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AERODYNAMIC INSTABILITY OF SPORTSCARS AT ABNORMAL YAW ANGLES
New research commissioned by the FIA has revealed that the current design of cars running under
sportscar and ‘sport prototype’ regulations exhibit aerodynamic characteristics that can cause them
to leave the ground and possibly invert, when they run at yaw attitudes greater than approximately
±30º, even at speeds well below their maximum (see Editors’ Note).
Exceeding the critical yaw attitude is only likely if a driver has lost control of a car. Adverse pitch
and roll attitudes, resulting from mechanical failure or external disturbance, accentuate these
characteristics and lower the speed at which take off can occur.
When a car leaves the ground, it is unable to engage effectively with the circuit safety features
such as run-off areas and barriers. If a car lands inverted, the safety of the driver depends on the
ability of the roll-over protection to withstand the forces involved.
Further research is now being conducted in order to reduce or eliminate this phenomenon.
Pending the outcome of this research and possible new technical regulations, the FIA recommends
that all competitors and organisers involved with sportscar, ‘sport prototype’ and similar
competition cars take the following minimum precautions:
1. Organisers should ensure that all spectators are sufficiently far from the circuit at any given
point to be in no danger from an airborne car, having regard to the speeds of the cars at the
relevant part of the circuit.
2. In collaboration with the constructors of their cars, competitors should reinforce the car’s rollover
structure so that it at least meets the latest proposals which have been issued as a draft
regulation for 1.1.2003.
3. Organisers should ensure that all marshals and other race personnel working in close proximity
to cars travelling at speeds greater than 150 kph are suitably protected.
4. Organisers should take measures to slow the cars at any part of a circuit which would be
particularly dangerous for competitors, track workers or members of the public in the event of a
car becoming airborne.
Editors’ Note:
Sportscars normally run at yaw angles of less than ±10º. The yaw angle is the angle of the airflow
relative to the heading (direction of travel) of the car. The problem that has been identified occurs
once the driver has lost control of the car and starts to spin. It is different to the problem
experienced by Mercedes at Le Mans in 1999, in which the cars took-off while running under
normal conditions. Following those incidents, the FIA instigated circuit modifications and made
changes to the Sportscar Technical Regulations. The 1999 problem has not reoccurred.
Funding for the new research was provided by the FIA Foundation.
Paris, 24 May 2002