A fly-by-wire system uses a computer to mix pilots’ demands with inputs from an aircraft motion sensor. It allows an ideal response at all flight conditions, irrespective of speed, altitude, configuration or loading. FBW aircraft therefore have the potential to give ideal handling over a wide range of conditions and provide much more freedom to manoeuvre since the system can compensate for any “rash” pilot demand .
Studies by British Aerospace and other European aircraft manufacturers indicated that the next generation of air superiority fighters should incorporate an unstable and unconventional aerodynamic design, relying on a fly-by-wire control system referred to as Active Control Technology (ACT). The major advantage of electrical signalling being the speed with which the signal from the cockpit controls could be remodelled electronically to control the flying surfaces.
In the mid 1970s, BAe embarked on a technology programme to demonstrate ACT feasibility. One RAF Jaguar, number XX765 was modified by replacing the mechanical rods with a digital fly-by-wire flight control system. This system was designed jointly by British Aerospace and Marconi Avionics.
This demonstrator flew for the first time on 20 October 1981 and Chris Yeo was the pilot. It was the first aircraft to fly with a full-time digital flight control system with no back up (electrical or mechanical).
The first 42 flights were performed in an aerodynamically stable configuration (i.e. similar to a standard Jaguar). The next 8 flights were made in a longitudinally unstable configuration, using up to a quarter of a ton of lead tail ballast to move the centre of gravity aft.
The aircraft was then fitted with large wing root forward extensions (strakes) to move the centre of lift forward and it was at this stage that it was called the ACT Jaguar Demonstrator. It performed 46 flights in this configuration, most of which were in a longitudinally very unstable aerodynamic configuration. The last two flights were made on 26 September 1984 by RAE pilot Sq. Ldr. Jon Pierce.
The total flying log of the ACT Jaguar Demonstrator consisted of 96 flights (with a total of 79 hrs 31 mins). BAe pilots Chris Yeo and Peter Orme flew all but 7 of the 96 flights. The success of this programme was significant for EAP and the forthcoming Eurofighter.
After the flying programme, the aircraft was used for four years by engineering students at Loughborough University. On 25 June 1996, it was transferred to the RAF Museum at Cosford, on loan from BAe, to join the collection of British research and development aircraft housed in the museum.
© Henry Matthews 2012 – Picture courtesy BAe/Andrew Bunce