Use of Garmin Autopilot Envelope Protection System for Simplified Vehicle Operations in General Aviation

Abstract

The general aviation industry suffers from high rates of fatalities and accidents occurring due to loss of control while in flight. This thesis research aims to implement a simple yet effective simplified vehicle operations (SVO) scheme that uses a Garmin autopilot system to create a pilot-on-the-loop controller to help prevent loss of control incidents from occurring. With this scheme, the pilot is controlling turns and climb rates instead of elevator and aileron deflections and is protected from the risk of under-speed and stall through the Garmin autopilots built-in limits. To interface with the autopilot system, a Raspberry Pi and Pythonbased software and hardware package is developed. This package is capable of reading any type of controller or joystick and translate its inputs into readable autopilot commands. The readable commands are generated in an ARINC 429 format, one of the standard communications formats for aviation electronics. Control logic and methods are developed that take in current autopilot flight state data from the aircraft, combine it with pilot joystick inputs, and generate heading and vertical speed commands that can be transmitted to the autopilot system if the proper setup is in place. Ground testing is performed before any flight testing to ensure that each major component of the software is functioning properly and will not cause any issues when integrating with systems onboard the aircraft. Flight testing is then performed, and the data recorded and presented in this thesis validates that the control logic properly interprets and utilizes the received flight state data to generate heading and vertical speed commands. Although the generated commands are not able to be transmitted to the autopilot due to a wiring issue onboard the aircraft, the pilot is able to simulate what the generated commands would be doing in terms of commanding climbs and level turns. The recorded data illustrates that while performing level turns using heading change commands, the rate of turn is influenced by the amount of heading change being commanded. This data also shows the correlation between bank angle, rate of turn, and heading change commands being given. Lastly, this thesis created a testbed for applicable future work to be conducted. Applicable work includes further flight testing that allows for commands to be transmitted to the autopilot system to test the envelope protection of the SVO scheme. Applicable work also includes further advancing the current simplified vehicle operations scheme as well as creating new capabilities through industry partnerships and future thesis research. Aircraft modifications and new control logic methods can be developed and easily integrated with the system that was developed in this thesis research. This research demonstrates the development of SVO schemes that can help create safer practices in the general aviation industry.