This monograph is a testament to the efforts of many people overcoming multiple technical challenges encountered while developing the XV-15 tilt rotor research aircraft The Ames involvement with the tilt rotor aircraft began in 1957 with investigations of the performance and dynamic behavior of the Bell XV-3 tilt rotor aircraft At that time, Ames Research Center was known as the Ames Aeronautical Laboratory of the National Advisory Committee for Aeronautics (NACA) As we approach the new millennium, and after more than 40 years of effort and the successful completion of our initial goals, it is appropriate to reflect on the technical accomplishments and consider the future applications of this unique aircraft class, the tilt rotor The talented engineers, technicians, managers, and leaders at Ames have worked hard with their counterparts in the US rotorcraft industry to overcome technology barriers and to make the military and civil tilt rotor aircraft safer, environmentally acceptable, and more efficient The tilt rotor aircraft combines the advantages of vertical takeoff and landing capabilities, inherent to the helicopter, with the forward speed and range of a fixed wing turboprop airplane Our studies have shown that this new vehicle type can provide the aviation transportation industry with the flexibility for highspeed, long-range flight, coupled with runway-independent operations, thus having a significant potential to relieve airport congestion We see the tilt rotor aircraft as an element of the solution to this growing air transport problem

/pdf/the-history-of-the-xv-15-tilt-rotor-research-aircraft-from-26e7djmxdk.pdf

The History of the XV-15 Tilt Rotor Research Aircraft: From Concept to Flight

Rotor/Airframe Interactions on Tiltrotor Aircraft

Aerodynamics of Airfoils at High and Reverse Angles of Attack

The compound helicopter has much to offer as a means of expanding the flight envelope of rotorcraft. There have been significant amounts of research performed, albeit disjointed, and many flight demonstrator compound helicopters produced and trialled since the end of the Second World War mainly with the aim of increasing the helicopter"s maximum forward speed. This paper aims to pool this knowledge, along with relevant developments in other fields, not only to state the current level of understanding of the compound helicopter configuration but also to use it to predict likely configurations and technologies that would be best suited to future compound helicopter designs. From this basis it is suggested that the most likely configuration will be a low wing of minimized area to alleviate retreating blade stall at a minimum hover blockage, with plain flaps for blockage reduction and control of the rotor-wing load share. In terms of propulsion a ducted fan or propeller are deemed most suitable, driven by either an advanced mechanical drive or variable cycle engine. The areas of rotor-wing interaction and advanced rotor design are also noted as subjects of significant interest in the optimal design of a compound helicopter.

The fundamental configuration and design of the compound helicopter

A test of a 0.658-scale V-22 rotor and wing was conducted in the 40 x 80 Foot Wind Tunnel at Ames Research Center. One of the principal objectives of the test was to measure the wing download in hover for a variety of test configurations. The wing download and surface pressures were measured for a wide range of thrust coefficients, with five different flap angles, two nacelle angles, and both directions or rotor rotation. This paper presents these results, and describes a new method for interpreting wing surface pressure data in hover. This method shows that the wing flap can produce substantial lift loads in hover.

Wing Download Results from a Test of a 0.658-Scale V-22 Rotor and Wing

: Wind tunnel tests were conducted to determine the drag og two-dimensional wing sections operating in a near-vertical flow condition. Various leading-and trailing-edge configurations, including plain flaps of 25, 30, and 35% chord were tested at angles of attack from-75 to -105deg. Reynolds numbers examined ranged from approximately 0.6 to 1.4 million. The data were obtained using a wind tunnel force and moment balance system and arrays of chordwise pressure orifices. The results showed that significant reductions in drag, beyond what would be expected by virtue of the decreased frontal area, were obtainable with geometries that delayed flow separation. Rapid changes in drag with angle of attack were noted for many configurations. The results, however, were fairly insensitive to Reynolds number variations. Drag values computed from the pressure data generally agreed with the force data within 2%. Keywords: Download; Two-dimension wing; Leading edge; trailing edge; Wing flap; Wing slots; Wing slats; Wing spoiler.

/pdf/aerodynamic-characteristics-of-two-dimensional-wing-54f5zx5qhh.pdf

Georgene Laub

Papers

Aerodynamic characteristics of two-dimensional wing configurations at angles of attack near -90 deg