IHS ESDU Example of statistical analysis of wet runway friction: aircraft with extensive set of test data. 99016

ESDU 99016 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 ESDU 99015, 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 ESDU 99015. Test data for a Boeing 727-100QC aircraft are used to illustrate, by example, the process of establishing a Friction Data Base. The background to the tests is described, the method of analysis is summarised and the results are presented in tabular and graphical form. A second example, for an aircraft where only a limited set of data is available, is given in ESDU 99017. An example of the application of the method to ground-test machine data is given in ESDU 00018. If the method of ESDU 99015 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 to predict operational braking performance of the aircraft from day-to-day measurements from the ground-test machine.