Hey there, ive been doing a research/computational project on the counterflow vectoring method and was completing some calculations based upon my results and then ended up being stuck on thrust efficiency! The procedure in which i intended to calculate the thrust efficiency was similar to what hunter and deere used in their computational investigation. You can download the pdf via this link: http://www.megaupload.com/?d=2ALT2UXM [Broken] The formula to calculate the thrust efficiency is resultant force divided by ideal isentropic force from the primary jet. where the resultant force is R = ( X.^2 + N.^2).^(1/2) X = axial force which is determined by multiplying the density, velocity squared and height which in my case is 0.03m. N = Normal force determined by the pressure difference multiplied by the suction collar length which in my case is 0.06m. My problem is that as the angle of my vectoring increases, my thrust efficiency increases too which is the opposite of what i was expecting thats mainly because my normal force increases rapidly (according to the formula used in Hunters report) and so does my axial force which adds to the total resultant force. So im basically stuck since when comparing my thrust vector angle against suction parameter to hunters graph, they are very similar but this thrust efficiency is doing my head in! Maybe is it the ideal isentropic formula for thrust im using is incorrect which is just mass flow rate at the exit multiplied by the velocity??? Any help will be much appreciated!