The Douglas X-3 Stiletto was an experimental jet aircraft manufactured by the Douglas Aircraft Company in the 1950s.
It featured a slender fuselage and a long-tapered nose and was primarily designed to investigate the design features of an aircraft suitable for sustained supersonic speeds.
Notably, the X-3 was the first aircraft to incorporate titanium in major airframe components.
Douglas aimed for a maximum speed of approximately 2,000 mph (3,200 km/h), but the aircraft was seriously underpowered and could not even exceed Mach 1 in level flight.
Despite its shortcomings, data from the X-3 tests proved valuable to Lockheed designers who incorporated a similar trapezoidal wing design in the successful Mach 2 fighter, the Lockheed F-104 Starfighter.
The Douglas X-3 Stiletto was an early experimental aircraft that boasted a sleek design, but its research achievements did not align with its original objectives.
Initially, the aircraft was intended for advanced Mach 2 turbojet propulsion testing, but it primarily served as a configuration explorer due to its inability to meet its original performance goals, which was attributed to inadequate engines.
The aircraft’s objectives were ambitious, as it aimed to take off from the ground under its own power, ascend to high altitude, maintain a sustained cruise speed of Mach 2, and land under its own power.
Additionally, the aircraft was designed to test the feasibility of low-aspect-ratio wings and the large-scale use of titanium in aircraft structures.
The Douglas X-3 Stiletto’s design is the subject of U.S. Design Patent #172,588, granted on July 13, 1954, to Frank N. Fleming and Harold T. Luskin and assigned to the Douglas Aircraft Company, Inc.
On June 30, 1949, the construction of two X-3s was approved.
However, during development, the planned Westinghouse J46 engines were unable to meet the thrust, size, and weight requirements.
As a result, lower-thrust Westinghouse J34 turbojets were substituted, producing only 4,900 pounds-force (22 kilonewtons) of thrust with afterburner instead of the planned 7,000 lbf (31 kN).
The first aircraft was built and delivered to Edwards Air Force Base, California, on September 11, 1952.
The X-3’s unique slender, streamlined shape featured a very long, gently tapered nose and small trapezoidal wings.
The objective was to create the thinnest and most slender shape possible to achieve low drag at supersonic speeds.
The extended nose allowed for the provision of test equipment, while the semi-buried cockpit and windscreen were designed to alleviate the effects of “thermal thicket” conditions.
The low aspect ratio and unswept wings were designed for high speed, and later, the Lockheed design team used data from the X-3 tests for the similar F-104 Starfighter wing design.
Due to both engine and airframe problems, the partially completed second aircraft was cancelled, and its components were used for spare parts.
Two aircraft were ordered, but only one was built, this completed 51 test flights. Specifications X-3 Crew 1 Length 66 ft 9 in (20.35 m) Wingspan 22 ft 8 in (6.91 m) Height 12 ft 6 in (3.82 m) Wing area 166.5 sq ft (15.47 m2) Aspect ratio 3 Empty weight 14,345 lb (6,507 kg) Gross weight 20,800 lb (9,435 kg) Max take-off weight 22,400 lb (10,160 kg) Powerplant 2 × Westinghouse XJ34-WE-17 afterburning turbojets, 3,370 lbf (15.0 kN) thrust each dry, 4,900 lbf (22 kN) with afterburner Performance Maximum speed 613.5 kn (706.0 mph, 1,136.2 km/h) at 20,000 ft (6,100 m) Maximum speed Mach 0.987 Range 432 nmi (497 mi, 800 km) Endurance 1 hour at 512.7 kn (590.0 mph; 949.5 km/h) at 30,000 ft (9,100 m) Service ceiling 38,000 ft (12,000 m) Absolute Rate of climb 19,000 ft/min (97 m/s) Wing loading 124.9 lb/sq ft (610 kg/m2) Thrust/weight
0.476 Sources McDonnell Douglas Aircraft Company 1st 75 Years Aviation Book-McDonnell Douglas. McDonnell Douglas Aircraft since 1920, Volume 1-René J Francillon. San Diego Air and Space Museum Archive. The National Museum of the U.S. Air Force. Skystreak, Skyrocket, & Stiletto: Douglas High-Speed X-Planes-Scott Libis.