## The radio-navigation block VOR (Nominal VOR signals)

The block VOR, from the VOR sublibrary of the NAVLIB block-library, calculates VOR signals which an aircraft receives when it flies at a certain position with respect to a certain user-specified reference VOR bearing. The coordinates of the VOR antenna, measured relatively to the Earth-bounded reference frame, must be defined by the user for t = 0. See the references below for more information.

Note: the block VOR determines the nominal VOR signals, without taking into account noise and/or steady-state errors. For the latter kind of errors in the VOR signal, a separate block VORerr has been created. The system VOR example demonstrates how these blocks can be combined.

### Inputsignals: uvor1 and uvor2

    uvor1 = [xe ye H]',
    uvor2 = psi.

    xe : X-coordinate of aircraft in Earth-fixed reference frame [m]
    ye : Y-coordinate of aircraft in Earth-fixed reference frame [m]
    H  : altitude of aircraft above sea level [m]
    psi: heading of the aircraft (yaw angle) [rad]

Note: these signals are outputs from the non-linear aircraft dynamics model (e.g. from the Beaver model).

### Outputsignals: yvor1, yvor2, and yvor3

    yvor1 = Gamma_VOR: Angle between chosen VOR-bearing and line
                       from aircraft's c.g. to VOR antenna [rad]
    yvor2 = R_VOR    : 2D-distance from origin Earth-fixed reference
                       frame to VOR (as seen from above) [m]

    yvor3 = [Cone-of-silence-flag, Range-flag]'
    yvor4 = ToFrom

The Cone-of-silence-flag is set to 1 if the aircraft enters the 'cone of silence'. The Range-flag is set to 1 if the aircraft flies outside the area where the VOR signals can be received with appropriate reliability.

The variable ToFrom is set to 1 if aircraft is flying towards the VOR antenna or 0 if the aircraft flies away from the antenna.

### References

For more information about the block VOR, consult the FDC user-manual, and/or:

1. M.O. Rauw: A Simulink environment for Flight Dynamics and Control analysis - Application to the DHC-2 'Beaver'. MSc-thesis, Delft University of Technology, Faculty of Aerospace Engineering, Delft, The Netherlands, 1993.