Example of statistical analysis of wet runway friction: aircraft with limited set of test data.
Abstract:ESDU 99017 is the second 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 small combat 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. The particular feature of this example is that only a small number of test runs was available - on a single runway - and the measured quantities were 'brakes-on' speed, stopping distance and weight. The first example, for an aircraft where an extensive set of data is available, is given in ESDU 99016. 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.
|Data Item ESDU 99017|