How investigators unlock air crash secrets

The disappearance of the Malaysia Airlines 777 has left 239 passengers presumably dead. Thankfully, air tragedies are rare. Investigators face the task of finding out what happened to the aircraft, as they have done since the first major jet air crash in 1954.

Parts of the Pan-Am Jumbo jet which broke up over Lockerbie in 1988. The reconstruction proved a terrorist bomb caused the crash. Peter Macdiarmid / Getty Images
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On a clear winter morning and in near perfect flying conditions, a modern passenger aircraft suddenly vanishes over the sea. There are no witnesses, no distress call and, within a few hours, no hope of any survivors.

What causes a sophisticated piece of machinery to fail without warning?

The question is as relevant today as it was 60 years ago, when a Comet aircraft, the world’s first passenger jet, suddenly plunged into the Mediterranean on a flight from Rome to London.

As the search continues off the coast of Vietnam for Malaysia Airlines flight MH370, procedures honed over six decades of aircraft crash investigation are swinging into action.

Back in January 1954, the loss of British European Airways flight 781 was as shocking as it was baffling. The British-built Comet was a technological marvel — the first commercial jet capable of speeds and altitude previously unobtainable in passenger aircraft.

It promised to open up the world to travellers, whisking them in comfort to destinations that might have taken days or weeks to reach before. But, as it turned out, there was a terrible price to pay.

BEA 781 was carrying 29 passengers and six crew when it took off from Rome’s Ciampino Airport on the morning of January 10. The aircraft was on the final leg of a flight from Singapore and heading to Heathrow, about two hours away.

Less than 20 minutes after take-off, all radio contact with the Comet was lost and fishermen spotted wreckage falling into the sea. All those on board were killed.

At first it was believed that only a bomb could have caused such instantaneous destruction. When that was ruled out, the manufacturers grounded the Comet for a series of modifications, particularly in the new turbine engines.

Two weeks after the aircraft was allowed to fly again, a chartered Comet heading to South Africa via Cairo plunged into the sea near Naples. This time 21 passengers and crew died.

The investigation that followed ushered in the new science of investigating aircraft crashes. At that point there were no black boxes or cockpit recorders or any international agreed method of determining the cause of such a crash.

For the Comet investigation, the hull of an existing aircraft was submerged in a tank, with water pumped in to simulate pressurised flight.

After 1,836 cycles, the roof of the test aircraft suddenly tore off. Metal fatigue, cause in part by the square design of the windows which cracked at the corners, was determined to be the cause of the two accidents.

Today, all passenger jets have rounded windows, just one example of how the industry learns from its mistakes. Over the subsequent years, cockpit voice-recorders were installed on all commercial aircraft, along with devices to monitor the aircraft’s systems in flight.

Designed to survive the most violent crash and submersion in seawater, the devices are painted bright orange to make discovery easier, but nevertheless became known as “black boxes”.

The job of the aircraft investigation team is sometimes to confirm the expected cause of a crash, but also sometimes to uncover the unexpected.

One of the most famous examples of the former is the destruction of Pan-Am flight 103 over the Scottish town of Lockerbie in December 1988. The 270 fatalities included 11 people on the ground.

From the start it was clear that the crash had been caused by a mid-air explosion. The question was, who or what was responsible?

The cockpit recorder in the tail was found in less than 24 hours and confirmed there had been no warning.

Parts of the Boeing 747 were shipped to the UK’s Air Accidents Investigation Board headquarters in southern England, where a three dimensional reconstruction of a section of the hull was carried out.

Meticulous examination determined that an explosion had destroyed the aircraft, with other fragments showing that it had been planted in a Samsonite suitcase.

Traces of a circuit board dug out of the Scottish soil showed it had been hidden in a Toshiba cassette player, similar to one that had been used in an earlier attempted terrorist attack in West Germany. Libyan intelligence was blamed for the crime, with an intelligence officer, Abdelbaset Al Megrahi, eventually convicted.

The deliberate destruction of an aircraft aside, crashes fall into two categories — human error, or mechanical failure, which is much less common. The sophistication of today’s investigative techniques means the causes of accidents are rapidly traced. But sometimes the path to discovery is far from straightforward.

Five years ago, Air France flight 447 took off from Rio de Janeiro for Paris.

Less than three hours into the 13-hour flight, the Airbus 330 plunged into the Atlantic Ocean. All 216 passengers and 12 crew were killed. There was no indication that the aircraft had been in any distress.

With the aircraft failing to make contact with Senegal air traffic control, it was clear something had gone catastrophically wrong. More than 24 hours later, search aircraft spotted wreckage and an oil slick. Most of the wreckage lay deep under the ocean, somewhere in a search area of 6,300 square kilometres and at a depth of 4,000 metres. It was two years before the fuselage, much of it intact and with bodies still trapped in their seats, was found, as were the cockpit voice recorder and flight recorders.

In July 2012, the final report from the accident investigators was released. It revealed a complex series of errors that individually might have passed without incident but collectively ended in disaster.

The first thing to go wrong was the failure of devices in the aircraft’s wing used to measure speed. These had frozen over as the jet entered a storm, causing the autopilot to disengage.

At this point the Air France pilot, Marc Dubois, was on a routine break. A co-pilot, Pierre-Cedric Bonin, was at the controls, but instead of responding to automated warnings that the aircraft’s speed was falling, he believed he needed to climb and began to pull back on the control stick, pushing the Airbus into a stall.

In the pitch-black of night and seriously disorientated, the crew allowed the aircraft to plunge towards the sea, only aware of their plight in the final seconds.

The recovered cockpit recorder played back the last words of the co-pilot: “Damn it, we’re going to crash. This can’t be happening.”

That the unthinkable can happen will be in the minds of the team investigating the disappearance of Malaysia Airlines flight MH370. The initial efforts will be search and rescue, although, tragically, with less and less prospect of the latter.

The first priority will be to identify the crash site and then to find the black-box recorders which will transmit their position for the next 30 days. If they can be found, they will provide the crucial clues both about the behaviour of the crew and the Boeing 777, an aircraft with a previously almost impeccable safety record.

If the crash was caused by a bomb, the remains of the aircraft and its passengers will both carry distinctive traces of the explosive used. At this point, the investigation becomes a criminal matter, a hunt not just for those responsible but also to find out how the stringent security measures designed to keep us safe in the air have failed again.

Whatever caused flight MH370 to fall from sky, its cause will be determined. It is quite possible though, that we cannot begin to guess the cause of this crash because the circumstances have never occurred before.

It will be of no consolation to the grieving relatives, but the number of people who die in scheduled aircraft crashes has been falling steadily. Last year, the International Civil Aviation Organisation announced in January, was the safest in the history of passenger flight.