It's not hard to miss the vivid yellow of The Breitling Racing Team's MXS-R, as it carves, rolls and speeds its way through the racetrack. But Nigel Lamb's race plane – one of two MXS-Rs flown in the Red Bull Air Race World Championship – is also easily distinguished from the pack, thanks to a pair of sizeable glossy black winglets that give the plane its distinctive shape.
Lamb's winglets are clearly the largest of any airframe modifications sported by the twelve planes in the Red Bull Air Race World Championship. So we caught up with the British ace to find out more about the reasoning, design and science behind his iconic plane modifications.
The winglets are an iconic feature of your MXS-R, so let's start with the basics – what is the fundamental function of the winglets?
NL: The main objective of the winglets is to reduce induced drag – the drag produced by creating lift. The more lift you produce, the greater the drag. A vortex is created at the wingtips by the differential in pressure below and above the wing; the higher pressure under the wing will flow towards the lower pressure above the wing. Since we're often turning at very high Gs near the maximum performance of the wing, we're generating massive vortices.
When the atmospheric conditions are right you see these vortices coming from the tips of airliners and other places on the wing, especially on take-off and landing. That's why modern airliners have winglets – to save fuel, increase range and reduce the cost to us passengers!
In the Red Bull Air Race World Championship, you've got lots of high G, so if you can come out of a turn quicker, then you gain the advantage.
What does that mean in terms of efficiency for your MXS-R?
NL: The winglets definitely increase the roll rate by controlling the airflow and making the end of the ailerons more efficient. In comparison to our other preferred wingtip option, our winglets also have the benefit of reducing the wingspan by a few inches each side.
Can you quantify the positive effects of the wingtips in any way – for instance, do they decrease lap times by a certain amount?
NL: Because we race on a three-dimensional, invisible track, it is very hard to measure or quantify the effects of modifications. The roll rate is easy to measure with a high-speed camera, and the benefit is around +5%. The top speed is unaffected. We haven't managed to measure any reduction in induced drag. But every time I take a gate at an angle and don't hit a pylon, it could be argued that this was as a result of the slightly reduced wingspan!
Aside from the increase in weight, are there any other disadvantages to using winglets, or can they negatively affect racing in any way?
NL: The only disadvantage I'm sure about is the increase in weight. That said, it wasn't a factor before 2014, because of the previous Red Bull Air Race World Championship regulations. The MXS was under the minimum weight so the winglets initially took the place of some lead weight we had to add to be race legal. Now I have to accept the added 5kg and hope that the aerodynamic benefits outweigh the disadvantage.
The size and shape of the winglets obviously vary from plane to plane. How do you make the perfect winglet for your plane?
NL: You ask an expert like Dr Mark Maughmer [Professor of Aerospace Engineering at Pennsylvania State University] to design them for you! Once Mark had finalised the shape, they were designed by Airboss, the MXS wing designer and then the moulds and components were made in Oregon by Composites Universal. These were then shipped to England where Nigel Huxtable [Breitling Racing Team technician] undertook the painstaking task of the final fit to our particular MXS. In all, it took 18 months from the drawing board to passing the pylon impact tests, and being approved into the Red Bull Air Race World Championship.
Are the winglets easily changed or modified throughout the racing season?
NL: We can easily remove the large winglets and replace them with a variety of smaller winglets that we have. Changing the shape and design of the winglets would mean starting from scratch. It being an incredibly time-consuming and expensive process, we will not change them unless we know there is a better design that would significantly save time on the track.
See Lamb's MXS-R in action at the next stop of the Red Bull Air Race in Rovinj, Croatia, between 12 and 13 April 2014. Tickets are on sale now via http://www.redbullairrace.com