Report details final minutes of doomed Rio-Paris flight

French investigators revealed new details Friday about the final minutes inside the cockpit of Air France Flight 447, which crashed into the Atlantic Ocean in June 2009, killing all 228 people on board. The first reports of data obtained from the flight’s black box recordings offered no new information on the suspected malfunction of the speed sensors aboard the A330 Airbus, nor did it provide new insight into the possibility of human error.

The report showed that the aircraft’s autopilot mode was shut off around two hours after it took off from Rio de Janeiro’s Galeao Airport, and that soon after the crew took the controls they noticed the aircraft’s speed indicators were defective. Then the plane suddenly stalled before plunging into the ocean four minutes later.

Snatches of those final tragic minutes appear in the report. The text describes the pilots’ struggle to regain control of the plane and includes some of their conversation.

Rapid descent from 38,000 feet

The Air France flight had been encountering stormy weather in the mid-Atlantic when its problems began. Capt. Marc Dubois told his two co-pilots that they were experiencing a “little bit of turbulence” and that “we should find the same ahead”. He then told his two colleagues: “We’re in the cloud layer. Unfortunately, we can’t climb much,” before leaving the cockpit to rest.

Pilots on long-haul flights often take turns at the helm in order to remain alert. Dubois was called back to the cockpit by the co-pilots after they encountered trouble, but never took back the controls.

The plane quickly lost speed but continued to climb on one of the co-pilot’s orders, reaching an altitude of almost 38,000 feet (11,500 metres). According to Thierry Laffitte, a former Air France captain, such high altitude is uncommon, and was probably what led to the crash.

The aircraft stalled, then plunged toward the Atlantic at a speed of almost 11,000 feet (3,350 metres) per minute. The plane’s engines were operational and responding to crew commands.

“There was no reason for [the engines] to stop,” Laffitte said. “But at a certain moment the engines could no longer make the plane re-accelerate.”

In the last exchange between the crew, one co-pilot tells the other, “Go ahead, you have the controls,” after they simultaneously move their side-sticks.

Pitot tubes remain principal suspect

The investigators did not provide any new information about the pitot tubes - the plane's speed sensors, which previous probes have identified as the likely cause of the accident.

Ongoing search efforts, which have retrieved the flight recorders and some of the victims’ bodies, have so far failed to recover the pitot tubes.

A renewed focus on the actions of crew members has followed the report’s release, according to Patrick Smith, a US pilot and aviation expert. “Perhaps they did not react exactly as they should have,” Smith said. “But bear in mind they were dealing with equipment failures, degraded flight controls, stormy conditions and darkness.”

“It’s important to note that an accident is always the result of a chain of events,” Laffitte explained. He is convinced that blocked pitot tubes were the source of the flight’s problems. “The pitot tubes should never have malfunctioned. After that, we are faced with human decisions – humans who couldn’t, or did not know how to, find the right solution to the problem,” he said.

While investigators were pressured by the media to reveal the initial data from the flight recorders, a full report on the crash – with a more detailed transcript of the crew’s conversation – is not expected until next year.