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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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45 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Application and Certification of Comparative Vacuum Monitoring Sensors for Structural Health Monitoring of 737 Wing Box Fittings

Multi-site fatigue damage, hidden cracks in hard-to-reach locations, disbonded joints, erosion, impact, and corrosion are among the major flaws encountered in today's extensive fleet of aging aircraft and space vehicles. The use of in-situ sensors for real-time health monitoring of aircraft structures are a viable option to overcome inspection impediments stemming from accessibility limitations, complex geometries, and the location and depth of hidden damage. Reliable, structural health monitoring systems can automatically process data, assess structural condition, and signal the need for human intervention. Prevention of unexpected flaw growth and structural failure can be improved if on-board health monitoring systems are used to continuously assess structural integrity. Such systems are able to detect incipient damage before catastrophic failures occurs. Condition-based maintenance practices could be substituted for the current time-based maintenance approach. Other advantages of on-board distributed sensor systems are that they can eliminate costly, and potentially damaging, disassembly, improve sensitivity by producing optimum placement of sensors and decrease maintenance costs by eliminating more time- consuming manual inspections. This report presents a Sandia Labs-aviation industry effort to move SHM into routine use for aircraft maintenance. This program addressed formal SHM technology validation and certification issues so that the full spectrum of concerns, including design, deployment, performance and certification were appropriately considered. The Airworthiness Assurance NDI Validation Center (AANC) at Sandia Labs, in conjunction with Boeing, Delta Air Lines, Structural Monitoring Systems Ltd., Anodyne Electronics Manufacturing Corp. and the Federal Aviation Administration (FAA) carried out a certification program to formally introduce Comparative Vacuum Monitoring (CVM) as a structural health monitoring solution to a specific aircraft wing box application. Validation tasks were designed to address the SHM equipment, the health monitoring task, the resolution required, the sensor interrogation procedures, the conditions under which the monitoring will occur, the potential inspector population, adoption of CVM into an airline maintenance program and the document revisions necessary to allow for routine use of CVM as an alternate means of performing periodic structural inspects. To carry out the validation process, knowledge of aircraft maintenance practices was coupled with an unbiased, independent evaluation. Sandia Labs designed, implemented, and analyzed the results from a focused and statistically-relevant experimental effort to quantify the reliability of the CVM system applied to the Boeing 737 Wing Box fitting application. All factors that affect SHM sensitivity were included in this program: flaw size, shape, orientation and location relative to the sensors, as well as operational and environmental variables. Statistical methods were applied to performance data to derive Probability of Detection (POD) values for CVM sensors in a manner that agrees with current nondestructive inspection (NDI) validation requirements and also is acceptable to both the aviation industry and regulatory bodies. This report presents the use of several different statistical methods, some of them adapted from NDI performance assessments and some proposed to address the unique nature of damage detection via SHM systems, and discusses how they can converge to produce a confident quantification of SHM performance An important element in developing SHM validation processes is a clear understanding of the regulatory measures needed to adopt SHM solutions along with the knowledge of the structural and maintenance characteristics that may impact the operational performance of an SHM system. This report describes the major elements of an SHM validation approach and differentiates the SHM elements from those found in NDI validation. The activities conducted in this program demonstrated the feasibility of routine SHM usage in general and CVM in particular for the application selected. They also helped establish an optimum OEM-airline-regulator process and determined how to safely adopt SHM solutions. This formal SHM validation will allow aircraft manufacturers and airlines to confidently make informed decisions about the proper utilization of CVM technology. It will also streamline the regulatory actions and formal certification measures needed to assure the safe application of SHM solutions.

42 ENGINEERING↗
NASA NTRS1977

Space Shuttle Orbiter approach and landing program status

The approach and landing test (ALT) phase of the Space Shuttle program aims at assessing the Orbiter's subsonic aerodynamic flight and landing characteristics along with the support equipment, ground facilities, and the approximate hardware and software to be used in the terminal phase of orbital missions. The program also evaluates the performance of the Shuttle carrier aircraft (SCA) as related to the transport of the Orbiter to the launch sites during the stages of Space Shuttle operations. Results are presented for the SCA inert Orbiter flight testing and the program plans up to the completion of the ALT program. Emphasis is placed on testing the airworthiness of the mated B-747 Shuttle carrier aircraft and Orbiter, checkout of the Orbiter systems in captive flight, and launching the Orbiter with and without the tail cone installed. Major program milestones before the first manned orbital flight are summarized in graphic form.

Andrews, W. H.↗
NASA NTRS2021

Retrospectively Documenting Satisfaction of the Overarching Properties: An Exploratory Prototype

Software-intensive aviation systems are typically developed in accordance with recognized development process, safety analysis, and software development standards such as SAE ARP4754A, SAE ARP4761, and RTCA DO-178C. Efforts to streamline assurance processes and make them flexible enough to handle future assurance challenges have produced the Overarching Properties (OPs) for airworthiness approval. Each of the three OPs is a property systems must possess to be certifiable. There is no mandated means of documenting possession of the OPs. To explore possible means, we have prepared retrospective documentation showing that a specimen software system possesses the OPs. The specimen system, Safeguard, enforces geofencing restrictions on unmanned aerial vehicles. Our OP-possession case for its airborne component comprises eight arguments in the Goal Structuring Notation (GSN): a main argument for each OP and five cross-cutting auxiliary arguments. We present this argument as an example for discussion and further research, e.g., into means of assessing OP possession.

safety case↗
NASA NTRS2023

CESO 22-4: Parabolic and Suborbital Glovebox in Support of Space Crop Production

Space crop production research approaches and technologies can be validated for microgravity using parabolic or suborbital flight opportunities, and this will save considerable risk, time, and money for implementing new strategies in spaceflight. While the durations of microgravity in these tests are insufficient to grow crops, there are numerous examples of the value of microgravity testing for subsystems such as plant water and nutrient delivery, where multiphase fluid flow can be elucidated in short durations, and horticultural operations, such as harvesting and produce sanitation where containment and contamination can be assessed. Containment in any operational test is essential, as crop operations involve fluids and biological samples, which are potential hazards. This project consists of designing, developing, and constructing a parabolic/suborbital glovebox for experiment containment. The design involves modifications and upgrades to an existing glovebox developed at the University of Louisville. The University of Louisville glovebox was used by KSC researchers for space crop parabolic flight tests in 2021, and lessons learned from that testing have driven design modifications and improvements in the KSC-generated glovebox. Requirements were identified, parts were ordered, an operational science glovebox was fabricated, and a detailed materials specification list was generated. Analyses that are required for flight, remain to be performed to meet airworthiness requirements, and that work will have to be conducted in the future before use in flight.

Food Production↗
NASA NTRSDate not supplied

X-57 Wing Structural Load Testing

The X-57 flight project will provide an opportunity to assess the benefits of distributed electric propulsion. The plan is to use a TECNAM P2006T twin-engine light aircraft (Aeronautiche TECNAM S.p.A., Capua, Italy) as the baseline aircraft, but design and fabricate a new wing to test the technology. The wing when fully integrated onto the X-57 TECNAM P2006T fuselage will incorporate two wingtip cruise electric motors and 12 high-lift electric motors along the wing span. The testing described in this paper confirmed the strength of the X-57 wing for flight and provided an opportunity to calibrate the wing flight strain gages for monitoring loads in flight. The X-57 wing was qualification tested in the National Aeronautics and Space Administration Armstrong Flight Research Center Flight Loads Laboratory. This paper documents the airworthiness approach, test setup, instrumentation, and preliminary results. The X-57 ground load testing lessons learned are also discussed.

Wing loading↗
NASA NTRS2015

Mock Certification Basis for an Unmanned Rotorcraft for Precision Agricultural Spraying

This technical report presents the results of a case study using a hazard-based approach to develop preliminary design and performance criteria for an unmanned agricultural rotorcraft requiring airworthiness certification. This case study is one of the first in the public domain to examine design and performance criteria for an unmanned aircraft system (UAS) in tandem with its concept of operations. The case study results are intended to support development of airworthiness standards that could form a minimum safety baseline for midsize unmanned rotorcraft performing precision agricultural spraying operations under beyond visual line-of-sight conditions in a rural environment. This study investigates the applicability of current methods, processes, and standards for assuring airworthiness of conventionally piloted (manned) aircraft to assuring the airworthiness of UAS. The study started with the development of a detailed concept of operations for precision agricultural spraying with an unmanned rotorcraft (pp. 5-18). The concept of operations in conjunction with a specimen unmanned rotorcraft were used to develop an operational context and a list of relevant hazards (p. 22). Minimum design and performance requirements necessary to mitigate the hazards provide the foundation of a proposed (or mock) type certification basis. A type certification basis specifies the applicable standards an applicant must show compliance with to receive regulatory approval. A detailed analysis of the current airworthiness regulations for normal-category rotorcraft (14 Code of Federal Regulations, Part 27) was performed. Each Part 27 regulation was evaluated to determine whether it mitigated one of the relevant hazards for the specimen UAS. Those regulations that did were included in the initial core of the type certification basis (pp. 26-31) as written or with some simple modifications. Those regulations that did not mitigate a recognized hazard were excluded from the certification basis. The remaining regulations were applicable in intent, but the text could not be easily tailored. Those regulations were addressed in separate issue papers. Exploiting established regulations avoids the difficult task of generating and interpreting novel requirements, through the use of acceptable, standardized language. The rationale for the disposition of the regulations was assessed and captured (pp. 58-115). The core basis was then augmented by generating additional requirements (pp. 38-47) to mitigate hazards for an unmanned sprayer that are not covered in Part 27.

Hayhurst, Kelly J.↗
NASA NTRS2008

Closing the Certification Gaps in Adaptive Flight Control Software

Over the last five decades, extensive research has been performed to design and develop adaptive control systems for aerospace systems and other applications where the capability to change controller behavior at different operating conditions is highly desirable. Although adaptive flight control has been partially implemented through the use of gain-scheduled control, truly adaptive control systems using learning algorithms and on-line system identification methods have not seen commercial deployment. The reason is that the certification process for adaptive flight control software for use in national air space has not yet been decided. The purpose of this paper is to examine the gaps between the state-of-the-art methodologies used to certify conventional (i.e., non-adaptive) flight control system software and what will likely to be needed to satisfy FAA airworthiness requirements. These gaps include the lack of a certification plan or process guide, the need to develop verification and validation tools and methodologies to analyze adaptive controller stability and convergence, as well as the development of metrics to evaluate adaptive controller performance at off-nominal flight conditions. This paper presents the major certification gap areas, a description of the current state of the verification methodologies, and what further research efforts will likely be needed to close the gaps remaining in current certification practices. It is envisioned that closing the gap will require certain advances in simulation methods, comprehensive methods to determine learning algorithm stability and convergence rates, the development of performance metrics for adaptive controllers, the application of formal software assurance methods, the application of on-line software monitoring tools for adaptive controller health assessment, and the development of a certification case for adaptive system safety of flight.

Jacklin, Stephen A.↗
NASA NTRS1991

Inspection of aging aircraft: A manufacturer's perspective

Douglas, in conjunction with operators and regulators, has established interrelated programs to identify and address issues regarding inspection of aging aircraft. These inspection programs consist of the following: Supplemental Inspection Documents; Corrosion Prevention and Control Documents; Repair Assessment Documents; and Service Bulletin Compliance Documents. In addition, airframe manufacturers perform extended airframe fatigue tests to deal with potential problems before they can develop in the fleet. Lastly, nondestructive inspection (NDI) plays a role in all these programs through the detection of cracks, corrosion, and disbonds. However, improved and more cost effective NDI methods are needed. Some methods such as magneto-optic imaging, electronic shearography, Diffractor-Sight, and multi-parameter eddy current testing appear viable for near-term improvements in NDI of aging aircraft.

Aging Aircraft↗
NASA NTRS1991

Thermal QNDE detection of airframe disbonds

Thermographic characterization of aircraft bonded lap joints offers a quick noncontacting technique to acquire information for structural integrity assessment. This paper discusses recent research to optimize the technique and determine the limits of its applicability. The temperature of the outer surface of the lap joint is increased by the application of heat flux from either flash or quartz lamp heaters. The time dependence of the surface temperature of the lap joint is imaged radiometrically. Measurements are presented for a range of specimens, ranging from samples fabricated with well characterized disbonds to actual aircraft. A technique for processing these images to enhance the contrast between bonded and disbonded regions of the lap joint is presented. Numerical models of the technique simulate the procedure. These simulations provide a cost efficient method for optimizing the technique by varying parameters such as the time for application of heat. These simulations facilitate the definition of parameters difficult to determine experimentally, such as the minimum air gap required for a disbond to be detected. Good agreement between measurements and these simulations is found.

Aging Aircraft↗