Air France Flight 447’s three-minute plunge from 38,000 feet into the Atlantic Ocean off Brazil, its wings rocking as alarms blared in the cockpit, was something the jet’s pilots weren’t trained to handle.
Pilots can’t practice responding to so-called aerodynamic stalls because flight simulators they train on don’t portray them realistically, French investigators said July 6 in their report on the 2009 accident.
Stalling, a sometimes-violent condition in which wings lose lift, remains a top cause of airline accidents as others such as wind shear and icing have been almost eliminated through better technology and training, according to Boeing Co. statistics.
“This is a horrible tragedy, but one of the things that would give it some kind of redemption would be the effort to improve the training,” said Jack Ralston, president of Bihrle Applied Research Inc. of Hampton, Virginia, which develops advanced computer models for simulators.
Congress in 2010 mandated stall training and the U.S. Federal Aviation Administration, which regulates airlines, last year endorsed such training in a proposed rule.
“We want to give pilots more and better training on how to recognize and recover from stalls and aircraft upsets,” FAA Acting Administrator Michael Huerta told an Air Line Pilots Association training forum today in Washington, according to a transcript of his remarks. “We will be able to do this in the advanced flight simulators we have today.”
It’s not known when airlines would begin simulator training for stalls. None use it now. The FAA’s proposal, part of a larger effort to revamp airline training rules projected to cost the industry $391.9 million over 10 years, isn’t expected to be completed until next year, according to a filing on a U.S. Transportation Department website.
The advent of computer-driven graphics in the late 1980s enabled the widespread use of simulators to train airline pilots. While they allow pilots to practice potentially dangerous maneuvers, such as flying with an engine failure or out of a thunderstorm, in a risk-free setting, simulators have a weakness: they’re programmed to display normal flight, according to last week’s report from France’s Bureau d’Enquetes et d’Analyses and similar findings by the U.S. National Transportation Safety Board.
Stalls in simulators appear to be smooth and easily controlled. In flight, they’re often sudden and violent, according to accident reports. Because the simulators can be so misleading, pilots are shown how to avoid getting into stalls, not how to recover from them.
Stalls aren’t portrayed accurately because mathematical models used to predict how a plane will behave are much more complex when an aircraft goes out of control, according to a 2005 paper by NASA researchers.
Aircraft manufacturers, such as Boeing and Airbus SAS, don’t supply simulator programmers with data on how aircraft behave while stalled, Ralston said.
Bihrle has been developing simulations of stalls and other out-of-control maneuvers for military planes for more than two decades, Ralston said.
Regulators have resisted requiring such techniques in commercial-jet simulators out of concern they wouldn’t be accurate, he said. Erroneous training in how to handle unusual flight situations has been cited by the NTSB in previous accidents.
Advances in aerodynamic modeling and wind-tunnel testing have made it possible to overcome those hurdles, according to the NASA research.
Simulator manufacturer CAE Inc. of Canada now believes stalls can be portrayed, Lou Nemeth, the firm’s chief safety officer, said in an interview.
Other companies that make simulators include France’s Thales SA, Berkshire Hathaway Inc.’s FlightSafety International Inc. of New York and Lockheed Martin Corp.’s Sim Industries BV of the Netherlands.
The FAA may write a separate rule to ensure simulators realistically portray stalls, according to an e-mailed statement yesterday.
The agency is weighing whether to require aircraft-specific testing for stalls or allow manufacturers to depict generic stalls, which would be less expensive and faster to install, Jeffery Schroeder, the FAA’s technical adviser for flight simulation systems, told the pilots’ union forum today.
From 2001 through 2010, 1,756 people died in crashes worldwide after pilots lost control, almost twice the next highest category of cause, according to Boeing. About half of those accidents involved stalls, John Cox, a former airline pilot and president of Washington-based Safety Operating Systems, said in an interview.
Cox, who with Nemeth serves on a U.K. Royal Aeronautical Society committee seeking solutions to these accidents, said pilots need to see realistic portrayals of stalls in training to know how to react. Simulators could recreate the surprise and confusion pilots have faced in real accidents, he said.
From the time pilots learn to fly, they’re taught to recover from a stall by pushing a plane’s nose down to increase speed and air flow over the wings. The Air France pilots did the opposite -- pulling up in a futile effort to gain altitude, worsening the stall, the BEA found.
The NTSB has found similar reactions by pilots in other investigations, including its probe into the last fatal U.S. airline accident, the February 2009 crash of a Pinnacle Airlines Corp. Colgan Air turboprop near Buffalo, New York. The board recommended as part of its investigation that simulators be upgraded to accurately depict stalls.
The June 2009 Air France disaster, involving an Airbus A330 carrying 228 people, was triggered by a confused pilot’s reaction to inaccurate speed readings, according to the BEA report. The pilot on the Rio de Janeiro-to-Paris flight yanked the jet’s nose up, climbing 3,000 feet in 65 seconds, according to the BEA report.
The abrupt maneuver caused a stall and the plane’s stall-warning system sounded an alarm, according to the report. It was accompanied by ineffectual controls and buffeting, both classic indications of a stall.
“Despite these persistent symptoms, the crew never understood they were in a stall situation and therefore never undertook any recovery maneuvers,” a summary of the BEA report said.
Even as they plummeted at speeds greater than 100 miles per hour (160.9 kilometers per hour), the pilots kept trying to pull the nose up, according to the report.
Four seconds before the jet hit the ocean, the pilot who’d begun the climb more than four minutes earlier voiced the confusion in the cockpit.
“But what’s happening?” he said, according to the BEA’s English translation of the cockpit recording.