Page 10 - The Future of Aerospace is X - X-Planes 2021

Douglas X-3 Stiletto

Research accomplishments were not those originally planned

The Douglas X-3 Stiletto was the Aug. 23, 1954, then conducting eight managed to bring the X-3 under control
sleekest of the early experimental air- research flights in September and Octo- and successfully landed.
craft, but its research accomplishments The Douglas X-3 Stiletto on the lake ber. By late October, the research pro- The post-flight examination showed
were not those originally planned. bed at Edwards Air Force Base, Calif. gram was expanded to include lateral the fuselage had been subjected to its
The goal of the aircraft was ambi- and directional stability tests. In these maximum load limit. Had the G forces
tious — it was to take off from the tests, the X-3 was abruptly rolled at been higher, the aircraft could have
ground under its own power, climb transonic and supersonic speeds, with broken up. Walker and the X-3 had
to high altitude, maintain a sustained the rudder kept centered. Despite its experienced “roll coupling,” in which
cruise speed of Mach 2, then land under shortcomings, the X-3 was ideal for a maneuver in one axis will cause an
its own power. The aircraft was also to these tests. The mass of its engines, fuel uncommanded maneuver in one or two
test the feasibility of low-aspect ratio and structure was concentrated in its others. At the same time, several F-100s
wings, and the large-scale use of tita- long, narrow fuselage, while its wings were involved in similar incidents. A
nium in aircraft structures. were short and stubby. As a result, the research program was started by NACA
Construction of a pair of X-3s was X-3 was “loaded” along its fuselage, to understand the problem and find so-
approved on June 30, 1949. During de- rather than its wings. This was typical lutions.
velopment, the X-3’s planned engines of the fighter aircraft then in develop- For the X-3, the roll coupling flight
failed to meet the thrust, size and weight ment or testing. These tests would lead was the high point of its history. The
requirements. As a result, lower-thrust NASA photograph to the X-3’s most significant flight, and
Westinghouse J34 turbojets were sub- the near-loss of the aircraft. aircraft was grounded for nearly a
stituted. The first aircraft was complet- made a total of 26 flights (counting the Force. The poor performance of the On Oct. 27, 1954, Walker made an year after the flight, and never again
ed and delivered to Edwards Air Force hop) by the end of the Douglas tests in X-3 meant only an abbreviated program abrupt left roll at Mach 0.92 and an al- explored its roll stability and control
Base, Calif., on Sept. 11, 1952. Due to December 1953. These showed that the would be made, to gain experience with titude of 30,000 feet. boundaries. Walker made another 10
both engine and airframe problems, the X-3 was severely underpowered and low-aspect ratio wings. Lt. Col. Frank The X-3 rolled as expected, but also flights between Sept. 20, 1955, and
partially completed second aircraft was difficult to control. Its take off speed Everest and Maj. Chuck Yeager each pitched up 20 degrees and yawed 16 the last on May 23, 1956. Although
canceled, and its components were used was an astonishing 260 knots! More made three flights. Although flown by degrees. The aircraft gyrated for five the X-3 never met its intention of pro-
for spare parts. seriously, the X-3 did not approach its Air Force pilots, these were counted as seconds before Walker was able to get viding aerodynamic data in Mach 2
The first X-3 “hop” was made on planned performance. Its first super- NACA flights. With the last flight by it back under control. He then set up cruise, its short service was of value.
Oct. 15, 1952, by Douglas test pilot sonic flight required that the airplane Yeager in July of 1954, NACA made for the next test point. Walker put the It showed the dangers of roll coupling,
Bill Bridgeman. make a 15 degree dive to reach Mach plans for a limited series of research X-3 into a dive, accelerating to Mach and provided early flight test data on
During a high-speed taxi test, 1.1. The X-3’s fastest flight, made on flights with the X-3. The initial flights 1.154 at 32,356 feet, where he made the phenomena. Its wing platform was
Bridgeman lifted the X-3 off the ground July 28, 1953, reached Mach 1.208 in a looked at longitudinal stability and con- an abrupt left roll. The aircraft pitched used in the F-104, and it was one of the
and flew it about a mile before settling 30 degree dive. trol, wing and tail loads, and pressure down and reached a g-loading of minus first aircraft to use titanium. Finally,
back onto the lakebed. The official first With the completion of the contrac- distribution. 6.7, then pitched upward to plus7 Gs. the X-3’s very high takeoff and landing
flight was made by Bridgeman on Oct. tor test program in December 1953, NACA pilot Joseph A. Walker made At the same time, the X-3 sideslipped, speeds required improvements in tire
20, and lasted about 20 minutes. He the X-3 was delivered to the U.S. Air his pilot checkout flight in the X-3 on resulting in a loading of 2 Gs. Walker technology.

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