Guy Norris/LOS ANGELES
PLANS ARE being drawn up to develop a "tailless" McDonnell Douglas F-15 supersonic research aircraft fitted with a thrust-vectoring system to provide data to the US/UK Joint Strike Fighter effort, other future combat-aircraft programmes and, possibly, the high-speed civil transport.
Plans for the STAR, or supersonic tailless-research programme, were being discussed in April at Edwards AFB, California, as the ACTIVE F-15 performed possibly the first ever super-sonic yaw-vectoring flight manoeuvre.
The Advanced Control Technology for Integrated Vehicles (ACTIVE) effort is aimed at demonstrating the benefits of thrust vectoring on overall performance, including range improvement and a reduction in cruise drag and signature. The milestone was achieved at Mach 1.2 and an altitude of 30,000ft (9,000m).
The STAR, if it goes ahead, will form the third phase of the ACTIVE programme from mid-1998 onwards. The ACTIVE is a joint NASA, US Air Force, McDonnell Douglas and Pratt & Whitney programme with the engine company providing the F-15's F100-229 engines and pitch-yaw balance beam nozzle (PYBBN) thrust-vectoring system.
Previous thrust-vectoring research aircraft have been flown supersonically and even vectored in pitch beyond Mach 1, but the 24 April flight is thought to be the first use of such a system to yaw the aircraft at such high speed.
More tests under Phase 1 are planned to extend the thrust-vectoring/speed flight envelope to cover all-axis movement up to Mach 2. Phase 2, running from early 1997 to mid-1998, will focus on tests of a fully integrated flight propulsion system in which the PYBBNs will be controlled "in the loop".
The nozzles are now used selectively and controlled by a vehicle-management system computer, which does not form part of the F-15's flight-control system.
The STAR will be introduced in Phase 3, beginning with a "quasi-tailless" phase when the F-15's vertical tails will be reduced by 50%. The eventual plan is to remove the tails altogether, using the PYBBN system in lieu of the fins and rudders.
Source: Flight International
