This Data Item is the second in a series of ESDU Data Items related to the mathematical modelling of tyre-runway forces. It provides a summary of mathematical models that can be used to determine the braking forces on a single tyre that is operating on dry and water-covered runways. The models are applicable to both aircraft-type tyres and tyres from ground-test machines. Additionally, mathematical models are included for determining various relevant runway parameters.

In order to calculate decelerating forces acting on a braked tyre operating on a water-covered surface using the model, knowledge of the following variables is necessary: tyre diameter, tyre width, tyre inflation pressure, tyre ground speed, vertical load on tyre, runway surface macro-texture depth, runway surface temperature, runway micro-texture sharpness parameter, runway surface type, contaminant depth, contaminant density and slip ratio. For the case where a braked tyre is operating on a dry runway surface, all of the aforementioned variables, with the exception of the contaminant depth, contaminant density and runway surface macro-texture depth are required.

ESDU 23001, entitled 'Introduction to ESDU tyre-runway modelling', provides the rationale behind the development of the mathematical models. The development of the models is described in a series of ESDU documents which are fully referenced, as are detailed worked examples which describe the application of the models.