Design Refinement and Flight Test of the AVMS Active External Load Stabilization System

As part of the Adaptive Vehicle Management Systems (AVMS) Phase II program, an Active External Load Stabilization (AELS) system was designed that consists of Flight Control Load Stabilization (FCLS) and Active Cargo Hook (ACH) methods to stabilize a load which can also be combined and operated simultaneously. Prior flight testing revealed issues with the performance of the AELS system that were a result of a modeling error as well as the need to utilize different underlying flight control system control law feedback gains when flying with an external load. Fixing the modeling error had a significant impact on the evaluation of the system in piloted simulation, particularly for the FCLS method. A more comprehensive control law gain optimization was employed using CONDUIT® in order to achieve all of the desired design requirements, such as stability margins, handling qualities (HQ), and load-damping (LD). Changes were also made to the mode switching between the FCLS-HQ and FCLS-LD modes. Following these updates, the system was re-evaluated in piloted simulations and flight test. The results show that the ACH and FCLS systems each performed extremely well; significantly reducing load motion and allowing the pilot to more quickly complete tasks with an external load. The combined ACH+FCLS system performed very well, however even better performance is expected with further refinements.