WW2F parameters vs. real parametersPage 3
Flight Model modification for Jane’s WWII Fighters
by Joe Hong
Now that the technical stuff is out of the way, we can comment on the specifics of the WW2F flight model. The shape of the derived Lift vs. Alpha curve is generally reasonable, and the maximum value of CL is within realistic limits. We traditionally expect the Lift curve to fall immediately to zero when the critical angle is exceeded (in this case, about 15°). Lift curves of the shape shown above, though, have been seen from analytical, wind tunnel, and computer simulations, so we have to accept the curve as reasonable.
Experimentation with the FLT file has shown, however, that changes to the coefficients at 20° and beyond result in very little effect. Much of the stall characteristics of each aircraft are actually hard coded into the flight engine.
The computed Drag Polar shows reasonable results as well. As expected, drag rises even as lift decreases when the critical angle is exceeded. The drag increase appears to be quite gradual, however.
Wind tunnel Lift/Drag curves of P-51 model
Wind tunnel Drag Polar of P-51 model
We can compare the Lift curve and the Drag Polar to results from wind tunnel tests of scale models of the P-51. The data in these graphs is from Dr. Lednicer’s paper on CFD analysis of the Mustang. The lift curves are somewhat close, but still noticeably different. The drag coefficients in the WW2F model appear to be too low compared to the data.
The min CD values are very close, but for the same CL value, the WW2F CD values are consistently lower than the data (meaning, less drag). In addition, Dr. Lednicer writes that derived drag values of these WWII aircraft—obtained from sophisticated analysis, simulation, and even scale wind tunnel tests—also appear too low versus real life values. Real aircraft are considerably dirtier than neat, ideal models used in analysis and testing.
Click Here for Printer Version
© 1997 - 2000 COMBATSIM.COM, Inc. All Rights Reserved.
