Flight recorders that are jettisoned when aircraft dynamics suggest a crash is imminent could speed up air accident investigations, according to a US patent application filed by Airbus.

The over-arching idea, the inventors say, is to reduce the investigative time wasted in the search for flight recorders amid extensive debris fields or, as in the case of Air France flight AF447, in the deep ocean, writes Paul Marks.

Airbus says such ideas have been proposed before, but have not been pursued because engineers could not work out how to eject a recorder quickly moments before a crash without using a small explosive charge, which posed a risk of accidental deployment.

But Airbus engineers in Getafe, Spain believe they have solved that problem. Their idea centres on packaging both the cockpit-voice and flight-data recorders in rounded, buoyant containers to "facilitate their ejection from tubular ducts" somewhere beneath the horizontal stabiliser where a jettisoned recorder "could not impact the aircraft".

These ducts could be customised for the task or form part of redesigned exhaust ducts for the aircraft's air conditioning and pressurisation system.

When early g-forces characteristic of a crash are sensed by accelerometers, a "frangible" grid in the duct is broken mechanically - but not explosively - allowing negative pressure in the duct to suck out and eject the recorder, whereupon a parachute will slow its fall. The patent does not say whether the threshold force for jettison would be higher than, for example, the ultimate design limit.

Although the patent was only filed in the USA on 28 June, Airbus originally published the idea as a Spanish patent in December 2010, five months before the flight recorders from the Airbus A330 that operated as AF447 were found after an extensive two-year underwater search. The accident generated an assessment of technological options for recovering lost recorders more easily.

While a patent is no guarantee the idea will be exploited, it is possible that Airbus's idea will feed into ICAO's post-AF447 attempts to make flight recorders easier to find. Recommendations to extend the duration of transmission of recorder locator beacons have already emerged since the accident.

Source: Air Transport Intelligence news