The experiments discussed here were performed to determine whether radiators having similar cooling properties offer less resistance when incorporated into the fuselage, than when the hitherto customary arrangement is employed, with the radiator in the free air current more or less independent of the fuselage. The experiments indicated that the quantity of air flowing through the radiator is greatest when the fuselage and the radiator are separate. However, separate radiators cause more air resistance. When the radiator is incorporated into the fuselage, it is only possible to obtain a quantity equal to that which flows through the radiator in the free air current if the lateral outlet vents are widened or the quantity of air in increased b...