Why black boxes can't always provide the answers

The mystery of flight MH370 is unlikely to be solved until the flight recorder - known as a black box - is found. It has two components - a cockpit voice recorder and a data recorder. But these devices have their limitations.

The voice recorder only captures the final two hours

Listening to the last moments of Air France flight 447, which crashed into the Atlantic in 2009, gives a chilling insight into the confusion that had overcome the pilots. Such a record of what went on in the cockpit would be a priceless tool for investigators trying to work out whether the Malaysia Airlines plane was the victim of foul play or a mechanical fault. But it's not that simple even if the black box is found. The cockpit voice recorder continually records over itself as the flight goes on. US firm Honeywell Aerospace says the black box on the missing airliner - which it provided - only retains two hours of recording. That's the length of time that regulations demand. The principle is in place because it is normally the last section of a flight that determines the cause of the crash. But in the case of the Malaysia Airlines 777 it might well be the case that the key events happened long before the actual crash. On the other hand, Steve Buzdygan, a former BA 777 pilot, says the data recorder would provide a wealth of useful information. "You can almost reconstruct the flight path from it."

The battery life is short

The black box sends out a ping - after activation by contact with water - that can be picked up by a microphone and a "signal analyser". Both the voice recorder and the data recorder each have their own pinger. But there's a problem - the battery of the pinger on MH370 will only last for 30 days, says Steve Brecken, media director at Honeywell. Some pingers last for 90 days. The variation stems from the fact the rules changed after Air France flight 447. It took nearly two years to find its black box and new guidelines were issued that the ping should last for 90 days to give search teams longer to find it. Some planes have since been updated, but apparently not the MH370. Even after the batteries for the pinger run out, the recorded data remains intact.

It is a small object to find

The black box is bolted into the tail of the aircraft to avoid damage in a head-on crash. It is small - about the size of a shoe box, says Dr Guy Gratton of Brunel University's Flight Safety Lab. Contrary to the name, it is bright orange. But it's not easy to see it in the middle of the ocean. The search will aim to try to locate the wreckage before moving in to pinpoint the black box by picking up the ping. If the pinger has expired then other techniques - such as magnetic detection - are going to be necessary.

It doesn't float

The box is made out of aluminium and designed to withstand massive impact, fierce fire or high pressure. That means it's heavy - about 10kg for what is a small box - and will sink quickly. The Indian Ocean has very deep sections. The search area ranges between 1,150m (3,770ft) and 7,000m (23,000ft), media reports suggest. So investigators will be have to consider the prospect of it being out of reach of many sonar devices. "You have to ask if there's terrain in the way. The seabed could be as mountainous as the Alps," says David Barry, an expert on flight data monitoring at Cranfield University.

The pinger's range is only a few miles

Honeywell, who made MH370's pinger, say the signal can typically only be picked up a mile away. But if it is deep on the ocean floor navies have hydrophone technology that has a better chance of locating it than conventional detectors. The Air France black box was not found until after its ping had expired. It was eventually located by slow moving unmanned underwater vehicles. A modern submarine - such as one of the Royal Navy's hunter-killer models - could potentially at least hear a ping from many miles away, Gratton says. The US, China and Australia all have similar submarines, he says. "By now there will be a submarine down there. I'm certain the Chinese will have put something out there." The US has deployed a ship that will tow a special black box locator through the water. According to the Associated Press, "the Towed Pinger Locator, which is pulled behind a vessel at slow speeds, has highly sensitive listening capability so that if the wreck site is located, it can hear the black box pinger down to a depth of about 20,000ft (6,100m)". However, there is a further complication, says Barry. The black box may be giving off pings from the ocean floor. But if those pings hit a layer of warmer or colder water above, the signal might be refracted or reflected.

Flight MH370 'crashed in south Indian Ocean' - Malaysia PM

                              Standing sombre before the world's media, Malaysia's prime minister ended weeks of limbo with a brief statement

Malaysia's prime minister has announced that missing flight MH370 crashed in the southern Indian Ocean.

Najib Razak said this was the conclusion of fresh analysis of satellite data tracking the flight.

Malaysia Airlines had told the families of the 239 people on board, he said.

The BBC has seen a text message sent to families by the airline saying it had to be assumed "beyond reasonable doubt" that the plane was lost and there were no survivors.

There were 227 passengers on flight MH370, many of them Chinese.

Relatives of those on board who watched the announcement at a Beijing hotel wept with grief, and some were taken away on stretchers by medical teams.

Passengers' relatives in China took in the news with a mixture of deep anguish and some anger

China has demanded that the Malaysian authorities make available the evidence on which they based their announcement about the jet's fate.

And some relatives of Chinese passengers expressed scepticism about their conclusion, as the plane has not been found yet.

Flight MH370 disappeared after taking off on 8 March from Kuala Lumpur.

A big international search operation has been taking place in the southern Indian Ocean, along the southern arc or corridor of the plane's possible route, more than 1,500 miles (2,500km) off the south-west coast of Australia.

However, the search had to be suspended on Tuesday due to bad weather, the Australian Maritime Safety Authority (Amsa) said.

Missing MH370: China rules out hijack, attack by Chinese passengers

                                                       China’s ambassador to Malaysia Huang Huikang

BEIJING: No evidence has been found linking the 153 Chinese passengers aboard missing Malaysia Airlines (MAS) flight MH370 to terror or hijacking, state media said Tuesday, citing Beijing’s envoy in Kuala Lumpur.

China’s ambassador to Malaysia Huang Huikang also said China had begun searching for the aircraft on its own territory amid a huge international search operation covering vast areas north and south of the plane’s last-known position.

Huang said background checks on all passengers from the Chinese mainland on board missing flight MH370 did not find any evidence that they were linked to a hijacking or terrorist attack on the jet, the official Xinhua news agency reported.

After taking off from Kuala Lumpur heading to Beijing, the jet disappeared on March 8 with 239 people on board.

Twenty-six countries are now helping to hunt for the plane after satellite and military radar data projected two huge corridors through which the plane might have flown.

The northern route stretches in an arc over south and central Asia, passing across far western China while the southern corridor swoops deep into the southern Indian Ocean west of Australia.

The investigation has zeroed in on the plane’s captain, Zaharie Ahmad Shah, and his co-pilot Fariq Abdul Hamid, with a key question being who was in control of the aircraft when it veered off course about an hour into its flight. – AFP

Malaysia Airlines Flight MH370: China finds no terror link to its nationals on jet

Malaysian police asked for help from intelligence agencies from countries with passengers onboard

The Associated Press Posted: Mar 18, 2014 12:54 AM ET Last Updated: Mar 18, 2014 2:03 AM ET

Flight engineer Mohd Khairul Amri Selamat and other passengers and crew who were onboard the missing Malaysia Airlines Flight MH370 are being investigated by officials. Malaysian police have asked intelligence agencies from countries with passengers onboard to carry out background checks on those passengers. (Stringer/Reuters)

Checks into the background of all the Chinese nationals on board the missing Malaysian jetliner have uncovered no links to terrorism, the Chinese ambassador in Kuala Lumpur said Tuesday.

The remarks will dampen speculation that Uighur Muslim separatists in far western Xinjiang province might have been involved with the disappearance of the Boeing 777 and its 239 passengers and crew early on March 8.

The plane was carrying 154 Chinese passengers, when Malaysian officials say someone on board deliberately diverted it from its route to Beijing less than one hour into the flight. A massive search operation in the Indian Ocean and beyond has yet to find any trace of the plane.

Chinese Ambassador to Malaysia Huang Huikang said background checks on Chinese nationals didn't uncover any evidence suggesting they were involved in hijacking or an act of terrorism against the plane, according to the state Xinhua News Agency.

Uighur groups have been involved in attacks inside China, and some have a presence in the Afghan-Pakistan border area, where al-Qaeda and other transnational jihadi groups are based.

Malaysian police are investigating the pilots and ground engineers of the plane, and have asked intelligence agencies from countries with passengers on board to carry out background checks on those passengers.

Malaysian authorities say that someone on board the flight switched off two vital pieces of communication equipment, allowing the plane to fly almost undetected. Satellite data shows it might have ended up somewhere in a giant arc stretching from Central Asia to the southern reaches of the Indian Ocean.

Huang also that authorities in China had begun searching for the plane on its territory.

Malaysian police say they are investigating the possibility of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or anyone else on board, but have yet to give any update on what they have uncovered.

Malaysian military radar spotted the plane in the northern reaches of the Strait of Malacca at 2:14 a.m. on March 8, just over 1½ hours after it took off from Kuala Lumpur. That is the plane's last known confirmed position. A signal to a satellite from the plane at 8:11 a.m. suggests that, by then, it was somewhere in a broad arc spanning from Kazakhstan to the Indian Ocean west of Australia.

Investigators are scouring over what little data they have to try and determine who was in control of the plane when it stopped communicating. They have indicated that whoever was in control must have had aviation experience and knowledge of commercial flight paths.

China urges Malaysia to intensify search for flight MH370

China has urged Malaysia to "step up its efforts" in the search for the Malaysia Airlines passenger plane that disappeared on Saturday.

Malaysia said it was widening the hunt, after days of searching found no trace of the plane or the 239 people on board - most of whom were Chinese.

Rescue teams from nine countries will now scour areas stretching from the Malacca Strait to the South China Sea.

Beijing-bound flight MH370 vanished shortly after it left Kuala Lumpur.

Relatives of the missing passengers have been told to prepare for the worst.

Chinese foreign ministry spokesman Qin Gang had earlier urged the Malaysian authorities to sharpen its search efforts.

"We have a responsibility to demand and urge the Malaysian side to step up search efforts, start an investigation as soon as possible and provide relevant information to China correctly and in a timely manner," he said.

Patience appears to be wearing thin in the search for the missing aeroplane, says the BBC's Celia Hatton in Beijing.

The Malaysian authorities are attempting to address Chinese concerns - they have reissued a pledge to fly worried family members to Kuala Lumpur so they can be closer to the search efforts, our correspondent adds.

But one victim's relative - Guo Qishun, whose son-in-law was on the plane - said he did not see the point of flying to Malaysia.

"If we go to Malaysia, we can do nothing but wait, just like we are doing in Beijing now. If we go to Malaysia, who can we rely on? Most of us don't speak English," he told the Associated Press news agency.