Aircraft black boxes, which hold key information in better understanding the final moments before fatal plane crashes, have again been at the centre of media attention after the Egypt Air Flight MS804 crashed into the deepest parts of the Mediterranean Sea in May 2016. However, a leading expert says that hurried technology upgrades would jeopardise safety.
Black box recorders. They can withstand acceleration forces of up to 3,400Gs; endure temperatures of 1,100 °C; the data stored in them can survive for extensive periods of time even in extreme environments. However, there is one problem with them – once they sink into deep water, the quest to find them is akin to the proverbial search for a needle in a haystack.
Once again, rescue teams have been virtually racing against time to detect the devices’ signal before the locators’ batteries run out of power in a month’s time. The situation has been reminiscent of the still unsuccessful hunt for Malaysia Airlines Flight 370, lost in March 2014, the costly search for Air France 447, which crashed in June 2009, as well as the December 2014 disaster of Air Asia Flight 8501.
Speaking exclusively to E&T, David Barry, Aviation Safety lecturer at Cranfield University, said, “The underwater locator beacon is only designed to last 30 days. The range of these devices is limited to three to five thousand metres, so in very deep water we have to tow a hydrophone very deep, which isn’t trivial. That can be a major task requiring specialist equipment and the signal can get refracted and bounce around at different temperature layers within the water, so it can take a very long time to find these devices.”
Since the 2009 loss of AF447, experts have been calling for changes to black box technology. It took two years of extreme effort and expenditure to locate the wreckage of the ill-fated Airbus and retrieve the Flight Data and Cockpit Voice Recorder, without which it was impossible to understand what exactly caused the tragic disaster.
“There is a new requirement for the new underwater locator beacon on flight data recorders to last 90 days. And that is coming to an effect from the start of January 2018,” Barry said.
“There is also another requirement for aircraft to carry another underwater locator beacon that would transmit a different frequency, which would be more easily identified by military equipment, rather than needing to have specialised equipment on scene. This means the signal could be picked up much more quickly. This requirement will be valid from January 2019.”
However, many have asked why such changes will only start taking effect almost ten years after the problems were first pointed out, in which time there have been three further major incidents of lost aircraft.
“The aviation industry is very, very conservative,” Barry explained. “And it has to be. The technology would be very easy to fit, but you have to think whether it presents risks, whether it affects avionics on the aircraft. You also can’t ground all the planes around the world at once to have new technology installed overnight. Such as with the new beacons, it requires some downtime to have them installed as you have to take the flight data recorders off the aircraft and refit them with the new beacons.”
Aircraft manufacturer Airbus wants to go much further and plans to start fitting some of its planes with the so-called deployable flight data and cockpit voice recorders. Such devices would be designed to float on water and would be ejected from the plane in case of severe distress.
"If we have a deployable recorder it will be much easier to find," Charles Champion, Airbus executive vice-president for engineering, told journalists this month. We have been working on that and this [the Egypt Air disaster] only reinforces our overall approach."
However, Barry, who has been part of a team at Cranfield developing an algorithm to detect severe distress, says the idea has many drawbacks.
“There is this problem with false positives,” he said. “Imagine an aircraft approaching Heathrow and some software bug suddenly triggers and the recorder is shot out from the side of the aircraft over some house. That could be introducing serious risk. This kind of technology implementing isn’t trivial. We really don’t want emergency distress signals to be sent out willy-nilly."
The algorithm could also initiate transmission of basic flight recorder data such as location, altitude or air-speed between the moment when the problems are detected and the actual impact.
“It will allow investigators to get a basic set of data very quickly and then also help them to find the main recorders and the wreckage much faster than today,” Barry explained.
Continuous streaming of flight recorder data throughout the flight is the ultimate goal, Barry said. However, with the amount if information collected by the recorders, it’s still quite far ahead.
“A typical modern flight data recorder will have 2,000 parameters, recording data up to eight times per second. That’s a huge amount of data about what’s happening in the aircraft and what the aircraft systems are doing,” said Barry.
“I think it would be a while before that amount of data is feasible to transmit via satellite communication links. Imagine every aircraft that is flying in the world transmitting that amount of data routinely. It will come eventually. In the shorter term, trigger transmission will be the way forward.”
Egypt Air black box recovery infographic