Acceleration onset cueing is a term for the motion cueing principle used by a simulator motion platform.
Motion platforms used in "Level D" Full Flight Simulators (FFS)(shortly to be re-named "Type 7" as a result of a rationalisation of Flight Training Device Categories), see Full Flight Simulators, have six jacks that can move the replica cockpit that is mounted on the platform in any of the six degrees of freedom (6-DoF) that can be experienced by any body free to move in space. These are the three rotations Pitch, Roll and Yaw, and three linear movements Heave (up and down), Sway (side to side) and Surge (fore and aft). Acceleration onset cueing works in three phases:
- The initial acceleration of the vehicle being simulated is replicated closely by the platform. However, the platform jacks cannot go on moving without reaching their "limit stops" and a technique is used that prevents the stops being reached without being discernible to the simulator crew.
- After the above initial acceleration, the jack movement is gradually decreased, eventually to zero (this is known as the washout phase).
- Finally, the motion platform is reset to the neutral position but at a rate below that of the sensory threshold of the simulator crew.
The human body motion sensors (inner ear, muscle-and-joint feedback, body movement) react to accelerations rather than steady-state motions and have thresholds below which they do not transmit signals to the brain. Furthermore, impulses from the set of body motion sensors are processed by the brain in a timescale of milliseconds compared to longer time intervals for visual cues of the Outside World (OTW).
The way the body signals motion to the brain coincides very well with acceleration-onset cueing in a simulator. This is the reason why well-designed and properly set-up modern low-latency motion platforms in simulators work well for all aircraft from large transports to the low-G envelope of fighter aircraft. Because fighter aircraft are capable of high-G, which cannot be modelled by a 6-jack motion platform, the majority of fighter simulators are not equipped with motion platforms, as are civil airliner Full Flight Simulators to the international Level D/Type 7 standard.