The object of the investigations at Cranfield is to investigate the effect of water depth, surface roughness — drainage characteristics and tyre pressure on aquaplaning and tyre ground friction. Tests at Cranfield are full scale on the single main— wheel undercarriage of a Vickers Supermarine Swift F.7. operated through ponds of water on a test surface. The test area is a precision surface, level to an accuracy of 1/16" over its entire width. The levelled area is built into runway 22-04 and consists of six different surfaces of varying texture, three of concrete and three of asphalt arranged as shown in fig. 1. The ponds are constructed of 1 1/2" T section rubber strip affixed to the surfaces by suitable adhesives which were selected after a series of tests. The Swift is fitted with an A.22 recorder giving traces of port and starboard wheel speeds, obtained by means of wheel speed generators, and airspeed. A modification is in hand to record oleo leg extension as a measure of wheel load and hydrodynamic force.