Use of Ground-Based Wind Measurements for Improved Guided Airdrop Accuracy

Abstract

Uncertainty in atmospheric winds represents one of the primary sources of landing error in airdrop systems. While guided airdrop systems can compensate for uncertainties in the wind profile, unexpected winds in the drop zone can still result in large errors in landing location, and they can even lead to damage or complete loss of the cargo if the system hits the ground while traveling downwind. This work examines the impact of real-time knowledge of the winds in the drop zone on guided aidrop landing accuracy and landing quality. Measurements of the horizontal wind profile at multiple altitudes above the target provided by a ground-based LIDAR are considered in addition to a simple ground wind measurement. The guidance logic running on the airdrop system’s onboard autopilot is modified to integrate the wind measurements near the intended landing zone with onboard wind estimates to provide an improved, real-time estimate of the wind profile. The strategy is first developed in the framework of a rigorous simulation model and then validated in flight test. In both simulated and actual flight tests, knowledge of the wind profile near the target provided from the LIDAR unit improved landing accuracy by 40%. Knowledge of the ground winds alone provided by a low-cost, lightweight, highly portable device, again in both simulated and actual flight tests, is enough to improve landing accuracy by 33% and completely eliminate potentially dangerous downwind landings.