Boeing is evaluating the radar cross-section (RCS) of a Lockheed T-33 which will act as a calibrated airborne target during tests of the Northrop Grumman APG-77 radar under development for the Lockheed Martin/Boeing F-22 Raptor fighter.
"We hung the T-33 in our compact range chamber and took measurements across a wide frequency band," says Boeing F-22 radar-analysis and integration manager, Paul Michelson. The readings were taken over a full 360¹ in azimuth and with the aircraft pitched at up to +/-20¹.
"We will now develop an RCS contour of the aircraft, and we'll take the RCS manoeuvres and load them in to predict what sort of performance we can expect from the radar," says Michelson.
The RCS data on the T-33, one of two elderly chase aircraft used for flight-test work, will initially be used to help in ground-based tests of the F-22's radar, which will be mounted on a 46m-high tower at Boeing Field, Seattle.
The first radar will be delivered on 26 March for testing at the company's $30 million Avionics Integration Laboratory, where overall integration of the F-22's electronics system will take place. The tower tests will be conducted against "targets of opportunity [ie, local air traffic] and the T-33", says F-22 radar programme manager, Ken Layman. "We have to understand what the T-33's RCS is, so we can determine if we are seeing him at the right spot and the right distance."
The T-33 will begin flying against the APG-77, mounted in Boeing's 757 flying testbed, in December 1998. The 757 is now flying against a Northrop Grumman-owned T-39 Sabreliner test aircraft. In August, the 757 will be fitted with a representative F-22 wing, which will be mounted on the crown of the fuselage aft of the cockpit. The full-up electronic systems will be installed in the fourth F-22 in 1999, with first flight expected late that year.
Source: Flight International
