RTOS system is driving the plane

Express Logic's ThreadX real-time operating system (RTOS) is driving Avidyne Corporation's DFC90 attitude-based digital flight-control system.

The DFC90 is an integrated flight computer and control panel designed as a slide-in replacement for existing rate-based STEC 55X flight computers.

Avidyne's DFC90 specifically targets Cirrus SR20 and SR22 aircraft with Avidyne's Entegra flight-deck systems.

ThreadX is an RTOS for deeply embedded real-time applications.

In a flight-control system, aircraft flight is controlled by servos that deflect aelerons and elevator control surfaces to induce turns and/or pitch changes for climb or descent.

The DFC90 system receives input regarding the aircraft's attitude, heading, and altitude, as well as input from the pilot and navigation system that specify the desired attitude, heading, altitude, and rate of climb/descent.

It calculates the precise commands that drive the servos in real time, so that the desired flight path is achieved.

As the operating system, ThreadX controls all functions in the DFC90.

The US Federal Aviation Administration requires that all operational software in an aircraft that flies in US airspace be developed and certified in conformance with DO-178B, a safety-critical software standard.

DO-178B requires detailed documentation and testing of the entire software system, including the RTOS.

Avidyne expects FAA certification for the DFC90 in mid-2010 and reported that ThreadX represented only a small percentage of the overall software system, adding minimal code requiring certification.

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