NASA 

National Aeronautics and 

Facts

Space Administration 

Dryden Flight Research Center 

P.O. Box 273

Edwards, California 93523 

Voice 661-276-3449 

FAX 661-276-3566 

pao@dfrc.nasa.gov FS-2003-06-0077 DFRC 

X-3

NASA Photo E-17348. In flight photo of the X-3, which made significant contributions to knowledge about inertial coupling. 

The Douglas X-3 Stiletto was the sleekest of the early experimental aircraft, but its research 

accomplishments were not those originally planned. The goal of the aircraft was ambitious - it 

was to take off from the ground under its own power, climb to high altitude, maintain a sustained cruise speed of Mach 2, then land under its own power. The aircraft was also to test the 

feasibility of low-aspect ratio wings, and the large-scale use of titanium in aircraft structures. 

Construction of a pair of X-3s was approved on June 30, 1949. During development, the X-3’s 

planned engines failed to meet the thrust, size and weight requirements. As a result, lower-thrust 

Westinghouse J34 turbojets were substituted. The first aircraft was completed and delivered to 

Edwards Air Force Base, Calif., on September 11, 1952. Due to both engine and airframe problems, the partially completed second aircraft was cancelled, and its components were used for 

spare parts. 

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The first X-3 “hop” was made on October 15, 1952, 

by Douglas test pilot Bill Bridgeman. During a highNASA Photo E-1996. X-3 on Ramp 

speed taxi test, Bridgeman lifted the X-3 off the 

ground and flew it about a mile before settling back 

onto the lakebed. The official first flight was made by 

Bridgeman on October 20, and lasted about twenty 

minutes. He made a total of 26 flights (counting the 

hop) by the end of the Douglas tests in December 

1953. These showed that the X-3 was severely underpowered and difficult to control. Its take off speed was 

an astonishing 260 knots! More seriously, the X-3 did 

not approach its planned performance. Its first supersonic flight required that the airplane make a 15 

degree dive to reach Mach 1.1. The X-3’s fastest 

flight, made on July 28, 1953, reached Mach 1.208 in 

a 30 degree dive. 

With the completion of the contractor test program in 

December 1953, the X-3 was delivered to the U.S. Air 

Force. The poor performance of the X-3 meant only an 

abbreviated program would be made, to gain experience with low-aspect ratio wings. Lt. Col. Frank 

Everest and Maj. ChuckYeager each made three 

flights. Although flown by Air Force pilots, these were 

counted as NACA flight. With the last flight by 

Yeager in July of 1954, the NACA made plans for a 

limited series of research flights with the X-3. The 

initial flights looked at longitudinal stability and 

control, wing and tail loads, and pressure distribution. 

ducting eight research flights in September and October. By late October, the research program was expanded to include lateral and directional stability tests. 

In these tests, the X-3 was abruptly rolled at transonic 

and supersonic speeds, with the rudder kept centered. 

Despite its shortcomings, the X-3 was ideal for these 

tests. The mass of its engines, fuel and structure was 

concentrated in its long, narrow fuselage, while its 

wings were short and stubby. As a result, the X-3 was 

“loaded” along its fuselage, rather than its wings. This 

was typical of the fighter aircraft then in development 

or testing. These tests would lead to the X-3’s most 

significant flight, and the near-loss of the aircraft. 

On October 27, 1954, Walker made an abrupt left roll 

at Mach 0.92 and an altitude of 30,000 feet. The X-3 

rolled as expected, but also pitched up 20 degrees and 

yawed 16 degrees. The aircraft gyrated for five seconds before Walker was able to get it back under 

control. He then set up for the next test point. Walker 

put the X-3 into a dive, accelerating to Mach 1.154 at 

32,356 feet, where he made an abrupt left roll. The 

aircraft pitched down and reached a g-loading of -6.7, 

then pitched upward to +7 Gs. At the same time, the 

NACA pilot Joseph A. Walker made his pilot check- NASA Photo E-1227. X-3 stiletto on Ramp. 

out flight in the X-3 on August 23, 1954, then con2
NASA Photo E-2889. NACA Research Aircraft: Bell X-1A, 

D-558-1, XF-92A, X-5, D-558-2, X-4, and X-3. 

X-3 sideslipped, resulting in a loading of 2 Gs. Walker 

managed to bring the X-3 under control and successfully landed. 

The post-flight examination showed the fuselage had 

been subjected to its maximum load limit. Had the G 

forces been higher, the aircraft could have broken up. 

Walker and the X-3 had experienced “roll coupling,” 

in which a maneuver in one axes will cause an 

uncommanded maneuver in one or two others. At the 

same time, several F-100s were involved in similar 

incidents. A research program was started by the 

NACA to understand the problem and find solutions. 

For the X-3, the roll coupling flight was the high point 

of its history. The aircraft was grounded for nearly a 

year after the flight, and never again explored its roll 

stability and control boundaries. Walker made another 

10 flights between September 20, 1955, and the last on 

May 23, 1956. The aircraft was subsequently retired to 

the Air Force Museum. Although the X-3 never met 

its intention of providing aerodynamic data in Mach 2 

cruise, its short service was of value. It showed the 

dangers of roll coupling, and provided early flight test 

data on the phenomena. Its wing platform was used in 

the F-104, and it was one of the first aircraft to use 

titanium. Finally, the X-3’s very high take off and 

landing speeds required improvements in tire 

technology. 

NASA Photo E-2274. X-3 towed to lakebed 

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