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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.

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.

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.

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.

Global warming concerns are stimulating accelerated research and development of alternative fuels and propulsion systems for automobiles. The potential application of these emerging technologies to airplanes is reviewed. Preliminary designs of zero greenhouse gas emission airplanes using hydrogen fuel and either internal combustion or fuel cell-electric motor propulsion are presented for a wide body jet transport, medium jet transport, business jet, and single engine propeller airplane. The hydrogen fueled internal combustion engine airplanes offer the easiest path to zero emissions, but the greater efficiency of the fuel cell airplanes allows designs requiring substantially less fuel. The single engine propeller airplane is the easiest to modify for hydrogen fuel, because of the relatively high mass and volume of the engine being replaced. Technology improvements needed to make zero emission airplanes viable are suggested.

Ice particles shed from aircraft surfaces are a safety concern because they can damage aft-mounted engines and other aircraft components. Ice shedding is a random and complex phenomenon. The randomness of the ice fragment geometry, size, orientation and shed location in addition to potential particle breakup during flight poses considerable simulation challenges. Current ice shedding analysis tools have limited capabilities due to the lack of experimental aerodynamic coefficients for the forces and moments acting on the ice fragment. A methodology for simulating the shedding of large ice particles from aircraft surfaces was developed at Wichita State University. This methodology combines experimental aerodynamic characteristics of ice fragments, computational fluid dynamics, trajectory analysis and the Monte Carlo method to provide probability maps of shed particle footprints at desired locations.

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.

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.

An experimental study was conducted to investigate ice-adhesion on clean and coated aluminum surfaces. A test apparatus using the parallel plate linear shear technique was designed along with a data acquisition system for conducting the tests and recording the experimental data. A low pulling rate was applied to specially prepared test specimens for measuring the strength of ice adhesion for a range of test conditions. The effects of surface roughness, surface contamination, and water impurity on ice adhesion were investigated. In addition, tests were conducted to evaluate the effectiveness of a low ice-adhesion coating applied to aluminum test specimens. The results obtained showed that the bond between ice and metal was considerably lower for tap water than for distilled water. For the clean and coated aluminum surfaces the strength of ice adhesion varied with specimen roughness. However, no clear trend was established between ice adhesion strength and surface roughness.

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.

During this study, a number of 8.5-inch by 11.5-inch flat honeycomb sandwich panels were inflicted with low energy impact damage, inspected non-destructively, and tested for residual in-plane compressive strength. Each panel had either a 3/8-inch or 3/4-inch low density Nomex honeycomb core, and either 2-ply, 4-ply or 6-ply face sheets. The face sheets were either carbon or Eglass (prepreg) fabric. The panels were either clamped or simply supported in a test fixture during impact from a gravity assisted drop mechanism, and impacted with either a 1-inch or 3-inch diameter spherical indenter. After impact the damage to each panel was characterized by (1) ultrasonic through-transmission to obtain a c-scan representing planar damage area, (2) indentation volume and depth, and finally (3) visual inspection to rate the damage according to a predetermined rating scale. The panels were then tested for in-plane compressive strength.

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.

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.