Mads Østberg interview and aerodynamics in a WRC jump

Colin’s crest in Sweden, Micky’s jump in Sardinia, Fafe in Portugal or El Brinco in Mexico, are some of the most famous jumps WRC drivers face every year. And, on top of them, the Rally of Finland with hundreds of jumps, crowned by the most famous, the Yellow House jump in Ouninpohja stage.

With the aerodynamics of the new generation cars, jumping becomes even more delicate, and how WRC drivers face jumps becomes crucial to avoid unbalancing the car, which could easily make it nose down or even overturn during landing.

To understand how they do manage to do it, WRCWINGS contacted the driver who has proven to better master jumps in recent years, while achieving the longest jumps, Mads Østberg, who gently answered our questions and gave some interesting clues to understand the dynamics of a WRC car during a jump. Here is the exclusive interview we made to Mads after wining (once again) the Colin’s Crest Award 2018 in Sweden.

mads jumping by richard simpsonpicture by Richard Simpson

M.Østberg/T.Eriksen, Citroën C3 WRC, Rally of Sweden 2018, 6th

WRCWINGS (W.): Mads, facing a jump with a car with a weight distribution around 60/40 it does not have to be easy.

MADS ØSTBERG (M.Ø.) Car weight distribution is more like 53/47, so jumping balance is not bad.

W. Then, how do you face a jump? Do you brake before at any time to adjust car balance?

M.Ø. Sometimes you brake before a jump to reduce speed, but you need to have the car in a neutral position before take off, so get off the brakes in time for the jump.

jan_65picture by Jakub Nazim

M.Østberg/O.Fløene, Ford Fiesta WRC, Rally Italia Sardegna, 7th

W. Is there anything you can do during the flight, to better re-undertake the stage?

M.Ø. Throttle can be used to control the angle of the car in the air. If you touch the brake in the air, the front will dive and you’re likely to crash

W. Your jumps are always very long, do you study/preview where you are going to land and prepare the car accordingly?

M.Ø. Nothing more than normal preparation with recce and pacenote work.

W. Any difference between jumps on gravel versus on snow roads?

M.Ø. Not really. But tarmac is quite different. You have smaller margins to control the car. The direction you land is the direction the car is going. On loose surface there is always room to land a bit sideways.

W. One last question: in Rally of Sweden 2017, you lost your rear wing and continued for several stages. I understand you lost many grip on the rear axis. How did it affect the car in the jumps, and how did you face it?

M.Ø. It was impossible to jump with the car. With no downforce at the rear, the car was diving, so I had to avoid jumping.

mads sweden no rear wing bogdan barabas.jpgpicture by Bogdan Barabas

M.Østberg/O.Fløene, Ford Fiesta WRC, Rally of Sweden 2017, 15th – car with no rear wing

Mads’ approach is very similar to that reported by Andreas Mikkelsen, Jari Matti Latvala or Tommi Makinen in previous interviews (see references at the end of the post). They all brake first and then full throttle, to start jumping with a balanced car….although Latvala reverse the process if the jump is small: he goes full throttle and then a little bit of brake. In all cases, goal is to start the jump with a car in a neutral position, that is, balanced.

But what really happens during a jump? Let’s analyse it by distinguishing between take-off, flight and landing.

  1. Take-off

In a jump, the car reaches the crest of the hill and, due to its inertia, instead of following the road contour, it takes-off. Depending on the actions taken by the driver before the crest, the car angle of incidence will change, and the consequence is a car taking-off in a balanced position, nosing down or nosing up. Why is that?

When the car is accelerating, angle is positive (at values around 5°). It has an effect on downforce generation: allowing more air to flow below the car, which makes it flow slower, results in a pressure increase that reduces downforce generated.

mads accelerating nuno dinis anglepicture by Nuno Dinis

M.Østberg/O.Fløene, Ford Fiesta WRC, Rally of Portugal 2017, 8th – car accelerating

If the car reaches the top of the crest at full acceleration, it will probably take-off nosing up, which is not bad, unless angle is too big.

AUTOMOBILE: WRC Finland - WRC -26/07/2017picture by Michelin

M.Østberg/T.Eriksen, Ford Fiesta WRC, Rally of Finland 2017, 10th

On the contrary, when the car is braking, the angle of incidence is negative (up to -5º), and also downforce is impacted: less flow enters below the car, allowing the air to flow faster. According to Bernouilli, this reduces pressure below the car, and by pressure difference, downforce is higher, in spite of the lower speed of the car.

mads catalunya 2017

M.Østberg/T.Eriksen, Ford Fiesta WRC, Catalunya Rally 2017, 5th -car braking

A car braking close to the top of the hill can easily take-off in a nose-down position, and the consequence can be an impact of the front of the car when landing.

AUTOMOBILE: WRC SWEDEN - WRC -09/02/2017picture by Michelin

T.Neuville/N.Gilsoul, Hyundai i20 Coupé WRC, Rally of Sweden 2017, 13th

But, if controlled, it can be helpful, in case there is a turn or a braking point right after the jump. Andreas Mikkelsen uses this technique to get the front wheels first on the ground, so he can start braking from the first moment the car hits the ground.

In any case, an aerodynamically balanced car will have more tendency to take-off in a neutral position, allowing the driver to better manage flight and landing, so best option seems to be to reach the top of the crest at high, stable speed. Although high self confidence and confidence on the car also helps, as Jari Matti Latvala appoints.

2. Flight

Taking-off results in a momentary loss of downforce, as the car separates from the ground, and underbody aerodynamics stop working. But the aero devices of the car will keep working during the flight, pushing it down, while the car describes an arch until it hits the ground again.

For the new WRC car generation, their bigger aero devices represent a bigger limitation on its flying capabilities, which is only compensated by the higher speed they are able to reach. In any case, if the car is aerodinamically balanced, it is more easy to keep it balanced during the flight. Or, the absence of one of these devices may turn it into an undriveable machine, as Østberg confirms from his experience in Sweden 2017, or Petter Solberg in Rally of Finland in 2004, as we already reviewed in a previous post.

mads ostberg sweden 2017 jumppicture by Bogdan Barabas

M.Østberg/O.Fløene, Ford Fiesta WRC, Rally of Sweden 2017, 15th

3. Landing

We have seen the risk of landing after taking-off with a car nosing-down. If the car is nosing up, it can help to get longer jumps. But, what if the angle is too high? Could a WRC car overturn during a jump? Evgeny Novikov almost succeeded in during Rally Finland 2009 (see video), but we have not found any report of any rally car overturning after a jump.

The main reference for comparison we found belongs to Sports Prototypes, and the different overturning incidents seen in the past (most famous in Le Mans 1999 with the Mercedes CLR overturning up to three times). Investigations carried out after those incidents (see references at the end of the post) reported that overturning was caused by a sudden bump, kerb or suspension failure, causing a high angle of incidence that, at such high speeds (between 200 and 300 km/h) allowed a high pressure air bundle entering below the car (with very large plan area) and leading to overturning.

In the case of WRC cars, and although undercar is also flat, velocities are not that high: a take-off speed of 152 km/h was reported at Colins Crest in 2015, while one of the top speeds ever recorded belongs to Markko Martin, when he flew up to 57 metres in the Finland’s Yellow House jump in 2003, after taking-off at 171 km/h. Also, angles of incidence are usually lower, so overturning conditions seems hardly to be met.

AUTOMOBILE: WRC Finland - WRC -26/07/2017picture by Michelin

H.Paddon/S.Marshall, Hyundai i20 Coupé WRC, Rally of Finland 2017, ret.

A third risk is to land with an unbalanced car on one side, which is normally due to irregularities in the road previous to the jump or a driver mistake in the ramp. This is one of the reasons why is so important to prepare the strategy of facing a jump during the recce, as Østberg pointed out.

hyundai portugal 2017picture by Michelin

H.Paddon/S.Marshall, Hyundai i20 Coupé WRC, Rally of Portugal 2017, ret.

Landing is always easier if the car is balanced during the jump…and suspension is stiff enough to absorb the impact, avoiding the car hitting the ground, as M-Sport engineer Mathieu Horsky confirms. And even more important with the new WRC generation, as a bad landing can damage some of the aero devices (easily the front splitter or the rear diffuser), with a significant impact on car performance for the rest of the stage.

Length of jumps has not been reduced with current WRC cars versus previous generation: Colin’s crest record was set by Eyvind Brynildsen in 2016 (with a Ford Fiesta R5!) at 45 m, while in 2017 max distance was achieved by Mads Østberg with the Ford Fiesta WRC at 44 m, and he also jumped 42 m in 2018 at the wheel of a Citroën C3 WRC.

The distance reached depends both on car balance and speed. Some drivers, like Tommi Makinen, prefer to shorten jumps, in order not to lose speed (car is slower when flying due to no traction) and due to risk of damaging the car after longer jumps. But it is undeniable that the images of WRC long jumps keep attracting thousands of spectators every year. Jump competitions in different rallyes have found a gap apart from pure rally competition, representing an extra motivation for most of the drivers, while giving incredible images for the pleasure of spectators, drivers and WRC promoters.

mads portugal 2017 jump.jpgpicture by Gonzalo Belay

M.Østberg/O.Fløene, Ford Fiesta WRC, Rally of Portugal 2017, 8th

This post includes opinions of the author, which are certainly not always right. If you detect any error or you disagree, do not hesitate to contact us, by sending an email to wrcwings@gmail.com. We love to learn!

References

Andreas Mikkelsen interview.

Tommi Makinen comments – Magazine l’Automobile, supplement of Nr. 635, Mai 1999.

Article on Rally Finland jumps.

We have lift off (again…), Simon Mcbeath, Racecar Engineering, Vol. 18, No 12, December 2008.

The aerodynamic stability of a Le Mans prototype race car under off-design pitch conditions, R.G.Dominy, A.Ryan, D.B. Sims-Williams, SAE Transactions 2000 Journal of Passenger Cars: Mechanical Systems, V109-6, DOI.

Mads Østberg Rally Finland 2017 jumps videos.

Videos of 10 of the craziest WRC jumps ever.

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