| The five models detailed here are frequently overlooked in Stearman history but are worthy of note. They can not truly be called Stearman although they were designed by former Stearman engineers and built in the Stearman plant. |
 X-85/X0SS-1 |
| X-85/X0SS-1
Built by Stearman under Stearman model and serial numbers, the X0SS-1 was not a Stearman design. Since the early 1920's the US Navy Bureau of Aeronautics designed some airplanes on its own. Sometimes it got the Naval Aircraft Factory to build prototypes. If production was desired, the Bureau turned to industry for bids. The building of this aircraft was turned over to industry. If the X00S-1 has any historical significance, it is that it was the last observation/scout biplane developed for the Navy. It differed very little from the 1933/34 Curtiss O3C/SOC, but did incorporate some new structural features, including a semi-monocoque fuselage. In 1934, the Navy adopted dual mission designations for some of its aircraft. The Curtiss O3C observation plane became the SOC for Scout-observation, the primary mission being presented first.The roles were reversed for the X00S-1, observation becoming the primary mission. The Navy worked up the basic design for size, proportions, powerplant and structure to be used. Stearman still had a lot of detail to develop. Model number X-85 was assigned, along with c/n 85000. The Navy serial was 1052. The 600 hp Pratt & Whitney R1340 "Wasp" engine, instruments and even floats were provided by the Navy as Government furnished equipment. Delivered in July, 1938 it was clear that the biplane S0 and 0S types had reached the end of the line. There was no production order. |
 X-90/X-91 |
X-90/X-91/XBT-17
Model X-90 was was designed and built at a time when the US military training program was expanding and the US faced an aluminum shortage. Every attempt was made to use non-strategic materials. The wings and tail surfaces were wood, with the fixed surfaces plywood covered. The forward section of the fuselage was steel tube; only the aft portion of the fuselage was semi-monocoque aluminum. X90 The basic design was for a dual purpose airplane. When fitted with a civil 225hp Lycoming R-680 it was a primary trainer. However, with plenty of other PT's in production, the military services were not interested in ordering this aircraft. X-91 A change to a civil 450 Pratt & Whitney R-985 Wasp Jr. under a full NACA cowling resulted in the Model X-91. Engines were changed back and forth several times during development before NX2194 was delivered to the Army as the XBT-17, 42-8726 in January, 1942. This was the last model in the Army's BT series, and there was no production. |
 X100/XA-21 |
X100/XA-21
Stearman started the design of a new twin-engine light bomber for a US Army attack plane competition and completed it after becoming Boeing's Stearman Division. The new model, c/n 100000, was delivered to the Army as the XA-21, 40-191 in September, 1939. Normal crew seating was for three, a bombardier, the pilot and a radioman/gunner, but an additional crew member could also be carried. In addition to being Stearman's first monoplane, Model X-100 incorporated other features that were new to the industry. Electrical actuated retractable landing gear, integral fuel tanks, fully feathering constant speed props and sealed compartments in the outer wing panels, central fuselage and tail for flotation in case of forced landings in water. The engines were the new Pratt & Whitney R2180-S1AG Twin Hornets that produced 1150hp but could be boosted to 1400hp for takeoff. The XA-21 and North American XB-21 were the only aircraft to use it. The Army did purchase the Stearman/Boeing prototype assigning designation XA-21. However, it was never put into production. |
 X-120/XAT-15 |
| X-120/XAT-15
The XAT-15 was developed to meet an Army requirement for an integrated aircrew trainer at a time of aluminum shortage. Wings and tail were wood; fuselage was steel tube with fabric cover. Engines were Pratt & Whitney 550hp R-1340 AN-1 Wasps. Two were built. The last one was delivered in October, 1942. A production order was cancelled. |
 Model 200 - 451/XL-15 |
| Model 200 - 451/XL-15
As a Wichita design, the L-15 for the Army Ground Forces carried the old Stearman design number of 200. It also had the Seattle number of 451. The first of two XL-15's flew on July 13, 1947. Engine was the 125 hp Lycoming 0-290-7 soon changed to a 145hp 0-290AZ. Features were cantilever wing and boom tail for superior visibility, full span "flaperons" separate from the wing for both flap and aileron functions, and quick dismantling for transport on an Army truck. Ten service YL-15's followed. In spite of spectacular performance for their low power, they did not fit their intended role; the Army released the YL's to the Department of Interior for use in Alaska. |
| Other Planes With Stearman Names |