ANOTHER FLYING LMP MIRACULOUS ESCAPE

Too bad one cannot actually see where the incident begins. By the time it enters the frame, it's already well into the "negative downforce" mode. No question that the flat bottoms present a problem in that once they catch a bit of air at high speed, it's all over. Gene was indeed lucky, as was Ortelli. The next person might not be.

 

From Mulsanne's Corner -

http://www.mulsannescorner.com/newsmay08.html

“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!

 

IMO this incident is quite a bit different than the LeMans flip or the Road Atlanta flip. Both of those incidents happened while the cars were driving straight ahead, with downforce being generated. This incident isn't that unique as it appears it spun, then while sideways with NO aero being generated, went airborne. You don't need a flat bottom car to do that. You see it frequently enough in nascar.

 

I would sort of agree with you PDX Tifosi. The car did not lift off the ground due to air getting under the front of the car, as in the LeMans/Road Atlanta crashes. However, after the car spun it caught air under it going sideways, and nearly flipped (it probably would have if it hadn't hit the catch fence first!). It actually reminds me of a crash Buddy Rice had in the IRL several years back.


http://www.youtube.com/watch?v=iIeInth3CQY

 

+a sideways 8 (how do you do the infinity symbol?)

 

Agreed, once these cars get sideways you can kiss virtually all the downforce goodby. Those who have driven a proper aero car, even a lowly Formula 2000 like myself, realize that during a turn you rely on the finely tuned/balanced aero you set for the track during the event/testing so you may get the most from the car. Naturally once the car is sideways are you lose the aero downforce, and usually as a result the mechanical grip, it is 'game over'. Thanks goodness for advancements in crash safety built into the car, HANS, etc. It is amazing how fast you can go from being on that fine edge going fast around a corner to set a record time to sideways and 'out of control'. Racing drivers are truly an amazingly talented group of people.

 

Thanx for the vid!

Also

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