What is it about?
A number of landing overruns on wet runways provide evidence that the wet runway wheel braking coefficients assumed in industry-standard models and airplane flight manuals overestimate the friction available on some wet runways. A NASA model for estimating the friction available to an airplane based on ground vehicle friction measurements (CFME) matches the actual friction obtained during the overrun events much better than the AFM or standard models.
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Why is it important?
The landing overrun events discussed in this paper underscore the need for more conservative models of wet runway friction, and more conservative use of existing airplane flight manual data and models in the meantime.
Perspectives
Landing overruns often involve operational errors, such as fast or long touchdowns, landing with a significant tailwind, or the delayed use of deceleration devices, such as spoilers and reverse thrust. These errors deservedly receive much attention following an event. However, an additional factor in many of the events is an achieved braking performance that is worse than both the performance indicated in the Airplane Flight Manual, and the performance predicted by models currently specified in transport airplane certification standards and guidance material. These findings indicate that more conservative models are required to more accurately predict the actual braking performance of airplanes on wet runways, and that these models, once developed, need to be validated by flight test.
Mr. John J O'Callaghan
National Transportation Safety Board
Read the Original
This page is a summary of: Slippery When Wet: The Case for More Conservative Wet Runway Braking Coefficient Models, June 2016, American Institute of Aeronautics and Astronautics (AIAA),
DOI: 10.2514/6.2016-4364.
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