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During ground operations of large commercial aircraft, pilots steer an aircraft by rotating its nose wheel with the tiller, and control its speed using the thrust levers and brake pedals. The thrust levers and brakes can also be used to aid steering 鈥� particularly in sharp turns 鈥� by applying differential braking/thrust. This method of taxiing requires the pilot to use multiple controls and can result in high workload, particularly at complex airports. In addition, the tiller is only used for taxiing and the left and right tillers are neither mechanically nor electronically linked.
ACSAGO proposes an alternative taxiing technology which uses active sidesticks. Many aircraft 鈥� including Airbus aircraft 鈥� are already equipped with sidesticks; however, these are passive sidesticks which do not provide any feedback to the crew. In contrast, active sidesticks provide tactile (haptic) and visual feedback in response to pilot and autopilot commands. Active sidesticks are already used by business jet manufacturers such as Gulfstream; however, their use is limited to in-flight operations.
Active sidestick characteristics can be modified in real-time, thus enabling the same inceptor to be used both on the ground and in the air. An active sidestick can bring several benefits to ground operations. For instance, it can be configured to control aircraft heading, thus rendering the tiller redundant. It can also be configured to control speed, thus enabling taxi manoeuvers to be completed just by using the sidestick. Furthermore, as mentioned above, an active sidestick provides feedback to the crew. The left and right sidesticks can also be electronically linked such that they track each other; thus, both pilots can feel and see their sidesticks moving.
ACSAGO focuses on the application of active sidesticks for conventional taxiing i.e. through the use of the aircraft鈥檚 engines. However, since active sidesticks are configurable, they can also be applied to (future) electric taxiing operations, whereby pilots would use an active sidestick to control electric motors installed in the aircraft鈥檚 landing gear. This would remove the need for a dedicated control inceptor in the flight deck for electric taxiing.
ACSAGO is developing control algorithms for the use of an active sidestick in ground operations. These include algorithms to control aircraft speed and heading and to provide haptic feedback to assist the crew to keep the aircraft on the taxiway centreline and prevent them from exceeding certain speed limits or steering angles which could damage the aircraft鈥檚 landing gear.
Following development, the control algorithms will be evaluated by pilots in a flight simulator in order to determine their suitability to taxi operations and assess their impact on workload, performance and aircraft handling qualities (when compared with taxi operations using conventional controls). It is expected that the proposed technology will improve situation awareness, performance and safety during taxiing.