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Meeting	ACGS Committee Meeting 116 - Charlotte, NC - October 2015
Agenda Location	7 SUBCOMMITTEE D – DYNAMICS, COMPUTATIONS, AND ANALYSIS 7.3 Augusta Westland 609 Autorotation Testing
Title	Augusta Westland 609 Autorotation Testing
Presenter	Dan Wells
Affiliation	Augusta Westland
Available Downloads*	presentation
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Abstract	INTRODUCTION AgustaWestland is pursuing Federal Aviation Administration Type Certification of the AW609 Civil Tiltrotor (figure 1). Part of the certification basis requires that the aircraft can be safely landed after losing all engine power. For the AW609, this means converting from airplane mode to vertical takeoff and landing or VTOL mode and executing a helicopter-like autorotation. This paper will discuss the up-and-away testing that was accomplished toward that goal. DESCRIPTION OF THE PROPOSED PAPER There have only been four tiltrotor aircraft ever built in the United States and very little autorotation testing has been conducted on any tiltrotor aircraft. AgustaWestland, in company testing of the AW609, developed and tested a method for converting the aircraft from airplane mode to VTOL mode with both engines simulated failed. The transition began with the aircraft’s proprotors windmilling in airplane mode and then through an emergency re-conversion of the nacelles, the maneuver ended with the tiltrotor aircraft in a steady-state helicopter-like autorotation. The challenge for transitioning from windmilling airplane to autorotating helicopter lies in maintaining the proprotor rpm as the proprotor disk passes through the edge-on flow area at approximately 65 degrees of nacelle angle. At this angle, the airflow is neither windmilling nor autorotating the proprotor system and the rpm will inevitably slow. Predictions showed the proprotor rpm dipping to values that produced very high loads on the aircraft yoke. Also, there was the consideration that the engines were operating at ground idle and if the proprotor slowed enough, the sprag clutch would re-engage and it would no longer be a true simulation of all-engines-inoperative flight. AgustaWestland experimental test pilots developed a method of pitching the nose up at a point that “hurried” the proprotor disks through the edge-on flow area and preserved rpm above the desired minimums. This allowed for a complete investigation of the range of centers of gravity, gross weights, and airspeeds in the aircraft envelope. The test program also investigated re-converting from a one-engine-inoperative VTOL mode to an autorotation, and investigated the flare effectiveness of the aircraft once established in autorotation. The program successfully cleared the entire gross weight and center of gravity envelope for performing the emergency re-conversion. The flare effectiveness of the aircraft was also shown to be very good, reducing the descent rate to zero. AgustaWestland believes that the AW609 can be safely autorotated to the ground after the loss of both engines.