile response to stalls proved inadequate to fulfill its intended purpose; as a result, the installation steel bite pro of triangular stall strips, made of wood, on its lower wings severely interrupted the air flow during high attack angles and remedied the deficiency.
The Navy, the more interested of the two, ordered 41 aircraft, plus spares, in May of 1934 for a version with a 200-hp Wright J5 radial engine called the Model 73, but designated NS-1 for the Navy. The first production aircraft was rolled out in December of that year.
A modified version, incorporating a new main undercarriage and alternatively powered by a 225-hp Wright R-760 and an equally powered, nine-cylinder Lycoming R-680 radial engine, had been designed that summer and had been targeted toward the Army Air Corps. When funding had ultimately been allocated the following year, the Army Air Corps itself had issued specifications to the Stearman Aircraft Company, resulting in an order for 20, as well as spares, of the Lycoming version designated Model X75, but called the PT-13 for Army operation.
The two-seat primary training biplane design, identical to both operators with the exception of some minor features, incorporated a rectangular welded steel tube fuselage which had been covered with metal panels on its forward section and fabric on its aft end and rendered a 25-foot, ¼-inch overall length. Its single-bay, unequally spanned, staggered upper and lower wings, using an NACA 2213 wing section, were built up of spruce-laminated spars and ribs. The center section of its upper wing was carried by wire-braced steel tube struts, while “N”-type steel tube interplane struts carried it on either of its sides. Fabric-covered, they attained motion about its longitudinal axis by the duralumin ailerons installed on the trailing edge of its lower wings, and collectively featured a 32.2-foot span and a 297.4-square-foot area.
The fabric-covered, welded steel tube, wire-braced tailplane and vertical fin featured trim tabs on its elevators.
The divided, cantilever undercarriage, incorporating a metal fairing-enclosed, torque-resisting oleo spring shock absorber in each of its main legs, had been fitted with hydraulic wheel brakes and a steerable tail wheel.
The dual, tandem, open cockpits accommodated a flight instructor and a student pilot, and baggage could be stored in the enclosed compartment behind the rear of the two.
Powered by a twin-bladed, adjustable-pitch, metal propeller mounted on a steel tube whose radial engine was fed by a center-section, 43 US gallon fuel tank and a four US gallon oil tank installed in the engine compartment itself, the aircraft, with a 1,936-pound empty weight and 2,717-pound gross eight, could climb at 840 feet-per-minute, attaining a maximum 124-mph speed and an 11,200-foot service ceiling. Range was 505 miles. Cruise speed, at a 65-percent power setting, was 106 mph, while landing speed was a docile 52 mph.
World War II’s momentum had both paralleled and dictated the aircraft’s production run. The war department’s increasing need for primary trainers resulted in the $243,578 order for 26 PT-13As for the Army Air Corps and the $150,373 order for 20 for the Navy, while a subsequent, $3 million order for PT-13Bs represented the highest in Stearman’s history and necessitated the expansion of its factory and the increase of its workforce to a hitherto record 1,000.
In addition to the United States, the design equally had foreign application. The Model 76D1, for instance, featured a nine-cylinder, 320-hp, twin-bladed, adjustable prop Pratt and Whitney R-985-T1B engine, three.30 caliber machine guns, a two-way radio, and floats, and ten were initially ordered by the Argentine Navy. The Model 73L3, featuring a 225-hp Lycoming R-680-4 engine, was flown in the Philippines, and the aircraft also saw service in Brazil.
Indeed, by 1940, Stearman produced one PT-13-type trainer every 90 minutes, and the momentum, once set in motion, had been unarrestable. On June 25 of that year, the Navy signed a $3.8 million contract for 215-hp Lycoming R-680-8-powered N2S-2s and -5s, sparking another 40,000-square-foot factory expansion. By August, 1,100 personnel worked two eight-hour shifts six days per week, while the following month 1,400 worked round the clock on three daily eight-hour shifts.