NLR’s Experience With Flight Testing On Wet And Flooded Runways

Gerard van Es, Senior advisor Flight Safety & Operations, Netherlands Aerospace Centre NLR,
Amsterdam, the Netherlands
Paul Koks, Senior R/D Engineer, National Aerospace Centre NLR, Amsterdam, the Netherlands

Abstract

Braking performance of aircraft is affected whenever a runway is wet or flooded. Aircraft manufacturers do wet runway braking tests during the certification of a civil transport aircraft. These are normally limited to tests on smooth runways. Additional tests are sometimes conducted on wet grooved or porous friction course runways when the manufacturer seeks for additional stopping performance credit for such runways. Braking tests on flooded runways are not conducted during certification. In the past such tests have been conducted in research programmes on runway friction. The Netherlands Aerospace Centre NLR has conducted braking tests on a highly textured runway under wet and flooded conditions.

The wet runway tests were conducted to demonstrate an equivalent performance of the test surface with grooved and porous friction course runways under wet conditions. The flooded tests were conducted as part of an European Research project on the prevention of runway excursions. All tests were conducted in the autumn of 2016 at a former Air Force base in the Netherlands (Twente Airport). This paper discusses in detail the preparation, logistics, and execution of the flight tests conducted with NLR’s Cessna Citation test aircraft. The use of large water trucks to wet the runway and the construction of a water pond to conduct the flooded runway tests is discussed in detail. Difficulties encounter during the preparation and execution of the flight tests are briefed and finally lessons learned are shared with the reader.