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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Advanced transport operating system software upgrade: Flight management/flight controls software description

The Flight Management/Flight Controls (FM/FC) software for the Norden 2 (PDP-11/70M) computer installed on the NASA 737 aircraft is described. The software computes the navigation position estimates, guidance commands, those commands to be issued to the control surfaces to direct the aircraft in flight based on the modes selected on the Advanced Guidance Control System (AGSC) mode panel, and the flight path selected via the Navigation Control/Display Unit (NCDU).

Clinedinst, Winston C.↗
NASA NTRS1976

Microwave holographic imaging of aircraft with spaceborne illuminating source

The conceptual development of a method for the high angular resolution and accurate angular position estimates for the surveillance and traffic control of aircraft is considered. A target volume several hundred kilometers in diameter is illuminated by a CW microwave source located on a satellite in geosynchronous orbit. Signals are received by a large array of random, conformally located receiving elements. Each element receives the direct signal from the satellite plus signals reflected from aircraft in the illuminated volume. Coherent combination of the signals received from the individual elements permits the equivalent of holographic imaging or multiple beam formation from which the useful target data can be obtained.

Berkowitz, R. S.↗
NASA NTRS2010

Multi-modal cockpit interface for improved airport surface operations

A system for multi-modal cockpit interface during surface operation of an aircraft comprises a head tracking device, a processing element, and a full-color head worn display. The processing element is configured to receive head position information from the head tracking device, to receive current location information of the aircraft, and to render a virtual airport scene corresponding to the head position information and the current aircraft location. The full-color head worn display is configured to receive the virtual airport scene from the processing element and to display the virtual airport scene. The current location information may be received from one of a global positioning system or an inertial navigation system.

Arthur, Jarvis J.↗
NASA NTRS2012

Adaptive Trajectory Prediction Algorithm for Climbing Flights

Aircraft climb trajectories are difficult to predict, and large errors in these predictions reduce the potential operational benefits of some advanced features for NextGen. The algorithm described in this paper improves climb trajectory prediction accuracy by adjusting trajectory predictions based on observed track data. It utilizes rate-of-climb and airspeed measurements derived from position data to dynamically adjust the aircraft weight modeled for trajectory predictions. In simulations with weight uncertainty, the algorithm is able to adapt to within 3 percent of the actual gross weight within two minutes of the initial adaptation. The root-mean-square of altitude errors for five-minute predictions was reduced by 73 percent. Conflict detection performance also improved, with a 15 percent reduction in missed alerts and a 10 percent reduction in false alerts. In a simulation with climb speed capture intent and weight uncertainty, the algorithm improved climb trajectory prediction accuracy by up to 30 percent and conflict detection performance, reducing missed and false alerts by up to 10 percent.

Seperation Assurance↗
NASA NTRS1979

Singular perturbation techniques for on-line optimal flight path control

This paper presents a partial evaluation on the use of singular perturbation methods for developing computer algorithms for on-line optimal control of aircraft. The evaluation is based on a study of the minimum time intercept problem using F-4 aerodynamic and propulsion data as a base line. The extensions over previous work on this subject are that aircraft turning dynamics (in addition to position and energy dynamics) are included in the analysis, the algorithm is developed for a moving end point and is adaptive to unpredictable target maneuvers, and short range maneuvers that do not have a cruise leg are included. Particular attention is given to identifying those quantities that can be precomputed and stored (as a function of aircraft total energy), thus greatly reducing the onboard computational load. Numerical results are given that illustrate the nature of the optimal intercept flight paths, and an estimate is given for the execution time and storage requirements of the control algorithm.

Calise, A. J.↗
NASA NTRS2008

Overview of the LaNCETS Flight Experiment and CFD Analysis. Supplemental Movies

This presentation focuses on nearfield airborne pressure signatures from the Lift and Nozzle Change Effect on Tail Shocks (LaNCETS) flight test experiment. The primary motivation for nearfield probing in the supersonic regime is to measure the shock structure of aircraft in an ongoing effort to overcome the overland sonic boom barrier for commercial supersonic transportation. LaNCETS provides the opportunity to investigate lift distribution and engine plume effects. During Phase 1 flight testing an F-15B was used to probe the F-15 LaNCETS aircraft in order to validate CFD and pre-flight prediction tools. A total of 29 probings were taken at 40,000 ft. altitude at Machs 1.2, 1.4 and 1.6. LaNCETS Phase 1 flight data are presented as a detailed pressure signature superimposed over a picture of the LaNCETS aircraft. The attenuation of the Inlet-Canard shocks with distance as well as its forward propagation and the coalescence of the noseboom shock are illustrated. A detailed CFD study on a simplified LaNCETS aircraft jet nozzle was performed providing the ability to more accurately capture the shocks from the propulsion system and emphasizing how under- and over-expanding the nozzle affects the existence of shock trains inside the jet plume. With Phase 1 being a success preparations are being made to move forward to Phase 2. Phase 2 will fly similar flight conditions, but this time changing the aircraft's lift distribution by biasing the canard positions, and changing the plume shape by under- and over-expanding the nozzle. Nearfield probing will again be completed in the same manner as in Phase 1. An additional presentation focuses on LaNCETS CFD solution methodology. Discussions highlight grid preprocessing, grid shearing and stretching, flow solving and contour plots. Efforts are underway to better capture the flow features via grid modification and flow solution methodology, which will help to achieve better agreement with flight data. An included CD-ROM provides animations of the nearfield probing procedure and of real data from one of the probings integrated with GPS positional and velocity data. An additional in-flight video from the rear seat of the probing aircraft is also provided.

Cliatt, Larry J., II↗
NASA NTRS1985

Advanced Propfan Engine Technology (APET) and Single-rotation Gearbox/Pitch Change Mechanism

The projected performance, in the 1990's time period, of the equivalent technology level high bypass ratio turbofan powered aircraft (at the 150 passenger size) is compared with advanced turboprop propulsion systems. Fuel burn analysis, economic analysis, and pollution (noise, emissions) estimates were made. Three different cruise Mach numbers were investigated for both the turbofan and the turboprop systems. Aerodynamic design and performance estimates were made for nacelles, inlets, and exhaust systems. Air to oil heat exchangers were investigated for oil cooling advanced gearboxes at the 12,500 SHP level. The results and conclusions are positive in that high speed turboprop aircraft will exhibit superior fuel burn characteristics and lower operating costs when compared with equivalent technology turbofan aircraft.

Sargisson, D. F.↗
NASA NTRS1997

On Use of Global Positioning Technology for Solution of Wake Vortex Problem

Improved precision of the flight paths used by aircraft to approach and depart airports is becoming available when the Global Positioning System (GPS) is implemented at airports. An overview will be given of published information on how GPS precision guidance at airports can be used to avoid encounters with the lift-generated vortices shed by preceding aircraft during landing. It is pointed out that GPS provides two needed services to bring about improved avoidance capability. Firstly, GPS pseudolites are being built and installed at airports so that, when coupled with autopilot systems currently available on subsonic transport aircraft, the aircraft can make precision approaches for zero visibility landings. The same equipment can also be used for precision approaches for wake-vortex avoidance. Secondly, regular monitoring of atmospheric motions along the approach corridor can be obtained by use of GPS equipment on board aircraft that are in the flight corridors. That is, wind velocity is determined by use of GPS equipment to measure the ground speed of the aircraft and then combined with onboard instrumentation to measure the airspeed of the aircraft. The difference between the two measurements yields the wind velocity. When the measured wind velocities are transmitted to an airport ground station they are used to monitor whether air motions adverse for safety in the flight corridor are present. If any parts of the corridor are unsafe, the spacing of the aircraft, or the location of the flight corridor being used, is modified. It is estimated that the spacings between any combination of aircraft can then be safely reduced to a uniform 3 n. mi. Information to be presented is contained in an article published in the AIAA Journal of Aircraft, May-June 1996.

Rossow, Vernon J.↗
NASA NTRS1980

Top inlet system feasibility for transonic-supersonic fighter aircraft applications

Top inlet flow field and inlet performance data are presented which provide preliminary insight into the feasibility of upper-fuselage mounted inlet systems for transonic-supersonic fighter aircraft. Presented data span the Mach 0.2 to 2.0 envelope and enable evaluation of the influence of key aircraft configuration variables - inlet location, wing position, wing leading-edge extension (LEX) planform area, and variable incidence canards - on top inlet performance. The viability of this concept relative to more conventional inlet/airframe integrations is assessed via comparative evaluation of top and conventional inlet flow field parameters at transonic and supersonic speeds. It is shown that the action of the wing LEX vortex system produces a significant improvement in top inlet performance. Currently available transonic-supersonic data indicate that top inlet systems pose a viable configuration option for fighter aircraft requiring moderate angle of attack capability. However, recently acquired data indicate that increased angle of attack capability may be obtained by increasing wing leading-edge sweep angle.

Williams, T. L.↗
NASA NTRS2002

Device and Method for Reducing Aircraft Noise

A noise abatement device that is positioned adjacent to a body. The noise abatement device generally includes tabs or cavities which thicken the shear layer created by fluid flow over, around, or near the body, by creating horseshoe-shaped vortices; this thickening of the shear layer reduces the strength of fluctuations in the flow which produce noise.

Craig L Streett↗
NASA NTRS1989

Blade surface pressure measurement on a pusher propeller in flight

Unsteady aerodynamics of a pusher propeller operating in the wake of a pylon is investigated through analysis of flight test data. Twenty-two surface-mounted miniature pressure transducers were installed at the 75 and 90 percent radius locations on a propeller blade on a test-bed aircraft. Twenty-six different flight conditions were flown to cover the range of speeds, rpm, altitudes, and flap positions encountered by an advanced turboprop general aviation aircraft. Preliminary analysis of the flight test data indicate a strong three-dimensionality to the perturbed flow at the 75 and 90 percent radii due to pylon wake encounter. Time-history of the pressure transducer waveforms recorded for 700 revolutions exhibit a one-per-cycle wave oscillation on the wake signature. No explanation is found for this behavior yet.

Farokhi, S.↗
NASA NTRS1986

Obtaining One-Degree Accuracy With Shaft Encoders

Circuit converts output of 1-pulse-per-revolution shaft encoder to precise 360-pulses-per-revolution output. Circuit allows shaft angular position to be measured with 1-degree accuracy. With simple modifications, circuit provides higher or lower resolution from single- or multiple-pulse-perrevolution sources. Circuit used to synchronize aircraft beacon transponder-based plan-position indicator (PPI) display to remote host interrogator search antenna. Constructed using standard, commercially available components.

Franke, J. M.↗
NASA NTRS1971

ATS-1/ATS-3 dual satellite navigation study

A study which illustrated the feasibility of implementing an on-board aircraft navigation system based on using the ATS-1 and ATS-3 satellites, the modified Omega Position Location Equipment (OPLE) Control Center, and a suitable aircraft terminal was conducted. The report provides: (1) a consideration of the problems of satellite navigation and an objective definition of the optimum system under the constraints of its specified components, (2) a description of the necessary modifications to the OPLE Control Center, the design of an aircraft terminal, and the design of ground reference terminals, and (3) an outline of an experiment plan and an estimate of the cost to be expected in conducting the program.

Hoover, W. M.↗
NASA NTRS1992

Correlation of forebody pressures and aircraft yawing moments on the X-29A aircraft at high angles of attack

In-flight pressure distributions at four fuselage stations on the forebody of the X-29A aircraft have been reported at angles of attack from 15 to 66 deg and at Mach numbers from 0.22 to 0.60. At angles of attack of 20 deg and higher, vortices shed from the nose strake caused suction peaks in the pressure distributions that generally increased in magnitude with angle of attack. Above 30 deg-angle of attack, the forebody pressure distributions became asymmetrical at the most forward station, while they remained nearly symmetrical until 50 to 55 deg-angle of attack for the aft stations. Between 59 to 66 deg-angle of attack, the asymmetry of the pressure distributions changed direction. Yawing moments for the forebody alone were obtained by integrating the forebody pressure distributions. At 45 deg-angle of attack, the aircraft yaws to the right and at 50 deg and higher, the aircraft yaws to the left. The forebody yawing moments correlated well with the aircraft left yawing moment at an angle of attack of 50 deg or higher. At a 45 deg-angle of attack, the forebody yawing moments did not correlate well with the aircraft yawing moment, but it is suggested that this was due to asymmetric pressures on the cockpit region of the fuselage which was not instrumented. The forebody was also shown to provide a positive component of directional stability of the aircraft at angles of attack of 25 deg or higher. A Mach number effect was noted at angles of attack of 30 deg or higher at the station where the nose strake was present. At this station, the suction peaks in the pressure distributions at the highest Mach number were reduced and much more symmetrical as compared to the lower Mach number pressure distributions.

Fisher, David F.↗
NASA NTRS1992

Correlation of Forebody Pressures and Aircraft Yawing Moments on the X-29A Aircraft at High Angles of Attack

In-flight pressure distributions at four fuselage stations on the forebody of the X-29A aircraft have been reported at angles of attack from 15 to 66° and at Mach numbers from 0.22 to 0.60. At angles of attack of 20° and higher, vortices shed from the nose strake caused suction peaks in the pressure distributions that generally increased in magnitude with angle of attack. Above 30° -angle of attack, the fore body pressure distributions became asymmetrical at the most forward station, while they remained nearly symmetrical until 50- to 55°-angle of attack for the aft stations. Between 59- to 66°-angle of attack, the asymmetry of the pressure distributions changed direction. Yawing moments for the forebody alone were obtained by integrating the forebody pressure distributions. At 45°-angle of attack, the aircraft yaws to the right and at 50° and higher, the aircraft yaws to the left. The fore body yawing moments correlated well with the aircraft left yawing moment at an angle of attack of 50° or higher. At a 45°-angle of attack, the forebody yawing moments did not correlate well with the aircraft yawing moment, but it is suggested that this was due to asymmetric pressures on the cockpit region of the fuselage which was not instrumented. The forebody was also shown to provide a positive component of directional stability of the aircraft at angles of attack of 25° or higher. A Mach number effect was noted at angles of attack of 30° or higher at the station where the nose strake was present. At this station, the suction peaks in the pressure distributions at the highest Mach number were reduced and much more symmetrical as compared to the lower Mach number pressure distributions.

Flight Testing↗
NASA NTRS2011

Safe, Advanced, Adaptable Isolation System Eliminates the Need for Critical Lifts

The Starr Soft Support isolation system incorporates an automatically reconfigurable aircraft jack into NASA's existing 1-Hertz isolators. This enables an aircraft to float in mid-air without the need for a critical lift during ground vibration testing (GVT), significantly reducing testing risk, time, and costs. Currently incorporating the most advanced technology available, the 60,000-poundcapacity (27-metric-ton) isolation system is used for weight and measurement tests, control-surface free-play tests, and structural mode interaction tests without the need for any major reconfiguration, often saving days of time and significantly reducing labor costs. The Starr Soft Support isolation system consists of an aircraft-jacking device with three jacking points, each of which has an individual motor and accommodates up to 20,000 pounds (9 metric tons) for a total 60,000-pound (27-metric-ton) capacity. The system can be transported to the aircraft by forklift and placed at its jacking points using a pallet jack. The motors power the electric actuators, raising the aircraft above the ground until the landing gear can retract. Inflatable isolators then deploy, enabling the aircraft to float in mid-air, simulating a 1-Hertz free-free boundary condition. Inflatable isolators have been in use at NASA for years, enabling aircraft to literally float unsupported for highly accurate GVT. These isolators must be placed underneath the aircraft for this to occur. Traditionally, this is achieved by a critical lift a high-risk procedure in which a crane and flexible cord system are used to lift the aircraft. In contrast, the Starr Soft Support isolation system eliminates the need for critical lift by integrating the inflatable isolators into an aircraft jacking system. The system maintains vertical and horizontal isolating capabilities. The aircraft can be rolled onto the system, jacked up, and then the isolators can be inflated and positioned without any personnel needing to work underneath the aircraft. Also, the system accommodates changes in aircraft configuration, automatically adapting to changes in mass, and it can adjust the height of the isolators in one basic setup. Dryden personnel used the Starr Soft Support system to successfully perform a GVT on an F-15 being structurally modified by Gulfstream, Dryden's Gulfstream III used for science research and the crew exploration module and adaptor cone assembly.

Ginn, Starr↗
NASA NTRS2005

Capacity Takes Flight: A Vehicle-Centered Approach to Sustainable Airspace Productivity

The National Airspace System (NAS) faces a significant challenge. With the nation's economy growing stronger, and passengers returning to the skies, the demand for air transportation is steadily rising once again. The capacity of the current airspace system will struggle to keep pace in the near term, and with demand expected to double within a decade, air traffic delays are likely to escalate, soon becoming intolerable for aviation businesses. Recognition in the aviation community is forming that retaining a growing, thriving air transportation system for the benefit of the traveling public and the world economy will likely require implementing transformational ideas in air traffic management. This video illustrates an approach NASA is pursuing to this end: the notion that a major untapped resource available to air traffic management can be leveraged, the aircraft itself. The thesis presented is that implementation of vehicle-centric air traffic management capabilities into the NAS could have a profound, positive, and sustainable impact on system capacity, individual aircraft operators, and the economy through its dependency on air.

Wing, David J.↗