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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 62 



center coincides with the OX axis. In figure 32, X, Z, and M are 

 plotted with angles of incidence as abscissae and with o degrees yaw. 

 The notation used is as follows : 



Subscript i — wing straight. 



Subscript 2 — wing swept back 10 degrees. 



Subscript 3 — wing swept back 20 degrees. 



Subscript 4 — wing swept back 30 degrees. 



Fig. 25. 



For the application of the theory of the dynamical stability of aero- 

 planes, reference should be made to the excellent papers by Mr. L. 

 Bairstow.^ 



It is shown that for longitudinal stability the rate of change of the 

 quantities X, Z, and M with angle of incidence determines the 

 so-called resistance derivatives. It appears from the observations 

 made on swept back wings that there is no appreciable change in the 

 slope of curves of X, Z, and M plotted on angle of incidence for the 



^ Technical Report of the Advisory Committee for Aeronautics, London. 

 1912-13. Report No. 79. 



