Two weeks after the disappearance of Egyptair flight MS804, the signal from one of the A320’s two black boxes has been detected. A discovery that we owe to the French Navy and the Detector, a 55 lb. (25 kg), three feet (one metre) long submersible detector. This is the latest acoustic detection system developed by the French company Alseamar, specialised in underwater acoustics for 20 years, and based about 20 miles (30 km) north of Marseille (south-eastern France).
The Detector is easy to use, and, attached to a cable, is lowered to a depth of up to 3,300 feet (1,000 metres) into the water. For several minutes, it records the sound waves within a radius of 3 miles (5 km). It is then brought back up to the surface where the audio recording is automatically sent to a computer, where it is analysed by specialised software, capable of detecting the well known ‘‘pings’’ - the signals emitted by flight recorder beacons.
The machine’s battery and recorder allows this operation to be repeated continuously for up to eight hours, and, depending on the received signal intensity, to determine the origin and therefore its location to within 550 yards (500 metres).
Once the search area is established, a robot submarine is sent into action to retrieve the recorder and bring it to the surface. Two years ago an identical system was used to try to detect Malaysia Airlines MH370’s flight recorder signals.