Poor cockpit coordination and possible pilot error have emerged as the most likely reasons a FlyDubai jetliner crashed earlier this month in Russia, according to independent air-safety experts and one person familiar with the probe.
There were apparently no mechanical or computer problems, according to these people, when the Boeing Co. 737’s crew abandoned a second landing attempt at Rostov-on-Don in stormy weather March 19 and attempted to climb away from the strip. One of the pilots calmly told air-traffic controllers the plane was executing a go-around and, according to a publicly available recording, confirmed a new radio frequency for communication—all indications that things were normal on the flight deck.
But during the ascent, these people said, the plane carrying 62 people apparently climbed too steeply, the wings lost lift, then it dropped rapidly and exploded in a fireball.
When pilots perform what is called a go-around, they are typically trained to apply maximum engine thrust to gain altitude quickly. But pilots and safety experts said the maneuver can be tricky in such a lightly loaded 737 jet—carrying few passengers and with relatively little fuel remaining in its tanks—because the cockpit crew simultaneously must use nose-down commands to avoid an excessive upward pitch.
Flight 981 had circled for roughly two hours after its first missed approach, burning off fuel in the process. Once the climb began, the pilots may have improperly coordinated automated engine-thrust settings with manual flight-control inputs, according to the person familiar with the probe, outside safety experts and Russian media reports. The result, these people said, seemingly left the plane with its autopilot disconnected but without adequate power to accelerate through the climb. In less than a minute, the plane’s nose was raised at an angle higher than would be considered normal during a go-around, according to the person familiar with the details.
Some of those reports, describing transcripts of comments supposedly gleaned from the cockpit voice recorder, have indicated the two pilots may have temporarily put in conflicting commands during one phase of the emergency.
Conflicting control inputs during stressful situations have been factors in various airliner accidents around the globe, even as regulators and training procedures have worked to mitigate the problem.
Russian officials, who are heading up an international team of investigators, have declined to comment on the specifics and indicated a preliminary report may be released in April. Data from the black-box recorders has been downloaded successfully. International rules typically stipulate a first crash report with basic facts be issued within a month of a crash, though those findings often don’t include full details gleaned from the black boxes.
The United Arab Emirates’ General Civil Aviation Authority said investigators were still examining data from the crew, aircraft maintenance and the wreckage. “Before the data is fully examined, it would be premature to hypothesize the cause of the accident,” the agency’s director general, Saif Mohamed Al Suwaidi, said Sunday.
Numerous studies and simulator sessions over the years have highlighted the hazards of improperly executed go-arounds, which can result in spatial disorientation, excessive pilot commands to raise the nose, crew confusion about the status of automated flight-control systems and other potentially dangerous missteps.
Similar accidents have occurred before, and safety experts world-wide have stressed the importance of pilot training to avoid aerodynamic stalls, or what are often called “loss-of-control accidents,” when perfectly functioning planes crash due to cockpit slip-ups or inattention.
An older 737 model, operated by Tatarstan Airlines, crashed in November 2013 in similar circumstances when an attempted landing was broken off, killing all 50 people on board. Russian investigators determined the crew improperly performed the go-around, allowing the aircraft to stall.
In addition to pilot training, the probe also is likely to delve into crew-scheduling practices at FlyDubai, the low-fare arm of Emirates Airline. The crash occurred before dawn local time, when the pilots may have been fatigued, or experienced stress from the landing delay.
Officials at the GCAA have seemed to rule out fatigue as contributing to the crash. “It is too early at this stage to say what caused the accident and what didn’t,” an agency official said, adding that “from the evidence available until now, we have no reason to believe” fatigue was a factor.
The crash also highlights one of the close links between the region’s regulators and its airlines. FlyDubai Chairman Sheikh Ahmed bin Saeed Al Maktoum also is a board member on the GCAA, in addition to being chairman of Emirates Airline, the world’s largest carrier by traffic.
(culled from www.wsj.com)
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