ESDU 99016:2010

INTRODUCTION

This Data Item is the first of a series of examples of the
application of a method for representing – and, if necessary,
relating – the braking performances of aircraft and ground-test
machines in wet conditions. The method, which is given in Reference
4, is essentially statistical and implies that there is a
clearly-defined level of probability that can be deduced from test
runs of an aircraft (or ground-test machine) in a given set of
wetness conditions on a particular runway. If the runway
macro-texture depth is known, then the parameter that defines the
variation of effective coefficient of braking friction in the given
conditions can be readily calculated from a pre-determined
Friction Data Base. The concept of a Friction Data Base is
explained in Reference 4.

Test data, taken from Reference 1 for a Boeing 727-100QC
aircraft, are used to illustrate, by example, the process of
establishing a Friction Data Base for that aircraft. The background
to those tests is described in Section 3. The method of analysis is
summarised and results are presented in Section 4.

A second example, for an aircraft where only a limited data set
is available, is given in Reference 5. An example of the
application of the method to ground-test machine data is given in
Reference 6. Many other examples are considered in Reference 3.

If the method of Reference 4 is to be used to relate
the braking performances of a given combination of aircraft and
ground-test machine, the procedure is comprised of two distinct
phases. The first is the establishment of separate Friction
Data Bases for the aircraft and for the ground-test machine.
The second is the prediction of operational braking performance of
the aircraft using day-to-day measurements from the ground-test
machine.