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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.
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

Spy Blimps Revisited: A Performance Comparison between Two Competing Approaches

While operational airships globally number in the low dozens, interest in buoyant or semi-buoyant platforms continues to arouse imaginations of commercial and military planners and developers alike. The airship-as-advertisement business model is the only model that has proven sustainable on any scale since the crash of the initially successful LZ-128 Hindenburg effectively ended regular passenger and cargo transport by airship, and the 1962 termination of the US Naval airship program terminated regular large-scale surveillance from airships. Efforts in the US and Japan during the 2000's to have a self-sustaining sight-seeing business model using the modern semi-rigid Zeppelin NT both failed. In theory, the buoyant nature of airships provides compelling endurance and cost-per-ton-mile capability which fills a niche arguably not currently occupied by other modes of transportation.
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

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

Damage Resistance Characterization of Sandwich Composites Using Response Surfaces

The coupled influence of material configuration (number of facesheet plies, core density, core thickness) and impact parameters (impact velocity and energy, impactor diameter) on the impact damage resistance characteristics of sandwich composites comprised of carbon-epoxy woven fabric facesheets and Nomex honeycomb cores was investigated using empirically based quadratic response surfaces. The diameter of the planar damage area associated with TTU C-scan measurements and the peak residual facesheet indentation depth were used to describe the extent of internal and detectable surface damage, respectively. Estimates of the size of the planar damage region correlated reasonably well with experimentally determined values. For a fixed set of impact parameters, estimates of the planar damage size and residual facesheet indentation suggest that impact damage development is highly material and lay-up configuration dependent.
Technical Paper

Characterization of the Effect of Material Configuration and Impact Parameters on Damage Tolerance of Sandwich Composites

A series of carefully selected tests were used to isolate the coupled influence of various combinations of the number of facesheet plies, impact energies, and impactor diameters on the damage formation and residual strength degradation of sandwich composites due to normal impact. The diameter of the planar damage area associated with Through Transmission Ultrasonic C-scan and the compression after impact measurements were used to describe the extent of the internal damage and residual strength degradation of test panels, respectively. Standard analysis of variance techniques were used to assess the significance of the regression models, individual terms, and the model lack-of-fit. In addition, the inherent variability associated with given types of experimental measurements was evaluated.