X-WING RESEARCH
 
 
     The X-wing Rotor Systems Research Aircraft (RSRA), is a
heavily-instrumented experimental vehicle designed to test a
flight concept that combines the vertical lift advantages of
the helicopter with the faster forward speed of the fixed
wing airplane.  Managed by Ames Research Center, the X-wing
program is a joint effort of NASA and the Defense Advanced
Research Projects Agency (DARPA).
 
     The test vehicle currently being flown at Ames is a
specially modified version of the RSRA, two of which have
been operating since 1978 as "flying wind tunnels" for
~}investigations of promising rotorcraft concepts with future
commercial or military potential.
 
     The X-wing's rotor, made of composite material, has
four extremely stiff blades that can be stopped in flight to
become fixed wing airfoils. For takeoff, hovering and low
speed forward flight, the rotor operates in the spinning
mode as a helicopter rotary wing.  At a speed of about 215
miles per hour, the rotor is stopped and locked in place,
becoming in effect, two wings--one pair of blades swept
forward at an angle of 45 degrees, the other pair swept
rearward at the same angle.  With the X-wing providing fixed
wing lift and two General Electric TF34 jet engines
providing 9,725 pounds of thrust, the craft can attain
forward speeds of more that 600 miles per hour.
 
     The goal of the flight test program is to demonstrate
conversion---stopping the rotor, then restarting it---
between rotary wing flight and fixed wing flight.  The
experimental rotor will not permit hovering or speeds
exceeding 288 miles per hour (250 knots), the limit of the
RSRA flight envelope.  A future operational prototype X-wing
would be capable of speeds approaching 500 knots in the
fixed wing mode and economical hovering in the rotary wing
mode.
 
     The X-wing concept is considered to have potential for
future commercial service---perhaps around the turn of the
century---as a short-haul transport.  In military service,
it has applications in tactical operations, electronic
intelligence, antisubmarine warfare and search and rescue.