Experimental evaluation of the drag curves of small fixed wing UAVs

Tight budgets often limit the scope of test campaigns within the development programmes of small uncrewed air vehicles (UAVs). This paper explores a range of combinations of instrumentation suites and protocols for both wind tunnel and flight evaluation, focusing on the key aspect of drawing up the drag curve of the airframe. Through extensive testing of a 5kg maximum take-off mass, fixed wing, twin motor, richly instrumented test platform, we show that automated glides over a range of airspeeds and the slow down manoeuvre are effective ways of determining power-off drag, while estimating thrust from propeller speed, and voltage and current sensing based methods work well for the power-on case. We also seek the most time-efficient and robust mix of the above manoeuvres to yield a given drag curve accuracy level and we find wind condition impacts the manoeuvre makeup of the optimal strategy.

Automated summary

This paper explores combinations of instrumentation suites and protocols for wind tunnel and flight evaluation of small uncrewed air vehicles. It focuses on determining the drag curve of the airframe through automated glides and the slow down maneuver for power-off drag, and estimation of thrust using propeller speed, voltage, and current sensing for power-on drag. The study also considers the impact of wind conditions on the optimal strategy for maneuver combinations.