With hopes fading in the search for the missing flight MH370, the focus is now on tracking the “ping” emitted by the aircraft's locator beacon before its battery runs out.
Dozens of ships and aircraft are hunting for debris and objects in the southern Indian Ocean but there are fears the battery attached to a tiny aluminium cylinder in the Boeing 777-200ER (9M-MRO) will die in the first week of April.
When it goes dead, the task of locating the flight data and cockpit voice recorders would be even more difficult, CNN said today.
The “ping” was inaudible to the human ear, it quoted Anish Patel, president of beacon manufacturer Dukane Seacom Inc, as saying.
Every commercial jet is required to have pingers, or known as underwater locator beacons, to help locate lost aircraft. One is attached to the flight data recorder and another to the cockpit voice recorder.
The pingers are activated when it comes into contact with fresh or salt water, and emit a signal at 37.5 kilohertz.
To detect the signals, searchers drag hydrophones behind boats, drop them from ships or planes, or use specially equipped submersibles, the CNN report said.
Under favourable sea conditions, the pingers can be heard 2 nautical miles away. But high seas, background noise, wreckage or silt can all make pingers harder to detect.
Recovering the flight data recorder is essential for investigators hoping to solve the mystery of flight MH370's disappearance.
Patel said after 30 days, the battery of the flight data recorder would continue to provide power and the beacon would ping, but the output would drop.
"As the battery 'wears down', the pinger output decreases until the battery reaches a point that no ping is emitted," Patel said in an email to CNN.
"The pings get lower and lower in 'volume' as the battery weakens.
"Our predictive models and lab tests show 33 to 35 days of output before we drop below the minimal value," he said.
"Depending on the age of the battery, it could continue pinging for a few days longer with progressively lower output levels, until the unit shuts down."
Since the 2009 crash of Air France flight 447, efforts have been made to increase the battery life of underwater beacons, CNN said.
In the case of the Air France crash, the battery died before searchers could locate the wreckage. It took another two years before the recorders were recovered.
Since then, regulators and the airline industry have worked towards increasing the beacon battery life from 30 to 90 days.
CNN reported that there were also efforts to require pingers to be attached to aircraft airframes, making it easier to locate the wreckage.
The next-generation pingers emit pings that can be heard almost 10km to 16km away, said Patel.
However, CNN said, the short battery life was not the only concern of investigators of MH370's disappearance.
Also worrying is the fact that the flight data recorder only have two hours of recording capacity – and this may pose a problem as investigators believed that the aircraft had flown for almost seven hours beyond its last-known position.
As such, there was a high chance that the crucial cockpit recordings have been erased.
On the positive side, however, the depletion of the battery would not wipe out data. Data has been known to survive years in harsh sea water conditions on modern recorders, said CNN.
The cockpit voice recorder, or black box, holds the key to solving the mystery of the aircraft's disappearance as it not only records the pilot's words but also the clicks and hums in the cockpit – sounds that reveal the actions taken by those in the cockpit.
Flight data recorders capture a wide array of data, including altitudes, air speeds, headings, engine temperatures, flap and rudder positions.
"The newer aircraft typically are to record 88 or 91 parameters now, but usually we see recorders that come in for the newer aircraft of at least a few hundred parameters if not more than 1,000," a National Transportation Safety Board official told CNN.
They must record the previous 36 hours of operations and so, by entering the data into a flight simulator, investigators can re-create the last moments of the flight.
Data recorders are built tough. They can survive short, hot blazes, such as a fuel fire, or longer but cooler blazes, such as a forest fire, were a plane to crash in the woods.
They are also required to survive an impact shock of 3,400 G-forces, and have standards for static crush and fluid immersion.
They must be able to withstand hydrostatic pressures found at 6,000m deep. The region where searchers are now looking for flight MH370 has depths of up to almost 4,000m.
Patel, meanwhile, believes that his company had manufactured the pingers on MH370.
"We are confident it could be one of ours," he told CNN.
Malaysia Airlines is a customer of Dukane Seacom and the company's pingers have been installed on Boeing 777s.
"We're preparing to address questions should it be ours," he added.
The search for the Malaysian jet is the longest in modern passenger-airline history. The previous record was the 10-day search for a Boeing 737-400 operated by Indonesia’s PT Adam Skyconnection Airlines, which went missing off the coast of that country’s Sulawesi island on January 1, 2007. – March 22, 2014