In the past few years pilots landing in very heavy rain, or just after it, have found their wheel-brakes ineffective due to the layer of water, and this has been called aquaplaning; the word is preferable to “hydroplaning” which already has a well-established meaning in a deep-water context. The nature of this phenomenon has been speculated upon by NASA since 1959 and by Mr. Gadd of the NPL in 1961 (see R.Ae.S. Journal, March 1963). The latter gives the impression that in Britain we are still speculating, but in fact we know quite a lot about it now; much has been described in an RAE Technical Note last November and this was added to at a Take-off and Landing Symposium at Farnborough in December 1962. These sources are being drawn upon here.