The expression “Old habits die hard” is harshly true when it comes to a pilot's response to a stall. Until recently, airline pilots around the world had been trained to minimize altitude loss when faced with the warnings signs of a stall. Training sequences became rote, and pilots were anticipating the stall warning with hands on the throttle and a trim setting that would ease pitch control when power was added.
The price of such training practice became clear in 2009, when three stall-related crashes—of theFlight 3407 near Buffalo, N.Y.; Flight 1951 -800 in Amsterdam; and Flight 447 in the Atlantic northeast of Brazil—made clear to regulators, the industry and pilots, that what was practiced in training was not effective in recovering from stalls in real life.
Airlines and training providers, with modernized guidance and rules from regulators, are now implementing new training programs and technologies designed to de-program pilots of the ingrained responses. Included are efforts to surprise or startle pilots with an unexpected unusual attitude or an automation action that sets off a stick shaker, stick pusher or other stall prevention system when least expected. While other factors were present in the three 2009 crashes, incorrect or insufficient recovery from a stall scenario was a common thread in the crash sequences.
The training standards before 2012 unwittingly led to stall recovery success in terms of lost altitude rather than the need to reduce angle of attack and aerodynamic load on the wing by immediately pushing the elevator control forward—the universally accepted solution to stalls that had been ignored in training.
To succeed, pilots would begin the maneuver at a medium altitude, slow down and hand-fly the aircraft, with the elevator trim set so it would not cause pitch-up problems when full power was brought in on the first warning of a stall. The net result was a programmed reaction to give power more priority than pitch, a fatal mistake in many accidents. Actual stalls were not required nor were they allowed in the simulators because the aerodynamic models driving the systems did not accurately reflect the non-linear behavior of an aircraft in the stall and post-stall regime.
Stall training before 2012 “was a choreographed event,” says Paul Kolisch, supervisor of flight operations training at regional carrier Endeavor Air, a wholly owned subsidiary of. “It was akin to synchronized swimming.”
An intense focus on the problem after the 2009 accidents led the industry to convene experts and the U.S. Congress to mandate several actions from the, including new flight-training rules that are based on the efforts of several rulemaking committees and technical groups. The new rules require airlines to teach not only the proper response to a stall warning, but also prevention and recovery from simulated, fully developed stalls and upsets, including “instructor-guided, hands-on” training in full stalls and stick-pusher activations. Upsets, which the FAA says are most often caused by a stall, occur when an aircraft's pitch or roll angles exceed the normal bounds of 25 deg. nose up, 10 deg. nose down and bank angles of more than 45 deg.
The core principles of the training emerged from an FAA advisory circular published in 2012 that was echoed by regulators globally: reduce the angle of attack when “confronted with a stall event” without being overly concerned with a “predetermined” value for altitude loss. The FAA also called on industry to create “realistic scenarios” for stall training—code for trying to surprise or startle pilots while flying on autopilot—and for making stick-pusher training part of the program for equipped aircraft.
Similar changes are underway in ICAO guidance, driven in part by the new FAA rules and work of the International Committee for Aviation Training in Extended Envelopes (Icatee).
“Had the [Colgan Air Flight 3407] flight crew been required to complete the extended envelope training provisions required by this final rule, that accident would likely have been mitigated,” says the FAA in the rule, noting that the captain may have been surprised by the activation of the stick shaker, pulling the control column aft rather than pushing it forward.
It is unclear how long it will take pilots to undo years of ingrained training. “There are so many professionals on the line that have habit patterns they are not going to give up,” says Clarke McNeace, a formerpilot who is now vice president of flight training and standards at Aviation Performance Solutions (APS) in Amsterdam. “We have an entire industry of simulator instructors and line pilots who have the traditional stall recovery method ingrained. It's going to be a long way down the road.” McNeace, who teaches upset prevention and recovery training (UPRT) at APS, says he is nonetheless encouraged that professional pilots coming for training in the past two years have told him they have “stopped doing it the old way” in their training departments.
Ten new students—instructor pilots with South African Airways (SAA)—are set to begin a professional pilot UPRT three-day training course with McNeace this spring as part of a new safety initiative within the airline to teach existing and newly hired pilots the correct methods of stall and upset recovery. The “prevention” aspect of UPRT relates to proper handling of stalls to avoid the upsets that typically follow. The course will include flights in APS's Slingsby T-67 Firefly aerobatic trainers.
“We have a potential situation in the future, where we will be bringing in less and less experienced pilots into the cockpit,” says Brad Bennetts, an SAA senior first officer, Airbusline pilot and UPRT project manager, who also flies competition aerobatics. “We feel that UPRT is an absolute necessity, but it has to be done properly.”
With grant money from its insurance company, the airline last year sent Bennetts as well as its chief pilot and senior instructors to an APS “train the trainer” program in Phoenix, a five-day course that includes four UPRT flights in an aerobatic Extra 300 and two sessions in a full-motion simulator to work on transferring the in-aircraft skills to the simulator. “'Train the trainer' is designed to take a simulator instructor and make him a subject-matter expert,” says McNeace.
The FAA did not mandate that pilots receive in-aircraft stall or UPRT training in the new rule, an action critics of in-aircraft training say points to the potential for negative training between a straight-wing aerobatic propeller aircraft and a swept-wing jet. McNeace disputes that notion. “The discipline needed to recover both types of aircraft is almost virtually the same,” he says, adding that the aerodynamics “are 90% the same between the prop and the jet.” Advocates of in-aircraft training believe the experience can help pilots understand the physiological stresses and g-forces that accompany upsets, regardless of the size and wing characteristics of the aircraft.
Bennetts says SAA considered giving all its pilots in-aircraft training to experience g-force issues with UPRT, but the $4,300 price for each pilot was prohibitive, “especially for an airline in financial woes,” he notes. Instead, instructors will try to ingrain in pilots “muscle memory” of a recovery technique that makes unloading the wing the first priority, he says.
Starting in July, SAA's instructor cadre will begin putting the airline's 800 pilots through Bennett's UPRT training module as part of a one-day initiation, followed by recurring simulator training every six months. The airline began developing the training two years ago, with help from Sunjoo Advani, president of Netherlands-based International Development of Technology. Included in the introductory session will be a 1.5-hr. briefing, 4-hr. simulator session and 1.5-hr. debriefing. Afterward, UPRT training, including high-altitude stall scenarios with an element of surprise, will be built into the regular six-month sessions in the airline's four simulators. Bennetts says the carrier's Airbus pilots receive approach-to-stall training during initial conversions, per the Airbus “footprint,” but rarely practice stalls afterward. That will change with the new program.
The FAA itself has discovered evidence of the unsatisfactory stall training in pilots during an unrelated study last year that looked at whether lower-cost generic or type-representative stall models may be adequate to upgrade full-motion simulators for the stall and upset training mandate. The gold standard is a “specific” model created by flight-test data, although aircraft manufacturers may not be willing to part with that data and the information may cost-prohibitive to obtain for aircraft that are out of production.
The agency brought in 45 line pilots from Southwest Airlines,and Delta, among other carriers, and put them through stall scenarios in its 737-800 full-motion simulator, augmented with the different extended envelopes. Pilots were divided up to fly the various models, in which each pilot “trained to proficiency” in stall recovery: apply nose-down pitch control first (and hold until the stick shaker stops), then apply roll control, followed by adding more thrust if needed. Each pilot flew two planned stall maneuvers, followed by a third, unannounced stall caused by a rapidly increasing (74 kt. in 5 sec.) severe tailwind on an instrument approach on the autopilot into a demanding airport (Reagan Washington National Airport).
“The results from the surprise scenario turned out to be one of the most valuable parts of the experiment,” says Jeff Schroeder, FAA chief scientific and technical adviser for flight simulation systems and lead author in a report on the study, presented at an American Institute of Aeronautics and Astronautics conference in January. “Instead of the choreographed maneuver training, where pilots are told, 'now we are going to do stall training,' the surprise scenario revealed what might happen if confronted with an unexpected stall in real life.”
Schroeder says only 10 of the 45 pilots applied the stall recovery “template” correctly on the surprise stall. The other 78% had issues with the correct recovery sequence. “Some pilots did not want to drop the nose below the horizon to eliminate the stall, and this experience hopefully served to reinforce the fact that an airplane can be stalled at any attitude or airspeed,” he says. Most of the pilots in the study “strongly agreed” that they were surprised by the tailwind stall, he notes. “It is exactly this type of scenario training that is needed in today's airline training programs,” Schroeder says. The same pilots, after being given hands-on stall recovery training, performed better.
Creating scenarios that produce the physiological response of surprise or startle in a pilot, while not introducing negative training in the recovery of the aircraft, will be key to effective next-generation flight training. Endeavor Air's Kolisch says his simulator instructors have already integrated realistic scenarios into their six-month simulator checks for more than 2,000 line pilots flying theand CRJ900. Distractions he likes to use to mask an impending surprise include a malfunction on the engine-indicating and crew-alerting system just before the stick shaker activates, introducing distracting conversations as airspeed bleeds off or even dropping a heavy book on the floor during a critical operation.
Some scenarios are ready-made for confusion, including low-altitude stalls, where the terrain-awareness warning system alerts the pilot to “Pull up!” in direct contrast to the stall recovery technique. Once the stall warning fires, the pilots are expected to disconnect the automation, lower the nose, add thrust and “clean up” the aircraft later. “You may not surprise everyone, and you may not surprise anyone more than once or twice, but one time is really valuable experience,” Kolisch says.
Tap the icon in the digital edition of AW&ST to watch a video of Safety Editor John Croft learning the difference between legacy and modern stall recovery training in a Bombardier CRJ900 simulator, or go to AviationWeek.com/video