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Technical Paper

ProRAPP: A Computer Program for Propeller/Rotor Noise Prediction

The current emphasis on environment protection by reducing noise pollution has led to stricter noise standards for general aviation aircraft. As a result, there is a growing demand for a computational tool to predict the noise during the design process. A computer program, called ProRAPP, has been developed for the prediction of noise generated by propeller/rotor blades. The acoustic pressure is calculated using a form of Ffowcs Williams-Hawkings equation which is suitable for numerical implementation. For noise predictions, the observer can either move with the propeller/rotor hub or it can be fixed to the ground. Experimental data from both wind tunnel and flight tests are used to validate the numerical results.
Technical Paper

A Fowler Flap System for a High-Performance General Aviation Airfoil

As part of a general aviation airfoil development program being carried out under the direction of the NASA Langley Research Center, a 30% chord Fowler flap has been developed for the GA(W)-1 airfoil.. Wind tunnel tests at Wichita State University have demonstrated a c1max value of 3.80 for 40 deg flap deflection at a Reynolds number of 2.2 × 106. Effects of flap slot geometry have been systematically tested and optimum flap settings for any flight c1 have been obtained. Modification of the reflexed lower surface contour resulted in a reduced c1max with flap nested. Vortex generators provided an increase in c1max of 0.2 for flap nested and 40 deg flap along with a drag penalty at low c1 values. Flow visualization studies show that the stalling patterns for the new airfoil are characterized by an absence of leading edge separation for both the flap-nested and the 40 deg flap cases.
Technical Paper

Studies of Flow Separation and Stalling on One- and Two-Element Airfoils at Low Speeds

Research has been conducted on the nature of airfoil behavior at pre- and post-separated angles of attack. Detailed wind tunnel studies have been made of boundary layer and wake fields for the GA(W)-1 airfoil, and the airfoil with a 0.3 chord Fowler flap. Experimental data are compared with theoretical predictions from a multi-element viscous flow computer program. Theoretical predictions are reasonably accurate for unseparated flows, but have serious errors when separation is present. Some recent techniques for modeling post-separated flow behavior are discussed in light of the present experiments.
Technical Paper

Wind Tunnel and Flight Development of Spoilers for General Aviation Aircraft

Wind tunnel tests have been carried out to develop a spoiler lateral control system for use with the GA(W)-1 airfoil with a 30% Fowler flap. Tests show that unfavorable aerodynamic interactions can occur between spoiler and flap for large flap deflections. Providing venting of lower surface air through the spoiler opening substantially improves performance. Results of tests with a number of spoiler and cavity shapes are presented and discussed. Applications of two-dimensional wind tunnel results to the design of satisfactory manual lateral control systems are discussed.
Technical Paper

Studies of Light-Twin Wing-Body Interference

The results of an analytical study of aerodynamic interference effects for a light twin aircraft are presented. The data presented concentrates on the influence of a wing on a body (the fuselage). Wind tunnel comparisons of three fillets are included, with corresponding computational analysis. Results indicate that potential flow analysis is useful to guide the design of intersection fairings, but experimental tuning is still required. While the study specifically addresses a light twin aircraft, the methods are applicable to a wide variety of aircraft.
Technical Paper

Studies of Hingeline Gap, Trailing Edge Treatment, Lower Surface Deflector on Spoiler Characteristics and Flow

Wind tunnel test have been conducted to determine effects of certain design variables on spoiler performance and spoiler flow field characteristics. Measurements include forces, oil flow surveys on a vertical splitter plate, and wake velocity and turbulence measurements using a dual split-film anemometer system. Results include the effects of spoiler design variables, such as: hingeline gap, lower surface venting and deflector, spoiler trailing edge notching and spoiler porosity. Hingeline gap, porosity, lower surface venting and lower surface deflector can be designed to reduce control dead-band tendency. Wake turbulence studies show that certain modifications can be utilized to diminish peak frequencies in the wake.
Technical Paper

Further Results of Natural Laminar Flow Flight Test Experiments

Flight test experiments were conducted to measure the extent and nature of natural laminar flow on a smoothed test region of a swept-wing business jet wing. Surface hot film aneraometry and sublimating chemicals were used for transition detection. Surface pressure distributions were measured using pressure belts. Engine noise was monitored by a microphone attached to the wing surface to study possible acoustic effects on stability of the laminar boundary layer, Side-slip conditions were flown to simulate changes in effective wing sweep. Flight instrumentation and ground data analysis techniques and a method for measuring intermittency of turbulence are described, Correlation was obtained between the hot film gage signals and chemicals for transition detection. Cross-flow vortices were observed for some flight conditions. Results of spectral and statistical analysis of the hot film signals for various flight test conditions are presented.
Technical Paper

Determination of the Operational Environment of the Propeller Blades on Beech 1900D Aircraft

Data obtained from digital flight data recorders are used to assess the actual operational environment of propellers on a fleet of Beech 1900D aircraft in commuter role. Information is given on various aerodynamic parameters as well as those pertaining to engine and propeller usage. The takeoff rotation has been identified as the most demanding phase of flight in terms of unsteady loads exerted on the propeller blades. Special attention is paid to ground operations.
Technical Paper

Refill Friction Stir Spot Joining Rivet Replacement Technology

The Refill Friction Spot Joining (RFSJ) is an emerging solid-state spot welding technology that thermo-mechanically creates a molecular-level bond between the work-pieces. RFSJ does not consume any filler or foreign materials so that no additional weight is introduced to the assembly. As the solid-to-liquid phase transition is not involved in RFSJ in general, there is no lack of fusion or material deterioration caused by liquefaction and solidification. Unlike the conventional friction stir spot welding, RFSJ produces a spot joint with a perfectly flush surface finish without a key or exit hole. Currently, the aerospace industry employs solid rivets for fastening the primary structures as they meet the baseline requirements and have well-established standards and specifications.
Technical Paper

Experimental Investigation of a Bleed Air Ice Protection System

The work presented in this paper is part of a long-term research program to explore methods for improving bleed air system performance. Another objective of this research is to provide detailed experimental data for the development and validation of simulation tools used in the design and analysis of bleed air systems. A business jet wing was equipped with an inner-liner hot air ice protection system and was extensively instrumented for documenting system thermal performance. The wing was tested at the NASA Glenn Icing Research Tunnel (IRT) for representative in-flight icing conditions. Data obtained include bleed air supply and exhaust flow properties, wing leading edge skin temperatures, temperatures and pressures in the interior passages of the bleed air system, flow properties inside the piccolo tube, photos of run back ice shapes and ice shape traces. Selected experimental results for a warm hold icing condition are presented in this paper.
Technical Paper

Parametric Experiment of Large Droplet Dynamics

An experimental study was performed to investigate large droplet dynamics in the vicinity of an airfoil. The investigation was conducted using the NASA Glenn Droplet Imaging Flow Tunnel (DrIFT). Mono-dispersed large droplets were released at the tunnel inlet and accelerated toward an airfoil that was mounted in the test section. The dynamic behavior of a droplet's encounter with the airfoil, which may involve droplet distortion, break-up, impingement and splashing, was recorded using a high-speed imaging system. The effects of the droplet size, tunnel velocity and airfoil configuration on the droplet dynamics were investigated in a parametric study. The droplet sizes used in the experimental study were 96 and 375 μm whereas tunnel velocities were varied from 80 to 130 mph. Three different airfoil geometries were used in the experimental study; a ‘clean’ and ‘iced’ airfoil, and a ‘clean’ three-element high-lift airfoil. The incidence angle of these airfoils was set to zero degrees.
Technical Paper

An Automated System for Drill Bit Verification

Aerospace manufactures purchase millions of drill bits each year for the manufacture of large aircraft structures. This paper describes an ongoing research project for the development of an automated system to detect poor quality drill bits before they are put to use.
Technical Paper

Aerodynamic Effects of Oversized Tires and Tall Landing Gear on a Small General Aviation Aircraft

An experimental investigation was conducted to identify the aerodynamic effects of oversized low-pressure (Tundra) tires and tall landing gear on a Piper Super Cub airplane. Water tunnel and wind tunnel tests were performed using, respectively, a 1/20 scale model and full-scale landing gear and tire components. Force and moment data suggest that larger tires and taller gear most affect the drag and side force. Small trim changes are apparent, but the basic static stability behavior appears unchanged.
Technical Paper

An Experimental Investigation of SLD Impingement on Airfoils and Simulated Ice Shapes

This paper presents experimental methods for investigating large droplet impingement dynamics and for obtaining small and large water droplet impingement data. Droplet impingement visualization experiments conducted in the Goodrich Icing Wind Tunnel with a 21-in chord NACA 0012 airfoil demonstrated considerable droplet splashing during impingement. The tests were performed for speeds in the range 50 to 175 mph and with cloud median volumetric diameters in the range of 11 to 270 microns. Extensive large droplet impingement tests were conducted at the NASA Glenn Icing Research Tunnel (IRT). Impingement data were obtained for a range of airfoil sections including three 36-inch chord airfoils (MS(1)-0317, GLC-305, and NACA 652-415), a 57-inch chord Twin Otter horizontal tail section and 22.5-minute and 45-minute LEWICE glaze ice shapes for the Twin Otter tail section. Small droplet impingement tests were also conducted for selected test models.
Technical Paper

Advanced Technology in Future Metal Cutting for Airframe Manufacturing

Metal cutting is a substantial constituent of airframe manufacturing. During the past several decades, it has evolved significantly. However, most of the changes and improvement were initiated by the machine tool industry and cutting tool industry, thus these new technologies is generally applicable to all industries. Among them, few are developed especially for the airframe manufacture. Therefore, the potential of high efficiency could not be fully explored. In order to deal with severe competition, the aerospace industry needs improvement with a focus on achieving low cost through high efficiency. The direction of research and development in parts machining must comply with lean manufacturing principles and must enhance competitiveness. This article is being forwarded to discuss the trend of new developments in the metal cutting of airframe parts. Primary driving forces of this movement, such as managers, scientists, and engineers, have provided significant influence to this trend.
Technical Paper

Tail Icing Effects on the Aerodynamic Performance of a Business Jet Aircraft

Experimental studies were conducted to investigate the effect of tailplane icing on the aerodynamic characteristics of 15%-scale business jet aircraft. The simulated ice shapes selected for the experimental investigation included 9-min and 22.5-min smooth and rough LEWICE ice shapes and spoiler ice shapes. The height of the spoilers was sized to match the horns of the LEWICE shapes on the suction side of the horizontal tail. Tests were also conducted to investigate aerodynamic performance degradation due to ice roughness which was simulated with sandpaper. Six component force and moment measurements, elevator hinge moments, surface pressures, and boundary layer velocity profiles were obtained for a range of test conditions. Test conditions included AOA sweeps for Reynolds number in the range of 0.7 based on tail mean aerodynamic chord and elevator deflections in the range of -15 to +15 degrees.
Journal Article

Comparative Usage of Two Similar Airframes

In-service data from two Bombardier business jets, a Global 5000 and a Global Express XRS, have been compared. Flight data has been analyzed from both airframes with comparable number of ground-air-ground cycles. Individual flight phase have been examined and compared between the two airframes. Primary emphasis has been placed on airframe usage. The influence of primary mission on ground-air-ground cycles has been highlighted in the form of ground and flight loads, as well as dynamics of the flights. It is demonstrated that safe-life maintenance approach may have to be adjusted to account for the airframe usage.