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At least 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

V/STOLAND avionics system flight-test data on a UH-1H helicopter

The flight-acceptance test results obtained during the acceptance tests of the V/STOLAND (versatile simplex digital avionics system) digital avionics system on a Bell UH-1H helicopter in 1977 at Ames Research Center are presented. The system provides navigation, guidance, control, and display functions for NASA terminal area VTOL research programs and for the Army handling qualities research programs at Ames Research Center. The acceptance test verified system performance and contractual acceptability. The V/STOLAND hardware navigation, guidance, and control laws resident in the digital computers are described. Typical flight-test data are shown and discussed as documentation of the system performance at acceptance from the contractor.

Baker, F. A.↗
NASA NTRS1983

Design, development, and flight test of a demonstration advanced avionics system

Ames Research Center initiated a program in 1975 to provide the critical information required for the design of integrated avionics suitable for general aviation. The program emphasized the use of data busing, distributed microprocessors, shared electronic displays and data entry devices, and improved functional capability. Design considerations included cost, reliability, maintainability, and modularity. As a final step, a demonstration advanced avionics system (DAAS) was designed, built, and flight tested in a Cessna 402, twin engine, general aviation aircraft. A functional description of the DAAS, including a description of the system architecture, is presented and the program and flight test results are briefly reviewed.

Denergy, D. G.↗
NASA NTRS2003

Development and Flight Testing of an Autonomous Landing Gear Health-Monitoring System

Development and testing of an adaptable vehicle health-monitoring architecture is presented. The architecture is being developed for a fleet of vehicles. It has three operational levels: one or more remote data acquisition units located throughout the vehicle; a command and control unit located within the vehicle; and, a terminal collection unit to collect analysis results from all vehicles. Each level is capable of performing autonomous analysis with a trained expert system. Communication between all levels is done with wireless radio frequency interfaces. The remote data acquisition unit has an eight channel programmable digital interface that allows the user discretion for choosing type of sensors; number of sensors, sensor sampling rate and sampling duration for each sensor. The architecture provides framework for a tributary analysis. All measurements at the lowest operational level are reduced to provide analysis results necessary to gauge changes from established baselines. These are then collected at the next level to identify any global trends or common features from the prior level. This process is repeated until the results are reduced at the highest operational level. In the framework, only analysis results are forwarded to the next level to reduce telemetry congestion. The system's remote data acquisition hardware and non-analysis software have been flight tested on the NASA Langley B757's main landing gear. The flight tests were performed to validate the following: the wireless radio frequency communication capabilities of the system, the hardware design, command and control; software operation; and, data acquisition, storage and retrieval.

Woodard, Stanley E.↗
NASA NTRS2002

Development and Flight Testing of an Adaptive Vehicle Health-Monitoring Architecture

On going development and testing of an adaptable vehicle health-monitoring architecture is presented. The architecture is being developed for a fleet of vehicles. It has three operational levels: one or more remote data acquisition units located throughout the vehicle; a command and control unit located within the vehicle, and, a terminal collection unit to collect analysis results from all vehicles. Each level is capable of performing autonomous analysis with a trained expert system. The expert system is parameterized, which makes it adaptable to be trained to both a user's subject reasoning and existing quantitative analytic tools. Communication between all levels is done with wireless radio frequency interfaces. The remote data acquisition unit has an eight channel programmable digital interface that allows the user discretion for choosing type of sensors; number of sensors, sensor sampling rate and sampling duration for each sensor. The architecture provides framework for a tributary analysis. All measurements at the lowest operational level are reduced to provide analysis results necessary to gauge changes from established baselines. These are then collected at the next level to identify any global trends or common features from the prior level. This process is repeated until the results are reduced at the highest operational level. In the framework, only analysis results are forwarded to the next level to reduce telemetry congestion. The system's remote data acquisition hardware and non-analysis software have been flight tested on the NASA Langley B757's main landing gear. The flight tests were performed to validate the following: the wireless radio frequency communication capabilities of the system, the hardware design, command and control; software operation and, data acquisition, storage and retrieval.

Woodard, Stanley E.↗
NASA NTRSDate not supplied

Development of an Ejectable Data Recorder Ejection Mechanism for the Low Earth Orbit Flight Test of an Inflatable Decelerator

On November 10, 2022, the 1100kg (2,425 lbs.) LOFTID Reentry Vehicle (RV) was launched on a United Launch Alliance Atlas V as a secondary payload with the Joint Polar Surveyor System-2. The 6-meter diameter (~20 ft.) aeroshell (a type of heat shield) entered the atmosphere at 8 kilometers per second (18,000 miles per hour), and flew nominally, enduring the intended heat pulse that saw temperatures exceeding 1371˚C (2500˚F) on the front side while the payload skin remained only about 38˚C (100˚F). The RV exceeded Mach 30 and the heat-affected aeroshell withstood a pressure pulse that exerted 9g’s deceleration maintaining stable flight through the hypersonic, supersonic, transonic, and subsonic regimes to the parachute deployment. As part of the Agency’s strategic goal “to extend human presence deeper into space and to the moon for sustainable long-term exploration and utilization”, the LOFTID inflatable aerodynamic decelerator or aeroshell technology could one day help land humans on Mars. As with any flight test, data collection is of utmost importance. Without a data downlink and a possibility of the RV sinking before the recovery crew got to it, a secondary data collection method was introduced. The RV would eject a data recorder, which would have a duplicate copy of the on-board flight date, before splashdown and be retrieved separately. This paper discusses the development of the ejection mechanism used to eject the data recorder from the RV during the test flight. The development includes discussions of design constraints, a design overview, the testing program, and lessons learned throughout the process all the way through successful data recorder recovery.

mechanism↗
NASA NTRS2002

Ground and Flight Test Structural Excitation Using Piezoelectric Actuators

A flight flutter experiment at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center, Edwards, California, used an 18-inch half-span composite model called the Aerostructures Test Wing (ATW). The ATW was mounted on a centerline flight test fixture on the NASA F-15B and used distributed piezoelectric strain actuators for in-flight structural excitation. The main focus of this paper is to investigate the performance of the piezoelectric actuators and test their ability to excite the first-bending and first-torsion modes of the ATW on the ground and in-flight. On the ground, wing response resulting from piezoelectric and impact excitation was recorded and compared. The comparison shows less than a 1-percent difference in modal frequency and a 3-percent increase in damping. A comparison of in-flight response resulting from piezoelectric excitation and atmospheric turbulence shows that the piezoelectric excitation consistently created an increased response in the wing throughout the flight envelope tested. The data also showed that to obtain a good correlation between the piezoelectric input and the wing accelerometer response, the input had to be nearly 3.5 times greater than the turbulence excitation on the wing.

Voracek, David F.↗
NASA NTRS2006

Flight Test Results for Uniquely Tailored Propulsion-Airframe Aeroacoustic Chevrons: Community Noise

The flow/acoustic environment around the jet exhaust of an engine when installed on an airplane, say, under the wing, is highly asymmetric due to the pylon, the wing and the high-lift devices. Recent scale model tests have shown that such Propulsion Airframe Aeroacoustic (PAA) interactions and the jet mixing noise can be reduced more than with conventional azimuthally uniform chevrons by uniquely tailoring the chevrons to produce enhanced mixing near the pylon. This paper describes the community noise results from a flight test on a large twin-engine airplane using this concept of azimuthally varying chevrons for engines installed under the wing. Results for two different nozzle configurations are described: azimuthally varying "PAA T-fan" chevrons on the fan nozzle with a baseline no-chevron core nozzle and a second with PAA T-fan chevrons with conventional azimuthally uniform chevrons on the core nozzle. We analyze these test results in comparison to the baseline no-chevron nozzle on both spectral and integrated power level bases. The study focuses on the peak jet noise reduction and the effects at high frequencies for typical take-off power settings. The noise reduction and the absolute noise levels are then compared to model scale results. The flight test results verify that the PAA T-fan nozzles in combination with standard core chevron nozzles can, indeed, give a reasonable amount of noise reduction at low frequencies without high-frequency lift during take-off conditions and hardly any impact on the cruise thrust coefficient.

Nesbitt, Eric↗
NASA NTRS1975

Flight test and evaluation of Omega navigation for general aviation

A seventy hour flight test program was performed to determine the suitability and accuracy of a low cost Omega navigation receiver in a general aviation aircraft. An analysis was made of signal availability in two widely separated geographic areas. Comparison is made of the results of these flights with other navigation systems. Conclusions drawn from the test experience indicate that developmental system improvement is necessary before a competent fail safe or fail soft area navigation system is offered to general aviation.

Hwoschinsky, P. V.↗
NASA NTRS1983

Flight-test of the glide-slope track and flare-control laws for an automatic landing system for a powered-lift STOL airplane

An automatic landing system was developed for the Augmentor Wing Jet STOL Research Airplane to establish the feasibility and examine the operating characteristics of a powered-lift STOL transport flying a steep, microwave landing system (MLS) glide slope to automatically land on a STOL port. The flight test results address the longitudinal aspects of automatic powered lift STOL airplane operation including glide slope tracking on the backside of the power curve, flare, and touchdown. Three different autoland control laws were evaluated to demonstrate the tradeoff between control complexity and the resulting performance. The flight test and simulation methodology used in developing conventional jet transport systems was applied to the powered-lift STOL airplane. The results obtained suggest that an automatic landing system for a powered-lift STOL airplane operating into an MLS-equipped STOL port is feasible. However, the airplane must be provided with a means of rapidly regulation lift to satisfactorily provide the glide slope tracking and control of touchdown sink rate needed for automatic landings.

Watson, D. M.↗
NASA NTRS1939

Flight Tests of N.A.C.A. Nose-slot Cowlings on the BFC-1 Airplane

The results of flight tests of four nose-slot cowling designs with several variations in each design are presented. The tests were made in the process of developing the nose-slot cowling. The results demonstrate that a nose-slot cowling may be successfully applied to an airplane and that it utilizes the increased slipstream velocity of low-speed operation to produce increased cooling pressure across the engine. A sample design calculation using results from wind-tunnel, flight, and ground tests is given in an appendix to illustrate the design procedure.

Stickle, George W↗
NASA NTRS1980

A variational technique for smoothing flight-test and accident data

The problem of determining aircraft motions along a trajectory is solved using a variational algorithm that generates unmeasured states and forcing functions, and estimates instrument bias and scale-factor errors. The problem is formulated as a nonlinear fixed-interval smoothing problem, and is solved as a sequence of linear two-point boundary value problems, using a sweep method. The algorithm has been implemented for use in flight-test and accident analysis. Aircraft motions are assumed to be governed by a six-degree-of-freedom kinematic model; forcing functions consist of body accelerations and winds, and the measurement model includes aerodynamic and radar data. Examples of the determination of aircraft motions from typical flight-test and accident data are presented.

Bach, R. E., Jr.↗
NASA NTRS1982

A Variational Technique for Smoothing Flight-Test and Accident Data

The problem of determining aircraft motions along a trajectory is solved using a variational algorithm that generates unmeasured states and forcing functions, and estimates instrument bias and scale-factor errors. The problem is formulated as a nonlinear fixed-interval smoothing problem, and is solved as a sequence or linear two-point boundary value problems, using a sweep method. The algorithm has been implemented for use in flight-test and accident analysis. Aircraft motions are assumed to be governed by a six-degree-of-freedom kinematic model; forcing functions consist of body accelerations and winds, and the measurement model includes aerodynamic and radar data. Examples of the determination of aircraft motions from typical flight-test and accident data are presented.

Bach, Ralph E. , Jr.↗
NASA NTRS2016

Enhancing Flight Test Safety with Real-Time Early Warning Techniques

Contemporary approaches to aerospace vehicle system monitoring rely heavily on thresholds that represent a compromise between providing warning early enough to avert a mishap while simultaneously minimizing false alarms. While this reliance on thresholds has been in place for decades and has permeated both cockpits and control rooms, we often find it insufficient when retrospectively analyzing data from an accident. To modernize and enhance flight test safety, we introduce new methods of monitoring for anomalous patterns of interaction rather than for thresholds exceedance. For systems with a well characterized baseline we show how the Inductive Monitoring System (IMS), utilized by NASA in the aftermath of the Columbia accident, might be implemented in real-time to provide earlier warning than currently employed techniques. For systems without such a baseline, we introduce new developments in statistical methods relating to critical slowing down, first applied in medicine and physics, which show promise for adaptation to flight test. Finally, the familiar resource constrained environment leads to a reliance on increased instrumentation that is challenging the limits of the current "one-sensor, one-indicator" threshold paradigm. Existing methods thus fail to accurately reflect the true complexity of a vehicle rich with interdependent interacting systems. We highlight these concepts in a brief summary of the 2001 Air Transat Flight 236 deadstick landing in the Azores. We then suggest control room and cockpit modifications to better display the information gleaned using these novel monitoring methods.

Javorsek, Daniel, II↗
NASA NTRS2009

Flight Test Performance of a High Precision Navigation Doppler Lidar

A navigation Doppler Lidar (DL) was developed at NASA Langley Research Center (LaRC) for high precision velocity measurements from a lunar or planetary landing vehicle in support of the Autonomous Landing and Hazard Avoidance Technology (ALHAT) project. A unique feature of this DL is that it has the capability to provide a precision velocity vector which can be easily separated into horizontal and vertical velocity components and high accuracy line of sight (LOS) range measurements. This dual mode of operation can provide useful information, such as vehicle orientation relative to the direction of travel, and vehicle attitude relative to the sensor footprint on the ground. System performance was evaluated in a series of helicopter flight tests over the California desert. This paper provides a description of the DL system and presents results obtained from these flight tests.

Pierrottet, Diego↗
NASA NTRS1997

Accuracy of Aerodynamic Model Parameters Estimated from Flight Test Data

An important put of building mathematical models based on measured date is calculating the accuracy associated with statistical estimates of the model parameters. Indeed, without some idea of this accuracy, the parameter estimates themselves have limited value. An expression is developed for computing quantitatively correct parameter accuracy measures for maximum likelihood parameter estimates when the output residuals are colored. This result is important because experience in analyzing flight test data reveals that the output residuals from maximum likelihood estimation are almost always colored. The calculations involved can be appended to conventional maximum likelihood estimation algorithms. Monte Carlo simulation runs were used to show that parameter accuracy measures from the new technique accurately reflect the quality of the parameter estimates from maximum likelihood estimation without the need for correction factors or frequency domain analysis of the output residuals. The technique was applied to flight test data from repeated maneuvers flown on the F-18 High Alpha Research Vehicle. As in the simulated cases, parameter accuracy measures from the new technique were in agreement with the scatter in the parameter estimates from repeated maneuvers, whereas conventional parameter accuracy measures were optimistic.

Morelli, Eugene A.↗
NASA NTRS1995

Determining the Accuracy of Aerodynamic Model Parameters Estimated from Flight Test Data

An important part of building mathematical models based on measured data is calculating the accuracy associated with statistical estimates of the model parameters. Indeed, without some idea of this accuracy, the parameter estimates themselves have limited value. In this work, an expression for computing quantitatively correct parameter accuracy measures for maximum likelihood parameter estimates with colored residuals is developed and validated. This result is important because experience in analyzing flight test data reveals that the output residuals from maximum likelihood estimation are almost always colored. The calculations involved can be appended to conventional maximum likelihood estimation algorithms. Monte Carlo simulation runs were used to show that parameter accuracy measures from the new technique accurately reflect the quality of the parameter estimates from maximum likelihood estimation without the need for correction factors or frequency domain analysis of the output residuals. The technique was applied to flight test data from repeated maneuvers flown on the F-18 High Alpha Research Vehicle (HARV). As in the simulated cases, parameter accuracy measures from the new technique were in agreement with the scatter in the parameter estimates from repeated maneuvers, while conventional parameter accuracy measures were optimistic.

Morelli, Eugene A.↗
NASA NTRS1986

Flight tests of a range-resolved airborne dial with two min-tea CO2 lasers

It is important to measure regional distributions of ozone concentrations in a short time for understanding a mechanism of photo-chemical smog development. An airborne Differential Absorption Lidar (DIAL) system with two low-power mini-TEA CO2 lasers was developed for measuring three-dimensional distributions of ozone in the lower troposphere. The CO2 DIAL is a nadir-looking system and is designed to measure ozone profiles between ground and airplane by using atmospheric aerosols as a distributed radar target. First flight test with a single laser were conducted in February 1985 over the Tokyo area. The system was operated at an altitude of 5000 ft. Results of the first flight tests show that the height profiles of the received power in the boundary layer were different between over land and ocean. The received power has to be inverted to an expression of a single optical parameter to see real aerosol distributions. Inversion of the lidar signal to the aerosol extinction was performed by using Klett's solution.

Itabe, T.↗