To summarize, the experiments with balloons, sailplanes and light airplanes conducted thus far, reveal the vertical velocities of the air to be primarily dependent on the vertical temperature distribution. Stable stratifications result in up-and-down currents forced by the contour of the ground, which are readily recognized in flight and, if need be, may be avoided.

Chiefly translations from foreign aeronautical journals.

The preliminary calculation of the airplane polar and hence of the flight performances and characteristics rests on the assumption of an elliptical lift distribution at all altitudes. For large angles of attack below C(sub a (sub max)), this method of calculation yields no satisfactory agreement with measurements made in flight. An attempt is made to eliminate the errors in the preliminary calculation by the assumption of a disturbance of the lift distribution in this angle-of-attack range, which is so important for the constructor. An explanation is also given of the great differences found in flight with and without propeller slipstream.