There are many variables in the world of motorsport. Most of these can be controlled or corrected by the pilot or a team member, but the one thing that nobody has any say over is the weather.
The raceplanes in the Red Bull Air Race have high-powered, six-cylinder Lycoming engines. These power plants are hardwearing and produce 315bhp, but differing meteorological conditions will greatly affect how the engines perform.
In Abu Dhabi this year, pilots found that due to the high temperatures and hot ambient air their aircraft were down on power, especially towards the end of their run. With the Red Bull Air Race visiting seven countries over three continents, there is a high chance that the raceplanes will have to perform in a variety of weather conditions.
Eckhard Möhle, the Red Bull Air Race's Technical Director explains what conditions offer the engine the most power. "Climate conditions affect engine performance," explained Möhle. "It's the same with a jogger or athlete. Running in high temperatures, at low density (meaning high altitude), in rain is not what you want. A clear, cool day close to sea level is what you need for good running. The best place for a race would be at one of the Poles. Perfect for the engine, but probably not for the pilot," joked Möhle.
The benefit of cold air is that it's dense and carries more oxygen. More oxygen going in the engine means the fuel will burn better giving more power. Each race location will offer different conditions, so the technicians will have to work out the fuel and air mixture for the climate. "A good calculation of what climate conditions the techs will have at a certain racetrack is the 'density altitude'. This calculates the real/actual altitude at the present weather situation," said Möhle.
The technicians will have to make sure they're bringing enough air through the air-cooled engine and oil cooler. "It's very important. The engine not only needs enough cool air to be sucked in, it also needs to get the air out pretty fast as well. Optimising the airflow over the cylinders and the oil cooler is a different challenge for every track and climate.
"Of course, a good basic setting helps a lot, but there are plenty of tweaks that need to be made at the top level. An example is Hannes Arch's cowling that he tested in 2014. It had been well optimised for straight and level flight on a computer, but it didn't work all the time in the 'real world,'" explained Möhle.
It's not just the engine that's affected by the weather, the entire raceplane's flying ability is altered by the conditions. "It's very similar to the ideal conditions for the engine," said Möhle. "Dense air offers better manoeuvrability for the aircraft but will produce more drag. So, like always, somewhere in the middle is the best condition.
"Every aircraft is developed under certain circumstances and will perform best under those conditions. Of course they will be similar, but every raceplane has its optimal condition – like in every motorsport."