Method and apparatus for conversion of GPS heading data for use by electronic flight director

1. A method for controlling an aircraft having an Auto-Pilot, a Horizontal Situation Indicator (HSI) module, a Flight Director module and display, and a GPS flight module which outputs a Bank Angle Command and/or waypoint data, the method comprising the steps of:

a. the HSI module accepting a Bank Angle Command and/or waypoint data from the GPS flight module;

b. the HSI module using the Bank Angle Command and/or waypoint data to determine a heading error;

c. the HSI module outputting the heading error to the Flight Director module;

d. the Flight Director module creating a Roll Command from the heading error; and

e. the Flight Director Module outputting the Roll Command to the Auto-Pilot.

2. The method as claimed in claim 1 wherein the aircraft also has an Attitude Director Indicator, the method further comprising outputting the Roll Command from the Flight Director to the Attitude Director Indicator.

3. The method as claimed in claim 1 further comprising outputting the Heading Error to the Flight Director display.

4. The method as claimed in claim 3 wherein the Heading Error outputted to the Flight Director display is outputted by the Flight Director module.

5. The method as claimed in claim 1 wherein a Bank Angle Command is generated by the aircraft's GPS Flight module and the HSI module uses the Bank Angle Command to determine the heading error.

6. The method as claimed in claim 1 wherein waypoint data is generated by the aircraft's GPS Flight module and the HSI module uses the waypoint data to determine the heading error.

7. The method as claimed in claim 6 wherein the waypoint data includes flyby waypoint data.

8. The method as claimed in claim 6 wherein the waypoint data includes flyover waypoint data.

9. An improved Horizontal Situation Indicator (HSI) module for use with an aircraft of the type having an Auto-Pilot, a Flight Director module and display, and a GPS flight module which outputs a Bank Angle Command and/or waypoint data, the improvement in the HSI module comprising:

the HSI module being configured for accepting a Bank Angle Command and/or waypoint data from the GPS flight module and for using the Bank Angle Command and/or waypoint data to determine a heading error, and wherein the HSI module is further configured for outputting the heading error to the Flight Director module where it can be used to create a Roll Command for output to the Auto-Pilot, whereby the Auto-Pilot can be commanded to follow a turn using the HSI and the Flight Director without requiring an additional module be added to the aircraft to create the heading error for use by the Flight Director.

10. The improved Horizontal Situation Indicator (HSI) module as claimed in claim 9 wherein the HSI module is further for outputting the Heading Error to the Flight Director display.

11. The improved Horizontal Situation Indicator (HSI) module as claimed in claim 9 wherein a Bank Angle Command is generated by the aircraft's GPS Flight module and the HSI module uses the Bank Angle Command to determine the heading error.

12. The improved Horizontal Situation Indicator (HSI) module as claimed in claim 9 wherein waypoint data is generated by the aircraft's GPS Flight module and the HSI module uses the waypoint data to determine the heading error.

13. The improved Horizontal Situation Indicator (HSI) module as claimed in claim 12 wherein the waypoint data includes flyby waypoint data.

14. The improved Horizontal Situation Indicator (HSI) module as claimed in claim 12 wherein the waypoint data includes flyover waypoint data.