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The next oil crisis will create a new round of interest in alternative energy, renewable sources. The economics of military and commercial sailing will again be hotly debated by naval architects and marine engineers. The difference this time will be the abundance of data from the large world fleet of unmanned air vehicles (UAV), which just might be the key to wind assisted freighters. Our pioneering efforts with recreational kite sailing and buggies have provided part of the database needed to apply UAV technology to the task of wind assist for global transport. This paper will tie the UAV and kitesailing technology to military and commercial needs. For example, the Boeing Condor (Fig 1), with her jumbo jet span and 40,000 lb lift capability, could generate 10,000 lbs of thrust from the trade winds, tethered to a ship at sea.

The desire of achieving faster cruise speed for rotorcraft vehicles has been around since the inception of the helicopter. Many unconventional concepts have been considered and researched such as the advanced tilt rotor with canards, the tilt-wing, the folding tiltrotor, the coaxial propfan/folding tiltrotor, the variable diameter tiltrotor, and the stopped rotor/wing concept, in order to fulfill this goal. The most notable program which addressed the technology challenges of accomplishing a high speed civil transport mission is the High Speed Rotorcraft Concept (HSRC) program. Among the long list of potential configurations to fulfill the HSRC intended mission, the stopped rotor/wing is the least investigated due to the fact that the existing rotorcraft synthesis codes cannot handle this type of vehicle. In order to develop such a tool, a designer must understand the physics behind this unique concept.

This is a progress report for the concept design for a roadable helicopter; i. e., a helicopter that can fold up its blades and drive off like a car. The study is funded by NASA's Langley Research Center, and is the result of a survey of the American helicopter industry two years ago to determine if there was any interest by those companies to study this concept which has the added features of a fully automatic stability / control / navigation system for complete hands-off flight, could be built at a rate of at least 500,000 units per year, and would sell for a price equivalent to a then-year luxury automobile. The unanimous response was that this would be a fantastically attractive engineering project, could undoubtedly be made to work, but reaching the suggested production rate and cost would be a substantial challenge. McDonnell Douglas Helicopter Systems (MDHS) agreed to look into the matter, and this paper describes where we were about three months into the study.

The Naval Research Laboratory is involved in the research and early development of a number of different type small air vehicles. Principle among these are: the expendable short duration decoy platform, reusable long duration vehicles, and multiple mission extended duration vehicles. Platform type selected for utilization is driven by the mission to be performed and the cost constraints imposed upon decoy systems researched and fielded by the Navy. Missions may include: reconnaissance, surveillance, targeting, training, and ship/aircraft decoy protection. The Variable Endurance, Tactical Use Resource (VENTURE) focuses on a multi-mission role potential. Recent experiments have proven-out and expanded upon a technology which promises to deliver a truly multi-mission vehicle.

This paper summarizes the results to date of an on-going research program being conducted by NASA in conjunction with the FAA vertical flight program office. The goal of the program is to reduce pilot workload and increase safety for rotorcraft category A terminal area procedures. Two piloted simulations were conducted on the NASA Ames Vertical Motion Simulator to examine the benefits of optimal procedures, cockpit displays, and alternate cueing methods. Measures of performance, handling qualities ratings and pilot comments indicate that such enhancements can greatly assist a pilot in handling an engine failure in the terminal area.

Collision avoidance is of concern to all aircraft, requiring the detection and identification of hazardous terrain or obstacles in sufficient time for clearance maneuvers. The collision avoidance requirement is even more demanding for helicopters, as their unique capabilities result in extensive operations at low-altitude, near to terrain and hazardous obstacles. To augment the pilot's visual collision avoidance abilities, some aircraft are equipped with “enhanced-vision” systems or terrain collision warning systems. Enhanced-vision systems typically project raw images from infrared or radar sensors, and can require a high degree of pilot interpretation and attention, as the sensor returns may be sparse and are devoid of memory from previous sensor returns. Terrain collision warning systems rely on stored terrain maps that are of low resolution and accuracy which do not represent hazards to the aircraft placed after map sampling.

Accurate information derived from monitoring the contamination level of the hydraulic fluid in an aircraft allows the development of a diagnostic system. Using this approach, maintenance can be based on actual condition of the aircraft's Fluid Power System. Servicing the system and its components based on known condition rather than on arbitrary service, or time intervals reduces unscheduled maintenance and has a major impact on reducing operating costs. Safety, reliability, and predictable availability of the aircraft are significant benefits of this approach to maintenance.

The Advanced Composites Repair Analysis Tool (ACRAT) has been under development for the USAF Advanced Composites Program Office under an Ogden ALC Design Engineering Program (DEP) Contractual Engineering Task (CET) Order. ACRAT is an integrated prototype software system consisting of commercial-off-the-shelf (COTS) and public domain CAE simulation codes and customized databases. The objective has been to develop Beta versions of this computer aided composite repair design and assessment engineering tool following the provisions and procedures of the ASTM Standard E 1340-90 (Reference 1). The standard guide produces working models early in the development cycle, which allows users and developers to learn functional requirements and appropriate system design details by actually interacting with a series of prototypes. Two Beta versions, of a planned six Beta cycle development effort (three-year program), have been completed to-date.

Advanced technology in both hardware and software design is being incorporated into today's military aircraft without fully considering the capabilities and limitations of the operator. Incorporating this new technology results in operators being disenchanted with the design due to the lack of a compatible human interface with that technology. Interface design, or in better terms, Pilot-Vehicle design, has been ignored or given minimal attention by the designers. Designers need to realize that implementing new software or hardware designs is more than coding a set of requirements or mounting a new system that ends up making the operator's tasks harder to complete. Programs at the conceptual phase need to seriously consider human capabilities meshed with the air vehicle design and its mission requirements. The antidote to this controversy is labeled Pilot-Vehicle Integration.

Both manufacturers and users of various products in today's competitive market must provide detailed tracking of malfunctions and corresponding maintenance actions. A Maintenance Management Information System (MMIS), developed with this aim should help perform failure cause analysis, reduce downtime, optimize maintenance resources and lower total maintenance expenses. ALD's V-FRACAS software system achieves these objectives and includes the following options: Failure and maintenance actions recording Corrective Action definition Reliability-Centered Maintenance (RCM) management An advanced RCM application allows to achieve an optimal balance between total expenditures for preventive and corrective maintenance versus total production losses arising from failures. The proposed maintenance policy incorporates periodic prediction of an item's remaining lifetime based on its status and elapsed operating time.

Aircraft hydraulic systems have operated at 3000 psi for many years. The hydraulic power within the aircraft however has consistently increased for each generation of aircraft. Higher pressure hydraulics has been studied based upon the smaller volume and lighter weight of the higher pressure hydraulics. The Model A/F27T-10 Hydraulic Component Test Stand is designed to provide the capability to test high pressure aircraft hydraulic components up to and including 8000 psi. The Test Stand is capable of automatic or fully independent manual operation and is designed for use in intermediate level activities in land based, ship board, or mobile van facilities.

A description is given of the outboard horizontal stabilizer (OHS) system in which the horizontal tail surfaces are mounted outboard of the mainplane tips, in the wing upwash, at the extremities of booms projecting downwind from the mainplane tips. The theory of operation of the OHS concept is reviewed together with the current development status. Configurational geometries of OHS and comparable conventional aircraft are defined and first order, comparative, performance analyses are presented for cruise, take-off and landing modes of operation. It is shown that the pitch-mode control of OHS aircraft does not present any problems relative to the control, in pitch, of comparable conventional aircraft. It was also shown that the OHS concept makes possible a reduction of the drag of the wing and tail surfaces of about 20% together with a reduction in planform area of, typically, 13%.

To optimize the hydraulic system design and evaluate the system performance at the airplane level, a complete dynamic integrated hydraulic model is needed. This paper describes the development and usage of a dynamic model for the Boeing 777 hydraulic system. This model dynamically simulates the hydraulic power available as a function of the airplane events. This not only allows the designers to test their design prior to building the hardware but it also serves as a tool to evaluate the hydraulic system performance at the airplane level.

“Operation Heli-STAR” (Helicopter Short-haul Transportation and Aviation Research) “An Olympic Moment” The microcosm of activity surrounding the 1996 Olympic Games provided researchers an opportunity for demonstrating state-of-the art technology in the first large-scale deployment of a prototype digital communication/ navigation/ surveillance system in a confined environment. At the same time it provided an ideal opportunity for transportation officials to showcase the merits of an integrated transportation system in meeting the operational needs to transport time sensitive goods and provide public safety services under a real-world conditions. Five aeronautical CNS functions using a digital datalink system were chosen for operational flight testing onboard 91 aircraft, most of them helicopters, participating in the Atlanta Short-Haul Transportation System.

As aero engines mature the operator, the repair base, and the manufacturer look for controlled means of extending operational life, as a means of controlling maintenance costs. The approach must focus on component integrity and performance to ensure a cost effective release life can be achieved. The program must be dynamic if it is to address the needs of today's sophisticated gas turbine.

The aim of the project described in this paper is to control the behavior and trajectory of a vehicle when different parameters - such as the lift and/or the aerodynamic parameters - change, i.e., increase or decrease. The problem is tackled, whatever the mode of propulsion of the vehicle ( combustion engine or electric motor and wheel transmission - or reactor ). This paper describes one way of developing the architecture of such a system for the control of the functions of route guidance, of the changes in attitude which lead to a modification of the aerodynamic forces according to the speed variations and more generally the vehicle's dynamics. An active system based on torque and slip controls of each wheel allows the control of rolling. The wheel propulsion mode and freewheel mode are considered in a similar way. The function of attitude correction uses an active system controlling a hydraulic jack mounted in the suspension.

A review is made of a number of flying automobiles that have been built and flown including two that were granted Approved Type Certificates by the CAA (now FAA). Also reviewed are conceptual or visionary designs by a number of innovators. The author, although critical of certain designs, encourages creativity and continued exploration of new flying automobile concepts. It is possible that high technology advances may lead to a flying automobile that will satisfactorily combine the comfort and convenience of the automobile with the high cruise speed and efficiency of the airplane. Dreamers are urged to dream on, and on, into the 21st Century.

The Focke-Wulf Fw 190 was one of the truly outstanding fighter aircraft of the Second World War. It distinguished itself over all fronts on which the Luftwaffe fought in conditions ranging from arctic wastes to the deserts of North Africa. The Fw 190 represented the epitome of conventional piston-engine fighter design on the threshold of the jet age. Conceived nearly sixty years ago, flying for the first time on the eve of the war in 1939 and acknowledged as “the best all-around fighter in the world” in the mid-war years, derivatives of the Fw 190 were still pushing the ultimate capability boundary for this class of aircraft at war's end in 1945 (reaching maximum level true airspeeds of 470 mph [about Mach 0.7] at altitudes of well over 40,000 feet). This paper assesses the design attributes and technology approaches, including innovative use of advanced electrical systems, that were used to make the Fw 190 one of the great all-around fighters in aviation history.

The intent of a balanced engine design process is to satisfy all systems requirements including operability, performance and durability. Due to the complexity of the trade-off process of the various metrics it is possible that system improvements may be required after a turbofan engine enters production. Also, in the case of derivative engines, configured for increased performance, the flowpath aerodynamics may be challenged and may have to be examined to ensure there is no flow field anomaly. By incorporating special diagnostic aero instrumentation at the earliest opportunity any required operability improvement can be identified and corrective action taken. The paper first delineates the component matching challenges of twin spool mixed flow turbofan engines. Then it discusses investigation of various potential destabilizing influences.

A series of aerodynamically driven model mounts for dynamic wind tunnel testing were designed, built and evaluated at Wichita State University. The mount proved to be very responsive, stable and capable of generating a wide variety of pitching motions. However, the response of an early variant of this mechanism displayed “stair-step” like behavior during slow pitching motions and damped oscillations at the end of rapid pitching motions. Numerical and experimental evaluations demonstrated that these undesired characteristics are minimized when the size of the control surface is increased and the inertia of the apparatus is reduced. In addition, this novel mechanism was utilized to demonstrate the type of valuable data that can be obtained. Force data for an oscillating NACA 0012 wing section is provided.