Search Results

The paper deals with a structural optimization of the main wing structure of a 2nd generation supersonic commercial transport using the optimization tool STARS to determine a first pre-design. The optimization revealed drastic design changes in stiffness and mass distribution relative to the initial design estimation. Large parts of the forward wing are determined by minimum thickness while the largest cover thickness moved from inboard to far outboard on the rear wing. In addition sensitivity investigation on material allowables are carried out and showed that an increase of 10% of the design allowables of the CFRP material results in a reduction of about 5% total wing weight. In addition, investigation on the elastic behavior indicate the need for further provisions.

In two experiments, strategic conflict avoidance maneuvers of 32 licensed pilots were analyzed when they flew a series of missions in a low fidelity (Experiment 1) and a high fidelity (Experiment 2) flight simulator, rendering an outside view and a cockpit display of traffic information. On various legs of the mission, aircraft generating traffic conflicts intruded from above, below and at the same altitude as ownship at various azimuth orientations. Pilot maneuvers were categorized in terms of the dimension of maneuver (vertical, lateral, airspeed), and the direction of change within that maneuver. Decision analysis revealed a strong tendency of pilots to use simple one dimensional maneuvers, and of these, to prefer vertical over lateral and airspeed maneuvers. Airspeed maneuvers in particular were avoided.

This paper presents an approach to pilots’ situation awareness (SA) that focuses on temporal issues. This approach must be complemented by other factors such as spatial awareness. The temporal aspects of SA are important for the flying task, for computer interaction, and for human communication. The presence of these three domains together inside the cockpit leads to difficulties with time management. Temporal aspects in human-computer interaction (HCI) are investigated in the context of aviation SA. Useful tools for their evaluation and anticipation are proposed. Finally, psychological, cognitive and philosophical studies on time consciousness that enable the investigation of relevant attributes of complex dynamic systems such as aircrafts are presented.

In nonlinear cases, the SDG method requires multidimensional search procedures. However, in linear cases only one-dimensional search procedures are required to identify the critical gust load conditions. In this study the application of the backpropagation ANN method as a multi-dimensional modeling tool has been proposed to model or identify the global and local extrema of one-dimensional gust load responses. The maximum and minimum response values of ramp-step input gust profiles were considered to investigate the ANN modeling capability and effectiveness. The actual SDG analysis for nonlinear cases was hypothesized to be performed over a large and sparse domain, therefore the ANN could be trained to quickly identify the region of the domain containing the global extrema. The SDG analysis, then, could be concentrated on a smaller region thereby reducing computation time.

In recent years, helicopter flight and mission information has migrated from conventional round mechanical dials mounted on the instrument panel to software-dependent head-mounted displays capable of showing many types of information. Test and evaluation techniques have not progressed commensurate with display technology. A formal test and evaluation program is proposed to ensure that new information displays support the pilot’s flight tasks. An outline of test requirements is presented for use in future flight display programs.

The selection of the design parameters of a perspective flightpath display must take into account the operational capabilities of the vehicle to be controlled. As a result, designs of perspective flightpath displays that have been optimized for fixed-wing aircraft may need to be modified in order to be useful for advanced approach procedures with tiltrotors. This paper discusses potential changes that are required as a result of the different range of flightpath angles used in approach trajectories and the different range of velocities.

The paper takes a total systems approach to the human factors challenges at the helicopter-ship dynamic interface. It examines the problems of operating large helicopters from small ships in all weather conditions from the start of the mission to completion with due emphasis on the launch and recovery phases. Research taking place at DERA Bedford in support of current and future naval operations is outlined. Although the prime focus is Royal Navy Anti-submarine Warfare operations, the paper also considers present and future maritime and marinised helicopter types. The paper is written from the perspective of developing requirements and reducing risk by demonstrating technical solutions. The main focus of the paper is the recovery from completion of task to securing in the ship’s hangar. It addresses the aspects of automatic flight path management and flight control systems and the role of automation during the recovery process, particularly in the case of the single pilot aircraft.

Advanced binocular Helmet Mounted Displays (HMD) capable of bisensor operation (I2 tubes and video images) with overlaid symbology have been developed for military use in various helicopters. Extensive flight testing of such helmets, as the French TOPOWL®, have provided so far a considerable amount of data relatively to Night Vision System design and use. Design options allowing improved mass and Center of Gravity in regard of classical NVG, as folded optics and visor projection, have been shown to give very effective results. Performance in various flight conditions, including fog, snow and obstacles, has been quite thoroughly investigated. Training issues with I2 and head-steered thermal imagery have also been addressed during test flight. Lessons learned from test flight open interesting possibilities for further use of such systems in civilian rotorcraft operation, provided acceptably low cost solutions could be achieved.

If an airplane crashes, the recorded radar data can be used to reconstruct a time history of the airplane’s calibrated airspeed, load factor, excess thrust, bank angle, etc. Previous work on this problem has used a rectilinear approach to the calculations involved in the flight parameter reconstruction. The rectilinear approach gives excellent results for relatively straight flight; however, it routinely underestimates the airspeed and the bank angle when the airplane is maneuvering. In the present study, the authors present a curvilinear approach to flight parameter reconstruction that addresses this shortcoming. The analysis presented shows that the curvilinear approach is a far superior tool than the rectilinear approach for the reconstruction of maneuvering flight including steep turns and high-speed spirals.

The use of jet-fuel, de-icing fluids, lubricants, hydraulics, engine oil and other fluids, are associated with single repeated/accidental or chronic exposure (s) to ground staff, flight-deck and cabin crew and passengers. These fluids can become airborne in vapor or aerosol phases, and are known to contain neurotoxicants, carcinogens, irritants and other toxic ingredients. Exposures (single or repeated) to these toxic materials are not rare events and some typical failures/working conditions include mechanical failures, seal leaks, and operational procedures, such as take off while fumes detected, pack burn outs. A method for calculation of exposure dose is proposed. The additional impact of exposure to toxicants in conditions of lowered pressure (and reduced oxygen level), other potentiation factors are still largely unknown, but are not presumed to be beneficial.

The desire to provide integrated surface pressures for aerodynamic loads measurements has been a driving force behind the development of pressure-sensitive paint (PSP). To demonstrate the suitability of PSP for this purpose, it is not sufficient to simply show that PSP is accurate as compared to pressure taps. PSP errors due to misregistration or temperature sensitivity may be high near model edges, where pressure taps are rarely installed. Thus, PSP results will appear good compared to the taps, but will yield inaccurate results when integrated. A more stringent technique is to compare integrated PSP data over the entire model surface with balance and/or CFD results. This paper describes a simple integration method for PSP data and presents comparisons of balance and PSP results for three experiments. PSP is shown quite accurate for normal force measurements, but less effective at determining axial force and moments.

The National Research Council Canada has collected a large number of corroded and non-corroded fuselage lap joints from retired and operational aircraft. A number of these corroded joints have been disassembled in order to quantify the level of corrosion. During the disassembly, it was often observed that common repair techniques resulted in damage to the structure. The damage observed was significant enough to raise concerns regarding the effect of the repair techniques on structural integrity. This paper describes the different types of damage found.

The General Atomics RQ-1A Predator has become an essential tool for battlefield commanders. However, its low maximum speed and poor performance in rain and icing conditions limit its usefulness. In the Spring of 1999, two 10-student sections of the aircraft design class at the United States Air Force Academy studied ways to improve Predator’s usefulness. They determined that small turbine engines, electro-expulsive de-icing systems, and several simple aerodynamic refinements would significantly improve Predator’s capabilities. These results and the methods used to generate them are described.

Different feasibility studies have been carried out over several years at the Royal Military College of Science (RMCS) into medium military airlifters aimed, in essence at replacing the C-130. The studies, each occupying a nominal 1,500 manhours (but probably 50% more) formed part of the final year of the AeroMechanical B.Eng degree at RMCS. The intention of this paper is to draw together their major findings and deals predominantly with the topics of: cargo hold sizing and body aerodynamics, powerplant selection, weight and performance.

This paper presents the results of a conceptual-level design sensitivity analysis of a lethal unmanned aerial vehicle (UAV). Cadet Smith conducted this analysis during his Spring Intern period at the Air Vehicles Directorate of the Air Force Research Laboratory (AFRL). The design was focused on a vehicle capable of carrying out missions that currently employ the F-15E, F-16, and F- 117A. These missions include a deep strike mission, a shorter mission of the same type, and a suppression of enemy air defenses mission (SEAD).

A well designed landing gear and a proper integration is of utmost importance for the success of any aircraft design. This should never be neglected but often is, especially in the conceptual design stage. This paper reflects the author’ s own experience in landing gear design on the Saab Gripen aircraft as well as experience gained on aircraft conceptual designs of later dates. The aim of the paper is to underline the importance of spending more time on landing gear design and integration in conceptual design. The paper reflects the importance of proper interaction between landing gear design and other disciplines and above all underlines the fact that landing gear design should be treated as an equally important design parameter, just as any other, in the final choice of aircraft configuration.

In recent years a clear trend has developed in the aerospace industry towards the procurement of integrated systems from major suppliers. In the process, Messier- Dowty, traditionally a landing gear supplier, became a provider of integrated landing gear systems. This paper concentrates on presenting how Messier- Dowty has implemented the ‘system’ approach and in particular how it affected engineering activity.

The autonomous control of an aircraft under the flare and touch-down maneuvers is an interesting problem of both theoretical and practical nature. In this paper, a concept of the autonomous landing system (ALS) for unmanned air vehicles (UAV) is presented. The flight control system is addressed to the low-cost, civilian, medium-size UAV with relatively low approach speed and typical nose-wheel landing gear. Final approach is executed automatically using differential GPS guidance system. When the flight control system selects the LANDING option at chosen altitude (based on GPS and pressure altitude), a change in aircraft’s attitude is executed. New attitude ensures safe flare and touchdown of the unmanned aircraft. Flight control system is based on the model-following design technique. Two kinds of flight control systems are taken into consideration.

This paper presents typical tire models used by the aerospace community for studying landing gear shimmy. Closed form solutions were developed for the tire models and fit to different types of laboratory tire data. The laboratory tests include the traditional windup tests on a Tire Force Machine, dynamic non-rolling tests on the dynamometer and tire force machine, and dynamic yaw and rolling tests on the dynamometer. Both bias and radial tire designs were studied in both the new and worn condition. Based on the testing performed, significantly different tire property information is obtained. For example, torsional stiffness measured for the non-rolling condition was nearly three times larger than that measured for the rolling tire. Also, very large differences in the torsional damping coefficient between tire types were only evident through dynamic yaw and rolling testing.