Carlos Varela, a licensed pilot and associate professor of computer science at Rensselaer Polytechnic Institute, is an expert in computer systems that detect and correct faulty sensor readings. Varela is currently developing a prototype framework for a data sharing “internet of airplanes” that would improve safety and efficiency by enabling them to share massive amounts of sensor data – meteorological, mechanical, environmental – that modern airplanes collect.
In previous research, Varela developed a computer system that could have detected and corrected faulty airspeed readings, such as those that contributed to the 2009 crash of Air France flight 447. The system -- funded by an Air Force Office of Scientific Research grant program aimed at developing “active data” -- uses established mathematical relationships between different data streams to monitor incoming data and detect errors. Their approach to detecting errors, first publicized in 2014, could be applicable in many systems that rely on sensor readings.
“Black box” flight recorders aboard Air France flight 447 revealed a chain of events beginning with erroneous readings from the pitot tubes – instruments that use air pressure to calculate airspeed. The pitot tubes, presumably blocked by ice, reported a drop in airspeed from 461 to 182 knots. The autopilot, unaware of the error, lowered the nose of the airplane in an attempt to increase airspeed. Unable to maintain altitude, the autopilot disengaged, at which point three human pilots were not able to correct for the error.
Varela and his research group focused on failure of the airspeed sensors. In the event of a pitot tube failure, airspeed can be accurately calculated using groundspeed and wind speed data gathered from onboard instruments that monitor GPS satellites, and weather forecasting information obtained prior to the flight. The relationship between the three data streams provided the group with an opportunity.
A computer system they developed, using about 30 lines of high-level code to govern a constant analysis of the data – detected the faulty readings within seconds and computed the correct airspeed.
Varela said the approach has many other applications. In the context of autopilot systems, Varela said active data could potentially prevent errors like those behind the 2005 crash of Tuninter Flight 1153, in which pilots trusted a faulty fuel indicator, and could aid pilots in situations like the 2009 controlled ditch of US Airways Flight 1549 into the Hudson River.