New pilot hires at Alaska Airlines soon will undergo a mandatory simulator training session that could very well save their lives and those of hundreds of others in their care. The “extended envelope” training session, complete with the use of a flight simulator that offers full stall capability, will be a 4-hr. immersion into the edges of the large swept-wing transport aircraft envelope, a realm that continues to lead to the deadliest commercial airline loss-of-control (LOC) accidents, but one in which virtually all pilots, until now, have had no realistic hands-on experience.
Alaska earlier this year became the first airline training provider to gain FAANational Simulator Program validation for the use of an extended aerodynamic envelope, stall-capable full-motionBoeing 737-800 simulator. The approval followed a similar nod in June 2015 to FlightSafety International for a Gulfstream G550 simulator for the business aviation sector.
That LOC is a problem is irrefutable, based on accident statistics for over a decade. TheInternational Air Transport Association lists LOC as its top risk in 2015 statistics, with more than twice the fatality rate of the next highest threat: controlled flight into terrain. While the airline industry is devising preventative measures—including providing FAA-mandated and associated required upgrades to flight simulators—carriers are on the lookout for gaps in understanding that could cause a pilot to respond to an upset incorrectly, a common theme in high-profile accidents.
“In the past, airlines would assume that since you arrived with an Air Transport Pilot (ATP) license, that you had really good academics, including high-altitude academics,” says Bryan Burks, an Alaska captain and the content developer for its upset prevention and recovery training (UPRT). “We can’t make that assumption anymore.” Alaska will provide instruction in the necessary aerodynamic fundamentals—including the difference in aircraft manual handling at low-versus-high altitude—during a new hire’s three months of ground school, which will be followed starting in 2018 by the initial 4-hr. simulator session.
Other airlines are following Alaska’s lead in advance of an FAA mandate that takes effect in March 2019 for extended-envelope training, generically known as UPRT. Included are:
- Full-stall and stick-pusher maneuvers (for equipped aircraft).
- UPRT maneuvers, including nose-high and now-low upsets.
- Maneuvers in icing conditions.
- Takeoffs and landings in gusting crosswinds.
- Bounced-landing recoveries.
All are based on forensics of actual accidents and incidents. The rule requires all U.S. airline pilots to undergo the specialized training initially by March 2020.
Alaska invited Aviation Week to Seattle in early July to experience the training session in an L-3-built 737-800 simulator augmented with the FAA-validated extended aerodynamic model and monitoring tool, called StallBox, built by Virginia-based Bihrle Applied Research. The FAA is requiring recurrent training for most of the maneuvers every two years, but only every three years for bounced landings. Alaska, which plans to have all of its simulators equipped with the extended model and its instructors trained by 2018, will give its pilots stall training every year, alternating between low- and high-altitude stalls year to year.
The carrier will use a mix of Bihrle and Boeing extended aerodynamic models in five 737 simulators, with Bihrle as “bolt-on” augmentation and Boeing modeling built into CAE simulators. Alaska is not equipping its 737-400 simulator, as that fleet is expected to be phased out by the end of 2017.
While airline pilots already have been training for upsets and approach-to-stall (prior to the critical angle-of-attack, where the 737’s stick-shaker system activates) for years, the advent of extended simulator models that accurately cover stall and post-stall behavior now will allow the vast majority of pilots to experience the cues and handling of large swept-wing aircraft beyond the stall angle-of-attack, and the peculiarities of recovering. Without the extended model, simulators tend to generate benign post-stall characteristics, leading to potential negative training if angle-of-attack thresholds are crossed. Under the new rules, the simulator must also generate angle-of-attack versus sideslip, aircraft operational limits and cockpit control positions at the instructor’s console, tools that verify the proper recovery technique were used and the training scenario remains within the capability of the simulator and the aircraft.
I met with Burks and Alaska’s director of flight operations and training, Scott Day, early on July 13 at the carrier’s flight operations and training center near Seattle–Tacoma International Airport. The pilots set the scene for my role in the simulator: a new hire having my first flight experience with a swept-wing jet in low and high-altitude operations. I would have already gained the academic knowledge for the simulator ride in my three months of ground school, but this would be the first hands-on opportunity to apply the knowledge to the 737-800. The carrier has a customized training program under the FAA’s Advanced Qualification Program.
Burks is no stranger to UPRT, having been the co-chairman for the training and regulations arm of the International Committee for Aviation Training in Extended Envelopes (Icatee) working group, which was set up in 2009 to investigate better ways to use flight simulation and training to help pilots handle the edge-of-the-envelope situations—including upsets—that were proving so fatal. Cementing the team’s resolve to improve safety was the Air France Flight 447 accident, later attributed to LOC, that occurred during the first day of its first meeting. Icatee was also part of a broader International Civil Aviation Organization group, known as the Loss of Control and Recovery Training initiative, which provided the foundational recommendations that the FAA used for its new UPRT flight-training rules.
Based on Burks’s work with Icatee, Alaska began analyzing and making changes to its pilot training starting in 2011, first by identifying any “negative” training—situations where a pilot can learn an improper response through a faulty or unrealistic simulator setup or scenario—and developing an UPRT program. While a believer in on-aircraft UPRT training in addition to simulators, Burks says it is not viable to send all airline pilots through on-aircraft programs from both cost and vendor-capacity standpoints. His plan at Alaska is to send a subset of simulator instructors to on-aircraft training, a path other airlines—such as South African, KLM and Delta—have followed.
“The primary goal [of the simulator UPRT] is prevention,” explains Burks. “We use the simulator to show and feel the negative consequences of poor strategy and see it on flight display.”
Even without the on-aircraft G-cues and in situ stress that complicate startle and upset situations—a formula for disaster with large swept-wing aircraft—I found the simulator session extremely valuable, and a powerful prevention aid and confidence builder. Included in the 4 hr. were more than a dozen “maneuvers” and scenarios, including:
- A hand-flown instrument departure to emphasize how to manage angle-of-attack with elevator control.
- Low-altitude maneuvers (10,000-15,000 ft.) demonstrating the handling, power reserve—approximately 35% margin remains above cruise thrust—and snappy response of the engines in the relatively thick air.
- High-altitude performance, or lack thereof, at 35,000-37,000 ft. where the thrust reserve is much smaller (less than 10% margin) and stick-shaker activations or upsets generally will require the pilot to descend to gain speed.
- Nose-high and nose-low upsets, overbank upsets (roll angle greater than 90 deg.), equipment failures, over-speed events, wind-shear incidents on landing, unstable go-arounds and full stalls at both low and high altitudes.
With Day in the left seat, I flew from the first officer side while Burks manned the flight instructor station, in which the Bihrle StallBox monitor is a key feature. Whereas instructors at the rear of the cockpit in the past typically would not know what the pilots were doing with the controls, with the StallBox the instructor sees control movements as well as a “V-n” diagram showing airspeed versus G-loading, with envelopes showing the regions where the simulator aerodynamic is valid. When outside of the valid region, data points are plotted in red, alerting the instructor to end the maneuver. The envelope for the extended model is significantly larger than for the standard model, including at least 10 deg. past the stall angle-of-attack in pitch.
Key to Alaska’s UPRT program is making pilots proficient in using cues already available on the 737’s primary flight display (PFD), including flight path vector, low- and high-speed warnings on the airspeed tape, and the acceleration caret, a trend indicator that shows whether airspeed is decreasing or increasing. On the airspeed tape, the 737 has an amber band, within which the pilot has “maneuver protection” above the stick-shaker for banks up to 40 deg. and a red “zipper” band, whose top corresponds to the stick shaker activation that occurs just prior to the aircraft’s critical angle-of-attack. There is also a high-speed warning band for over-speed, a visual cue accompanied by a loud “clacker” sound. While in early-generation jets over-speed could lead to LOC from Mach “tuck” issues, today’s jets are largely free of that problem. However, pilots must make a logbook entry.
As for recovering from upsets and stalls, Alaska’s typical protocol matches Boeing and FAA guidance:
- First turn off the autopilot and autothrottle.
- Unload the wing by decreasing the pitch angle and hence the angle-of-attack.
- Adjust the thrust (based on speed trends, possibly including application of speed brakes).
- Roll the wings level (the ailerons/spoilers are more effective with the wings unloaded).
- Recover in pitch when able.
Starting with the first maneuver, the pilot is shown the connection between the dynamically changing energy state symbology on the PFD and manual control of the elevators, as well as approximating the aircraft’s angle-of-attack based on the angle between the flight path vector and the pitch reference. Familiarity with those aids helps later, when executing recovery procedures, most of which start with unloading the wing (reducing angle-of-attack) once the automation is turned off (autopilot and autothrottle).
While I have substantial experience in actual stalls of light aircraft at low altitude, what was the most eye-opening was the dramatic difference in performance by large swept-wing aircraft at high altitudes. In one approach-to-stall maneuver, the recovery from onset of the stick-shaker to the beginning of the level-out (after dropping the nose and losing significant altitude to regain speed and watching the airspeed and acceleration trends on the PFD) took 31 sec. Attempts to raise the nose too early are met with the stick-shaker, indicating an imminent secondary stall. Handling at high altitudes is also counterintuitive—while the wing is flying relatively close to stall speed during cruise, the elevator control is highly sensitive, inviting over-control (and possible injuries to passengers and damage to the airframe) for the uninitiated.
Also eye-opening was the realization that stalls continue to occur despite numerous warnings, highlighting the potency of distractions and task saturation to divert a pilot’s attention. Along with the various energy state cues on the PFD, the 737-800 has an “Airspeed!, Airspeed!” aural warning and a very noticeable buffet, or rumble, as airflow begins to separate on the wing in advance of the stall, as well as marked increase in negative vertical speed (sink rate).
Despite the advanced warnings, too often in LOC accidents pilots will prioritize a futile attempt to level the wings rather than reducing the pitch angle to unload the wing before trying to exit the stall. If all else fails, Burks says he wants pilots to remember and act on three words: “Unload, unload, unload.”
Ingen kommentarer:
Legg inn en kommentar
Merk: Bare medlemmer av denne bloggen kan legge inn en kommentar.