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How The Red Bull Air Race uses telemetry to judge pilots and conjure ghost planes

Since the dawn of the running shoe, technology has played a key role in the evolution of sports, with perhaps no greater synergy between tech and athletics than the fusion of human and machine found in motorsports. The Red Bull Air Race World Championship represents the pinnacle example of this, where technology isn’t just critical to how the planes are engineered, but also to how the competitors are judged, how spectators watch the event, and how pilots safely return to the ground.

Each plane is equipped with an electronic flight instrument system, or EFIS, that communicates telemetry data to judges, technicians, and camera operators on the ground. Since the sport’s return in 2014 after a three-year hiatus for safety improvements, Álvaro Paz Navas Modroño has been the person in charge of overseeing installation and operation of the EFIS devices. The telemetry data helps ensure pilots fly within the rules as they try to push their lightweight planes to the limit.

As Sport Technical Manager, Navas travels with the Red Bull Air Race to each race – a global journey that this year will take him from Abu Dhabi to Indianapolis with six additional stops in between. Before joining Red Bull Air Race, he worked for the company that supplies the EFIS units and even spent time designing autopilot systems for unmanned aerial vehicles (UAVs). In short, he knows what he is talking about. Digital Trends recently spoke with him about how the Red Bull Air Race uses telemetry data for judging and entertainment, a conversation that just about left our heads spinning.

Unlike car racing, judging air racing is much more complicated. Even the seemingly simple task of timing competitors requires a much more complex solution. The usual setup with cars involves a transponder in the vehicle that triggers a signal on an underground cable at the timing splits and finish line, a system that provides very accurate times.

“We can’t use transponders because the planes can fly at different attitudes, so the triggering signal would not be sharp enough, thus lowering the accuracy,” Navas explained. “We use line scans based on laser technology and custom photo finish cameras that capture up to 10,000 frames per second.”

But timing is only one part of the equation. Like auto racing, it’s possible to incur penalties in air racing that will see judges tack on a second or two to a pilot’s time. The rules are unique to air racing and so nuanced that they can only be enforced with accurate telemetry data, as being able to visually confirm compliance would be impossible to do in real time. For example, the incorrect level rule states that planes must pass through the gates with their wings within 10 degrees of level. Even monitoring that a pilot stays within course boundaries requires accurate GPS positioning data – an important task as crossing over the safety line results in an immediate disqualification (DQ).

But perhaps the most interesting rule is the one limiting G-force. Pilots are allowed to pull up to 12G in a high-speed turn, but anything above 10G can only be held for 0.6 seconds. If a pilot holds it any longer, or goes past 12G at all, then it’s a “Did Not Finish (DNF).”

For those unfamiliar with the concept, one G is equal to the force of earth’s gravitational pull. If you weigh 180 pounds at one G, you will feel like you weigh 1,800 pounds at 10G.

Like a video game, fans can see pilots compete against a “ghost plane” of the leader.

It is beyond us why anyone would want to sustain a turn above 10G for any length of time, but it is just another aspect of racing for the Red Bull Air Race pilots. The reasons for the hard 12G limit rule are simple: It’s all about safety. Extreme G-forces aren’t just hard on the human body, they could even compromise the aircraft.

As Navas explained, “10G is a soft limit based on the structure of the wing. Anything over 10G but under 12G has a strict time limit of 0.6 seconds to ensure the structure is not compromised. If a pilot exceeds 12G he or she receives a DNF and the structure of the aircraft must be thoroughly checked before they can fly again.”

The EFIS provides everything the judges need in order to monitor a given flight. Data on the plane’s attitude (pitch, yaw, and roll), speed, G forces, and position in three-dimensional space is transmitted in real-time back to the race venue. This helps keep the competition fair, honest, and, most importantly, safe.

But all of that telemetry data is also used to make the sport more audience-friendly and exciting to watch. Just like in a video game, fans can see pilots compete against a “ghost plane” of the leader, recreated from saved telemetry data and overlaid on the video monitors in real time.

To make this all function properly, “there’s a lot of technology and work not only on the plane, but also on the cameras,” Navas said. While the event is covered by numerous angles, including onboard cameras in the planes, the ghost plane can only be inserted into the video feeds from two specific cameras on the ground, called “Virtual Cameras.” These cameras have special equipment to track their own telemetry (in this case, position, pan, tilt, and zoom). Camera operators can also see the ghost plane in their monitors, and with the combined telemetry data of the plane and the video, any camera movement will affect the position of the ghost plane within the frame. This allows operators to zoom out or adjust their panning speed to keep both the ghost plane and the active racing plane in the shot together.

Extreme G-forces aren’t just hard on the human body, they could even compromise the aircraft.

If this sounds incredibly complex, that’s because it is. Navas and the technical teams he supervises show up seven days before the race to begin setting up and testing the EFIS and related systems. Over the years, experience has led to the inclusion of redundant systems, with each plane now carrying a secondary sensor box that acts as a backup in case the main one fails. The backup isn’t suitable for use in the ghost plane system, but it is still accurate enough to be used for judging.

“Before that, if any telemetry system failed, we just didn’t have the possibility to judge one of the guys,” Navas said. Now, if the main unit fails, the only thing lost is the ghost plane image. He added with a short laugh, “My job has gotten a lot easier.”

Navas will next head to San Diego for the second race of the 2017 season on April 15 and 16, presumably aboard a large, relaxing airliner where he can casually sip a drink without worrying about suddenly banking into a sustained 10G turn.