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Technical Paper

Enhanced Vision System Option on Future Aircraft

1991-09-01
912204
Abstract An Enhanced Vision System (EVS) displays sensor derived information to the pilot, usually on a Head Up Display (HUD). The use of at least one on-board sensor would allow the pilot to visualize the runway environment when conventional flight visibility would not permit this. The components of the system are integrated in a way that takes into account the specific task to be accomplished and the associated human factors. The technology for EVS appears to be available. There is a potential for EVS to provide added situational awareness for flight crews. One challenge is to determine whether EVS can be economically justified. However, its potential for improving situational awareness may outweigh any economic disadvantage. Airport capacity during fog conditions could be improved. Additionally, the pilot's ability to avoid runway incursions under night/low visibility conditions could be substantially improved.
Technical Paper

Advanced Power Generation Systems for More Electric Aircraft

1991-09-01
912186
This paper describes the technologies pursuant to more electric aircraft. The title “More Electric Aircraft” is an appropriate appellation to describe the inexorable trend towards the use of more electrics in future advanced military and commercial aircraft. This trend is sponsored and supported by the U.S. Air Force/WRDC, USN/NADC and NASA. Most recently, the Department of the Air Force issued a solicitation with the acronym MADMEL: Power Management and Distribution for More Electric Aircraft. This is a major multi-year program which includes a MADMEL ground demonstrator and flight testing of electric technologies that will replace the several multiple power sources now resident in current aircraft.
Technical Paper

Process Control Challenges During the Manufacture of Large Superplastically Formed/Diffusion Bonded Structure

1991-09-01
912195
This paper discusses technological aspects of the combined metal stretch and superplastic forming/diffusion bonding (SPF/DB) process applied to the manufacture of large and structurally complex engine nacelle components of the C-17 Advanced Military Airlifter. The manufacturing approach uses the McDonnell Douglas four-sheet SPF/DB process as the principal fabrication method, which in combination with the concurrent stretch is perceived as the most innovative and technologically advanced concept undertaken by the industry. The component is a compound curvature titanium 6AI-4V weld assembly made up of four, 20 mm (0.75 inch) thick sandwich segments approximately 90 cm by 120 cm (3 feet by 4 feet) in size. Also addressed are the engineering and manufacturing concepts, quality criteria, and the need for, and challenges of predicting and controlling the SPF/DB process, a prerequisite for the economic viability of the technology.
Technical Paper

Auxiliary Power System Requirements for Commercial Air Transports - Past, Present and Future

1991-09-01
912188
The auxiliary power unit (APU) requirements for commercial air transports have evolved from those of a convenience item to those of a highly integrated, heavily utilized, automated and sometimes essential, airplane system. This evolution has been driven by increasing demands for reliable airframe electrical and pneumatic power, fuel and weight efficiency, reduced crew workload, maintainability, and environmental accordance. Moreover, with the growth of extended range twin operations (ETOPS), the APU has become an essential back-up to primary airframe systems. This paper reviews the APU design criteria of past and present Boeing commercial jet transports and suggests the direction of future installations.
Technical Paper

Secondary Power System Preliminary Design

1991-09-01
912189
Commercial gas turbine auxiliary power unit (APU) requirements are in many respects more demanding than those for propulsion engines of a similar power level. The successful modern APU design must provide high reliability and durability in a flight weight package which also satisfies diverse and often conflicting performance requirements. The preliminary design phase represents the first crucial step towards meeting these objectives. This paper examines how the primary APU requirements influence turbomachinery configuration selection, and then flow down through the preliminary design process into individual APU component and sub-system design criteria, using a load compressor APU example.
Technical Paper

Concorde Flight Testing - Powerplant and Performance Flying

1991-09-01
912192
The certification of the Western world's first supersonic civil transport did not have the benefit of past experience as has been the case in the subsonic field. Supersonic experience was limited to military aircraft which possessed in the main a relatively short duration supersonic dash capability. Concorde has been in Airline service since 1976 and has built up over 150,000 hours of which over 112,000 are at supersonic speeds on a worldwide basis. This achievement came about following a flight development and certification programme covering approximately 5,500 hours over six and a half years. This wealth of experience creates a totally different scene to that existing at the time of Concorde's conception and many lessons are available for the next generation of supersonic civil transport.
Technical Paper

Concorde Propulsion - Did We Get It Right? The Rolls-Royce/Snecma Olympus 593 Engine Reviewed

1991-09-01
912180
Abstract The Olympus 593 together with its reheat, primary nozzle and secondary nozzle systems was designed and developed jointly by Rolls-Royce in Britain and Snecma in France. The design objectives were met so that the Concorde aircraft still carries a full payload of 100 passengers between Europe and America. 600,000 hours of operational experience, over half at Mach 2.0, have shown the control philosophies adopted were correct and are showing that the most significant difference between civil subsonic and supersonic engines is the cruise at high inlet air temperatures which has produced some unexpected mechanical affects.
Technical Paper

Concorde Development - Powerplant Installation and Associated Systems

1991-09-01
912181
Responsibilities for the various aspects of the design of Concorde were shared between Aerospatiale and British Aerospace. This paper covers some of the lessons learnt during the design, development and in-service phases of the last 30 years in the fields covered by BAe, namely the power plant installation and its services - fuel, fire precautions, engine-intake compatibility, control systems etc. Structural problems have been dealt with extensively elsewhere. The experience gained so far in 150,000 hours of operation of which 112,500 hours have been at supersonic speeds with approximately 100,000 hours at Mach 2.0 have provided a very sound basis for the development and operation of the next series of supersonic transports.
Technical Paper

270-Vdc/Hybrid 115-Vac Electric Power Generating System Technology Demonstrator Evolution to a Dual-Channel, More Electric Aircraft Technology Development Testbed

1991-09-01
912183
Abstract Sundstrand has been investigating 270-Vdc/hybrid 115-Vac electrical power generating systems (EPGS) technology in preparation for meeting the electrical power generating system (EPGS) requirements for future aircraft (1). Systems such as the one being investigated are likely to be suitable for the More-Electric Aircraft (MEA) concepts presently under industry and military study. The present Sundstrand single-channel testbed is being further expanded to better understand the electrical system performance characteristics and power quality requirements of an MEA in which traditional mechanical subsystems are replaced by those of a “more-electric” nature. This paper presents the most recent Sundstrand 270-Vdc system transient performance data, and describes the modifications being made to the 270-Vdc/hybrid 115-Vac testbed.
Technical Paper

High Speed Civil Transport Electrical Power System Technology Requirements

1991-09-01
912185
Abstract The Boeing Company is investigating a High Speed Civil Transport (HSCT) aircraft which will transport 300 passengers at speeds up to Mach 2.4. Such a high speed, high altitude aircraft presents unique environmental and safety requirements. The aircraft electrical power system configuration must provide the required redundancy and reliability necessary to supply power for fly-by-wire flight control buses as well as other aircraft loads. Emergency power backup must be considered for various power failure conditions. This paper presents some of the issues affecting the electrical power system design, and some of the possible solutions which will be considered.
Technical Paper

Testing of a Titanium Matrix Composite Landing Gear

1991-09-01
912175
The testing of a titanium matrix composite (TMC) F-15 nose gear outer cylinder is discussed. Two cylinders were fabricated. An entire F-15 nose gear was assembled using the first cylinder. This test gear underwent static structural tests to three critical loading conditions and functional evaluations including load-stroke, rebound snubbing, jig drops and strut stroke cycling. The TMC cylinder successfully completed both groups of testing with no signs of structural or functional degradation.
Technical Paper

Future Military APU Requirements

1991-09-01
912176
Future tactical aircraft will have increased capabilities that will place greater demands on their secondary power systems. Added capabilities such as low observability or internal weapons storage are being planned for without significantly increasing the aircraft's size and weight. The power system must therefore have reduced volume, weight, and complexity, while also being more reliable and maintainable. The auxiliary power unit (APU) is a critical component that must be improved to upgrade the capabilities of the power system. Increasing the APU's power density is one important way for reducing the power system's size and weight. Increased power density, however, will require a power unit operating with higher gas generator temperatures, so this condition will be the major challenge for new APU designs.
Technical Paper

Challenging Power Density Requirements for Future Fighter APUs

1991-09-01
912177
Future fighters will require more compact, lighter weight, small gas turbine auxiliary power units (APUs) capable of faster starting, and operation, up to altitudes of 50,000 ft. The US Air Force is currently supporting an Advanced Components Auxiliary Power Unit (ACAPU) research program to demonstrate the technologies that will be required to accomplish projected secondary power requirements for these advanced fighters. The requirements of the ACAPU Program represent a challenging task requiring significant technical advancements over the current state-of-the-art, prominent among which are: Small high heat release high altitude airbreathing combustors. High temperature monolithic ceramic and metallic small turbines. Capability to operate, and transition from non-airbreathing to airbreathing modes. This paper discusses these challenging requirements and establishes technology paths to match and exceed the required goals.
Technical Paper

A Ground Test Program to Support Condition Monitoring of a Spacecraft Attitude Control Propulsion System

1991-09-01
912169
Abstract The Comet Rendezvous Asteroid Flyby (CRAF) mission involves seven years of flight from 0.6 to 4.57 Astronomical Units (AU), followed by about 915 days of maneuvering around a comet. Ground testing will characterize the very critical attitude control system thrusters' fuel consumption and performance for all anticipated fuel temperatures over thruster life. The ground test program characterization will support flight condition monitoring. A commercial software application hosted on a commercial microcomputer will control ground test operations and data acquisition using a newly designed thrust stand. The data acquisition and control system uses a graphics-based language and features a visual interface to integrate data acquisition and control.
Technical Paper

Condor: An All Electric Airplane

1991-09-01
912184
Boeing has designed and built an unmanned experimental Autonomously Piloted Vehicle called Condor, which has successfully flown. The flight control surfaces are operated using four basic types of electromechanical actuators (EMAs). A common controller design is used to operate all EMAs. This airplane utilizes only electrical secondary power to operate all the subsystems in the vehicle. So it is truly an “All Electric” airplane. This paper describes the Condor flight control actuation, propulsion control actuation, and electrical power generation and distribution systems. Each propulsion system is controlled by a single full authority digital Control Electronics Unit (CEU) with electrical actuators. A separate electronic Ignition Control Unit (ICU) drives the spark plugs, processes camshaft position sensors, and sends speed signals to the CEU and the mission computer.
Technical Paper

The Use of High Voltage Direct Current in Aircraft Electrical Systems - A Navy Perspective

1991-09-01
912173
The simplicity, reliability, and weight reduction potential promised by high voltage direct current (HVDC) electrical power systems has enticed aircraft developers to propose the use of such systems in modified form for advanced aircraft. However, HVDC systems have not been flown on any military or commercial aircraft and little has been done to independently validate the tradeoffs made and to analyze the impact a HVDC system will have on Naval aviation and its support. To rectify this, the Naval Air Systems Command established a working group consisting of Defense Department activities concerned with aircraft electrical power research and development, testing, avionics development, logistics, and safety. The working group was free to examine all aspects of the development, implementation, and use of HVDC aircraft power systems.
Technical Paper

Sealed NiCad vs. Sealed Lead Acid Batteries - Charge Control and Monitor

1991-09-01
912172
Batteries which are used in airborne electrical systems must provide a very high discharge current for APU starting and offer virtually maintenance free service. To achieve this kind of performance for hundreds of operational cycles, it is important to consider the behavior of a battery under actual operating conditions. Several functional parameters such as terminal voltage, state of charge, internal impedance and temperature are continuously changing depending on past and present operating conditions. In order to evaluate the available energy which a battery can deliver at any given time, it is necessary to maintain a log of the State Of Charge Index (SOCI). This numerical indicator is based on a functional relationship between terminal voltage, current flow, elapsed time and internal temperature. These parameters are continuously monitored and periodic measurements are converted into a standard index factor.
Technical Paper

Quantification of Aircraft Carbon Brake Wear Using Regression Analysis and Periodic Wave Forms

1991-09-01
912174
A new method has been developed to measure and quantify aircraft brake wear. This information is used to evaluate brake life, investigate the effects of design changes, and predict worn brake performance. The process is based on digital acquisition of worn brake disk data. Regression analysis is used to fit the profile data to a specially developed 3-D linear model which quantifies total wear and linear taper. Fourier transforms of the profile data yield frequencies, wave lengths, and phases of the dominant periodic wave forms, which define the profile nonlinearities. Development of these methods has resulted in a new and unique technique for evaluation of aircraft brake wear.
Technical Paper

Static Pressure Measurement in a Torque Converter Stater

1991-09-01
911934
The objective of this paper is to experimentally investigate the static pressure field in a torque converter stator. Static pressure is the most reliable and useful quantity to measure since it is based on good fundamental physics and the experimental procedure is simple. Although the automotive torque converter is one of the most complicated turbomachines, static pressure measurement in this device has not been reported in the literature. Static pressure measurements were made in a stator blade passage. The measurements were taken at 72 locations under several operating conditions.
Technical Paper

Total Flexibility in Cartridge Valve Porting Through Innovative Sealing Technology

1991-09-01
912134
A new one-piece seal provides great flexibility in sealing and porting miniature multi-port fluid control components. The new seal provides sealing both axially and radially allowing for distinct ports to be located within the same radial plane. The seal is expanded after insertion, preventing shearing or other damage.
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