Speed Secrets of the Red Bull Air Race

The voice of Red Bull Air Race director Jimmy DiMatteo over the loudspeakers entices the crowds to crane their necks skyward, their eyes tracking a small racing airplane pointing its nose toward the inflatable starting Air Gate. A white line of smoke appears behind the airplane, indicating its twisting track around the highly technical course. In the span of about a minute, the airplane goes through a chicane slalom segment, vertical turns comprising half Cuban eights to bring it back into the course, and several Air Gates (two parallel pylons through which the airplane has to fly, wings level, at a specified height). The pilot is not just fighting for the win in this race. They are also pining for points toward the ultimate prize — standing atop the podium of the Red Bull Air Race World Championship — based on the annual points accumulation of eight races at scenic urban locations around the world. When each race is over, the top 10 racers get points, ranging from 1 to 15. Whoever has earned the most points at the end of the season is crowned the champion. Each competition starts with qualifying heats, followed by competitive eliminations. In the Round of 14 and Round of 8, the faster of two paired airplanes moves on to the next round. Watching the races beside the big jumbotrons adds to the excitement; the racetrack of the paired competitor can be seen as a ghosted band with a flag indicating the racer’s nationality and whether they’re trailing or leading the pilot flying, giving an instant visual representation of who is likely to win the heat. In the Final 4 round, the fastest racer wins. The competition is fierce, and sometimes the winner and loser are separated only by a fraction of a second. To ensure accuracy, the timing is measured with laser technology accurate to 1/10,000th of a second. The Airplanes

To win, the pilot must fly a race airplane that is fast, maneuverable and reliable. Three types of aerobatic airplane designs are used in the Red Bull Air Races. The Zivko Edge 540 is flown by most of the Master Class racers. The exception in the 2017 series is Mikael Brageot, of France, who is flying MX Aircraft’s MXS-R. The Challenger Class pilots (the rookies) all fly the Extra 330LX.

Each Red Bull Air Race pilot works closely with a team, much like a pit crew in Formula One racing. The teams spend the winter season modifying the airplanes. Pablo Branco, Mike Goulian’s team manager, walked me around Goulian’s race plane, explaining some of the mods the team made this year. The engine cowling was streamlined and sculpted to provide better cooling for the engine. New winglets were added to improve aerodynamics. The airplane also has “shark skin” adhesives on the upper surface of the wings, which help reduce drag.

Through various mods, about 18 pounds were removed from Goulian’s airplane this winter, Branco said, partially by drilling holes in nonstructural parts. Those 18 pounds may not seem like much, but with margins as slim as they are in the Red Bull Air Races, every pound counts. The rules require the gross weight of the airplanes to be at least 1,535 pounds. But where the weight is located matters too.

“The way the rules are written, there is a minimum race weight. But there is no minimum pilot weight,” said Paulo Iscold, race engineer and team tactician for Kirby Chambliss, who is by far the tallest race pilot in the competition. “We have the lightest airplane and the heaviest pilot. If the pilot is small, they can put more equipment on the airplane and put ballast to move the [center of gravity]. We cannot afford that at all, and that’s bad for us.”

Sometimes, modifications can have unintended effects too. The tail of Chambliss’ airplane was modified last year. “They said they’re going to take two-thirds of the stabilizer off. The whole thing about a stabilizer is to keep it stable,” Chambliss joked. “It was like Mr. Toad’s wild ride in there.”

When the Red Bull Air Races first began in 2003, the heats were very much like Mr. Toad’s wild ride. “It was all seat-of-the-pants flying back then,” Chambliss said. Essentially, the pilot who flew the craziest lap would win. “Run the airplane straight down, pull as many Gs as you want, fly as fast as you want to go, go as low as you want to go. Several times some guys almost hit the ground.” In 2010, it happened. Brazilian pilot Adilson Kindlemann hit the Swan River in Perth, Australia, flipping his race plane over in the water. With the help of a swift rescue team, Kindlemann survived. But the accident was the catalyst for a new set of rules to make the Red Bull Air Races safer.

The rules begin at the starting Air Gate with a 200-knot speed limit, beyond which the pilot will incur a penalty or be disqualified. If the pilot flies too fast or too tight through the course, there is also a good chance that the airplane will be pushed beyond the load factor limits, which will also result in disqualification (past 12 Gs, or past 10 Gs for more than 0.6 second), or hit a pylon (a three-second penalty for each). So in addition to designing a fast airplane, the team must focus on finding the best line that will allow the pilot to fly the fastest lap time without breaking the rules or hitting a pylon.

Each Red Bull Air Race course is different depending on the location. All the courses have Air Gates, a chicane and vertical turns. But there are always differences in the track, based on the location. After Red Bull designs the course, a simulator is used to make sure it can be flown safely. Then Red Bull sends the course to the teams, and the work begins.

In 2008, Iscold started designing software to find the fastest line. Today, all of the teams use some form of software to provide their pilots with the optimal track and trajectory through the course, but each team’s software is different. The data is very detailed, said Branco: angles through gates, speeds, bank angles, load factors and so on for each segment of the course. While the optimal line from the software Branco uses takes into consideration the aerodynamics of the airplane, human factors are not part of the equation, so modifications have to be made to make sure the planned course is actually flyable. “We all go through it about 1,000 times before we get to the race,” Branco said. “Preparation leading into the race is very important.”

Also, the computer’s data can get too in depth: where to pull, how much, the exact angle of bank and pitch, and so forth. “To present that information is not always very useful,” Branco said. “It has to be super fluid.” Simple information, such as “you should be pointing to the pier” or “you should be pointing to the bridge,” for each segment of the course is more helpful.

Race pilots are given just three practice sessions — each is two to three laps — before the qualifying heats begin. Various strategies discussed before the team arrives at the location are explored in these rounds. With each lap being about one minute long, the pilot gets only about 10 minutes of practice. Every second counts.

Each airplane is equipped with an EFIS, custom made for Red Bull Air Races. The units were installed to help the audience track the action instantly, and to ensure the accuracy of the penalty-incurring parameters. The data also allows the teams to make further analyses and plans for the pilot.

The proprietary software that Iscold developed to analyze these flights records pages’ worth of data and produces color-coded graphs and flight tracks. Iscold can click on points on the graphs to see what the pilot did during each second of the flight, and what the results were. He looks at parameters as varied as oil-pressure changes, load factors, bank and pitch angles, acceleration and much more.

The data is analyzed and compared with the optimal course track to determine what parameter needs to be adjusted. “The problem is, I have all of these numbers that I need to translate to Kirby, and he has no instrument to follow,” said Iscold. “There is no flight director. It’s all muscle memory. And we are really looking at details.” It’s also very challenging for a pilot to make one minor adjustment without changing other components of the flight. That, Iscold said, is one ability that set apart Paul Bonhomme, the most successful race pilot in the Red Bull Air Race World Championship to date.

Iscold presented an example of how the software helped him guide Bonhomme to greater results before his retirement in 2015. The graph that shows the control deflection had a slightly squiggly section. This indicated Bonhomme was pitching up and down ever so slightly in the vertical turn, bleeding off his speed. Iscold told him to hold the stick steady, an adjustment that was one component that helped make the difference between winning and losing.

“It’s all about this relationship between professionals in different areas trying to achieve the same goal with different skills and different terminology and different ways to express. Sometimes I’m an engineer, and sometimes I’m a psychologist,” Iscold said. “Sometimes I see a mistake in a flight and I know it’s better to keep quiet. It may become a distraction.”

And no matter how much data is analyzed, how good the communication is and how perfectly the pilot follows the plan, there is always an unpredictable element of excitement in the Red Bull Air Races. With the inflatable pylons, the course is a living entity in itself, particularly when the race takes place over water.

“It’s never the same course,” said Chambliss. “It’s always changing. The winds are changing it, the tides are changing it. So there is always some portion of luck.”

The Air Gates that the racers fly through have two inflatable pylons. The inside of each is straight, and the nonflying side is angled for stability.

The pylons are designed with material that is strong enough to hold them upright, but breakable to prevent damage to the airplanes when they hit the pylons — an inevitable event. However, in the early days of the races, the breakable material would sometimes get stuck on the wings or the horizontal or vertical stabilizers, creating a flight hazard. Also, the early pylons took about 20 minutes to erect.

With pylon hits being frequent events during the races, a new construction was required. Today’s pylons are 82 feet tall and built in nine sections connected with zippers. The bottom segments are made of a thick plastic material for structural support. The top sections — the red flight window — are made of an extremely thin spinnaker sail material, which is 40 percent lighter than paper for the same amount of material. The spinnaker material is very strong, but will rip immediately if hit by an airplane, creating no damage to the plane itself other than some red badges of shame in the paint around the wingtips.

A damaged section can be replaced by an experienced Airgator in about 90 seconds by zippering in a new piece.

Pylons are held erect by differential pressure produced by a gas-powered engine and a big fan at the bottom of the structure. An electronic system monitors the pressure inside and outside, and compares it to the revolutions per minute of the fan engine to ensure the pylon remains erect. The pressure differential makes the pylon shatter as soon as a wingtip breaks the material, and the pylon collapses in 10 to 15 seconds.

Paulo Iscold is a talented engineer who, together with his students at the Federal University of Minas Gerais in Belo Horizonte, Brazil, designed several record-breaking airplanes, including the CEA-311 Anequim, which shattered multiple FAI records for speed and altitude in 2015 (see story in the January 2016 issue of Flying). In 2010, Iscold set off to help Paul Bonhomme and his team find the best lines in the Red Bull Air Race World Championship tracks.

Using his proprietary software and his ability to communicate the required changes, Iscold had such great success that he was referred to as "Bonhomme's secret weapon." Today, Iscold works in the same capacity with Kirby Chambliss' team.