GLIDING IN GERMANY — QEORGU 279 



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It has long been known that cumulus clouds are associated with 

 rising currents of air, but few measurements were available. Ke- 

 searcli was directed to the determination of these currents in the 

 spring of 1928 from measuremonts of the vertical rate of a power 

 plane gliding beneath a cumulus cloud with its airscrew stopped. 

 Repeated glides of as long as 10 minutes without loss of height were 

 obtained. 



Plate 10, Figure 2, shows a meteorgram of experimental flight, 

 April 30, 1928. It is seen that there was no loss of height from 

 point 7 to point 10 of the barogram, which implies a rising current 

 of 2 m./sec. 



Plate 11, Figure 1, shows a reduction of experimental flight meas- 

 urements in a rising current, July 12, 192S, and the observed descent 

 of the airplane gliding. From this is subtracted the Imown sinking 

 speed in still air. about 1.0 m./sec. The dillerence measures the 

 vertical motion of the air. 



Fr(nn time 20 minutes to time 28 minutes there is a rising current 

 of from 1 m./seo. to 2 m./sec, and from 28 minutes to 30 minutes 

 of 2 m./sec. to 5 m./sec. These are high values and give excellent 

 conditions for soaring in gliders, which have sinking speeds as low 

 as 0.7 m./sec. 



Plate 11, Figure 2, shows a reduction of rising current measure- 

 ments before a line squall, June 26, 1928. A " cold front " produced 

 a line squall of moderate intensity, and the airplane, with airscrew 

 stopped, maintained itself without loss of height for 15 minutes. 

 From these results it was inferred that a soaring glider starting from 

 the Wasserkiippe could reach the region of rising currents under a 

 cumulus cloud or the front of an approaching squall, and this was 

 successfully accomplished. 



Plate 12, Figure 2, shows a barogram of soaring flight by the 

 Dannstadt, August 10, 1928. The barogram shows clearly the vig- 

 orous efl'ect of the rising current under a cloud in comparison with 

 that produced by a hill barrier. 



The Darmstadt maintained itself over the west slope of the 

 "Wasserkuppe at 100 meters above the .starting point. In 20 minutes, 

 the boundary of the up-current below an approaching cloud was 

 reached and the glider was quickly carried up to a height of 400 m. 



Plate 12, Figure 1, shows a record of Kronfeld's flight at the Him- 

 meldankberg, August, 1928. The plan of the course is .shown in full 

 line under the cloud, in dotted line outside their influence. 



Kronfeld started from the western slope of the Wasserkuppe, and 

 flew at once toward an approaching cumulus cloud, which he fol- 

 lowed toward the east with continual gain of height, reaching 

 Anally 470 m. above the starting point. The cloud began to dissipate 

 and the up-current became ineflective, so that Kronfeld left it and 



