62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 62 



designated as O'X', O'Y', and O'Z'. The origin of these axes is 

 coincident with the origin of axes about which rolHng and pitching 

 moments were measured. 



Forces along axes OX, OY, OZ are called AX, AY, AZ, A being 

 the area of model in square feet ; and moments about these axes are 

 called L, M, and N . Forces along and moments about axes O'X' , 

 O'Y' , and O'Z' are represented in the same way, i. e., AX' , AY' , etc. 



The notation used for the measured forces and moments is as 

 follows : 



(i) Force along O'Z^^Vp. Measured on vertical force lever. 



(2) Moment about O'Z/^iW^. Measured on torsion wire. 



(3) Moment about O'Y' =V p. Measured on vertical force lever. 



(4) Moment about 0' X ^ = V j^. Measured on vertical force lever. 



(5) Moment about an 

 axis parallel to O'Y^ 



and distant /below it =M^. Measured on drift beam. 



(6) Moment about an 

 axis parallel to O'X J 



and distant /below it =M(--. Measured on cross wind beam. 



The forces and moments desired can then be calculated by the fol- 

 lowing equations : ^ 



L'=V\ cos B-]VL_ sin 0. 

 M'=Vp. 



N'=Vp sin 6 + Mz cos 0. 

 AX =~Vp sin 6+ (M^ cos </)-M^ sin <^-Vp) S2ii. 

 Ay — ^"^R — ^'^c COS <^ — Mp, sin (^ 



AZ =Vp cos e+{M^ cos <^-Mc sin <^-Vp)^-^. 



L=L' + cAY. 

 M =M'-cX + aAZ. 

 N =N'-aAY. 

 Where a and c are the X and Z coordinates of the origin taken 

 from axes O'X', O'Y', and O'Z'. 



Figures 24 to 31 show the forces X, Y, Z, and moments L, M, N 

 plotted on angles of yaw as abscissae for constant angles of incidence 

 of o, 3, 6, and 9 degrees. At any incidence the chord of the wing at its 



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

 1912-13. Report No. 75. 



