Object: To study the relative merits of air-speed tubes from the standpoint of their effectiveness in operating satisfactorily when exposed to raindrops and freezing rain. Note: The tests which simulated actual flight through raindrops and freezing rain were conducted in a 6-inch suction wind tunnel constructed especially for the investigation and operated in a refrigeration chamber during the freezing rain tests. For the sale of simplicity, the conclusions are listed according to the type of the individual tube. ... The sectional sketch, Figure 15, may be valuable to the person unfamiliar with air-speed tubes to form a fair conception of the general construction of the different types. The manner in which ice builds on the tubes is also represented.