PREDICTING DRAG POLARS FOR FIXED -WING MICRO AIR VEHICLES

Drag polars for three fixed-wing Micro Air Vehicles (MAVs) ‡ were measured at Reynolds numbers of 70,000, 50,000, and 30,000 and compared to predictions generated using a classical approach. The MAVs tested had aspect ratios varying from 1.2 to 1.6 and ratios of wetted surface area to planform area from 2.6 to 3.9. A force balance was used to measure the lift and drag on the MAVs at angles of attack ranging from -5° (or -10°) to 10°. The force balance allowed the MAVs to rotate in the pitching axis. The MAV angle of attack was set using an elevator installed on the MAV and controlled using a standard radio control used by RC plane enthusiasts. Uncertainty analysis performed on the data showed the uncertainty for high Reynolds numbers was dominated by velocity uncertainty, and uncertainty for the lower Reynolds numbers was dominated by uncertainty in the force measurements. The measured and predicted drag polars agreed with each other, with the measured drag generally being no more than 2.5 times the predicted drag. For the majority of the tests, the drag coefficients followed the expected Reynolds number trend: increasing with decreasing Reynolds number.