X-47B: Taxi testing an unmanned, carrier-based, prototype aircraft

Brandon Jones, Aerospace Engineer, Naval Air Warfare Center, Aircraft Division, NAS Patuxent River, MD, USA
Michael Harris, Aerospace Engineer, Naval Air Warfare Center, Aircraft Division, NAS Patuxent River, MD, USA
Peter Dougherty, Aerospace Engineer, Naval Air Warfare Center, Aircraft Division, NAS Patuxent River, MD, USA
Brian J. Loustaunau, Aerospace Engineer, Naval Air Warfare Center, Aircraft Division, NAS Patuxent River, MD, USA

Abstract

The X-47B is a tailless, strike fighter-sized, unmanned experimental prototype aircraft under development by Northrop Grumman as part of the U.S. Navy’s Unmanned Combat Air System Carrier Demonstration (UCAS-D) program. The X-47B is undergoing initial envelope expansion testing to allow for demonstration of interoperability with Carrier Controlled Area (CCA) operations, catapult launch, and arrested landing onboard an aircraft carrier in 2013.

A long list of test concerns and potential areas of risk were identified and mitigated during the initial flight test planning for envelope expansion of the unmanned prototype aircraft. Surprisingly, one of the greatest challenges during the initial X-47B test program was taxi testing. Low and medium speed testing revealed asymmetric ground handling performance that climaxed during high speed taxi tests. Observed asymmetries seemed random and unpredictable. These particular results were unexpected and concerning, requiring a series of unplanned tests specifically focused on understanding the characteristics. Challenges were faced to safely proceed while exploring the ground handling characteristics of the autonomous aircraft. This required the team to establish a smart limit methodology based on system design, test results, and simulation. These test techniques facilitated safe exploration to the edge despite uncertainty in system performance. The final solution for these issues was a redesigned ground control law.

This paper will discuss the discovery and source of issues while focusing on how the team developed test strategy to sufficiently characterize those issues for resolution. The strategies discussed are applicable to a variety of flight test situations beyond the X-47B program. This paper will also summarize specific flight test lessons learned from autonomous aircraft taxi testing.