Developmental flight test of a powered approach stability augmentation system on the U.S. Navy's E-2C Hawkeye 2000 aircraft

by 1968- Williams, Robert K.

The E-2C aircraft is a Navy carrier based high-wing, twin engine turboprop powered aircraft used for the Airborne Early Warning (AEW) mission. In the power approach configuration, the aircraft displays strong adverse yaw, weak directional stability, and excessive rudder control power. These antagonistic characteristics, when coupled together, result in an extremely high workload for the pilot during both carrier and field landings. Although the aircraft has a yaw axis stability augmentation system, it is currently only applicable to cruise conditions. Engaging the stability augmentation in the power approach configuration results in a 1 Hz directional oscillation due to the system’s high gain schedule. Additionally, another attribute of the existing system design results in extremely high rudder pedal forces while maintaining sideslip in crosswind conditions. Northrop Grumman developed Flight Control Computer (FCC) software patches designed to improve the handling qualities on landing approaches. These patches are designed to change the rudder control gain schedule to allow the use of stability augmentation in the power approach configuration and suppress the divergent Phugoid characteristic throughout the flight envelope. The system is a directional axis controller only and termed the Powered Approach Stability Augmentation System (PASAS). Initial flight tests on a developmental system provided the design parameters for the production system, which was eventually installed in the Navy’s newest E-2C variant, termed Hawkeye 2000. The ensuing flight test program consisted of land based test flights during the summer of 2001, and culminated in a ship trial consisting of multiple landings on the USS Truman in March of 2002. iv