Appendix I – On-the-ground status Test and Validation Guidance for Aeroplanes

ED Decision 2013/031/R

The ADS-B Out system installer should verify that the air-ground status inputs (or algorithms) are functioning properly and that the ADS-B Out system transmits the appropriate airborne messages or surface messages based on the On-the-ground status. This can be accomplished with simulated inputs to the appropriate sensors or accomplished in conjunction with the flight test.

The following tests provide guidance to the aircraft integrator for the verification of the ADS-B Out system installation, as appropriate. Separate cases are presented depending on the need to validate the status within the ADS-B transmit unit.

(a)     Directly determined On-the-ground status being validated outside the ADS-B transmit function:

Modern aircraft with integrated avionics suites commonly contain sophisticated algorithms for determining the On-the-ground status based on multiple aircraft sensors. These algorithms are customised to the airframe and designed to overcome individual sensor failures. These algorithms are an acceptable means to determine the On-the-ground status and do not require additional validation.

(b)     Validation of directly determined On-the-ground status not being validated outside the ADS-B transmit function:

If ground speed or airspeed is larger than the aeroplane’s typical rotation speed, then the On-the-ground status is (changed to) airborne and the airborne position message is broadcast irrespective of the directly determined On-the-ground status (i.e. as indicated to the ADS-B transmit function).

(c)      Indirectly determined On-the-ground status validation within the ADS-B transmit unit:

If an aircraft is not equipped with a means, such as a weight-on-wheels switch, to determine whether it is airborne or on the ground, then the following tests should be performed to determine whether to broadcast the Airborne or Surface Position Messages.

(1)     If the aircraft’s radio height (RH) parameter is available, and RH is less than 15 m (50 feet), and at least ground speed (GS) or airspeed (AS) is available, and the GS or the AS are less than 51 m/s (100 knots), then that aircraft broadcasts the surface position message.

If all three parameters are available, the decision to broadcast the Airborne or Surface Position Messages is determined by the logical AND of all three parameters.

(2)     If radio height (RH) is not available, and if the aircraft’s ground speed (GS) and airspeed (AS) are available, and GS<26 m/s (50 knots) and AS<26 m/s (50 knots), then that aircraft broadcasts the surface position message.

Otherwise, the aircraft broadcasts the Airborne Position Message.

On-the-ground status Test and Validation Guidance for Helicopters, Lighter-than-Air Vehicles and Fixed-under-Carriage Aeroplanes

Installations intended for this category that are unable to provide a compliant direct or indirect ground status detection function, should only broadcast the Airborne Position Message. In addition, the “CA” capability field in downlink format DF 17 should be set accordingly.