by the large number of systems the pilot had to monitor. For its role as a research aircraft it had comprehensive recording equipment. The common throttle lever for the four vertical lift engines was the only additional primary control in the cockpit; it was operated in a similar manner to that of the Collective pitch level of a rotorcraft. Two ways to control the attitude of the aircraft were required depending on its forward speed; aerodynamic surfaces were used during conventional flight, and air-jet nozzles for transitioning from horizontal flight, hovering and vertical flight. Bleed air from the four lift engines (approximately 10 per cent of the intake airflow) was supplied to the variable nose, tail and wing tip nozzles, for pitch, roll and yaw control at low speeds during which there would be insufficient airflow over the aerodynamic surfaces for conventional controls to be effective. The SC.1 was also equipped with the first "fly-by-wire" control system to be fitted to a VTOL aircraft. This electrically-signalled control system, which also comprised the auto-stabiliser, not only transferred signals from cockpit controls such as the position of the stick, but also monitored feedback signals from the servos to provide stability of the systems itself. A total of three modes of control for the aerodynamic surfaces and/or the nozzle controls were permitted by the system: Aerodynamic surfaces and air-jet nozzles controlled electrically via three independent servo-motors (with "three-way parallel" or "triplex" fail-safe operation) in conjunction with three autostabilizer control systems ("full fly-by-wire") Hybrid-mode, in which the nozzles were controlled by servo/autostabilizer and the aerodynamic surfaces were linked directly to the manual controls Direct mode, in which all controls were linked to the control stick Modes 1 and 2 were selected on the ground; whenever the autostabilizer was in use, the pilot had an emergency override lever available with which to revert to direct control mode in flight. The outputs from the three control systems were compared and a "majority rule" enforced, ensuring that a failure in a single system was overridden by the other two (presumably correct) systems. Any failure in a "fly-by-wire" pathway was indicated to the pilot as a warning, which he could either choose to ignore or respond to by switching to direct (manual) control. In common with other VTOL aircraft, the Short SC.1 suffered from vertical thrust loss due to the ground effect. Research into this performed on scale