The Boeing XP-15 was an American prototype monoplane fighter aircraft developed in the late 1920s by Boeing, designated as Model 202 by the company. It was a derivative of the Boeing P-12 biplane, sharing some of its features but introducing a monoplane design. Though it underwent testing with the U.S. Army Air Corps (USAAC), it did not progress into production due to performance issues, and only one prototype was built.

Design and Development

The Boeing XP-15 represented an attempt by Boeing to innovate on the successful Boeing P-12 biplane design by developing a monoplane version of the aircraft. The XP-15 (Model 202) was essentially a modification of the P-12, retaining much of the fuselage and other design elements but featuring a single-wing monoplane configuration. The lower wing of the P-12 was removed, which necessitated several structural changes to maintain stability and improve aerodynamics. The XP-15 also boasted an all-metal construction, which was a significant departure from the mixed wood and metal framework of the P-12.

Other key changes included the alteration of the aileron design, the inclusion of a split-axle undercarriage, and the replacement of the traditional tail skid with a tail wheel, which improved ground handling. The XP-15 was powered by a Pratt & Whitney SR-1340D Wasp radial engine, which produced 525 hp (391 kW). This powerplant was also used in the P-12, but the XP-15’s single-wing design was meant to push the aircraft’s speed and performance higher than its biplane predecessor.

Despite these innovations, the XP-15 was not purchased by the USAAC, and it retained its civil registration number X-270V, never receiving a military serial number.

Operational History

 

The first flight of the Boeing XP-15 took place in January 1930, when the aircraft was introduced to the U.S. Army for evaluation. Early tests quickly revealed that the aircraft’s vertical stabilizer, which had been adapted from the P-12C, was too small to provide the necessary stability for a monoplane. To correct this issue, Boeing engineers enlarged the tail surfaces and added a Townend ring cowling around the engine to improve airflow and reduce drag. These modifications improved the XP-15’s top speed from 178 mph to 190 mph at 8,000 feet.

Despite this increase in speed, the aircraft’s performance remained underwhelming. The XP-15 exhibited a poor rate of climb and had a high landing speed, which complicated landing operations. These performance drawbacks, combined with the availability of other superior designs, meant that the Army did not pursue production orders for the aircraft.

On February 7, 1931, disaster struck during a test flight. One of the propeller blades failed, causing the engine to detach from its mounts, leading to the destruction of the aircraft. The crash marked the end of the XP-15 program.

Navy Variant: XF5B-1

Alongside the XP-15, Boeing proposed a similar design to the U.S. Navy, known as the Model 205. The Navy’s version, designated XF5B-1, was nearly identical to the XP-15 but was tailored for naval operations. The aircraft made its first flight in February 1930, and the Navy acquired one example for testing. However, by the time flight evaluations were completed in 1932, newer and more capable aircraft had been developed, and the Navy opted not to order the XF5B-1 into production.

Technical Challenges and Legacy

The Boeing XP-15 was Boeing’s foray into monoplane fighters, representing a significant leap from the biplane designs of the 1920s. However, the aircraft was not without significant challenges. The single-wing configuration, while intended to improve speed, compromised other aspects of performance such as maneuverability and climb rate. Additionally, the aircraft’s high landing speed proved to be a serious limitation in an era when short-field performance was critical for military operations.

While the XP-15 never saw production, it provided valuable insights into monoplane design that would influence future Boeing aircraft. The all-metal construction was a precursor to the more robust and durable designs of the 1930s and 1940s. The XP-15 also contributed to the transition from biplanes to monoplanes in the U.S. military, as aircraft manufacturers began to embrace the superior performance capabilities of monoplanes.

Specifications (XP-15)

• Crew: 1
• Length: 21 ft 0 in (6.40 m)
• Wingspan: 30 ft 6 in (9.29 m)
• Height: 9 ft 4.5 in (2.84 m)
• Wing Area: 157.3 sq ft (14.61 m²)
• Empty Weight: 2,052 lb (931 kg)
• Gross Weight: 2,746 lb (1,246 kg)
• Powerplant: 1 × Pratt & Whitney SR-1340D Wasp, 525 hp (391 kW)

Performance:

• Maximum Speed: 190.2 mph (306 km/h, 165.3 kn)
• Cruise Speed: 160 mph (257 km/h, 140 kn)
• Range: 420 mi (676 km, 360 nmi)
• Service Ceiling: 27,650 ft (8,428 m)
• Rate of Climb: 1,800 ft/min (9.15 m/s)

Armament:

• 2 x .30-inch machine guns

Variants

• XP-15: Prototype version for the U.S. Army Air Corps. One aircraft was built.
• XF5B-1: Naval version of the XP-15 for the U.S. Navy. One aircraft was built.

Operators

• United States Army Air Corps: Tested but did not adopt the XP-15.
• United States Navy: Tested the XF5B-1 but did not order it for production.

Related Development

• Boeing P-12: The XP-15 was a monoplane version of this successful biplane fighter.

XP-15 / XF5B-1
General information
Type	Fighter
National origin	United States
Manufacturer	Boeing
Status	XP-15 – Destroyed
Primary users	United States Army Air Corps United States Navy
Number built	2 (1 XP-15, 1 XF5B-1)
History
First flight	XP-15 – 30 January 1930 XF5B-1 – February 1930

References

• Angelucci, Enzo. The American Fighter from 1917 to the Present. New York: Orion Books, 1987.
• Jones, Lloyd S. U.S. Fighters, Army-Air Force: 1925 to 1980s. Fallbrook, California: Aero Publishers Incorporated, 1975.