Improvements in Aerial Refueling Flight Control System for a Large Receiver Aircraft

摘要

This paper describes recent updates to the Flight Control System of the C-17A Globemaster Ⅲ transport aircraft as a receiver aircraft during aerial refueling. The Flight Control upgrades, which were in response to past pilot reports indicating some difficulties in accomplishing the aerial refueling task, were designed to enhance the aircraft handling qualities during the task by improving the aircraft response characteristics and predictability, while minimizing any tendencies for Pilot-Induced Oscillations. In addition to describing high-level innovative design features that affected all 3 principal axes, specifically pitch, roll, and thrust, this paper focuses on the project's flight test results of the final control law function, which were collected during the flight test at the USAF EAFB using two different tankers, in order to verify and validate the flight control system updates. More specific and quantifiable details are planned for future papers. The new flight control laws for the C-17A aerial refueling mode were part of the C-17A fiscal year 2015 (FY15), maintenance build (MX), software operational flight program (OFP). The Flight Test program, intended to evaluate the overall FY15 MX software, was conducted by the Air Force Test Center at EAFB in California, from 6 January through 17 March 2020, and consisted of 20 sorties, with a total of 87 flight hours. The resulting data showed marked improvements over the Legacy software for aerial refueling, and the evaluation pilots deemed the handling qualities in all three axes as satisfactory. The handling qualities for the complete refueling task, handling qualities during fuel on-loads, thrust performance, engaging/ disengaging dynamic data, and human systems integration, were all deemed satisfactory by the evaluation pilots.