On a tractor for towing aeroplanes the engine is controlled by the accelerator via a governor in such a way that when accelerating the increase in the tractive force exerted by the tractor on the nose undercarriage unit of the aeroplane is limited. The increase in tractive force is regulated as a function of the increase in the engine speed and/or the acceleration of the vehicle. The latter can be detected by means of speed measurements on all vehicle wheels, averaging and differentiation.
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