ESDU 99015:2010

INTRODUCTION

This Data Item provides a method for representing – and, if
necessary, relating – the braking performances of aircraft and
ground-test machines in wet conditions. The method 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.

Section 3 defines the model used to represent
wet runway braking friction. Section 4 describes
procedures for generating a Friction Data Base for aircraft and
ground-test machines and introduces examples based in existing test
data. Section 5 discusses several ways in which Friction Data Bases
can be used. Within the context of this Data Item the primary uses
are,

to represent measured aircraft braking performance data on a
statistical basis,

to provide means of relating the braking performances
of ground-test machines and aircraft.

Section 6 addresses the possibilities of
interpreting existing Friction Data Bases for use elsewhere.

Section 7 reviews the limitations of the method
and various aspects of its implementation.

If the method is to be used to relate the braking
performances of a given combination of aircraft and ground-test
machine, the procedure comprises 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 from
day-to-day measurements from the ground-test machine.

ESDU 99016 and ESDU 99017 (References 7 and 8) provide two
examples of the derivation of Friction Data Bases for individual
aircraft. The former of these considers an aircraft for which an
extensive set of test data is available; the latter considers an
aircraft for which a limited set of test data is available.
Reference 9 provides a detailed example for a ground-test
machine.

See Reference 42 for methods appropriate to runways contaminated
with significant depths of water, slush, snow or ice. Reference 3
gives a general introduction to many aspects of aircraft ground
performance.