In another aviation first, the unique maneuvering capabilities of the X-31
high-performance experimental fighter aircraft were demonstrated Saturday to
the international aerospace community in a performance at the 1995 Paris Air
Show. The X-31's performance is the first international air show flight
demonstration by an X-plane.
The X-31's demonstration included a series of unique maneuvers in which the
aircraft dramatically exceeded the aerodynamic stall angle, a condition in
which ordinary aircraft lose control. The X-31 is able to exploit this high
angle-of-attack "post stall" capability to turn and maneuver more quickly and
over shorter distances than can conventional aircraft.
The specific maneuver set demonstrated during the air show included a
post-stall loop after takeoff, followed immediately by a rapid, so-called
"helicopter turn" in the opposite direction; a low-altitude, horizontal,
post-stall break turn termed the "mongoose"; a slow-speed, high angle-of-attack
turn in the opposite direction called the "Herbst turn"; and, finally, a
climbing, high-speed entry into a post-stall loop, followed by rapid,
sequential repointing of the aircraft in opposite directions.
In preparation for the low-altitude air show demonstration, the X-31 had
conducted 34 flights in less than a month. This represents a record for
X-aircraft, bettering the previous achievement of 22 flights during one month;
the previous record was also held by the X-31.
Two X-31 experimental aircraft were built and flew during a four-year
exploration and test program to demonstrate the feasibility of thrust vectoring
control in the post-stall flight regime. The X-31 used maneuvers similar to
those in its air show repertoire in mock, close-in air combat engagements
against a variety of front-line fighter aircraft, dramatically dominating many
of these "adversaries."
The X-31's maneuvering achievements have also been complemented by another
significant aviation first when the aircraft demonstrated that flight without a
tail is possible at supersonic as well as subsonic speeds. Designing aircraft
without tails offers the potential for reduced weight and increased
performance, efficiency and stealth. The X-31 demonstrated flight without a
tail through a novel supersonic in-flight experiment in which the flight
control system was fooled into reacting as though the aircraft had no tail.
The thrust vectoring capability was then used to provide necessary aircraft
stability, trim and control.
One aircraft crashed during a test flight in January 1995, after a departure
from controlled flight not attributed to any of the aircraft's unique systems
or maneuvering capabilities. The remaining X-31 aircraft was brought back to
flight status in April.
The X-31 aircraft was developed jointly by Rockwell International's North
American Aircraft Division and Daimler-Benz Aerospace (formerly
Messerschmitt-Bolkow-Blohm), under sponsorship by the U.S. Department of
Defense and the German Federal Ministry of Defense. The program has been
operating under the auspices of the X-31 International Test Organization (ITO)
from the NASA-Dryden Flight Research Center, Edwards, Calif. The ITO is
comprised of participants from the DoD's Advanced Research Projects Agency,
NASA, the U.S. Navy, U.S. Air Force, the German Government, German Air Force,
and the two prime contractors, Rockwell International and Daimler-Benz.
Note: Video footage of the X-31 performing maneuvers similar to those
performed at the air show is available from Ken Carter, Room 2E765, Pentagon,
at (703) 697-6161.
Stock photos of the X-31 are available on-line at the World Wide Web site
maintained by NASA-Dryden Flight Research Center at the following URL:
http://www.dfrc.nasa.gov/PhotoServer/photoServer.html
