Data-Driven Modeling and Regulation of Aircraft Brakes Degradation via Antiskid Controllers

In ground vehicles, braking actuator degradation and tire consumption do not represent a significant maintenance cost as the lifespan of both components, at least in common situations, is rather long. In the aeronautical context, and for aircraft in particular, instead, braking actuator degradation and tire consumption significantly contribute to an aircraft maintenance cost due to the frequency of their replacement. This is mainly due to the fact that aircraft braking maneuvers last significantly longer than those in the automotive context. So that the antilock braking system is always active during the braking maneuver, making its impact on the consumption of the two components significant. This work proposes an innovative data-driven model of brake and tire degradation, showing how they are related to the antiskid controller parameters. The analysis is carried out in a MATLAB/Simulink environment on a single wheel rigid body model, validated experimentally, which includes all the nonlinear effects peculiar of the aeronautic context. The results show that by using an appropriate antiskid control approach, it is possible to directly regulate the consumption of these components while at the same time guaranteeing the required braking performance

Loads technology for supersonic cruise aircraft

A flight program to measure atmospheric turbulence at high altitudes (long wavelengths) in a variety of meteorological conditions is described and some results obtained in high altitude wind shear are discussed. Results are also presented from wind tunnel test programs to measure fluctuating pressures associated with over-the-wing configurations. A flexible aircraft take off and landing analysis and an active control landing gear analysis, are developed and their capabilities are described. Efforts to validate these analyses with experimental data are also discussed as well as results obtained from parametric studies

Active and Data-driven Health and Usage Monitoring of Aircraft Brakes

Aircraft brakes are a safety-critical subsystem, and their prolonged use in each landing maneuver makes them subject to significant wear. Thus, it is crucial to devise efficient methods for monitoring their correct functioning and their health and usage status using the signals available in the Brake Control Unit. This paper proposes and validates an innovative data-driven approach to this problem. The proposed architecture is integrated with the Anti-lock Braking System algorithm providing combined health monitoring and anomaly detection for aircraft brakes in addition to an online estimate of the residual useful life of these components

Studies of some unconventional systems for solving various landing problems

Solutions to various landing problems were obtained through unconventional systems. The first, of these is the air cushion landing system, where efforts were concentrated on development of adequate braking and steering systems and an improved understanding of scaling laws and behavior. The second was concentrated on use of a wire brush skid as a drag producing device, which was shown to have good friction coefficients and reasonable wear rates at ground bearing pressures up to 689 kPa and forward speeds up to 80 km/hr. The third showed great promise in an active control landing gear where significant load reductions were possible during landing impact and subsequent rollout

Shock Absorber Leakage Impact on Aircraft Lateral Stability During Ground Handling Maneuvers

Aircraft braking maneuvers are safety-critical on-ground motions that exhibit complex dynamics and significant dependence on system operating conditions. The fundamental interface between the aircraft and the ground is the landing gear. Among the landing gear components, the shock absorbers may be subject to gas leakage during their lifetime, which is an anomaly that could compromise the lateral stability properties of the aircraft on the operating regimes found during braking maneuvers. In this paper, an explicit link is established between main landing gear shock absorber leakage and aircraft lateral stability. To investigate lateral stability, a high-fidelity multibody nonlinear aircraft simulator is developed in a MATLAB/Simulink framework and validated against experimental data. To generate insight into the problem and to quantify shock absorber leakage impact on aircraft lateral stability, two simple but descriptive analytical models are also developed, each one on a different operating mode of the system. The analysis of the models reveals that shock absorber leakage can have a significant effect on aircraft lateral stability, especially at high velocities and highly damped nose wheel steering conditions. The models developed in this work may be used by aircraft control system designers to come up with more effective lateral stability controllers in the event of main landing gear shock absorber leakage

Assessment of the State of the Art of Integrated Vehicle Health Management Technologies as Applicable to Damage Conditions

A survey of literature from academia, industry, and other Government agencies assessed the state of the art in current integrated vehicle health management (IVHM) aircraft technologies. These are the technologies that are used for assessing vehicle health at the system and subsystem level. This study reports on how these technologies are employed by major military and commercial platforms for detection, diagnosis, prognosis, and mitigation. Over 200 papers from five conferences from the time period of 2004 to 2009 were reviewed. Over 30 of these IVHM technologies are then mapped into the 17 different adverse event damage conditions identified in a previous study. This study illustrates existing gaps and opportunities for additional research by the NASA IVHM Project

A symbolic sensor for an Antilock brake system of a commercial aircraft

The design of a symbolic sensor that identifies thecondition of the runway surface (dry, wet, icy, etc.) during the braking of a commercial aircraft is discussed. The purpose of such a sensor is to generate a qualitative, real-time information about the runway surface to be integrated into a future aircraft Antilock Braking System (ABS). It can be expected that this information can significantly improve the performance of ABS. For the design of the symbolic sensor different classification techniques based upon fuzzy set theory and neural networks are proposed. To develop and to verify theses classification algorithms data recorded from recent braking tests have been used. The results show that the symbolic sensor is able to correctly identify the surface condition. Overall, the application example considered in this paper demonstrates that symbolic information processing using fuzzy logic and neural networks has the potential to provide new functions in control system design. This paper is part of a common research project between E.N.S.I.C.A. and Aerospatiale in France to study the role of the fuzzy set theory for potential applications in future aircraft control systems

Flight and Ground Operations in Support of Airframe Noise Reduction Tests

The National Aeronautics and Space Administration (NASA) Acoustic Research Measurements (ARM) project was established to evaluate via flight tests the noise reduction benefits of the Adaptive Compliant Trailing Edge (ACTE) technology along with various main landing gear noise reduction concepts. The ACTE replaces the original Fowler flaps on the NASA SubsoniC Research Aircraft Testbed (SCRAT), thus creating a seamless trailing edge that provides significant noise abatement benefits. The various main landing gear noise reduction concepts are grouped under the LAnding Gear noisE Reduction (LAGER) task and consist of fairings placed on the main landing gear along with two separate treatments applied to the main landing gear wheel well cavities. This paper discusses the tasks necessary to prepare each of these technologies for the ARM flights. The LAGER hardware was taken from model-scale concepts tested in wind tunnels to flight hardware, which had to be cleared as airworthy for the ARM flights. The ACTE flaps were initially intended to be removed from the SCRAT prior to the start of the ARM project. Retaining the ACTE flaps on the aircraft for a longer period of time to support the ARM flights resulted in additional inspections and considerations since the ACTE flaps were flown longer and at certain flight conditions for longer periods of time than initially analyzed. The flight and ground operations required for the ARM tests required extensive coordination among multiple groups and organizations in order to be successful. This paper provides an overview of the hardware development, ground operations, and flight operations which went into acquiring the desired acoustic measurements. In general, the flights were successful and demonstrated the noise reduction benefits of the ACTE flaps, the LAGER gear fairings, and the LAGER gear cavity treatments

Optimization of Takeoffs on Unbalanced Fields using Takeoff Performance Tool

Unbalanced field length exists when ASDA and TODA are not equal. Airport authority may add less expensive substitutes to runway full-strength pavement in the form of stopways and/or clearways to basic TORA to increase operational takeoff weights. Here developed Takeoff Performance Tool is a physics-based total-energy model used to simulate FAR/CS 25 regulated airplane takeoffs. Any aircraft, runway, and environmental conditions can be simulated, while complying with the applicable regulations and maximizing performance takeoff weights. The mathematical model was translated into Matlab, Fortran 95/2003/2008, Basic, and MS Excel computer codes. All existing FAR/CS 25 takeoff regulations are implemented. Average forces are calculated for takeoff accelerate-go and accelerate-stop scenarios with all-engine-operating and one-engine-inoperative conditions. Special attention was paid to simulating increase in FLLTOW as the clearways and/or stopways are added in varying ratios. From the limited parametric study it appears that clearway-to-stopway ratio addition of 4:1 gives good overall performance increase while keeping decision/action speed constant. The critical clearway length exists for which both TORA and TODA are equally limiting. Corrections for effective runway slopes and wind were derived. The presented takeoff performance model provides a platform for more in-depth optimization studies and economic analysis of runway-airplane-engines synergy

A Summary of NASA Rotary Wing Research: Circa 20082018

The general public may not know that the first A in NASA stands for Aeronautics. If they do know, they will very likely be surprised that in addition to airplanes, the A includes research in helicopters, tiltrotors, and other vehicles adorned with rotors. There is, arguably, no subsonic air vehicle more difficult to accurately analyze than a vehicle with lift-producing rotors. No wonder that NASA has conducted rotary wing research since the days of the NACA and has partnered, since 1965, with the U.S. Army in order to overcome some of the most challenging obstacles to understanding the behavior of these vehicles. Since 2006, NASA rotary wing research has been performed under several different project names [Gorton et al., 2015]: Subsonic Rotary Wing (SRW) (20062012), Rotary Wing (RW) (20122014), and Revolutionary Vertical Lift Technology (RVLT) (2014present). In 2009, the SRW Project published a report that assessed the status of NASA rotorcraft research; in particular, the predictive capability of NASA rotorcraft tools was addressed for a number of technical disciplines. A brief history of NASA rotorcraft research through 2009 was also provided [Yamauchi and Young, 2009]. Gorton et al. [2015] describes the system studies during 20092011 that informed the SRW/RW/RVLT project investment prioritization and organization. The authors also provided the status of research in the RW Project in engines, drive systems, aeromechanics, and impact dynamics as related to structural dynamics of vertical lift vehicles. Since 2009, the focus of research has shifted from large civil VTOL transports, to environmentally clean aircraft, to electrified VTOL aircraft for the urban air mobility (UAM) market. The changing focus of rotorcraft research has been a reflection of the evolving strategic direction of the NASA Aeronautics Research Mission Directorate (ARMD). By 2014, the project had been renamed the Revolutionary Vertical Lift Technology Project. In response to the 2014 NASA Strategic Plan, ARMD developed six Strategic Thrusts. Strategic Thrust 3B was defined as the Ultra-Efficient Commercial VehiclesVertical Lift Aircraft. Hochstetler et al. [2017] uses Thrust 3B as an example for developing metrics usable by ARMD to measure the effectiveness of each of the Strategic Thrusts. The authors provide near-, mid-, and long-term outcomes for Thrust 3B with corresponding benefits and capabilities. The importance of VTOL research, especially with the rapidly expanding UAM market, eventually resulted in a new Strategic Thrust (to begin in 2020): Thrust 4Safe, Quiet, and Affordable Vertical Lift Air Vehicles. The underlying rotary wing analysis tools used by NASA are still applicable to traditional rotorcraft and have been expanded in capability to accommodate the growing number of VTOL configurations designed for UAM. The top-level goal of the RVLT Project remains unchanged since 2006: Develop and validate tools, technologies and concepts to overcome key barriers for vertical lift vehicles. In 2019, NASA rotary wing/VTOL research has never been more important for supporting new aircraft and advancements in technology. 2 A decade is a reasonable interval to pause and take stock of progress and accomplishments. In 10 years, digital technology has propelled progress in computational efficiency by orders of magnitude and expanded capabilities in measurement techniques. The purpose of this report is to provide a compilation of the NASA rotary wing research from ~2008 to ~2018. Brief summaries of publications from NASA, NASA-funded, and NASA-supported research are provided in 12 chapters: Acoustics, Aeromechanics, Computational Fluid Dynamics (External Flow), Experimental Methods, Flight Dynamics and Control, Drive Systems, Engines, Crashworthiness, Icing, Structures and Materials, Conceptual Design and System Analysis, and Mars Helicopter. We hope this report serves as a useful reference for future NASA vertical lift researchers