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High altitude, high speed flight will push vehicles into regions wherein the density of the surrounding medium is so low that vehicle aerodynamics cannot be described on the basis of the continuum equations of fluid motion. Typical flight trajectories and the characteristic flow regions they traverse are illustrated, and the prediction techniques based on molecular flow physics are outlined. Some analytical, experimental, and flight test results which clearly illustrate the importance of low density effects on the flight performance of vehicles -- particularly lift, drag, and moment -- are discussed. The data presented bring out some fundamental physical principles of molecular interactions in the definitions of aerodynamic behavior, and some of the underlying physical mechanisms are discussed. Molecule-to-molecule interaction is only one of the processes which determine flow field characteristics.

Although radial tires have been used in automobiles, they are still in the stage of testing for a possible future use in aircraft. An important consideration is the tire's average life when subjected to various loading conditions. Along with this consideration, tire deformation is one of the concerns. This paper presents a study of deformation comparison between F16 bias and radial aircraft tires subjected to loading conditions against flat plate and flywheel with different percentages of tire deflection and different yaw angles. Optical fringe projection technique is used to determine the three dimensional tire deformation. Like any other similar optical technique, the deformed surface is measured relative to the selected reference point. Therefore, in order to find the absolute geometry of the deformed tire surface, a close-range fiber optic displacement sensor was installed to accurately detect the point's height change in a direction parallel to the wheel axle.

Directed Energy Weapons (DEW) require switches that are capable of switching hundreds to thousands of amperes of current at thousands of volts potential. Present and near term available devices must be packaged in parallel and in series to achieve the power ratings required for DEW applications. High voltage silicon (Si) devices such as recent advances in MOS turn-off thyristors (MTOs) can be used along with the high speed, soft-recovery Trench Oxide P-i-N Schottky (TOPS) diodes to reach high power density and high efficiency. However, wide bandgap, high thermal conductivity silicon carbide (SiC) power switches and diodes in development offer orders of magnitude improvement in terms of power density and power efficiency, and are much more ideal for DEW applications. In addition, SiC power switches can be operated at much higher temperatures than silicon (present developments to at least 300°C) with an increased Radiation Hardness.

This paper presents an optical technique called fringe projection to measure three dimensional tire deformation subjected to different loads, percentages of deflection and yaw angles. Unlike the well-known Moire method, the proposed technique uses a single light source and a grating, thus requiring no image superposition. As a result, the measurement is not as sensitive to vibration as the Moire method. The fringe projection also differs from the commonly used optical inspection technique in manufacturing industry via line scanning known as structured light, which cannot be applied to dynamic deformation measurements. The recently developed subpixel resolution was employed to accurately locate the optical fringe centers, which in turn improves the accuracy in 3-D geometry determination. A fiber-optic displacement sensor was also placed close to the tire sidewall in order to measure the deformational change of a selected reference point.

Fly-by-wire in aircraft flight control design is more than adding a simple wire -- it is a sophisticated system that changes the way aircraft are designed and the way they fly. Prepared and written by experts who directed or staffed fly-by-wire research and development programs, this book includes explanations of the system's design and application, providing both the "how" and the "why" of this remarkable technology. Chapters include: Introduction Background of Fly-by-Wire Required Programs The Survivable Flight Control System (SFCS) Program Technology Transition and Application

This paper reports the results of a limited flight evaluation of Direct Lift Control (DLC) on a modified B-52 aircraft. The evaluation was made in conjunction with concluding flights of the Load Alleviation and Mode Stabilization (LAMS) Program and represents the first flight testing of a blended closed loop DLC system on an aircraft of this size and weight. By allowing the pitch and heave motions in the longitudinal axis to be decoupled, the system provided positive control of altitude displacements while holding pitch attitude constant. In both ILS approaches and aerial refueling tasks, controllability was significantly improved and pilot workload was reduced.

This paper presents the results of a study in which the free rolling behavior of a F-16 tire was numerically modeled. The tire contact patch normal and shear stresses as well as the displacement distributions were obtained from a three dimensional finite element computer program used at the Wright-Patterson Air Force Base, Ohio. It is shown how the predicted deflections are in reasonable agreement with the rated load vs. deformation characteristics, while predicting the effective rolling radius using a theoretical solution. A significant development of this work is the formulation and execution of a finite difference algorithm to evaluate the contact patch slip velocity distribution by methodically manipulating the above computer program results. Slip velocities are then utilized in assessing the rate of slip energy generation at the contact patch, which directly contributes to tire wear. Finally, it is shown how even a low brake slip ratio can increase the contact patch slip energy.

The main objective of this research was to apply an optical technique called fringe projection to quantifying the aircraft tire deformation and strains. The proposed fringe projection technique, using a single light source and a grating, requires no image superposition. Thus, the measurement is not very sensitive to vibration. Three different types of tires in static and dynamic conditions, subjected to different amounts of tire deflections, were tested. A common practice in three dimensional optical measurement is that a fixed reference plane has to be established, from which a fixed reference point is selected. The main technical difficulty in this research is that a tire subjected to an applied load not only moves and rotates, but deforms as well. Therefore, the selected reference point changes its position in three dimensions all the time.

Phase Change Materials once were an interesting phenomena in search of applications. This is no longer true. Advances in encapsulating phase change materials into microscopically thin shells permits their insertion into a wide varity of host materials. As the technology has developed, new applications are being found in a wide variety of areas. Some applications include temperature controlled suits for firefighters and military personnel, structural panels that absorb transient heat loads, and high heat capacity cooling fluids. This paper will cover the current applications being studied for these materials and propose possible future applications. In many cases, the application of these materials is only hampered by not enough people being aware of their capabilities. This paper will detail the Phase Change Materials (PCM) effort and future directions as developed by the U.S. Air Force Wright Laboratory's Flight Dynamics Directorate.

An automatic takeoff and landing system has been developed for remotely piloted vehicles (RPV) operating from prepared runways. This system consists of a scanning beam microwave landing guidance system and a high performance flight control system. Interfaced with the automatic system is a remote operator, who, using a special control station, monitors system performance, evaluates approach quality and may remotely control the vehicle in the event of contingencies. This paper describes briefly the RPV Automatic Takeoff and Landing (Autoland) system development program: the design approach, simulation and flight test results, and conclusions.

Statement of the Problem: Since the Airline Deregulation Act of 1978 the U.S. Airlines have experienced many changes involved with the competitive free market system. For one they have been forced to change their thinking which now lets the balance sheets and bottom line dictate their routes, schedules and pricing. Another is they are forced to operate at lower budgets looking at ways of attracting customers while reducing costs. Both these changes have resulted in the airlines operating close to bankruptcy. With this in mind we see many of the Airlines operating an older fleet of aircraft and not replacing them with newer aircraft. The same is true for the Department of Defense who's mainstay bomber and transport fleet is on average 20 plus years old. So what can the DOD and the airlines do together under the auspices of Dual Use so as to reduce costs and improve their operations?

Advanced centrifugal compressor vapor cycle refrigeration systems are being tested extensively in the laboratory before they are introduced to new affordable fighter aircraft. It was determined that further testing was needed to establish the effects on a centrifugal compressor system due to high and rapidly varying G forces encountered during fighter aircraft maneuvers. Flight weight aircraft vapor cycle components were tested up to 4Gx, 4Gy and 9GZ on the Air Force Armstrong Laboratory Dynamic Environment Simulator Centrifuge Facility under the Integrated Closed Environmental Control System (ICECS) Program at Wright-Patterson AFB, Ohio. The tests demonstrated that a properly designed digital controlled integrated vapor cycle system will operate in the variable G field (9GZ) of a fighter aircraft. It showed that heat exchangers can be designed with minimum effect to gravity “G” fields. The future for vapor cycle systems in new affordable aircraft looks promising.

Experimental results are used to explore the physical mechanism of lift augmentation and the drag due to lift, and to show the inadequacies of the Taylor-Spence thin jet model of the jet flap. In the jet-flapped wing-fuselage configuration, 3D effects, particularly due to the wing-fuselage interference, are shown to have major effects on the performance of the jet flap. At large sweeps the 3D vortical nature of the shock-induced separation is shown to also play a dominant role.

A multi-axial dynamic test instrument was designed to perform wear testing of actual aircraft tires as well as tread/carcass composite specimens under laboratory loading conditions which simulate the elements of take-off, landing and taxiing operations. The wear tester consists of a self-spinning abrading head, mounted on the actuator of a servo-hydraulic test system, which faces either (1) the tread surface of a composite specimen clamped by a horizontal stretch frame or (2) the tread region of actual inflated tires. The test concept has been partially proven in the case of tread/carcass composite specimens by building a proto-type test apparatus and operating it successfully. In the current test set-up, the specimen is subjected to static tension to simulate a circumferential load in the tire footprint and the tread surface is in periodic contact with an abrading head under a specific level of pressure.