AN ABC STATUS REPORT

The XH-59A Advancing Blade Concept (ABC™) demonstrator aircraft has recently completed extensive flight testing and evaluation under contract to the U.S. Army. Funding for these tests was provided by the U.S. Army, U.S. Navy, NASA and the U.S. Air Force. These tests have demonstrated that the ABC Aircraft can achieve speeds approximately 100 knots above those of current helicopters and can fly at higher altitudes, without giving up the conventional helicopter's advantages in hover and low speed flight. In some areas, such as maneuverability and compactness, it is a better low speed vehicle than the conventional helicopter. In these tests, the demonstrated speed envelope was expanded to 263 knots, with flight to higher speeds restricted by blade and rotor head stresses. Maximum altitude achieved was 25,500 feet. The XH-59A also demonstrated high rates of climb and descent. The theoretical improvement in hovering figure of merit with a coaxial rotor was verified by flight test. The high control power, high damping and resulting maneuverability of the hingeless rotors were confirmed. Blade loading coefficients (CT/σ) higher than those predicted were demonstrated. The noise reductions due to the lack of a tail rotor and to a low main rotor tip speed were documented. The XH-59A also provided necessary data on pilot work load, rotor loads, vibration, yaw control in autorotation, and control loads. In its current configuration, the XH-59A can only be used for additional minor development tests. It requires a new rotor system, with improved geometry and composite materials, for further orderly development of the Advancing Blade Concept. Future ABC development should also be accomplished with an aircraft which uses an integrated propulsion system with two engines to power both the rotor and auxiliary propulsion systems.