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Preliminary results from testing of 26 X 6.6 radial-belted and bias-ply aircraft tires at NASA Langley's Aircraft Landing Dynamics Facility (ALDF) are reviewed. These tire tests are part of a larger, on going joint NASA/FAA/Industry Surface Traction and Radial Tire (START) Program involving three different tire sizes. The 26 X 6.6 tire size evaluation includes cornering performance tests throughout the aircraft ground operational speed range for both dry and wet runway surfaces. Static test results to define 26 X 6.6 tire vertical stiffness properties are also presented and discussed.

A method for thermally analyzing convectively cooled flight experiments is presented in this paper. A three-dimensional fluid flow analysis code was used to optimize air circulation patterns and predict air velocities in thermally critical areas. A comparison between a fan flow analysis using this code and the performance characteristics of a typical isothermal free jet was made. The velocity profiles and radial distribution agree well for downstream mixing of the flow. Predicted air velocities from the fluid analysis were used to calculate forced convection coefficients for the flight experiment. These convection coefficients were used in a finite difference thermal analysis code to describe the response of air temperature and heat loss for the LIDAR Atmospheric Sensing Experiment (LASE) during transient flight profiles. The performance of the existing thermal design is described and the analytical techniques used to arrive at this design are presented.

Tests with specially instrumented NASA B-737 and B-727 aircraft together with several different ground friction measuring devices have been conducted for a variety of runway surface types and wetness conditions. This effort is part of the Joint FAA/NASA Aircraft/Ground Vehicle Runway Friction Program aimed at obtaining a better understanding of aircraft ground handling performance under adverse weather conditions and defining relationships between aircraft and ground vehicle tire friction measurements. Aircraft braking performance on dry, wet, snow-, and ice-covered runway conditions is discussed together with ground vehicle friction data obtained under similar runway conditions. For a given contaminated runway surface condition, the relationship between ground vehicles and aircraft friction data is identified. The influence of major test parameters on friction measurements such as speed, test tire characteristics, and surface contaminant type are discussed.

An overview is given of the ongoing joint NASA/FAA/Industry Surface Traction And Radial Tire (START) Program being conducted at NASA Langley's Aircraft Landing Dynamics Facility (ALDF). The START Program involves tests using three different tire sizes to evaluate tire rolling resistance, braking, and cornering performance throughout the aircraft ground operational speed range for both dry and wet runway surfaces. Preliminary results from recent 40 x 14 size bias-ply, radial-belted, and H-type aircraft tire tests are discussed. The paper concludes with a summary of the current program status and planned ALDF test schedule.

Results are presented of an experimental and analytical study of the dynamic response to crash loadings of five different load-limiting subfloors for general aviation aircraft. These subfloors provide a high-strength structural floor platform to retain the seats and a crush-able zone to absorb energy and limit vertical loads. Experimental static load-deflection data and dynamic deceleration response data for the five subfloors indicated that the high-strength floor platform performed well in that structural integrity and residual strength was maintained throughout the loading cycle. The data also indicated that some of the subfloor crush zones were more effective than others in providing nearly constant load for a range of displacement. The analytical data was generated by characterizing the nonlinear crush zones of the subfloor with static load-deflection data and using the DYCAST nonlinear finite element computer program.

Although the number of possible applications of boundary-layer control is large, a discussion is given only of those that have received the most attention recently at NASA Langley Research Center to improve airfoil drag characteristics. This research concerns stabilizing the laminar boundary layer through geometric shaping (natural laminar flow, NLF) and active control involving the removal of a portion of the laminar boundary layer (laminar flow control, LFC) either through discrete slots or a perforated surface. At low Reynolds numbers, a combination of shaping and forced transition has been used to achieve the desired run of laminar flow and control of laminar separation. In the design of both natural laminar flow and laminar flow control airfoils and wings, boundary layer stability codes play an important role. A discussion of some recent stability calculations using both incompressible and compressible codes is given.

Emerging advanced controls technology will allow future generation fighter aircraft to aggressively maneuver at high angles-of-attack. Currently there is a need to develop flight-validated design methodologies and guidelines to effectively integrate this technology into future aircraft. As part of the NASA High-Alpha Technology Program (HATP), advanced controls technology is being developed in ground-based research and demonstrated using the High-Alpha Research Vehicle (HARV) as a flying testbed. Efforts are in progress to develop flight validated control law design methodologies and design guidelines which could be used to effectively exploit the capabilities provided by advanced controls at high angles of attack. This paper outlines this research effort and summarizes the design process and preliminary methodologies and guidelines developed to date.

Tests of the Space Shuttle Orbiter nose-gear tire have been completed at NASA Langley's Aircraft Landing Dynamics Facility. The purpose of these tests was to determine the cornering and wear characteristics of the Space Shuttle Orbiter nose-gear tire under realistic operating conditions. The tire was tested on a simulated Kennedy Space Center runway surface at speeds from 100 to 180 kts. The results of these tests defined the cornering characteristics which included side forces and associated side force friction coefficient over a range of yaw angles from 0° to 12°. Wear characteristics were defined by tire tread and cord wear over a yaw angle range of 0° to 4° under dry and wet runway conditions. Wear characteristics were also defined for a 15 kt crosswind landing with two blown right main-gear tires and nose-gear steering engaged.

Message exchange for air traffic control (ATC) purposes via data link offers the potential benefits of increasing the airspace system safety and efficiency. This is accomplished by reducing communication errors and relieving the overloaded ATC radio frequencies, which hamper efficient message exchanges during peak traffic periods in many busy terminal areas. However, the many uses and advantages of data link create additional questions concerning the interface among the human-users and the cockpit and ground systems. A flight test was conducted in the NASA Langley B-737 airplane to contrast flight operations using current voice communications with the use of data link for transmitting both strategic and tactical ATC clearances during a typical commercial airline flight from takeoff to landing. Commercial airplane pilots were used as test subjects.

An investigation was conducted to determine the fore and aft elastic response characteristics and footprint geometrical properties of 30 × 11.5 −14.5, Type VIII, bias-ply and radial-belted aircraft tires. Stiffness and damping characteristics of each tire were obtained from load-deflection curves generated from static tests. Tire footprints were obtained for various vertical loads, and geometrical measurements were obtained from the resulting silhouettes. Results of this investigation show considerable differences in stiffness and damping characteristics between the bias-ply and radial-belted tire designs. Footprint geometrical data indicate that footprint aspect ratio effects may interfere with improved hydroplaning potential associated with the radial-belted tire operating at higher inflation pressures. Tire-wheel slippage problems encountered when testing the radial-belted tire design required special attention.

The design and analysis of the National Aerospace Plane (NASP) depends heavily on developing critical technology areas through the Technology Maturation Program (TMP). The TMP is being completed almost entirely in government laboratories with technology dissemination to all prime NASP contractors immediately upon completion of any portion of the technology development. These critical technology areas span the entire engineering design of the vehicle; included are structures, materials, propulsion systems, propellants, propulsion/airframe integration, controls, subsystems, and aerodynamics areas. There is currently a heavy dependence on Computational Fluid Dynamics (CFD) for verification of many of the classical engineering tools. Quite often the design of an aircraft uses wind tunnel tests for much of this verification, but for NASP, this task is almost impossible from a practical standpoint.

Airplane flight tests have been conducted to determine the effects of wing leading-edge modifications and a ventral fin addition on the spin resistance of a typical high-wing, single-engine, general aviation airplane. Drooped wing leading-edge modifications which improve lateral stability at high angles of attack were tested in combination with a ventral fin that improves directional stability. Each modification was evaluated using spin resistance criteria which have been proposed for incorporation into the Federal Aviation Regulations for certification of light aircraft. The best configuration tested, a combination of outboard wing leading-edge droop and a ventral fin, provided a very significant increase in overall airplane spin resistance, but was not sufficient to satisfy all requirements of the spin resistance criteria.

Large space structures will be a key element of our future space activities. They will include spacecraft such as the planned Space Station and large antenna/reflector structures for communications and observations. These large structures will exceed 100 m in length or 30 m in diameter. Concepts for construction of these spacecraft on orbit and their materials of construction provide some unique research challenges. This paper will provide an overview of our research in space construction of large structures including erectable and deployable concepts. Also, an approach to automated, on-orbit construction will be presented. Materials research for space applications focuses on high stiffness, low expansion composite materials that provide adequate durability in the space environment. The status of these materials research activities will be discussed.

Discontinuous wing leading-edge droop designs have been evaluated as a means of modifying wing autorotative characteristics and thus improving airplane spin resistance. Addition of a discontinuous outboard wing leading-edge droop to three typical light airplanes having NACA 6-series wing sections produced significant improvements in stall characteristics and spin resistance. Wind tunnel tests of two wings having advanced natural laminar flow airfoil sections indicated that a discontinuous leading-edge droop can delay the onset of autorotation at high angles of attack without adversely affecting the development of laminar flow at cruise angles of attack.

An investigation was conducted in the Langley 14- By 22-Foot Subsonic Tunnel to determine the low-speed aerodynamic characteristics of a powered generic NASP-like configuration in ground effect. The model was a simplified configuration consisting of a triangular wedge forebody, a rectangular mid-section which housed the propulsion simulation system, and a rectangular wedge aftbody. Additional model components included a delta wing, exhaust flow deflectors, and aftbody fences. Six-component force and moment data were obtained over an angle of attack range from −4° to 18° while model height above the tunnel floor was varied from 1/4 inch to 6 feet. Variations in freestream dynamic pressure, from 10 psf to 80 psf, and engine ejector pressure yielded a range of thrust coefficients from 0 to 0.8. Flow visualization was obtained by injecting water into the engine simulator inlets and using a laser light sheet to illuminate the resulting exhaust flow.

An experiment was conducted to measure the surface pressures and sectional side forces on a 5° cone with three nose tips. The nose tips included a sharp, an 8.7% blunt, and a 17.5% blunt nose tip. Rings of pressure orifices were located at 40% and 80% of the model length and the model was rolled from ±180° in 9° increments to determine roll dependence. The sectional side force data for the sharp cone showed a strong dependence on the roll orientation of the model. The blunt nose cone configurations also showed a dependence on roll orientation. The blunt nose configurations were effective in reducing the sectional side force for angles of attack up to 25°. However, at angles of attack greater than 35°, the reduction was no longer significant. Pressure distributions for three angles of attack are presented to highlight details of the flow when: vortex asymmetries are just beginning; the vortices are in a steady asymmetric state; a vortex has shed between the 40% and 80% stations.

A future requirements and advanced market evaluation study indicates derivatives of current wide-body aircraft, using 1980 advanced technology, would be economically attractive through 2008, but new dedicated airfreighters incorporating 1990 technology, would offer little or no economic incentive. They would be economically attractive for all payload sizes, however, if RD and T costs could be shared in a joint civil/military arrangement. For the 1994-2008 cargo market, option studies indicate Mach 0.7 propfans would be economically attractive in trip cost, aircraft price and airline ROI. Spanloaders would have an even lower price and higher ROI but would have a relatively high trip cost because of aerodynamic inefficiencies. Dedicated airfreighters using propfans at Mach 0.8 cruise, laminar flow control, or cryofuels, would not provide any great economic benefits.

This paper represents a first step in developing the criteria for pilot interaction with advanced controls and displays in a single pilot IFR (SPIFR) environment. The research program presented herein is comprised of an analytical phase and an experimental phase. The analytical phase consisted of a review of fundamental considerations for pilot workload taking into account existing data, and using that data to develop a SPIFR pilot workload model. The rationale behind developing such a model was based on the concept that it is necessary to identify and quantify the most important components of pilot workload to guide the experimental phase of the research which consisted of an abbreviated flight test program. The purpose of the flight tests was to evaluate the workload associated with certain combinations of controls and displays in a flight environment. This was accomplished as a first step in building a data base for single pilot IFR controls and displays.

One of the factors needed to describe the wear behavior of the Space Shuttle Orbiter main gear tires is their behavior during the spin-up process. An experimental investigation of tire spin-up processes was conducted at the NASA Langley Research Center's Aircraft Landing Dynamics Facility (ALDF). During the investigation, the influence of various parameters such as forward speed and sink speed on tire spin-up forces were evaluated. A mathematical model was developed to estimate drag forces and spin-up times and is presented. The effect of prerotation was explored and is discussed. Also included is a means of determining the sink speed of the orbiter at touchdown based upon the appearance of the rubber deposits left on the runway during spinup.

Wind tunnel investigations were conducted as part of an effort to develop a stability and control database for an aerospace plane concept across a broad range of Mach numbers. The generic conical design used in these studies represents one of a number of concepts being studied for this class of vehicle. The baseline configuration incorporated a 5° cone forebody, a 75.96° delta wing, a 16°leading-edge sweep deployable canard and a centerline vertical tail. Tests were conducted in the following NASA-Langley facilities spanning a Mach range of 0.1 to 6:30- by 60-Foot Tunnel,14- by 22-Foot Subsonic Tunnel, Low Turbulence Pressure Tunnel, National Transonic Facility, Unitary Plan Wind Tunnel, and the 20 Inch Mach 6 Tunnel. Data were collected for a number of model geometry variations and test conditions in each facility. This paper highlights some of the key results of these investigations pertinent to stability considerations about all three axes.