Douglas X-3 Stiletto - High Speed Experimental Jet Aircraft
The US Air Force, Navy and NACA (predecessor to NASA) all invested in this extraordinary research craft that looked like it was going supersonic while sitting on the ground, but barely achieved it in the air. Many new construction techniques and materials were needed to build the X-3 to withstand its anticipated flight regime, and large amounts of expensive titanium were used.
The primary purpose of the X-3 was to test the aerodynamics that were to be incorporated in the design of a radical new interceptor conceived by Lockheed in 1951, at a time when the lessons of the Korean War were bringing about profound changes in the design of combat aircraft. That aircraft, the F-104 Starfighter, eventually flew in February 1954, only 11 months after a contract had been placed for two XF-104 prototypes.
Although the airframe was designed to reach Mach 2.2, the best it ever achieved was Mach 1.21, in a dive. This meant it achieved little towards its objective of studying kinetic heating research. The USAF only flew the X-3 six times before handing it to NACA, who made but 20 more flights before it wound up in a museum.
Douglas X-3 Stiletto
Visually one of the most striking aircraft ever, the Douglas X-3 was dubbed 'Stiletto'. A product of the post-war pioneering days of experimental 'X-planes' tested over the Californian desert in the 19405 and 19505, the X-3 appeared ready to pave the way for new discoveries at the outer edge of the performance envelope. Unfortunately, although it provided some useful research data, the X-3's performance did not live up to expectations.
Intended for research into the extreme temperatures and stresses encountered during high-altitude, high-speed flight, the X-3 began life on the designers' drawing boards in 1945. The programme was so complex that three years elapsed before construction of a mock-up was approved, in August 1948. In June 1949 Douglas won a contract for two aircraft plus a static-test example but, in the end, only one prototype was built, with the second partly completed machine providing spare parts for the first.
Flying for the first time in 1952, the X-3 looked weird. The pilot sat in a pressurized cabin on a downwards-firing ejection seat, which also served as an electric lift to provide access from the ground. The X-3 was difficult to handle when taxiing, tricky on take-off and very difficult to fly.
Design of the X-3 was of unprecedented complexity because of the use of titanium and other advanced materials. Unfortunately, despite its rakish appearance and revolutionary construction, the X-3 was underpowered and offered little to researchers. The USAF new the aircraft only six times, Douglas 25 times and the NACA (National Advisory Committee for Aeronautics) funded 20 flights before retiring the X-3 in 1956.
Facts and Figures
Douglas had expected the X-3 to reach speeds in excess of Mach 2, but it became clear at an early stage to both the manufacturer and the USAF that this would not happen.
Futuristic design Contemporary engine technology could not match the potential of the advanced airframe design.
After completing its test duties the X-3 was handed over to the US Air Force Museum, in Ohio, where it can still be seen.
Even in the company of the 0-558-1 Skystreak and 0-558-2 Skyrocket, the 'Stiletto' looks futuristic. The two earlier Douglas aircraft enjoyed far greater success than the X-3.
Douglas used a long, slender fuselage with low-aspect ratio straight wings for the X-3.
On 15 October 1952 the X-3 made an unscheduled, but brief, trip aloft and an official first flight five days later.
The X-3 used 850 pinholes, spread over its structure, to record pressures and 185 strain gauges to record air loads.
There were 150 temperature recording points spread across the X-3 airframe.
In its fastest flight on 28 July 1953 the X-3 was clocked at Mach 1.21 in a dive.
The X-3 is on display at the US Air Force Museum, Wright-Patterson AFB, Ohio.
The X-3 had one of the fastest take-off speeds in history - 260 mph.
The gloss white fuselage and tail surfaces contrasted with the highly polished aluminum wings.
|Cockpit of the Douglas X-3 Stiletto.|
Specifications for the Douglas X-3 Stiletto
Length: 66 ft 9 in
Wingspan: 22 ft 8 in
Height: 12 ft 6 in
Wing area: 166.5 ft²
Empty weight: 16,120 lb
Max takeoff weight: 23,840 lb
Powerplant: 2× Westinghouse J34
afterburning turbojet, 3,370 lbf,
4,850 lbf with afterburning each
Maximum speed: 700 mph
Range: 497 mi
Service ceiling: 38,000 ft
|A: An air data boom extended ahead of the long nose. All details of every flight could be recorded and analyzed by the large numbers of sensors Incorporated in the airframe of the X-3.||B: Douglas developed a special flight suit and helmet for the pilot, allowing a supersonic ejection. The cockpit was pressurized and air-conditioned, which was particularly important Since X-3 cockpit temperatures were expected to be high.||C: Internally the fuselage had aluminum framing covered with heavy-gauge aluminum skinning. In all, 1200 lb. of test equipment was carried, but all data had to be analyzed after landing.||D: Westinghouse continually revised its estimates of the thrust available from the J46 (which was never used) and J34 turbojets. As power ratings were falling, Douglas designers found that airframe weight was increasing.|
|E: The very long nose provided extra space for test equipment and allowed Douglas to keep the X-3's frontal area to a minimum.||F: The unusual shape of the X-3's glazing was yet another result of the need to keep the aircraft as thin and aerodynamically clean as possible. In flight, the windscreen was expected to get very hot.||G: Lockheed's 'Kelly' Johnson used data relating to the low aspect ratio wing of the X-3 when finalizing his F-104 design.||H: The underside of the tailboom on the X-3, where heat from the engine exhaust was expected to be greatest, was covered by a sheet of titanium and was left unpainted. The slab tailplanes also had titanium skins.|