How software saved a stealth fighter jet—and its pilot—from crashing in Alaska

Lockheed Martin F-22A Raptor

The 2020 incident occurred in an F-22 and involved software called Auto GCAS. Plus, what to know about two additional incidents in the same aircraft type.

In June of 2020, a pilot flying an F-22 in Alaska reportedly became disoriented, and the aircraft likely would have crashed were it not for the intervention of a software system on the fighter jet. The F-22 in question had departed Joint Base Elmendorf–Richardson in Anchorage, and was operating in “Instrument Meteorological Conditions” or IMC, which is when weather and visibility require the pilot to fly using their instruments. The incident, according to a short summary of the event provided to Popular Science by the Air Force Safety Center, occurred due to the pilot’s “spatial disorientation.”

The pilot of the stealth fighter jet “was focused on their situation display and over-banked the aircraft to 135 degrees angle of bank and began to accelerate rapidly as the nose continued to fall,” the Air Force Safety Center reported.

When the aircraft was at an altitude of 13,520 feet above sea level, with its nose pointed downwards, traveling at a speed of about 600 mph, a software system onboard the aircraft “initiated an automatic fly-up” and steered the fighter jet out of its descent. The aircraft was also reportedly inverted at the time that the software activated. The plane was about 2,600 feet above the ground by the time the system had finished recovering the jet from its plunge.

The previously unreported F-22 event highlights the role of the software, called the Automatic Ground Collision Avoidance System, or Auto GCAS, and also represents the only completely confirmed save of a stealth fighter jet with this software, meaning that the pilot likely owes their life to the system.

Here’s what to know about the Auto GCAS software, the ways in which spatial disorientation can be a threat for pilots, as well as two additional incidents in F-22s that also involved the Auto GCAS system.

Auto GCAS and spatial disorientation
Auto GCAS is not on every fighter jet. It is, however, on 100 percent of active F-22s, nearly 100 percent of the F-35A models that the Air Force flies, and roughly two-thirds of F-16s, according to the Air Force Safety Center.

The F-22 is a stealth fighter jet known as the Raptor. It predates the Air Force’s more modern stealth fighter jet, the F-35. The Air Force would like to retire 33 of the Raptors, leaving 153 of them remaining in the F-22 fleet.

Lockheed Martin officially credits the software with saving 11 pilots in F-16s, and now one pilot in an F-22 due to that June 2020 event.

Spatial disorientation can happen in fighter jets, helicopters, or other aircraft if the pilot flying the machine becomes tricked by their senses. For example, the semicircular canals in a pilot’s inner ears can be fooled into “thinking motion is occurring when it’s not, or the vice-versa,” says Brian Pinkston, who is a physician with an expertise in aerospace medicine and former flight surgeon in the Air Force. A pilot in an aircraft that’s banking in bad visibility could, after a bit, stop noticing that the plane is banking because their “inner ear becomes habituated to that movement,” Pinkston says. In brief: An airplane can be gradually banking, but the pilot might not feel or notice that it’s doing so.

The way to avoid being tricked by the inner ear when visibility is poor is to rely on the aircraft’s instruments for the ground truth “every single time,” Pinkston says. “And that’s the problem—the thing in fighters is, you’re a single person, and you may have multiple inputs coming in.” With a myriad of factors to juggle, it’s still possible for a pilot to still get disoriented.

Over the Gulf of Mexico and the Pacific
Another incident in an F-22 also involved Auto GCAS and took place over the Gulf of Mexico in a Raptor that had flown out of Tyndall Air Force Base in Florida on December 6, 2016. Like with the Alaska incident, the Air Force Safety Center also attributes this event to spatial disorientation.

In this case, an alert from the software informed the pilot of trouble. The aviator in question “did not recognize a nose-low attitude while rolling to 45 degrees angle of bank and descending below 2,000 feet MSL [mean sea level] over water,” the Safety Center said. At 1,540 feet above sea level, the alert sounded in the cockpit and the pilot was able to recover the aircraft on their own, even though it had been dropping at an indicated rate of 9,400 feet per minute. The Safety Center said: “It was determined to be a save because the pilot was spatially disoriented and unaware of the altitude and attitude of the aircraft at the time of the Auto-GCAS alert and likely would have flown below the 1,000 feet floor or impacted the water without the aural warning.” The plane reached a low altitude of 1,430 above sea level.

While that incident took place more than five years ago, another one in an F-22 occured over the Pacific on March 2 of last year. The pilot, who had departed out of Marine Corps Air Station Miramar in California, was practicing basic fighter maneuvers with another aircraft. While executing a specific dogfighting move, “the pilot lost sight of the other aircraft,” according to a summary of the incident provided by the Air Force Safety Center.

From there, the pilot tried to find the other plane, but “inadvertently flew the aircraft into a nose-low acceleration toward the water,” the Safety Center said. When the aircraft was 4,520 feet over the water, with its nose angled down by 42 degrees, and traveling some 800 miles per hour, Auto GCAS took over control of the jet and righted it, according to the Safety Center. The F-22 got within 1,730 of the ocean below during the dive.

In basic fighter maneuvers like what the F-22 pilot was practicing in the March incident, “probably the most dangerous thing that the pilot has to worry about is the other aircraft, because it’s moving relative to him or her,” Pinkston observes. In this case, it was reportedly the process of searching for that other aircraft that resulted in the pilot’s dive towards the ocean below.

An incident like this one can “happen very easily,” says Cheryl Lowry, also a physician with a speciality in aerospace medicine and former flight surgeon with the Air Force. (Together, Pinkston and Lowry run a company called Kinetic Medical Consultants.) In incidents in which the “air speed is very fast, there’s a lot going on, you’re trying to watch that guy and potentially lock on him; you’re trying to navigate, you’re trying to use the radio communication equipment, and all of the distractions in the cockpit. And sometimes it’s easy to get target-fixated on that one thing, which is ok, ‘where is he? Where is he? Where is he?’”

In this case, Lowry adds, it “sounds like the Auto GCAS worked as advertised—that’s exactly what it’s for.”

A differing analysis
Of the three incidents in 2021, 2020, and 2016, defense contractor Lockheed Martin—which developed the software along with NASA and the Air Force Research Laboratory—only considers the Alaska event in 2020 to be definitely a save that is attributable to the Auto GCAS software, while the Air Force Safety Center considers all three events to be software-based saves.

The differing analysis of the events stems from a couple factors. One of them has to do with what are apparently different conclusions reached internally at the Department of Defense. In a statement, Lockheed Martin said: “Lockheed Martin’s ‘one confirmed save’ [in an F-22] number is based on guidance from DoD’s Safety department, i.e. Force Safety & Occupational Health division, which conducted an internal analysis for all three referenced incidents using available data from the resulting Class E Mishap Reports as well as pilot interviews and concluded that only the June 2020 event was an actual Auto GCAS save.”

Meanwhile, the Air Force Safety Center says that all three F-22 incidents do have the software to thank for saving the aircraft and pilot. The Safety Center said: “The Air Force Safety Center and the F-22 Program office thoroughly reviewed the three F-22 incidents and consider all three of them to be Auto-GCAS saves.”

A related reason why the analysis of the events differs is because of slightly varied ways that the software works on F-35s and F-16s as compared to F-22s. In the Raptor, the ground-collision-avoidance software “uses a minimum altitude set by the pilot as an artificial floor,” the Air Force Safety Center explained. Meanwhile, the other two jets employ a system that’s more dynamic in regards to the terrain below, allowing the “system to automatically set a recovery altitude that changes throughout a flight to ensure the aircraft does not enter a buffer zone above the terrain which prevents ground impact.”

In short, the F-22’s software employs a static “line in the sky” below which the jet shouldn’t go, whereas the software in the other aircraft allows for more variation. Lockheed Martin said in a statement: “Due to the limited availability of related Line-in-the-Sky on-board algorithm data, Lockheed Martin was unable to conduct the typical Auto GCAS analysis (as is accomplished for F-16 activations) for the referenced three F-22 incidents.”

The Air Force Safety Center also says that because of the different way the software on the F-22 functions, it “allows for more variation when interpreting whether a reported event is considered a valid save.”

The human, the machine, and trust
In the past, Auto GCAS has been credited with saving the lives of fighter pilots who have passed out while flying—here’s footage of one such event. A phenomenon called GLOC (G-induced loss of consciousness) can occur when a pilot, experiencing the pull of Gs as they maneuver, passes out because blood drains away from their brains. While both a physical exercise called the Anti-G Straining Maneuver and a piece of equipment called the G-suit on the jet can help an aviator avoid this potentially deadly problem, it still does happen.

Incidents like these highlight the complex relationship between high-performance aircraft and the relative physical fragility of the humans who pilots them; they also highlight the question of when or whether software should take over in aircraft if needed, and how much trust the pilots might have in that software, an issue that’s even been the topic of academic research.

“Things like Auto GCAS are definitely a life-saver, and will continue to advance as we look forward to newer fleets of fighter aircraft, and perfect this technology so that it continues to act as advertised, despite the growing speed and capability of our new-generation fighters,” says Lowry. “It’s not a negative that humans have to rely on systems like this—in fact it’s a testament to our ingenuity.” www.popsci.com