It's happening again... Peugot 908 flip

[JasonDTM]

Wooooow, you'd think after the Mercedes, the 911 GT1 98, BMW LMR, Courage Oreca Judd, and the Mcnish Audi R10, you'd think the ACO would have done another in depth study on why the cars are doing this.

Stephane Ortelli is okay.

[Jim Richards]

That car was side ways and slightly ass-backwards before lift off.

[Jeff Higgins]

Looks like it got sideways first. I do remember seeing some articles in the various mags about taking steps to reduce lift under these conditions; i.e. when the relative wind is not coming under the front of the car. They do realize there is a problem, and have taken some measures to correct that problem. It also looks as though it may have hit the grass, and possibly a berm, while going sideways, but it's unclear from the film. If that's the case, even a 3400 pound NASCAR brick can kite up and flip like that. I would like to know more about what happened here before deciding it's an aero problem.

[URY914]

Time to wave the white flag and give up on that car.

[masraum]

Originally Posted by JasonDTM

Wooooow, you'd think after the Mercedes, the 911 GT1 98, BMW LMR, Courage Oreca Judd, and the Mcnish Audi R10, you'd think the ACO would have done another in depth study on why the cars are doing this.

Stephane Ortelli is okay.

Yeah, not really the same thing. Well, technically, it's the same thing that causes them to go airborne, but a car going airborne when going straight and forward is a little different than one doing it when going sideways. Nascar had a problem with this. They made some changes to the cars to try to ameloriate the issue. They put flaps in the rooves of the cars, and made some other changes to try to keep the air from getting under the cars when they go broadside.

[legion]

I've always been surprised that something like NASCAR's roof flaps have not been adopted by other forms of motorsports. They are passively activated, and do not interfere with the car's aerodynamics when they are not deployed.

[Jim Richards]

Originally Posted by legion

I've always been surprised that something like NASCAR's roof flaps have not been adopted by other forms of motorsports. They are passively activated, and do not interfere with the car's aerodynamics when they are not deployed.

+1

Maybe it's the not invented here syndrome.

[JasonDTM]

Here's a nice article about it from RacecarEngineering

Originally Posted by Mike Fuller

“There is not a problem until something unusual happens and than it seems there is too often a problem. That is particularly a problem when high speeds are involved and of course here that is very often the case. It should certainly be looked at very carefully.” That’s how Hugues de Chaunac assessed the events that led up to Stefan Ortelli’s rather horrific accident at the Monza Le Mans Series round. Ortelli’s Courage-Oreca LC70 shot off the track in the braking zone for the first chicane and became airborne, narrowly missing Alan McNish’s Audi as the Oreca-Courage careened back onto the track and started a series of barrel rolls. In addition to Ortelli’s accident, Rinaldo Capello’s Audi R10 nearly rolled over when the car became sideways while avoiding the Rollcentre Pescarolo on track. The roll angle was so lurid that damage was inevitable and subsequent repairs cost the second Audi any shot at victory.

As a result, many are asking this question, how is it that these types of incidents are still occurring given the 2004 LMP regulations were designed to address the issues of downforce loss at high yaw angles? Indeed, but the 2002 FIA commissioned Piper study seems to have produced a vehicle who’s critical take off speed is much reduced, especially compared to the 2002 baseline. But perhaps the "much reduced" should be emphasized? With the hindsight of the Piper Report we can see, for example, at a 180 degree yaw angle the critical take off speed was increased to more than 500 km/h by the 2004 LMP regulations (this at a 4 degree roll and 55/45mm front/rear ride height). That’s a substantial positive change given the old-rules-car would take off at 281 km/h when backwards and effectively the LMP2004 modifications have eliminated issues if a car is ever to get completely backwards. But at angles exceeding 45 degrees the critical take off speed of the new rules car is still surprisingly low going from 282 km/h to a mere 192 km/h at 90 degrees.

The common factor in these most recent incidents seems to be low downforce and high speed as the accidents have occurred at circuits that require low drag/high speed (to put it into perspective, the top speeds at Monza are sufficient for a light aircraft to take off and fly!). The Mazda-Lola Sebring incident is the lone standout. The other common factor is that none of these incidents has occurred "insitu". That is, other elements, namely the off track topography (grass, gravel traps, curbing), have come into play. In all these cases the cars in question have been launched into yaw and roll angles that are impossible to escape from due to cresting curbing. And as the cars careened off the track into the grass the tire-road friction component was eliminated therefore little speed reduction was occurring as the accidents unfolded. And as these incidents are a relationship of yaw angle to speed, if you have a way to bleed off speed in a hurry (adding a massive drag component [tire friction or aerodynamic drag] forgetting about generating downforce or reducing lift for the moment) you're in better shape than if you didn't.

And this is where the NASCAR roof flap solution comes up, though ultimately this solution is vastly more complicated for road racing cars as they tend to turn left and right. How do you devise a system that is so sensitive to note when a slid is just a slid versus truly getting it all wrong? The situation is further complicated by the fact that stock cars tend to be at their worst when facing backwards, they are generating more lift than car weight at yaw angles of 180 degrees. So the roof flaps are designed to deploy in that worse case situation. But LMPs, as they pass 45 degrees of yaw, are already in the danger zone of lift off. And then how do you homogenize it so that it will fit onto every car given that every chassis design is different? Of course this also overlooks specifics in where do you mount the flaps? Understand the yaw induced flips are a essentially case of getting aero balance all wrong (one end's generating lift, the other still generating downforce). The Piper study showed that front downforce falls off at yaw angles above 20 degrees but that rear downforce actually increases approaching 10 degrees. So if you place flaps in one area of the car (towards the rear for instance), they might only help in some incidents and hurt in others. So the flap solution, while seemingly obvious, is indeed not an easy one.

The easier solution could very well lie in looking at track design and eliminating grass verges as well as gravel traps, and reducing the heights of curbing.

In conclusion, I'm certainly not advocating that nothing be done. But it isn't a situation where the solutions are easy. All modifications to the chassis regulations need to be done with study. Simply reducing the size of the rear wings or front splitters, as some advocate, will only further complicate things (and reduce efficiency while reducing drag--so you then have a car with a higher terminal velocity yet even less downforce!). Solutions that look at major alterations to the cars need to be made in concert with the data derived from the Piper report. Hacking willy nilly isn't a scientific way to go about this and could (dare I say will) lead to further muddying the waters. But ultimately it is up to the ACO to tread in a premeditated fashion and certainly (thankfully!) not up to forum monkeys!

Adding Nascar flaps would be a hard solution to intergrate in all honesty, all of the cars aerodynamics and designs are vastly diffrent. The ACO will have to think long and hard on how to keep these cars on the ground once the reach these extreme yaw angles that induce the lift required to get these cars off the ground.

I should have kept the Mercedes, Porsche and BMW flips out of this as they were heading in a straight line.

[JasonDTM]

Here's a video of the Audi monza incident.



Same thing again.

[Jim Richards]

Good post, Jason.

[tchanson]

Originally Posted by Jim Richards

Good post, Jason.

And this is where the NASCAR roof flap solution comes up, though ultimately this solution is vastly more complicated for road racing cars as they tend to turn left and right.

+1. Great post, Jason.

A simple flap on uniformly shaped spec cars such as the CoT all going in one basic direction would seem to not have much applicability to road racing.



Maybe the ACO should go with fuel cans and lug bolts, though...








Tim

[JasonDTM]

I didnt write the article, sorry for the confusion. It was written by Mike Fuller of Mulsannes Corner.

[legion]

NASCAR is up to what? Four road courses a year on their schedule? They run the roof flaps on those courses too...