FUNDS SOUGHT FOR ADDITIONAL X-31 FLIGHTS.

Byline: Charles F. Bostwick Daily News Staff Writer

Officials with the X-31 "thrust vectoring" experimental aircraft program are trying to arrange funding to continue test flights for three more years.

If the officials are successful, the German-American plane would make more than 200 additional flights at a cost of $60 million to $80 million, employing more than 100 people - about the same as its peak before testing wound down last summer.

"Hopefully, we're going to start up in spring with the phase two program," said Fred Knox, an engineering test pilot with Rockwell International, co-builder of the aircraft.

Besides Rockwell, the test program is a joint effort by the National Aeronautics and Space Administration, the U.S. Navy, the U.S. Air Force, Daimler-Benz and the German government, officials said. In the second phase of testing, the participants may expand to include Great Britain and Sweden, Knox said.

"The contracts are not signed," Knox added, speaking after a Lancaster Chamber of Commerce luncheon at which he explained the test program to local business people. "This is all in the preliminary (stages)."

A recipient in November of the Smithsonian Institute's Air and Space Award, the X-31 first flew in 1990, and - with a second X-31 that crashed in January 1995 - completed more than 580 test flights.

The size of a small fighter jet, the delta wing X-31 uses paddlelike blades around its exhaust nozzle to direct the jet blast - a system called thrust vectoring.

The ability to direct the exhaust enables the jet to twist and turn under conditions when other aircraft lose control. In close-quarters aerial combat, the plane that can do that has an advantage in aiming its short-range guided missiles, pilots say.

In the second phase of testing, the primary focus would be on examining the ability of the plane to use thrust vectoring to take off and land in extremely short distances, Knox said.

The X-31 can fly as slow as 60 mph, less than half the speed at which other jets would stall, he said.

"That 60 mph is down in the Cessna-type speed," Knox said.

The proposed flights also would test a new thrust-vectoring nozzle, suitable for mounting on production aircraft, in place of the simple paddles used on the test plane.

And they would fly the X-31 without its vertical tail fin. Although the aerodynamics of tailless subsonic aircraft, like the B-2 stealth bomber, are understood, there are no tailless supersonic aircraft.

Removing the tail is attractive to military designers because it makes a plane harder to spot on radar, and to commercial designers because it would reduce fuel consumption.

Near the end of the first phase of testing, the X-31 flew at Mach 1.1 with its flight control computers programmed to simulate flight without the tail fin.