The Douglas X-3, often known as the Stiletto, was schemed for the investigation of the thermodynamic problems of flight at up to Mach 3, the performance of turbojet engines at high Mach numbers, and the characteristics of double-wedge flying surfaces at high speed. Built by Douglas Aircraft, the X-3 was jet powered and used conventional take-off and landing methods, instead of being air launched. Two X-3s were ordered. However, due to limited funding, lack of expected performance, and on-going engine difficulties, only one was completed for flight - the second was used for spare parts.
The US Air Force, Navy and NACA (predecessor to NASA) all invested in this research craft. To build the X-3 to withstand its anticipated flight regime, large amounts of titanium were used construction. Engine choice was the Westinghouse J34, one of several turbojets that failed to perform as advertised. The pilot's ejection seat fired downwards. It raised and lowered electrically on the ground to allow access to the cockpit.
The X-3 first flew on 20 October 1952, but failed to live up to its potential because the powerplant of two 4200-lb (1905-kg) afterburning thrust Westinghouse J34-WE-7 turbojets was wholly inadequate.
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. The last of a total of 51 flights being made on 23 May 1956, It did, however, contribute somewhat to the understanding of the roll-coupling phenomenon, and pioneered the short-span low-aspect ratio wing used on several later aircraft. But the X-3’s most significant contribution may have been in the field of aircraft landing gear, namely the tires. Because the X-3 had to achieve high speeds to maintain lift, take-off and landing speeds were very high (260 mph for takeoff, 200 mph for landing), and it was common for the tires to come apart. Several aircraft tire manufacturers used data gathered by the X-3 when developing new tires for high speed applications.
To withstand the anticipated high temperatures, the glazed area was as small as possible, giving the pilot a very restricted view. The X-3 was covered in strain gauges and recording points for temperatures and pressures.
The X-3 is currently on display at the Air Force Museum in Dayton, Ohio.
Engines: 2 x Westinghouse J34 turbojets, 1900kg
Max take-off weight: 10160 kg / 22399 lb
Wingspan: 6.91 m / 22 ft 8 in
Length: 20.35 m / 66 ft 9 in
Height: 3.81 m / 12 ft 6 in
Fastest Flight: 0.95 Mach (650 mph)
Highest Flight: 35,000+ feet