The run-up to the annual 24 Hours of Le Mans endurance race is always a nail-biting enterprise for race teams. Naturally, techs are most concerned with assuring cars' ability to sustain the day-night race, which is the ultimate test for GT cars and sportscar prototypes that will wind through the Circuit of the Sarthe -- on a combination of racetrack and public roads -- in Le Mans, Sarthe, France. This year there's an added kink keeping teams up nights. It appears the gods of aerodynamics have been sending LeMans prototype-class racecars into the ether with a cosmic finger flick.
This past weekend, the Peugeot team lost a racecar, though thankfully not a race driver, when it spun out of control, catapulting across the tarmac during a practice session. It's is the fourth lift-induced crash among the flattish-bottomed LeMans Prototype 1 (LMP1) cars in just four weeks, according to Racecar Engineering, which reports on concern among LeMans watchers that regulations regarding underbody airflow are no longer relevant. In what is perhaps the most famous of these lift, or "blowover" accidents, a Mecedes Benz CLR-GTR went airborne in 1999. Driver Mark Webber was fortunately uninjured:
A similar fate befell Yannick Dalmas, whose Porsche 911 running in the now-defunct GT1 class during Petit le Mans 1998. Dalmas also escaped uninjured:
Considering those accidents, and other similar ones, the LeMans governing body Automobile Club de l'Ouest (ACO) in 2003 instituted new protocols that increased the critical take-off speed (the speed at which the cars' aerodynamics body profile causes lift), to prevent blowovers. As a result, no blowovers occurred until this past April, when Stefan Ortelli’s Courage-Oreca LC70 shot off the track during the Monza 1000k and went airborne, narrowly missing Alan McNish’s Audi, before barrel-rolling across the infield. He got lucky too:
But what's changed? “There is not a problem until something unusual happens, and then it seems there is too often a problem." Oreca team boss Hugues de Chaunac told Racecar Engineering. Aerodynamics engineers are constantly aiming to balance between creating enough downforce to keep cars grounded, but not so much as to require an oppressive degree of extra power and fuel consumption, especially in a race where every bit of fuel conserved is time in the bank. Racecar Engineering wonders whether the ACO will take further action to slow the cars before competitive running starts just over a week from now. Most race engineers believe it could very well be impossible to eliminate the blowover phenomenon, but it may be possible to reduce blowovers further, without causing a disruption in the sport.
[via Racecar Engineering]
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