Identifying and Correcting First Order Effects in Explanatory Variables for Longitudinal Real Time Parameter Identification Methods in Atmospheric Turbulence

The use of real time parameter estimation methods for dynamic flight modeling in atmospheric turbulence was studied. Real time parameter estimation results of flight data in atmospheric turbulence and in a calm atmosphere were used to explain the problem and identify potential error sources. The use of indirect atmospheric turbulence measurements for real-time parameter estimation in a linear longitudinal dynamics model was studied to account for atmospheric turbulence. It is shown that measuring the air data angles correctly makes it possible to account for atmospheric turbulence as a measured explanatory variable in the parameter estimation problem. Commercial off-the-shelf sensors were researched and evaluated, then compared to air data booms. Frequency response of airflow angle vanes, structural response of the air data boom, and the frequency-dependent upwash and time delay were identified and studied as sources of colored noise in the explanatory variables resulting from typical atmospheric turbulence measurement techniques. The theory explaining the frequency dependent upwash and time delay of airflow angle vanes was studied. The resulting upwash and time delay corrections were analyzed and compared to previous time shift dynamic modeling research. Simulation data, as well as flight test data in atmospheric turbulence, were used to verify the upwash and time delay behavior. A methodology was developed to apply real time upwash and time delay corrections to the airflow angle vanes, dramatically improving parameter estimation results over the existing state of the art. Recommendations are given for follow-on theoretical development, flight research, and instrumentation

Using Indirect Turbulence Measurements for Real-Time Parameter Estimation in Turbulent Air

The use of indirect turbulence measurements for real-time estimation of parameters in a linear longitudinal dynamics model in atmospheric turbulence was studied. It is shown that measuring the atmospheric turbulence makes it possible to treat the turbulence as a measured explanatory variable in the parameter estimation problem. Commercial off-the-shelf sensors were researched and evaluated, then compared to air data booms. Sources of colored noise in the explanatory variables resulting from typical turbulence measurement techniques were identified and studied. A major source of colored noise in the explanatory variables was identified as frequency dependent upwash and time delay. The resulting upwash and time delay corrections were analyzed and compared to previous time shift dynamic modeling research. Simulation data as well as flight test data in atmospheric turbulence were used to verify the time delay behavior. Recommendations are given for follow on flight research and instrumentation

Augmented and Virtual Reality for In-Flight Simulator Aircraft

A brief history on in-flight simulator aircraft will be provided. Recent advancements in fused, augmented, and virtual reality will be discussed. The advantages of augmented reality over simulation training will be presented. This will include sustained-acceleration maneuvers, motion related artifacts, low cost aircraft, and the added realism of actual out-the-window scenes. Relevant optical illusions (runway slope, runway width, approach path terrain slope, etc.) and tasks (stall, runway approach, formation, carrier approach, night vision goggles, etc.) will also be presented. Future research opportunities and training will be addressed for commercial, military, and flight test environments

Evaluation of Piloted Inputs for Onboard Frequency Response Estimation

Frequency response estimation results are presented using piloted inputs and a real-time estimation method recently developed for multisine inputs. A nonlinear simulation of the F-16 and a Piper Saratoga research aircraft were subjected to different piloted test inputs while the short period stabilator/elevator to pitch rate frequency response was estimated. Results show that the method can produce accurate results using wide-band piloted inputs instead of multisines. A new metric is introduced for evaluating which data points to include in the analysis and recommendations are provided for applying this method with piloted inputs

Flight Test Results of a GPS-Based Pitot-Static Calibration Method Using Output-Error Optimization for a Light Twin-Engine Airplane

As part of the NASA Aviation Safety Program (AvSP), a novel pitot-static calibration method was developed to allow rapid in-flight calibration for subscale aircraft while flying within confined test areas. This approach uses Global Positioning System (GPS) technology coupled with modern system identification methods that rapidly computes optimal pressure error models over a range of airspeed with defined confidence bounds. This method has been demonstrated in subscale flight tests and has shown small 2- error bounds with significant reduction in test time compared to other methods. The current research was motivated by the desire to further evaluate and develop this method for full-scale aircraft. A goal of this research was to develop an accurate calibration method that enables reductions in test equipment and flight time, thus reducing costs. The approach involved analysis of data acquisition requirements, development of efficient flight patterns, and analysis of pressure error models based on system identification methods. Flight tests were conducted at The University of Tennessee Space Institute (UTSI) utilizing an instrumented Piper Navajo research aircraft. In addition, the UTSI engineering flight simulator was used to investigate test maneuver requirements and handling qualities issues associated with this technique. This paper provides a summary of piloted simulation and flight test results that illustrates the performance and capabilities of the NASA calibration method. Discussion of maneuver requirements and data analysis methods is included as well as recommendations for piloting technique

Systems and Methods for Noise Mitigation for Hybrid and Electric Aircraft

A system and method of noise mitigation for hybrid and electric aircraft, the aircraft having a controllable pitch propeller or rotor(s) with a plurality of blades. The propeller or rotor(s) are driven by a drive system to provide thrust for the aircraft, and the blades of the propeller or rotor(s) are further movable about pivot axis to vary a pitch thereof. A controller on-board the aircraft is operable to cause rotation or movement of the blades of the propeller or rotor(s) about their pivot axis to alter and/or focus at least one aspect of the propeller generated noise to reduce or mitigate such noise while maintaining a substantially constant thrust, altitude, and/or air speed of the aircraft

Systems and Methods for Noise Mitigation for Hybrid and Electric Aircraft

A system and method of noise mitigation for hybrid and electric aircraft, the aircraft having a controllable pitch propeller or rotor(s) with a plurality of blades. The propeller or rotor(s) are driven by a drive system to provide thrust for the aircraft, and the blades of the propeller or rotor(s) are further movable about pivot axis to vary a pitch thereof. A controller on-board the aircraft is operable to cause rotation or movement of the blades of the propeller or rotor(s) about their pivot axis to alter and/or focus at least one aspect of the propeller generated noise to reduce or mitigate such noise while maintaining a substantially constant thrust, altitude, and/or air speed of the aircraft

Flight Test Results of an Angle of Attack and Angle of Sideslip Calibration Method Using Output-Error Optimization

As part of a joint partnership between the NASA Aviation Safety Program (AvSP) and the University of Tennessee Space Institute (UTSI), research on advanced air data calibration methods has been in progress. This research was initiated to expand a novel pitot-static calibration method that was developed to allow rapid in-flight calibration for the NASA Airborne Subscale Transport Aircraft Research (AirSTAR) facility. This approach uses Global Positioning System (GPS) technology coupled with modern system identification methods that rapidly computes optimal pressure error models over a range of airspeed with defined confidence bounds. Subscale flight tests demonstrated small 2- error bounds with significant reduction in test time compared to other methods. Recent UTSI full scale flight tests have shown airspeed calibrations with the same accuracy or better as the Federal Aviation Administration (FAA) accepted GPS 'four-leg' method in a smaller test area and in less time. The current research was motivated by the desire to extend this method for inflight calibration of angle of attack (AOA) and angle of sideslip (AOS) flow vanes. An instrumented Piper Saratoga research aircraft from the UTSI was used to collect the flight test data and evaluate flight test maneuvers. Results showed that the output-error approach produces good results for flow vane calibration. In addition, maneuvers for pitot-static and flow vane calibration can be integrated to enable simultaneous and efficient testing of each system

Development, Implementation, and Pilot Evaluation of a Model-Driven Envelope Protection System to Mitigate the Hazard of In-Flight Ice Contamination on a Twin-Engine Commuter Aircraft

Fatal loss-of-control accidents have been directly related to in-flight airframe icing. The prototype system presented in this report directly addresses the need for real-time onboard envelope protection in icing conditions. The combination of prior information and real-time aerodynamic parameter estimations are shown to provide sufficient information for determining safe limits of the flight envelope during inflight icing encounters. The Icing Contamination Envelope Protection (ICEPro) system was designed and implemented to identify degradations in airplane performance and flying qualities resulting from ice contamination and provide safe flight-envelope cues to the pilot. The utility of the ICEPro system for mitigating a potentially hazardous icing condition was evaluated by 29 pilots using the NASA Ice Contamination Effects Flight Training Device. Results showed that real time assessment cues were effective in reducing the number of potentially hazardous upset events and in lessening exposure to loss of control following an incipient upset condition. Pilot workload with the added ICEPro displays was not measurably affected, but pilot opinion surveys showed that real time cueing greatly improved their awareness of a hazardous aircraft state. The performance of ICEPro system was further evaluated by various levels of sensor noise and atmospheric turbulence

Development and Implementation of a Model-Driven Envelope Protection System for In-Flight Ice Contamination

Fatal loss-of-control (LOC) accidents have been directly related to in-flight airframe icing. The prototype system presented in this paper directly addresses the need for real-time onboard envelope protection in icing conditions. The combinations of a-priori information and realtime aerodynamic estimations are shown to provide sufficient input for determining safe limits of the flight envelope during in-flight icing encounters. The Icing Contamination Envelope Protection (ICEPro) system has been designed and implemented to identify degradations in airplane performance and flying qualities resulting from ice contamination and provide safe flight-envelope cues to the pilot. Components of ICEPro are described and results from preliminary tests are presented