Blade Angle of Attack. The BK 117 helicopter has the following characteristics: m = 3200 kg f = 1.55 m2 (estimated) _T = 8 = 0.074 = 6.61 (at sea level) R = 5.5 m V_tip = 221 m/s a = 5.79 per radian Make a contour plot showing blade angle of attack as a function of azumuth and dimensionless radius for a trimmed1 rotor in the following 2 flight conditions: = 0.1 at sea level ( = 1.225 kg/m^3) = 0.4 at sea level Discuss the plots and resulting calculations. Do they make sense, meaning are they correct from both a calculation and an operational point of view? Explain why there is a limit on the maximum feasible advance ratio. The following MATLAB code will produce a contour plot in polar coordinates. The polar coordinates are (rbar,psi) and the value of b is in the array, alpha. Note that rbar and psi are two-dimensional arrays set up using: r = linspace(0,1,lengthr); angle = linspace(0,2*pi,lengtha); % lengthr is the number of radial locations and lengtha is the number of angular locations for i = 1:lengthr for j = 1:lengtha rbar(j,i) = r(i); psi(j,i) = angle(j); end end [X Y] = pol2cart(psi,rbar); h = polar([0 2*pi],[0 1]); delete(h); hold on contours = -5:1:10; [C h] = contour(X,Y,alpha,contours); clabel(C,h); hold off You may wish to experiment with the 'contours' and/or the 'clabel' command to give a readable plot.