| sblack |
01-26-2016 07:30 AM |
Quote:
Originally Posted by BillL
(Post 1048584)
So what does the fuel see from tank level to mechanical pump when the plane is at 4 G's vertical into a loop? Where is the vector? Wouldn't AOA be more applicable here, or should we just do the vector calculations and get the relative "height" of the fuel column? Is it pitch?
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Hmm I might have engaged keyboard before brain there. The true longitudinal angle that the fuel sees is the angle between whatever your pitch reference is, say the top longeron, and the resultant acceleration vector which is the vector sum of the vertical and longitudinal accelerations and gravity, or as we call it in engineering nomenclature Nx, Ny and g. But this is over-complicating it. In a 4g loop it would be the vector sum of the acceleration of the airplane in pitch about the center of the loop (Vsquared/r), the longitudinal acceleration which would probably be -ve on the way up and the gravity vector so it would depend where you were in the loop and yes, angle of attack would figure into that because it is the difference between your pitch datum and the flight path. But this is all academic. When you do your fuel flow test in preparation for first flight you generally use your max climb pitch attitude.
Interestingly, if you look at the fuel angle in the tank on the runway during the takeoff roll, when the airplane is accelerating, and the same angle in the tank on climb at constant speed, they are the same. I've done this simulation for large airplanes.
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