Search Results

This paper describes a hypersonic cruiser concept for the 21st century. It is based on studies conducted by The Boeing Company and the National Aeronautics and Space Administration (NASA - Langley) to assess the capability of a hypersonic vehicle concept to conduct cruise and/or space launch missions. It details a Mach 10 cruise vehicle from NASA's Dual-Fuel Airbreathing Hypersonic Vehicle Design study (1995/96), and a Mach 10 cruise/space access vehicle, which resulted from follow-on work. Vehicle performance is presented showing that the Mach 10 cruise vehicle can operate over a significant mission radius, and that the Mach 10 cruise/space access configuration can accomplish desired space launch and cruise missions. A rocket based combined cycle (RBCC) variant is also introduced showing favorable cruise and space launch capability. NASA's Hyper-X flight experiment, which is the next step towards achieving this vision, is also described.

Transportation aspects of commercial spaceflight in the opening decades of the Twenty-first Century are envisioned. A specific Spaceliner concept is described, one predicated on combined-cycle airbreathing/rocket (“Synerjet”) propulsion. Its technical literature recorded heritage is reviewed. NASA's long-term goals, and its ongoing program relevant to this class of transportation concepts are discussed. A key observation, one of potentially distant, but great significance to the future of aviation and the air carrier industry, is that Spaceliner class systems, once available, can -- in addition to providing orbital payload service -- fly transglobally, conducting point-to-point terrestrial transportation services, all at ‘highest speed.” Providing an aviation/air-carrier perspective on all of this, in an annex paper attached, the candid views of an esteemed former airlines executive, the late Willis Player, are highlighted.

The Boeing Company in Mesa, Arizona, has been conducting a concept design study of a roadable helicopter called the “Converticar” to assess its feasibility. This is a twin-engine vehicle with twin retractable coaxial counter-rotating rotors. The purpose of the study is to describe a vehicle that carries four passengers in the equivalent of a luxury car that also can fly like a helicopter, and can be priced like a luxury car. To come near this cost goal, the production rate must be on the order of 500,000 units a year. At that rate there is no chance of training a comparable number of pilots each year. So the machine must fly and navigate autonomously, with the pilot just dialing in where he/she wants to go. Technologically, the concept appears to be feasible. Modern design processes, new materials, and improved manufacturing process should allow the Converticar to be built at the prescribed rate when the proper infrastructure for manufacturing it is made available.

This paper describes the history, design objectives, design process, and regulatory limitations applicable to the development of a new flying car, the AEROCAR 2000. The author owns and operates (fly and drive) one of the five AEROCAR Model 1 flying cars produced in early 1950. From this perspective and experience, the author has examined the needs and demands of a future flying car that would be similar in concept tot he original AEROCAR machine but thoroughly modern in design, performance and safety. The methodology has included five computer based design studies, eleven remote controlled model aircraft and an active flight simulation system of the proposed car and flight control system. Drawings and specifications are included.

It has been suggested that the conventional air data probes used on modern high performance aircraft can be eliminated by exploiting the capabilities of the Inertial Navigation System (INS) and obtaining analytic estimates of angle-of-attack (α), sideslip angle (β), and possibly of dynamic pressure (q). The reasons for wanting to eliminate the probes are that they are vulnerable to ground handling damage, bird strikes, icing, and hostile action in the case of combat aircraft. To determine the feasibility of this approach, three methods for obtaining α and β estimates from INS information were programmed into a nonlinear simulation of a relaxed stability aircraft which requires a high level of artificial stability augmentation through its flight control system. It was found that none of the three methods provided satisfactory stabilizing feedbacks to the control system when the subject aircraft was disturbed by severe atmospheric turbulence.

In this paper, an intelligent autonomous deck landing system is designed for an Unmanned Air Vehicle (UAV). First, the design specifications and requirements are identified for the design of UAV flight control and landing systems. Then the longitudinal models of the UAV are established for the design of an autonomous UAV landing system. The system is designed using fuzzy logic, which is able to provide longitudinal stability and to improve the tracking performance. Simulation results show that the developed landing control system has very good robustness against aerodynamic uncertainty, and good fault tolerance against actuator failures. This indicates that the intelligent landing system has the ability to stabilize a damaged aircraft without knowledge of the types of fault or system parameters. Wind disturbances are also investigated by using the turbulence model for the ship-landing environment.

DARcorporation developed an interactive, user-friendly windows based computer program to perform preliminary design and analysis functions for fixed wing airplanes. This paper shows the development of AGDA: Airplane Geometry Design Assistant, a program used to facilitate the geometric data transfer between analysis and CAD software. One major problem with the use of standard CAD programs is how to recognize different parts of the airplane in the analysis programs. Most routines need certain geometric parameters of the airplane e.g. wing span, fuselage length etc. An easier and user-friendlier method is to use an interface program between the analysis and the standard (commercially available) drafting program, which takes away the drawing instructions. In this way the user can concentrate on making the drawing without having to worry about how the program wants the different parts drawn.

This paper critically evaluates the use of Neural Networks (NNs) as metamodels for design applications. The specifics of implementing a NN approach are researched and discussed, including the type and architecture appropriate for design-related tasks, the processes of collecting training and validation data, and training the network, resulting in a sound process, which is described. This approach is then contrasted to the Response Surface Methodology (RSM). As illustrative problems, two equations to be approximated and a real-world problem from a Stability and Controls scenario, where it is desirable to predict the static longitudinal stability for a High Speed Civil Transport (HSCT) at takeoff, are presented. This research examines Response Surface Equations (RSEs) as Taylor series approximations, and explains their high performance as a proven approach to approximate functions that are known to be quadratic or near quadratic in nature.

The objective of this paper is to examine ways in which to implement probabilistic design methods in the aircraft engine preliminary design process. Specifically, the focus is on analytically determining the impact of uncertainty in engine component performance on the overall performance of a notional large commercial transport, particularly the impact on design range, fuel burn, and engine weight. The emphasis is twofold: first is to find ways to reduce the impact of this uncertainty through appropriate engine cycle selections, and second is on finding ways to leverage existing design margin to squeeze more performance out of current technology. One of the fundamental results shown herein is that uncertainty in component performance has a significant impact on the overall aircraft performance (it is on the same order of magnitude as the impact of the cycle itself).

This paper records progress on design and construction of a roadable airplane called Starcar 4. Starcar 4 is intended to be simple, with one seat, two wing panels, three wheels, and a gross weight of 1200 lbs. The wing panels are removed by hand and hung on the sides for road travel. The core of the structure is a 4130 steel tube frame, covered by a composite aeroshell. The propulsion system is based on a modified Subaru motor and four wheel drive transaxle, which drives a pusher propeller in place of a rear axle. The project has been underway since late 1996 and was first published at the 1997 World Aviation Congress. Engineering design is now well advanced, a wood frame mockup has been built, and the chassis is under construction for delivery at the end of 1998. Road tests will take place in 1999, and the aeroshell and wings should be completed in the year 2000.

Computational Fluid Dynamics (CFD) methods have been employed to provide aerodynamic data in support of Eglin Air Force Base (AFB) in-house engineering analyses. The Beggar CFD code was used to generate numerical solutions for multiple cases addressing a diverse set of complex weapon system issues including the prediction of aircraft/store carriage loads, determination of the aerodynamic changes caused by geometry modifications, calculation of shock wave effects, determination of thermal effects, prediction of weapon separation characteristics, characterization of flowfield wake effects, and prediction of mass flow characteristics. The use of CFD in these efforts yielded notable reductions in program costs and time investment in each of the projects supported.

Effectiveness of active flow control for twin-tail buffet alleviation is investigated. Tangential leading-edge blowing (TLEB) and flow suction along the vortex cores (FSVC) of the leading edges of the delta wing are used to delay the vortex breakdown flow upstream of the twin tail. The combined effect of the TLEB and FSVC is also investigated. A parametric study of the effects of the spanwise position of the suction tubes and volumetric suction. flow rate on the twin-tail buffet response are also investigated. The TLEB moves the path of leading-edge vortices laterally towards the twin tail, which increases the aerodynamic damping on the tails. The FSVC effectively delays the breakdown location at high angles of attack. The computational model consists of a sharp-edged delta, wing of aspect ratio one and swept-back flexible twin tail with taper ratio of 0.23.

Global Hawk is a high altitude, long endurance unmanned aerial reconnaissance system designed to provide military field commanders with high resolution, near real time imagery of large geographic areas. With an objective of operating for 20 hours at an altitude of 19.8 km and at ranges up to 5,556 km from its launch area, it is in the forefront of DOD initiatives to achieve battlefield information dominance. Satellite and line-of-sight communications links ensure world wide operational capability. Global Hawk's state-of-the-art sensors provide all weather, day or night, reconnaissance capability. This paper provides an overview of the Global Hawk system.

This paper looks at the future potential of uninhabited air vehicles, UAVs. The paper begins with a rationale as to why UAVs are needed. A taxonomy of future potential UAVs is presented. Three generic types of UAVs are identified as surveillance and reconnaissance, combat and support aircraft. A total of sixteen possible UAVs are identified. Each one is discussed in terms of mission capabilities. The paper concludes with several “out of the box” concepts, and concludes with a summnary of the potential role of UAVs.

The 98,000 lb. thrust Pratt & Whitney PW4098 high-bypass turbofan engine recently completed a flying test-bed program on the Boeing 777-300 airplane. The purpose of the one-month program was to validate engine operability and to gather data that can be used for upcoming engine certification to the standards of Federal Aviation Regulations part 33. Testing included engine transient operation, steady-state performance, in-flight starting, component cooling, and inlet compatibility. When engine certification is complete, an airplane certification program will be conducted for the 777-300/PW4098, a combination of the world's largest twin engine airplane and the world's largest turbofan engine yet to fly.

Fast closing of actuator servovalves in airplane hydraulic systems can often cause unacceptably high pressure spikes in these systems. This paper describes and discusses a method of reducing these hydraulic system pressure spikes by suitable limiting of the rate at which the servovalve current can change. Analytical and test results are presented to show that with this method, the pressure spikes can be reduced without significantly affecting the actuator dynamic response characteristics.

With regard to the development and quality control of slip-controlled multi-disc clutches, different test procedures were previously used in Europe. These employed test procedures are presented and the requirements for future systems outlined. A new test bench concept is presented, which allows all the necessary procedures previously performed on separate test benches to be performed on a single test bench. This allows considerable time and money savings to be made during development and quality control of slip-controlled multi-disc clutches and transmission oils. Suppliers are presented with the opportunity to perform all the required tests themselves.

A new PC-based hardware and software system has been developed to automate the data acquisition and analysis of brake noise and vibration. The system integrates advanced signal conditioning and software to acquire data rapidly in a consistent and objective manner that overcomes many testing problems. Once data has been acquired, a special algorithm is used to determine when brake noise or vibration occurs during a stop event and from which corner of the vehicle it originates. It also records speed, brake line pressures, temperatures on the pads, ambient temperature, and ambient relative humidity, so engineers will know under what operating conditions the brake noise events occurred. The system can be utilized both on vehicles running city traffic tests and on dynamometer applications.

A test rig which replicates a one quarter vehicle of a rear wheel drive vehicle, including the suspension system, is used to investigate a low frequency noise. The cross beam is included along with the vehicle suspension spring which is loaded against a sprung loaded mechanism which represents the tyre stiffness exactly and supports the brake geometrically as the tyre would. Drive to the drum is from a DC motor through the wheel drive axle. Holographic Interferometry is used to observe the modes of vibration of the drum with mirrors strategically placed to observe additional features such as the backplate, spring pan and cross beam. Initial results show the mode of vibration of the backplate to be of a diametral mode order and to be moving in the direction of drum rotation. Additionally it is seen that the spring pan and cross beam exhibit high amplitudes of vibration.

Thermal judder occurs when differential thermal expansion is experienced around the rotor during a brake application. A temporary circumferential disc thickness variation (DTV) is created which can lead to brake torque variation. The cause of the uneven heating of the rotor can be an imperfection; often a permanent DTV caused by periods of off-brakes contact between pad and disc. Using a dynamometer test combining dynamic disc thickness measurement and pyrometric techniques the evolution of thermal DTV may be studied. It can be demonstrated that increasing thermal DTV is accompanied by increasing brake torque variation. Hot spot formation is also evident but this is shown not be the primary cause of brake torque variation.