## Autopilot model, subsystem Sensors / Subtract initial conditions

The autopilot subsystem Sensors / Subtract initial inputs contains the dynamics of the sensor models for the 'Beaver' autopilot and it determines small-deviation signals (i.e. the difference between the outputs from the Beaver model and their initial values), which are needed by the control laws.

This subsystem is used by the systems APILOT2 and APILOT3 (APILOT1 only contains the subtraction of the initial conditions). The outputs from this block are sent to the subsystems Symmetrical autopilot modes and Asymmetrical autopilot modes.

The current implementation is actually only intended to provide a framework for future enhancements of the autopilot models: only a few airdata-sensor models have actually been implemented; most 'sensor' blocks are still empty. The most important sensor block is a quantization effect in the altitude measurement due to a relatively large least-significant bit used in the airdata computer of the 'Beaver' autopilot.

The framework from this subsystem makes it very easy to add new sensormodels if required.