Abstract
Aircraft braking distance is dependent on the friction between the main gear tires and runway pavement surface.Pavement texture, which is divided into macrotexture and micro-texture, has a noticeable effect upon friction, especially when the surface is wet. A risk analysis framework is developed to study the effects of longitudinal and transverse slopes on the aircraft braking distance in wet runway conditions and their influences on the probability of landing overrun accidents.This framework is operating under various water-film thicknesses, Maximum Landing Weights (MLW), and touchdown speed probability distributions for an acceptable range of longitudinal/transverse slopes and pavement texture depths.A simulator code is developed that initially computes the existing water-film thickness, as the result of intense precipitation,under aircraft main gear (depend on aircraft category) and then applies this variable as one of the main inputs to the aircraft braking distance computation. According to the obtained results, longitudinal gradient does not have a significant effect on the existing water depth on the surface although it affects the flow path length. Furthermore, 1% to 1.5% transverse slope causes rapid drainage of water from the runway surface and considerably decreases the probability of runway excursion accidents.
Highlights
Runway-related incidents/accidents based on aircraft operations can be categorized as incursions and excursions
This MATLAB-based model is simulating the footprint of aircraft main gear and its interaction with the pavement for different water-film thicknesses existing on the runway
After rain drops fall on a sloped pavement surface, the runoff takes a path to the pavement edge, which is called the resultant flow path and its length (Lf) and its slope (Sf), as presented in Figure 1, can be determined as following (American Association of State Highway and Transportation Officials (AASHTO), 1992): ( ) S f =
Summary
Runway-related incidents/accidents based on aircraft operations can be categorized as incursions and excursions. – Macrotexture is visible roughness that allows existing water on the pavement escape from beneath the aircraft tires It is detectable by touch rather than appearance and allows the aircraft tire to break through the residual water-film on the pavement after running off the main volume of water because of the runway slopes This parameter is especially crucial at low speeds. A probabilistic risk analysis framework is developed to study the influence of longitudinal and transverse slopes on the probability of occurrence of landing overrun incidents/accidents in wet/dry runway conditions This framework is simulating the aircraft braking distances for different; Water-Film Thicknesses (WFT) on the runway, aircraft Maximum Landing Weights (MLW), touchdown speed probability distributions for a range of longitudinal/transverse slopes, and Mean Texture Depths (MTD) of pavement
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