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Technical Paper

Concorde Operations

1991-09-01
912161
After seven years of test flying and more than fifteen years of commercial operations Concorde remains unrivalled and unique among civil transport aircraft. Many problems, technical, political and financial have been overcome and the aircraft, flagship of both Air France and British Airways, is now proven, safe and reliable. The aircraft's unmistakable low aspect ratio delta wing, optimized for supersonic cruise, brings with it the penalty of high drag at low speed; a factor impressed on flight crews during initial conversion to type. Concorde's large flight envelope is severely restricted by the need to balance the movement of the aerodynamic centre of pressure by a shift of aircraft Centre of Gravity. The dual-compressor axial flow Rolls-Royce Olympus engines, augmented by afterburning for take-off and transonic acceleration, provide the high jet velocity and high thrust needed for Mach 2 flight.
Technical Paper

Passive Control of Supersonic Cavity Flowfields

1991-09-01
912153
A computational investigation has been conducted to study the effect and mechanisms of the passive control of a supersonic flow over a rectangular two-dimensional cavity. The passive control was included through the use of a porous surface over a vent chamber in the floor of the cavity. The passive control effectively suppressed the low-frequency pressure oscillations for the open type cavity, (length-to-depth ratio = 6.0). The mechanism for the suppression was observed to be the stabilization of the motion of the free shear layer. For the closed type cavity flow, (length-to-depth ratio = 17.5), the passive control modified the flow field to nearly that of an open type cavity flow; further the cavity drag was reduced by a factor of 4. The computational results of both cases showed good agreement with the available experimental data and the predictions of a semi-empirical formula.
Technical Paper

Turbine Blade Heat Transfer Prediction Using Coupled Turbulent Prandtl Number and Transition Models

1991-09-01
912152
A study was undertaken to improve the prediction of heat transfer coefficients on the suction surface of turbine blades. The study specifically investigated the effects of coupling turbulent Prandtl number models with boundary layer transition models. A two-dimensional boundary layer code, STAN5, was selected and the turbulence model modified by incorporating several turbulent Prandtl number and boundary layer transition models found in the literature. Results indicated that subtle effects were attributable to the modified turbulence model. However, desired improvements were not obtained in the heat transfer coefficient predictions. It appears that boundary layer transition models predicting natural transition are not appropriate for use in a turbine blade flow field.
Technical Paper

Cut Progression During Dynamometer Testing of Foreign Object Damaged Type VII Extra High Pressure Aircraft Tires

1991-09-01
912155
Ground operations over rough surfaces and/or debris strewn taxiways and runways may result in cut damage to the tires. Cut progression during continued flight operations has not been seriously studied. This report will follow a group of Type VII Extra High Pressure tires which were damaged by running them over a debris strewn test bed, then run through alternating taxi-takeoff and landing-taxi tests on the 3.05 meter (120 inch) dynamometer in the Landing Gear Development Facility at Wright-Patterson Air Force Base. Only 1.3 - 23% of the debris struck by these tires resulted in cuts. While testing on the dynamometer, the cut depth grew rapidly until it reached the outer carcass ply, then slowed. The test group included new and recapped bias ply, and prototype radial main landing gear tires. This paper will summarize the tire tests and offer recommendations for future evaluation of the tires and materials.
Technical Paper

Runway Drainage Characteristics Related to Tire Friction Performance

1991-09-01
912156
The capability of a runway pavement to rapidly drain water buildup during periods of precipitation is crucial to minimize tire hydroplaning potential and maintain adequate aircraft ground operational safety. Test results from instrumented aircraft, ground friction measuring vehicles, and NASA Langley's Aircraft Landing Dynamics Facility (ALDF) track have been summarized to indicate the adverse effects of pavement wetness conditions on tire friction performance. Water drainage measurements under a range of rainfall rates have been evaluated for several different runway surface treatments including the transversely grooved and longitudinally grinded concrete surfaces at the Space Shuttle Landing Facility (SLF) runway at NASA Kennedy Space Center in Florida. The major parameters influencing drainage rates and extent of flooding/drying conditions are identified.
Technical Paper

Velocity Dependence of High Angle of Attack Longitudinal Flying Qualities Criteria

1991-09-01
912149
Piloted simulations were conducted to investigate flying qualities requirements for longitudinal maneuvering at 30° angle of attack. Pilot evaluations of various longitudinal dynamics were gathered using acquisition and tracking tasks representative of future fighter air combat maneuvering. Pilot comments and Cooper-Harper Ratings were used to define desired regions of aircraft dynamics. These criteria were then compared to previously developed 30° angle of attack criteria for a lower speed flight condition to determine airspeed effects. The desired region of dynamics was found to depend on equivalent airspeed. This dependency can be used to help design control law gain schedules which provide good high angle of attack flying qualities over a wide speed range.
Technical Paper

Controls for Agility Research in the NASA High-Alpha Technology Program

1991-09-01
912148
Emerging advanced controls technology will allow future generation fighter aircraft to aggressively maneuver at high angles-of-attack. Currently there is a need to develop flight-validated design methodologies and guidelines to effectively integrate this technology into future aircraft. As part of the NASA High-Alpha Technology Program (HATP), advanced controls technology is being developed in ground-based research and demonstrated using the High-Alpha Research Vehicle (HARV) as a flying testbed. Efforts are in progress to develop flight validated control law design methodologies and design guidelines which could be used to effectively exploit the capabilities provided by advanced controls at high angles of attack. This paper outlines this research effort and summarizes the design process and preliminary methodologies and guidelines developed to date.
Technical Paper

Dynamic Response of Landing Gears on Rough Repaired Runway

1991-09-01
912154
A general purpose computer program DADS has been used to study the landing gear response on battle damaged, repaired runways during aircraft landing, taxing and take off. Two types of gears have been modeled. One is a cantilever type gear, the other is an articulated gear. The hydraulic orifice damping, pneumatic air spring, bearing friction forces in the shock strut and the tire-load deflection curve are all included in the models. The output includes the tire-ground reaction force, the shock strut dynamic load and the forces in each members of the gear. These two gear models are built in a three dimensional space, and they can be used either as a single gear running over a runway repair mat, or combined together to simulate a whole aircraft operating on a rough field. The study shows the great capability of DADS in the modeling, simulation and analysis of aircraft ground operations.
Technical Paper

CFD Calculations of Closely Coupled Scissor Wings-Inviscid, Viscous, and Vortex Lattice with Rollup Results

1991-09-01
912150
The Scissor Wing Configuration was investigated in the takeoff, landing, and low speed maneuverability area. In this area of operation the scissor lifting surfaces are close to each other and are strongly coupled aerodynamically. Two dimensional viscous and three dimensional vortex lattice results are presented for the scissor wings both of which used a NASA 64A-006 wing section. A multi-element vortex panel code was utilized for the inviscid predictions along with a momentum integral boundary layer code for the viscous predictions. A non-linear vortex-lattice code with wake roll-up was used for the induced drag predictions. Studies were conducted with gap variations between the two wings, longitudinal variation between the two wings, variations in the relative angle between the two wings, leading edge flap variations, and trailing edge flap variations.
Technical Paper

Air Data Measurement for Hypersonic Vehicles

1991-09-01
912143
The advent of vehicles capable of broad-envelope hypersonic flight requires the development of advanced methods for the measurement of air data parameters for vehicle flight and propulsion control. The requirements for hypersonic air data measurement are reviewed, and techniques for the measurement of air data parameters for hypersonic vehicles are presented and assessed. Today's hypersonic vehicles, primarily the space shuttle, have had restricted flight envelopes and required minimal air data measurement performance. Advanced hypersonic vehicles are now being designed that will greatly expand the envelope of hypersonic travel. Accurate measurement or derivation of vehicle altitude, rates, Mach number, angle of attack, and sideslip are required to ensure that operation of a hypersonic vehicle over a broader envelope is possible.
Technical Paper

AGILITY AND HIGH ANGLE OF ATTACK: AN AIR FORCE RESEARCH PERSPECTIVE

1991-09-01
912145
Current efforts to extend controlled flight into the post-stall regime will bring about major changes in aircraft dynamic capability. These changes will have far-reaching implications in terms of the specification, design, evaluation, and operational use of future fighter aircraft. Significant research continues to be accomplished in developing the technologies required to design and build supermaneuverable fighters. This paper discusses some of the background to current agility research and addresses the research which must be accomplished in order for the Air Force to specify requirements for and evaluate these aircraft.
Technical Paper

Development of a Pneumatic High-Angle-of-Attack Flush Airdata Sensing System

1991-09-01
912142
A nonintrusive high-angle-of-attack flush airdata sensing system was installed and flight tested on the F-18 High Alpha Research Vehicle at the NASA Dryden Flight Research Facility. This system consists of a matrix of 25 pressure orifices arranged in concentric circles on the nose of the vehicle to determine angles of attack and sideslip, Mach number, and pressure altitude. During the course of the flight tests, it was determined that satisfactory results could be achieved using a subset of just nine ports. The high-angle-of-attack flush airdata sensing system was calibrated and demonstrated using reference airdata generated by way of minimum variance estimation techniques which blended airdata measurements from two wingtip airdata booms with inertial velocities, aircraft angular rates and attitudes, precision radar tracking, and meteorological analyses. Calibration results are presented.
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

High Speed Civil Transport Electrical Power System Technology Requirements

1991-09-01
912185
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

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

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

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

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

1991-09-01
912180
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.
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