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NASA NTRS2015

Development and Preliminary Tests of an Open-Path Airborne Diode Laser Absorption Instrument for Carbon Dioxide

Carbon dioxide (CO2) is well known for its importance as an atmospheric greenhouse gas, with many sources and sinks around the globe. Understanding the fluxes of carbon into and out of the atmosphere is a complex and daunting challenge. One tool applied by scientists to measure the vertical flux of CO2 near the surface uses the eddy covariance technique, most often from towers but also from aircraft flying specific patterns over the study area. In this technique, variations of constituents of interest are correlated with fluctuations in the local vertical wind velocity. Measurement requirements are stringent, particularly with regard to precision, sensitivity to small changes, and temporal sampling rate. In addition, many aircraft have limited payload capability, so instrument size, weight, and power consumption are also important considerations. We report on the development and preliminary application of an airborne sensor for the measurement of atmospheric CO2. The instrument, modeled on the successful DLH (Diode Laser Hygrometer) series of instruments, has been tested in the laboratory and on the NASA DC-8 aircraft. Performance parameters such as accuracy, precision, sensitivity, specificity, and temporal response are discussed in the context of typical atmospheric variability and suitability for flux measurement applications. On-aircraft, in-flight data have been obtained and are discussed as well. Performance of the instrument has been promising, and continued flight testing is planned during 2016.

Diskin, Glenn S.↗

NASA NTRS1985

A strategy for advancing tilt-rotor technology

Tilt-rotor technology has many features which make it a very promising development in aviation which might have application to a wide variety of transportation and logistics situations. However, aside from military applications and rather specialized industrial applications, little is known regarding the potential of tilt-rotor for commercial transportation and hence it is difficult to plan a development program which would gain support and be likely to produce a stream of significant benefits. The purpose is to attempt to provide some of this information in a manner that would be useful for preparing a strategy for development of tilt-rotor aircraft technology. Specifically, the objectives were: to identify promising paths of development and deployment of tilt-rotor aircraft technology in the air transportation system considering both benefits and disbenefits, and to identify any particular groups that are likely to benefit significantly and propose plans for gaining their support of research and development of this technology. Potential advantages of the tilt-rotor technology in the context of air transportation as a door-to-door system were identified, and then promising paths of development of such tilt-rotor systems were analyzed. These then lead to recommendations for specific studies, information dissemination and development of awareness of the tilt-rotor among specific transport-related groups.

Morlok, Edward K.↗

NASA NTRS1989

Initial flight test of a ground deployed system for flying qualities assessment

In order to provide a safe, repeatable, precise, high-gain flying qualities task a ground deployed system was developed and tested at the NASA Ames Research Center's Dryden Flight Research Facility. This system, the adaptable target lighting array system (ATLAS), is based on the German Aerospace Research Establishment's ground attack test equipment (GRATE). These systems provide a flying-qualities task, emulating the ground-attack task with ground deployed lighted targets. These targets light in an unpredictable sequence and the pilot has to aim the aircraft at whichever target is lighted. Two flight-test programs were used to assess the suitability of ATLAS. The first program used the United States Air Force (USAF) NT-33A variability stability aircraft to establish that ATLAS provided a task suitable for use in flying qualities research. A head-up display (HUD) tracking task was used for comparison. The second program used the X-29A forward-swept wing aircraft to demonstrate that the ATLAS task was suitable for assessing the flying qualities of a specific experimental aircraft. In this program, the ground-attack task was used for comparison. All pilots who used ATLAS found it be highly satisfactory and thought it to be superior to the other tasks used in flying qualities evaluations. It was recommended that ATLAS become a standard for flying qualities evaluations.

Shafer, Mary F.↗

NASA NTRS1990

Stochastic performance robustness of aircraft control systems

Stochastic robustness, a simple technique used to estimate the robustness of linear, time-invariant systems, is applied to a twin-jet transport aircraft control system. Concepts behind stochastic stability robustness are extended to stochastic performance robustness. Stochastic performance robustness measures based on classical design specifications and measures specific to aircraft handling qualities are introduced. Confidence intervals for both individual stochastic robustness measures and for comparing two measures are presented. The application of stochastic performance robustness, the use of confidence intervals, and tradeoffs between performance objectives are demonstrated by means of the twin-jet aircraft example.

Stengel, Robert F.↗

NASA NTRS1979

Alternative jet aircraft fuels

Potential changes in jet aircraft fuel specifications due to shifts in supply and quality of refinery feedstocks are discussed with emphasis on the effects these changes would have on the performance and durability of aircraft engines and fuel systems. Combustion characteristics, fuel thermal stability, and fuel pumpability at low temperature are among the factors considered. Combustor and fuel system technology needs for broad specification fuels are reviewed including prevention of fuel system fouling and fuel system technology for fuels with higher freezing points.

Grobman, J.↗

NASA NTRS1977

Lightning effects on aircraft

Direct and indirect effects of lightning on aircraft were examined in relation to aircraft design. Specific trends in design leading to more frequent lightning strikes were individually investigated. These trends included the increasing use of miniaturized, solid state components in aircraft electronics and electric power systems. A second trend studied was the increasing use of reinforced plastics and other nonconducting materials in place of aluminum skins, a practice that reduces the electromagnetic shielding furnished by a conductive skin.

Franklin A Fisher↗

NASA NTRS1984

Economic impact of fuel properties on turbine powered business aircraft

The principal objective was to estimate the economic impact on the turbine-powered business aviation fleet of potential changes in the composition and properties of aviation fuel. Secondary objectives include estimation of the sensitivity of costs to specific fuel properties, and an assessment of the directions in which further research should be directed. The study was based on the published characteristics of typical and specific modern aircraft in three classes; heavy jet, light jet, and turboprop. Missions of these aircraft were simulated by computer methods for each aircraft for several range and payload combinations, and assumed atmospheric temperatures ranging from nominal to extremely cold. Five fuels were selected for comparison with the reference fuel, nominal Jet A. An overview of the data, the mathematic models, the data reduction and analysis procedure, and the results of the study are given. The direct operating costs of the study fuels are compared with that of the reference fuel in the 1990 time-frame, and the anticipated fleet costs and fuel break-even costs are estimated.

Powell, F. D.↗

NASA NTRS2014

Pair-Wise Trajectory Management-Oceanic (PTM-O)

This document describes the Pair-wise Trajectory Management-Oceanic (PTM-O) Concept of Operations (ConOps). Pair-wise Trajectory Management (PTM) is a concept that includes airborne and ground-based capabilities designed to enable and to benefit from, airborne pair-wise distance-monitoring capability. PTM includes the capabilities needed for the controller to issue a PTM clearance that resolves a conflict for a specific pair of aircraft. PTM avionics include the capabilities needed for the flight crew to manage their trajectory relative to specific designated aircraft. Pair-wise Trajectory Management PTM-Oceanic (PTM-O) is a regional specific application of the PTM concept. PTM is sponsored by the National Aeronautics and Space Administration (NASA) Concept and Technology Development Project (part of NASA's Airspace Systems Program). The goal of PTM is to use enhanced and distributed communications and surveillance along with airborne tools to permit reduced separation standards for given aircraft pairs, thereby increasing the capacity and efficiency of aircraft operations at a given altitude or volume of airspace.

Jones, Kenneth M.↗

NASA NTRS2019

Far Term Noise Reduction Roadmap for the NASA D8 and Single-Aisle Tube-And-Wing Aircraft Concepts

A portfolio of noise reduction technologies is applied to two advanced single-aisle class vehicle concepts in order to evaluate the prospects for these aircraft to meet the NASA Far Term noise goals, beyond 2035. TheNASAD8 (ND8) aircraft is an unconventional configuration with boundary-layer ingesting engines mounted in the aft dorsal location. The 160-passenger tube-and-wing (TW160) aircraft is a conventional configuration with podded engines located under the wing, which represents an incremental evolution of current design philosophies. The noise reduction technologies were chosen to be compatible with each aircraft’s specific configuration requirements. The acoustic effects were predicted based on experimental and numerical studies, andwere incorporated into the prediction of total system noise usingNASA’s research-level Aircraft NOise Prediction Program (ANOPP-Research). Results suggest that the unfavorable Propulsion Airframe Aeroacoustic (PAA) effects of the two aircraft considered here significantly limit their prospects of meeting NASA’s Far Term noise goal, and that further development of the technology portfolio is key to ensuring future success in addressing the noise challenges for single-aisle class vehicles.

Clark, Ian A.↗

NASA NTRS1974

A study of KC-135 aircraft antenna patterns

Numerical solutions for the radiation patterns of aircraft antennas are evaluated. Designing and locating antennas in order to achieve the desired performance is discussed. The high frequency solutions presented in this report are based on fuselage antennas mounted on a general-type aircraft but applied specifically to the KC-135 aircraft. The roll and elevation plane patterns are computed for a monopole, axial slot, and circumferential slot mounted both over and forward of the wings. In each case the calculated patterns compare very favorably with the measured patterns. The precision pattern measurements were taken on a 1/25 scale model of the KC-135 aircraft at NASA (Langley, Virginia) with special emphasis on reducing the mount and background effects.

Burnside, W. D.↗

NASA NTRS1975

A study of KC-135 aircraft antenna patterns

Numerical solutions for the radiation patterns of aircraft antennas provide and excellent means of designing and locating antennas in order to achieve the desired performance. The high frequency solutions presented in this paper are based on fuselage antennas mounted on a general-type aircraft but applied specifically to the KC-135 aircraft. The roll and elevation plane patterns are computed for a monopole, axial slot, and circumferential slot mounted both over and forward of the wings. In each case the calculated patterns compare very favorably with the measured patterns. The precision pattern measurements were taken on a 1/25 scale model of the KC-135 aircraft at NASA (Hampton, Va.) with special emphasis on reducing the mount and background effects.

Burnside, W. D.↗

NASA NTRS1994

On the use of controls for subsonic transport performance improvement: Overview and future directions

Increasing competition among airline manufacturers and operators has highlighted the issue of aircraft efficiency. Fewer aircraft orders have led to an all-out efficiency improvement effort among the manufacturers to maintain if not increase their share of the shrinking number of aircraft sales. Aircraft efficiency is important in airline profitability and is key if fuel prices increase from their current low. In a continuing effort to improve aircraft efficiency and develop an optimal performance technology base, NASA Dryden Flight Research Center developed and flight tested an adaptive performance seeking control system to optimize the quasi-steady-state performance of the F-15 aircraft. The demonstrated technology is equally applicable to transport aircraft although with less improvement. NASA Dryden, in transitioning this technology to transport aircraft, is specifically exploring the feasibility of applying adaptive optimal control techniques to performance optimization of redundant control effectors. A simulation evaluation of a preliminary control law optimizes wing-aileron camber for minimum net aircraft drag. Two submodes are evaluated: one to minimize fuel and the other to maximize velocity. This paper covers the status of performance optimization of the current fleet of subsonic transports. Available integrated controls technologies are reviewed to define approaches using active controls. A candidate control law for adaptive performance optimization is presented along with examples of algorithm operation.

Gilyard, Glenn↗

NASA NTRS1996

Validation of bonded composite doubler technology through application oriented structural testing

One of the major thrusts established under the FAA's National Aging Aircraft Research Program is to foster new technologies associated with civil aircraft maintenance. Recent DOD and other government developments in the use of bonded composite patches on metal structures has supported the need for research and validation of such doubler applications on U.S. certificated airplanes. Composite patching is a rapidly maturing technology which shows promise of cost savings on aging aircraft. Sandia Labs is conducting a proof-of-concept project with Delta Air Lines, Lockheed Martin, Textron, and the FAA which seeks to remove any remaining obstacles to the approved use of composite doublers. By focusing on a specific commercial aircraft application - reinforcement of the L-1011 door frame - and encompassing all 'cradle-to-grave' tasks such as design, analysis, installation, and inspection, this program is designed to prove the capabilities of composite doublers. This paper reports on a series of structural tests which have been conducted on coupons and subsize test articles. Tension-tension fatigue and residual strength tests attempted to grow engineered flaws in coupons with composite doublers bonded to aluminum skin. Also, structures which modeled key aspects of the door corner installation were subjected to extreme tension, shear, and bending loads. In this manner it was possible to study strain fields in and around the Lockheed-designed composite doubler using realistic aircraft load scenarios and to assess the potential for interply delaminations and disbonds between the aluminum and the laminate. The data acquired was also used to validate finite element models (FEM) and associated Damage Tolerance Analyses.

Roach, Dennis↗

NASA NTRS1977

Preliminary analysis of aircraft fuel systems for use with broadened specification jet fuels

An analytical study was conducted on the use of broadened specification hydrocarbon fuels in present day aircraft. A short range Boeing 727 mission and three long range Boeing 747 missions were used as basis of calculation for one-day-per-year extreme values of fuel loading, airport ambient and altitude ambient temperatures with various seasonal and climatic conditions. Four hypothetical fuels were selected; two high-vapor-pressure fuels with 35 kPa and 70 kPa RVP and two high-freezing-point fuels with -29 C and -18 C freezing points. In-flight fuel temperatures were predicted by Boeing's aircraft fuel tank thermal analyzer computer program. Boil-off rates were calculated for the high vapor pressure fuels and heating/insulation requirements for the high freezing point fuels were established. Possible minor and major heating system modifications were investigated with respect to heat output, performance and economic penalties for the high freezing point fuels.

Pasion, A. J.↗

NASA NTRS1995

Part A: Cirrus ice crystal nucleation and growth. Part B: Automated analysis of aircraft ice particle data

Specific measurement of cirrus crystals by aircraft and temperature modified CN are used to specify measurements necessary to provide a basis for a conceptual model of cirrus particle formation. Key to this is the ability to measure the complete spectrum of particles at cirrus levels. The most difficult regions for such measurement is from a few to 100 microns, and uses a replicator. The details of the system to automate replicator data analysis are given, together with an example case study of the system provided from a cirrus cloud in FIRE 2, with particles detectable by replicator and FSSP, but not 2DC.

Arnott, William P.↗

NASA NTRS1979

Analysis of the impact of the use of broad specification fuels on combustors for commercial aircraft gas turbine engines

An analytical study was conducted to assess the impact of the use of broad specification fuels with reduced hydrogen content on the design, performance, durability, emissions and operational characteristics of combustors for commercial aircraft gas turbine engines. The study was directed at defining necessary design revisions to combustors designed for use of Jet A when such are operated on ERBS (Experimental Referee Broad Specification Fuel) which has a nominal hydrogen content of 12.8 percent as opposed to 13.7 percent in current Jet A. The results indicate that improvements in combustor liner cooling, and/or materials, and methods of fuel atomization will be required if the hydrogen content of aircraft gas turbine fuel is decreased.

Szetela, E. J.↗

NASA NTRSDate not supplied

Investigation of Aerodynamic Matching Sensitivities for Conceptual Design

A methodology for aerodynamic matching was implemented in the Higher fidelity Conceptual Design and structural optimization (HCDstruct) tool to support transonic flutter simulations. The Enhanced Factor Correction Technique was implemented in HCDstruct to correct the Nastran doublet lattice method using data from corresponding computational fluid dynamics simulations. In this paper, sensitivities associated with this aerodynamic matching technique were investigated using HCDstruct and a Boeing 737-200-like aircraft configuration. Specifically, sensitivities of the aerodynamic matching method were investigated with respect to changes in flight conditions, such as changes in Mach number and angle of attack, and also in key design variables for the main wing, such as changes in aspect ratio and sweep angle. The variations in flight conditions and design parameters were mapped to estimated prediction error in sectional lift for the main wing, which helps to demonstrate the extent to which a user may expect a given aerodynamic correction matrix to provide suitable aerodynamic predictions for a realistic aircraft wing.

Jesse R. Quinlan↗

NASA NTRSDate not supplied

Investigation of Aerodynamic Matching Sensitivities for Conceptual Design

Jesse Ray Quinlan↗