It was on this day in aviation history that the 10th flight of the Douglas X-3 "Stiletto" nearly ended in disaster.
The Douglas X-3 Stiletto on the dry lake bed at Edwards Air Force Base
Joseph A. Walker, the Chief Testpilot for the Douglas X-3 supersonic research aircraft, was scheduled to perform 20 flights in the aircraft in the period between August 1954 and May 1956.
The Douglas X-3 Stiletto in flight
On the tenth flight at an altitude of 30.000' (9144 meters) with initially all controls neutral the test program called for an abrupt left aileron input at different speeds. First at Mach .92 and a second time at Mach 1.05. Each time the aircraft yawed violently to the right, followed by a sharp pitch down. Each time the pilot managed to regain control and recover the aircraft before the X-3 was totally out of control.
This aerodynamic behaviour was called inertial roll coupling. It was caused by the majority of the aircraft's mass being inside the fuselage. Together with the gyroscopic effect of the engines and the limits of the flight controls it was difficult to overcome its rolling tendency. After a safe landing and a thorough post-flight inspection, it was determined that the aircraft reached its design load limit. The aircraft was subsequently grounded for 11 months for repairs. AfterwarAfter repairs were maid the test program continued.
The Douglas X-3 "Stiletto", serial number 49-2892, was designed to explore flight in the Mach 1 to Mach 2 range. It had a long thin fuselage with a needle-sharp nose and tiny wings. Only one X-3 was built, out of an order for two, reasons unknown.
Three view drawing of the Douglas X-3 Stiletto
In 1955 flights with the X-3 resumed and on the 23rd of May 1956 the final flight was made and the program was closed down. Results from the test program with the X-3 were used for the development of the Lockheed F-104 Starfighter. The aircraft was subsequently put on display at the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio. Specifications of the Douglas X-3 Stiletto;
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 takeoff 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
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)