As the Gulfstream G200 simulator edged closer and closer to flying too slowly, below landing reference speed (Vref), the pilot at the controls feigned inattentiveness and allowed the airspeed to continue to deteriorate. Before the stick-shaker began its vibratory dance to let the pilot know that the speed was too low and to do something about it right away, a bright ring of green lights in the pilot’s peripheral view started flashing amber. The pilot didn’t react but maintained the same pitch angle and didn’t add power, and the flashing amber lights turned steady. The airspeed slowed even further, and it wasn’t until the light ring flashed and then turned red that he finally started a recovery, just moments before the G200 stalled.
We had gathered inside the G200 simulator at CAE’s Morristown, New Jersey, training facility, to see how Skov Aero’s Q-Alpha Flight Energy Awareness Display, also known as a low-airspeed alerting system (LAAS), might work in a typical business jet. The group included Skov Aero founder and chief engineer Andrew Skow and his son Geoff, a CAE technician, and four business aviation pilots. Only two pilots at a time were inside the simulator, which was not running on motion so we could observe and shoot video while the pilots tested the Q-Alpha device.
The fundamental idea of Q-Alpha is simple. Until 2010, FAA regulations required that transport category (Part 25) airplanes be equipped with stall warning and mitigation systems, which in many jets consist of a stick shaker (warning) then a stick pusher (mitigation). In airplanes where pilots simply can’t feel a stall, which includes many jet types, the shaker should help catch their attention. If the stall characteristics are such that handling is severely compromised after a stall or the aircraft is likely to enter a deep stall, the stick pusher is designed to prevent the stall before it gets any worse. But these devices don’t always work to prevent an accident, because they don’t give enough warning to pilots. After 2010, newly type certificated airplanes had to be equipped with a LAAS, but there was no retrofit requirement for older jets.
Andrew Skow’s solution is Q-Alpha, a relatively simple LAAS that gives pilots plenty of advance warning prior to the stall and that is easily retrofittable to those aircraft for which a LAAS is not mandated.
Skow first became aware of the opportunity to develop a stall-alerting system after the Air France Flight 447 accident on June 1, 2009, where the crew stalled the Airbus A330 and held it in a stalled condition for more than four minutes until it impacted the ocean, killing all on board. The February 12, 2009, Colgan Flight 3409 crash was another example of a deadly stall but this time during approach to landing. Skow realized that a significant number of accidents could be prevented with a stall-alerting system, and he partnered with his long-time friend, former Bombardier v-p of flight test Pete Reynolds, to explore the problem of poor energy management. The result was the Q-Alpha Flight Energy Awareness Display.
Modern jets have amber and red bands on the primary flight display speed tape along with audible warnings as the speed decreases to those levels. That type of warning system, Skow said, “is flat ineffective. The Asiana 777 at San Francisco had an amber band on the airspeed tape and aural alerts—quad chimes—intended to cause the pilots to look at the PFD. They came on 11 seconds before the crash.”
Whether or not the amber and red bands are supposed to be a LAAS, it didn’t help in that particular accident. “People are defending the amber band ridiculously,” he said. And in any case, retrofitting an older business jet or airliner with a display and the color bands could be prohibitively expensive, if that were the only reason for the upgrade. “We wanted to focus on low-cost, low-tech solutions,” he said. “Our value proposition is simple: it’s unambiguous, you don’t have to look, but it’s in your scan. It’s monitoring you, [telling you], ‘you might want to pick up some knots.’ Without knots, you got nothing.”
A recent accident illustrates the problem: the July 26, 2021, Challenger 605 crash in Truckee, California. While maneuvering in the traffic pattern, the pilots lost control of the Challenger in a turn and despite the stick shaker and pusher both activating, the jet stalled and crashed.
In a YouTube video, test pilot Bill Scott, who was also bureau chief for Aviation Week & Space Technology, described the stall characteristics of the early Challenger 600 series. During the certification program for the Challenger 600, Scott was a test pilot exploring the stall characteristics of the new jet. During one sortie, the jet entered an unrecoverable deep stall and he and the other pilot—Norman Ronaasen—had to bail out of the airplane. Ronaasen didn’t survive.
“The natural aerodynamic stall on the Challenger was pretty unpredictable,” he explained in the video. “You get quick roll-offs, but the big danger was the deep stall on that supercritical wing and that T-tail design. And as a result, we lost the first test aircraft—Challenger 1—when it crashed when we got into a deep stall. Eventually, the Challenger was, of course, certified by the FAA with a stick shaker system that warns of an impending stall and then at a little higher angle of attack, the stick pusher activates to force the nose down and break the stall before the aircraft reaches the actual aerodynamic stall.”
Nevertheless, Scott raises the question of whether such systems give pilots enough time to react and recover. “Having personally experienced at least 1,200 stalls during this development test program, I've seen how rapidly the angle of attack can build, especially when maneuvering…turning approach to stall. There we have actually seen several fatal accidents that raised the question: is the Challenger's existing stall-protection system adequate? And that was raised again in July 2021 when a Challenger 605 crashed at Tahoe Truckee Airport in California…making a circling approach [with a] low altitude loss of airspeed and steep bank angle. And although the stick shaker and pusher evidently activated, the airplane was too low and the pilot didn't have time to recover before they hit the ground.
“I personally believe that all transport category aircraft would definitely benefit from being equipped with a stall-alerting system of some kind that provides a distinct warning to the pilot—before you approach that shaker and pusher angle of attack—that gives pilots a little more time to take corrective action. Especially when you're doing this high bank angle maneuvering like we saw in the 605 accident and clear back when we were doing the testing on Challenger 1; if we had had some kind of an independent stall-alerting system it might have given us enough time to avoid getting into the deep stall and the chain of events that led to the fatal accident and loss of the airplane. We definitely could have used it back then, and if we had had it, Norm Ronaasen would be alive today.”
The Learjet 35 crash at Gillespie Field in San Diego on Dec. 21, 2021, is another example. The pilots and aeromedical crew were flying a short hop to their home base in marginal weather. A circling approach to the desired runway wasn’t available at night, and it appears that the pilots elected to cancel their IFR clearance to fly in the traffic pattern visually. But the visibility was low, and they crossed the center of the airport at less than 500 feet agl, then stalled and crashed while maneuvering toward the runway.
Q-Alpha’s main attribute is that it commands attention, day or night. The current design is a ring or donut shape of LED lights mounted at the corner where the glareshield meets the instrument panel, one on each side of the flight deck. Of course, the donut/ring design is just a suggestion; LED lights can be configured in almost any layout, and there may be better options than a ring. Whatever the placement, it’s critical that the lights be easily visible in the pilot’s peripheral vision, and our demo in the G200 simulator showed that the corner glareshield placement worked well.
There are three main operational modes for the Q-Alpha device: it works as a stable approach monitor for approach, landing, and go-around; provides low-speed alerting in climb, cruise, and descent; and can provide a backup in case of loss of airspeed indication.
By using dynamic pressure and angle-of-attack to set the alerting thresholds, the thresholds “can be set at higher airspeeds than existing low airspeed alerting systems,” according to Skov Aero. “This allows pilots more time to take corrective action. The 'industry standard' low-airspeed alerting system, the so-called 'amber band,’ uses only angle-of-attack.”
When flying at slower speeds on approach and in the airport environment in the G200, Q-Alpha’s thresholds are set as follows: it lights up green for Vref +10/-5 knots, so it would be green during most of the final approach and landing. The next threshold is flashing amber at Vref -5 to -15 or 25 percent above stall speed, accompanied by an audible “airspeed” every two seconds. When Q-Alpha turns solid amber, speed is Vref -15 to -25 (18 percent above stall) and the audible warning says “airspeed low.” Flashing red corresponds with the stick shaker speed (7 percent above stall) and solid red with the stick pusher speed (1 percent above stall), accompanied by the audible word “stall.”
“The problem we’re trying to fix is an inattentive pilot who for some reason decided not to monitor the energy state of the aircraft,” Skow said. “Maybe they’re tired, bored, or task saturated. There are a lot of accidents where energy management is the root cause, and task saturation is the biggest [factor]. Everybody else is working this by putting more information on the PFD or adding an angle-of-attack display. But what if the pilot is looking out the window?”
Skov Aero held the demonstrations of the Q-Alpha stall alerting system in the G200 simulator on April 21 and 23 at CAE’s training center in Morristown, New Jersey. Participants during the session that I observed included Bob Wilson, experimental test pilot at Gulfstream Aerospace; and Joe Chignarella, a pilot for a Gulfstream operator and member of the Teterboro Users Group. We couldn’t all fit into the simulator at the same time, even with motion off, so participants took turns trying out the Q-Alpha device. Tom Huff, Gulfstream aviation safety officer, took his turn later, along with his brother Scott, a Falcon pilot.
Chignarella was first to test the Q-Alpha device in the G200 simulator, which was set up for a medium-weight, mid-CG condition with 10,000 pounds of fuel onboard on a standard no-wind day at 5,000 feet. The test started with straight-ahead stalls, then turning stalls at a 20-degree bank, followed by landings on Runway 4L at Kennedy International Airport in New York City, then the ILS Runway 6 approach to Teterboro ending in a circling maneuver to line up with Runway 1. The latter was the same scenario in which two pilots were killed turning too steeply in a Learjet 35 while trying to line up with Runway 1 on May 15, 2017.
During his time at the controls, Chignarella clearly saw the Q-Alpha device light up and, he said, “I knew I had to add power.”
Wilson ran through the same scenario, but during one of the Teterboro approaches, the simulator technician “blocked” the left pitot tube, shutting off air data to the captain’s instruments. While he still had an airspeed indication via the copilot’s air data computer, the yellow and red low-speed bands disappeared. He was easily able to back up the airspeed tape’s lack of warning information using Q-Alpha and reported that in that scenario, it was invaluable for continuing the approach. “It was a lifesaver,” he said. “It’s impossible to miss. If you have any kind of an airspeed failure, it’s wonderful.”
Wilson did have a criticism, that during a normal landing flare, Q-Alpha flashes amber. Although pilots can safely ignore it at that point, he worries that this would be negative learning. He also noted that when flying just at the point where Q-Alpha lights up green, it sometimes flashes on and off. “My brain just sees the flash,” he said, “and I can’t tell the difference between flashing green and amber.” Overall, he said, “I think it’s a good system and has a lot of advantages.”
Huff did the next series of tests, and he agreed that the transition from solid to flashing and color changes weren’t optimal. Skow said that optimizing the color transition and other interface factors are easy to fix.
“Leading up to the sim evaluation," Huff said, "I thought Q-Alpha was an elegant solution for a systemic problem and one that still remains to be satisfactorily addressed out of the NTSB recommendation for low-speed awareness cueing. Recognizing the limitations for this evaluation—principally, no unique tuning for the G200, suppression of audio alerts, and no prior human factor assessment of the mounting location, the evaluation still showed—in my view—the exceptional utility and potential for this capability.
“During my session, we attempted to stress the system with circling approaches, immediate return-to-land, airspeed miscompare, and single-engine approach/go-around scenarios. Q-Alpha provided enhanced situational awareness and subjectively would be hard to ignore. Of course, this is a key enhancing trait of Q-Alpha…to overcome a distracted or 'cognitively unavailable’ pilot experiencing insufficient speed conditions or undetected airspeed decay.
“I think additional experimentation and human factors evaluation is warranted to resolve those minor observations and truly optimize the salience and discernibility of the status lights.
“I believe Andy [Skow] is to be commended for his determination to address this well-documented contributor to loss-of-control accidents and his eagerness to have abundant feedback on the efficacy of the system. In my view, a cost-affordable and easily-integratable solution is a must, and certainly a strong point for Q-Alpha, particularly for legacy platforms that rarely see avionics upgrades.”
The bottom line is that Q-Alpha is a simple LAAS that is designed to catch the pilot’s attention before it’s too late to recover. Certainly, an angle-of-attack indicator can do the same, but the pilot has to be looking at the indicator at the precise moment that loss of control is about to occur, and likely there are other issues commanding his or her attention.
Instead of forcing the pilot to notice that there is a problem, Q-Alpha issues a clear alert to the pilot before the condition worsens. The crash of the Asiana 777 on a clear day in calm winds at San Francisco International Airport makes a good case for Q-Alpha, according to Skov Aero, which analyzed the flight data recorder data for that accident and assessed when Q-Alpha would have issued its warnings. “[We] found that Q-Alpha would have provided its first alert (solid amber/’airspeed’ voice) 30 seconds prior to impact (132 knots and 350 feet) [and the] second alert (flashing amber/’low airspeed’ voice) at 23 seconds (124 knots and 245 feet). Both alerts are significantly earlier than the amber band.” The pilots would have had enough time to recover, which was not the case by the time the amber band and quad chimes alerted the pilots just 11 seconds before impact.
A 2021 report from the Avionics System Harmonization Working Group addressed this issue. The group’s regulator and industry members were tasked with determining requirements for a “context-dependent” (simultaneous low airspeed, low altitude) low-energy alerting system. The report noted, referring to the Asiana crash: “As indicated in the NTSB report, although a subsequent low airspeed alert (notably present but not required for autoflight certification at the time) was effective in drawing the flight crew’s attention to the condition, the probability of a safe recovery may have been increased if the alert had been generated earlier and/or in a more compelling manner, or the airplane’s systems provided protection against a low energy condition.”
Jeff Wofford, director of aviation for Challenger 300 operator Commscope, hopes to install the Q-Alpha system in his company’s airplanes. “One of my big concerns is the rash of accidents we’ve seen where people are having loss of control in flight at low altitudes, primarily maneuvering around in the traffic pattern,” he said in a video about his experience evaluating Q-Alpha.
“The nice thing about the Q-Alpha system is it doesn’t require any interpretation. You’ve got a system where you have a light that’s at your periphery…it doesn’t require a lot of interpretation and especially in a situation where you’ve got an issue when you’re maneuvering low to the ground, you don’t need to worry about trying to interpret what’s going on or listen to audio cues or buzzers going off. Having something that’s simple and something you can react to and that’s predictive is key.
“The difference between Q-Alpha and some of our current stall warning systems is when the stick shaker goes off, you’re already approaching the stall. With Q-Alpha, you’ve got a system that’s looking at predictive situations and you get a warning prior to getting yourself into the stall. It would be great to add this into our Challenger 300s.”
So far, according to Skow, companies that have expressed interest through letters of intent or made plans to install Q-Alpha systems in their aircraft or simulators include CommScope for its Challenger 350s; Porter Airlines and its Q400 turboprops; Textron Aviation, which is working with FlightSafety to add Q-Alpha to the FlightSafety Citation CJ3 simulator in Wichita; Viking Air and its CL415 waterbomber; and other simulators such as the G550, King Air, and Simcom and Precision Flight Controls devices. Q-Alpha has also been tested in a Boeing 737 simulator and in a single-engine Cessna 182RG.
Because Q-Alpha supplements and doesn’t replace any existing stall-warning or low-airspeed alerting systems, Skow doesn’t see any major certification hurdles. Q-Alpha just needs data from the aircraft’s 429 bus. Retrofit to a typical business jet would take from two to six hours.