Keeping an ear to the sky

An air traffic control system that uses acoustic sensor technology to ‘hear’ aircraft as they take off and land is ready for full-scale testing.

An air traffic control system that uses acoustic sensor technology to ‘hear’ aircraft as they take off and land is ready for full-scale testing.

The EU-funded Safe-Airport project uses acoustic sensors that are claimed to be able to detect and track aircraft up to six miles away to complement conventional radar-based control systems in the immediate vicinity of airports.

The sensors consist of two banks of 512 phased-array microphones able to pick up acoustic waves from the aircraft within a specific frequency range. The signal is transmitted to the control centre computer system via fibre optic cables. The computer’s software is then able to guide the array towards a specific acoustic target by steering the microphones to lock on to the strongest signal.

One of the major problems the project’s engineers had to tackle was the effect that differing wind angles might have on the signal and make allowances for it in the development of the software.

The rotating motors that move the sensor bank were also a potential stumbling block. Their noise was creating background interference that was affecting the spectrum of the detected signal. To avoid this, the project team came up with a possible alternative design by arranging the sensors in a pyramid shape that can span 120º without needing to rotate.

The system, which is part-developed by UK company Hytec Electronics, will undergo a full-scale simulation in Rome later this year.

One potential application for the technology is to monitor each aircraft’s adherence to airport guidelines, said project co-ordinator Alessandro Ferrando. ‘The project will provide a new tool to enable the airport management companies to fine aircraft operators that violate the prescribed take-off and landing trajectories,’ he said.

Ferrando claimed the Safe-Airport system is cheaper, uses less power and, unlike radar, does not cause electromagnetic pollution. It can also pass through solid obstacles that radar cannot easily overcome — hangars, for example — and can be used by airport authorities more easily as it is subject to fewer regulations than radar.