The UK Defence Evaluation and Research Agency's (DERA) Vectored-thrust Aircraft Advanced-flight Control (VAAC) Harrier has embarked on the Royal Navy's HMS Invincible for a 10-day sea trial of short take-off and vertical landing flight control concepts for the Joint Strike Fighter.

The tests, largely funded by Italy's JSF programme contribution, will involve pilots from Italy, the UK and USA. "We will be looking at various alternative concepts for STOVL flight control based on work done in the UK and by NASA," says former VAAC project pilot and now the UK's Lockheed Martin X-35 test pilot, Sqn Ldr Justin Paines.

"We will be looking at radically different control concepts from the Harrier, and the results will be fed into the JSF engineering and manufacturing development phase in 2001," adds Paines. "In the Harrier, one of the biggest workloads is axis coupling, so we are examining concepts to reduce this."

The two control concepts are under evaluation - both eliminate the need for the Harrier's third (nozzle) control lever.

In unified mode, the pilot pulls back on the stick to go up and pushes forward to go down, regardless of airspeed. While flying on the wing, centring the stick and throttle will hold speed and attitude. In the hover, centralising everything maintains height, position and heading.

In fusion mode, the throttle controls height and the stick controls speed through attitude, as with a helicopter. The angle of the nozzles are controlled by the digital flight control system.

The trial will also evaluate a thumb-operated wheel on the throttle to control speed, with a centre detent for holding speed. Lateral and directional controls are the same as in unified mode.

Source: Flight International