LOCKHEED MARTIN will begin hover testing of its Joint Advanced Strike Technology (JAST) candidate in June at NASA Ames, California.

Its JAST contender is now being re-assembled at NASA Ames before the start of engine and lift-fan tests.

The aircraft is an 86%-scale version of the full size, to match the Pratt & Whitney F100-220 "plus" engine which simulates the slightly larger F119 power plant planned for the full-scale demonstrator.

The airframe model was moved to Ames, after the Lockheed Martin Skunk Works, fitted the JAST fuselage with a 9.1m-span wing, fore-planes and twin canted vertical tails, for the new tests.

Initial testing of the aircraft's hovering capabilities will be performed at the Outside Aerodynamic Reference Facility (OARF) from late June, carrying on through July. Aerodynamic testing inside the 24 x 36m wind tunnel will begin in September, says Skunk Works ASTOVL deputy programme manager Paul Bevilaqua.

A vertical-lift fan, located aft of the cockpit on the spine of the model, is the most distinctive design feature. Immediately aft of the lift fan, taken from the F119, is a large, rectangular auxiliary inlet for the F100-220. "We just went with one big auxiliary inlet instead of lots of small ones around the intake, like in the Harrier," says Bevilaqua.

Air from the compressor is fed by a Rolls-Royce duct system to simple roll-control nozzles buried in the root of each wing. "We're looking at trade studies to see whether we could vector them aft," comments Bevilaqua.

The main engine exhaust is a two-dimensional lift/cruise nozzle with thrust vectoring and a variable-area control. The nozzle can vector up to 10° up, for increased manoeuvrability, and up to 20° forward, to aid deceleration for approaches to vertical landing.

Lockheed Martin also experimented with other techniques for reducing roll out in a short landing, including using the "Euro-canard" fore-planes as air brakes. "We discovered, however, that aerodynamics are not very effective at VSTOL speeds," the company says. The slight anhedral of the delta wing is offset by an equivalent dihedral angle of the fore-planes. This ensures that the fore-planes do not interfere with airflow over the wing.

Source: Flight International