kolibri282
Super Member
In the Glasgow report "Application of Parameter Estimation to Improved Autogyro Simulation Model Fidelity" table 1 shows the speed derivative Xu (here it is called drag derivative, see fig. 9a) contributions from various components. It was this table that prompted my interest in propeller analysis programs (see: http://www.rotaryforum.com/forum/showthread.php?t=46870 )
I have currently no model for the Montgomerie Parsons propeller, so can not really say whether an analysis would reproduce those values but for the Bensen propeller from post #1 things are quite different. While the speed derivative becomes larger with speed for the MP prop it gets smaller for the Bensen (see attachment #1). The tangent to the curve has a negative slope at every point. Image #2 shows a graph of finite differences I calculated from curve 1. I think this is due to the fact that the pitch of the Bensen propeller was selected such that the aircraft would not exceed a speed of about 60 mph. If the last finite difference value (V=55mph) of about -5 is normalized by aircraft mass is gives a value of -0.02 which is close to what my program calculates. For lower speeds my values increase (-0.04 at 25mph) but are much smaller than what the propeller thrust derivatives suggest (-0.144 at 25mph)
Looking forward to your comments
I have currently no model for the Montgomerie Parsons propeller, so can not really say whether an analysis would reproduce those values but for the Bensen propeller from post #1 things are quite different. While the speed derivative becomes larger with speed for the MP prop it gets smaller for the Bensen (see attachment #1). The tangent to the curve has a negative slope at every point. Image #2 shows a graph of finite differences I calculated from curve 1. I think this is due to the fact that the pitch of the Bensen propeller was selected such that the aircraft would not exceed a speed of about 60 mph. If the last finite difference value (V=55mph) of about -5 is normalized by aircraft mass is gives a value of -0.02 which is close to what my program calculates. For lower speeds my values increase (-0.04 at 25mph) but are much smaller than what the propeller thrust derivatives suggest (-0.144 at 25mph)
Looking forward to your comments
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