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All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

A Comparison of Metallic, Composite and Nanocomposite Optimal Transonic Transport Wings

Current and future composite material technologies have the potential to greatly improve the performance of large transport aircraft. However, the coupling between aerodynamics and structures makes it challenging to design optimal flexible wings, and the transonic flight regime requires high fidelity computational models. We address these challenges by solving a series of high-fidelity aerostructural optimization problems that explore the design space for the wing of a large transport aircraft. We consider three different materials: aluminum, carbon-fiber reinforced composites and an hypothetical composite based on carbon nanotubes. The design variables consist of both aerodynamic shape (including span), structural sizing, and ply angle fractions in the case of composites. Pareto fronts with respect to structural weight and fuel burn are generated. The wing performance in each case is optimized subject to stress and buckling constraints. We found that composite wings consistently resulted in lower fuel burn and lower structural weight, and that the carbon nanotube composite did not yield the increase in performance one would expect from a material with such outstanding properties. This indicates that there might be diminishing returns when it comes to the application of advanced materials to wing design, requiring further investigation.

Kennedy, Graeme J.↗
NASA NTRS1998

Experimental Study of Lift-Generated Vortices

The flow fields of vortices, whether bouyancy-driven or lift-generated, are fascinating fluid-dynamic phenomena which often possess intense swirl velocities and complex time-dependent behavior. As part of the on-going study of vortex behavior, this paper presents a historical overview of the research conducted on the structure and modification of the vortices generated by the lifting surfaces of subsonic transport aircraft. It is pointed out that the characteristics of lift-generated vortices are related to the aerodynamic shapes that produce them and that various arrangements of surfaces can be used to produce different vortex structures. The primary purpose of the research to be described is to find a way to reduce the hazard potential of lift-generated vortices shed by subsonic transport aircraft in the vicinity of airports during landing and takeoff operations. It is stressed that lift-generated vortex wakes are so complex that progress towards a solution requires application of a combined theoretical and experimental research program because either alone often leads to incorrect conclusions. It is concluded that a satisfactory aerodynamic solution to the wake-vortex problem at airports has not yet been found but a reduction in the impact of the wake-vortex hazard on airport capacity may become available in the foreseeable future through wake-vortex avoidance concepts currently under study. The material to be presented in this overview is drawn from aerospace journals that are available publicly.

Rossow, Vernon J.↗
NASA NTRS2015

Development of Stitched Composite Structure for Advanced Aircraft

NASA has created the Environmentally Responsible Aviation Project to develop technologies which will reduce the impact of aviation on the environment. A critical aspect of this pursuit is the development of a lighter, more robust airframe that will enable the introduction of unconventional aircraft configurations. NASA and The Boeing Company are working together to develop a structural concept that is lightweight and an advancement beyond state-of-the-art composites. The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is an integrally stiffened panel design where elements are stitched together and designed to maintain residual load-carrying capabilities under a variety of damage scenarios. With the PRSEUS concept, through-the-thickness stitches are applied through dry fabric prior to resin infusion, and replace fasteners throughout each integral panel. Through-the-thickness reinforcement at discontinuities, such as along flange edges, has been shown to suppress delamination and turn cracks, which expands the design space and leads to lighter designs. The pultruded rod provides stiffening away from the more vulnerable skin surface and improves bending stiffness. A series of building blocks were evaluated to explore the fundamental assumptions related to the capability and advantages of PRSEUS panels. These building blocks addressed tension, compression, and pressure loading conditions. The emphasis of the development work has been to assess the loading capability, damage arrestment features, repairability, post-buckling behavior, and response of PRSEUS flat panels to out-of plane pressure loading. The results of this building-block program from coupons through an 80%-scale pressure box have demonstrated the viability of a PRSEUS center body for the Hybrid Wing Body (HWB) transport aircraft. This development program shows that the PRSEUS benefits are also applicable to traditional tube-andwing aircraft, those of advanced configurations, and other structures where weight and through-the-thickness strength are design considerations. An overview of the development of PRSEUS technology for commercial transport aircraft is the subject of this paper.

Jegley, Dawn↗
NASA NTRS2007

Piloted Simulation Study of Rudder Pedal Force/Feel Characteristics

A piloted, fixed-base simulation was conducted in 2006 to determine optimum rudder pedal force/feel characteristics for transport aircraft. As part of this research, an evaluation of four metrics for assessing rudder pedal characteristics previously presented in the literature was conducted. This evaluation was based upon the numerical handling qualities ratings assigned to a variety of pedal force/feel systems used in the simulation study. It is shown that, with the inclusion of a fifth metric, most of the rudder pedal force/feel system designs that were rated poorly by the evaluation pilots could be identified. It is suggested that these metrics form the basis of a certification requirement for transport aircraft.

Hess, Ronald A.↗
NASA NTRS1984

The revolutionary impact of evolving aeronautical technologies

Recent advances in aeronautical technologies which could produce revolutionary changes in transport aircraft if fully implemented are delineated. Laminar flow control offers a L/D improvement from the current 18 to 22 if used with a 767 configuration. Higher aspect and thickness/chord ratios could yield more efficient structural designs and further drag reduction. High-strength, fiber-reinforced composite structures can reduce structural weight by 10-30 percent. Improved engine cooling methods, higher stage loadings and exhaust temperatures can lower the SFC by 15 percent, engine weight by 15 percent, and the parts count by 50 percent. Aft-mounted counterrotating propellers can potentially decrease the SFC an additional 15-20 percent. Supersonic transport aircraft with L/D ratios of 18 and 70 seat miles/gal fuel efficiency can now be built that weigh half as much as the Concorde and carry the same load. The new SST would have superplastic-molded Al alloy structures.

Kayten, G. G.↗
NASA NTRS1998

Wake-Vortex Hazards During Cruise

Even though the hazard posed by lift-generated wakes of subsonic transport aircraft has been studied extensively for approach and departure at airports, only a small amount of effort has gone into the potential hazard at cruise altitude. This paper reports on a studio of the wake-vortex hazard during cruise because encounters may become more prevalent when free-flight becomes available and each aircraft, is free to choose its own route between destinations. In order to address the problem, the various fluid-dynamic stages that vortex wakes usually go through as they age will be described along with estimates of the potential hazard that each stage poses. It appears that a rolling-moment hazard can be just as severe at cruise as for approach at airports, but it only persists for several minutes. However, the hazard posed by the downwash in the wake due to the lift on the generator aircraft persists for tens of minutes in a long narrow region behind the generating aircraft. The hazard consists of severe vertical loads when an encountering aircraft crosses the wake. A technique for avoiding vortex wakes at cruise altitude will be described. To date the hazard posed by lift-generated vortex wakes and their persistence at cruise altitudes has been identified and subdivided into several tasks. Analyses of the loads to be encounter and are underway and should be completed shortly. A review of published literature on the subject has been nearly completed (see text) and photographs of vortex wakes at cruise altitudes have been taken and the various stages of decay have been identified. It remains to study and sort the photographs for those that best illustrate the various stages of decay after they are shed by subsonic transport aircraft at cruise altitudes. The present status of the analysis and the paper are described.

Rossow, Vernon J.↗
NASA NTRS1992

Evaluation of microwave landing system approaches in a wide-body transport simulator

The objective of this study was to determine the suitability of flying complex curved approaches using the microwave landing system (MLS) with a wide-body transport aircraft. Fifty pilots in crews of two participated in the evaluation using a fixed-base simulator that emulated an MD-11 aircraft. Five approaches, consisting of one straight-in approach and four curved approaches, were flown by the pilots using a flight director. The test variables include the following: (1) manual and autothrottles; (2) wind direction; and (3) type of navigation display. The navigation display was either a map or a horizontal situation indicator (HSI). A complex wind that changed direction and speed with altitude, and included moderate turbulence, was used. Visibility conditions were Cat 1 or better. Subjective test data included pilot responses to questionnaires and pilot comments. Objective performance data included tracking accuracy, position error at decision height, and control activity. Results of the evaluation indicate that flying curved MLS approaches with a wide-body transport aircraft is operationally acceptable, depending upon the length of the final straight segment and the complexity of the approach.

Summers, L. G.↗
NASA NTRSDate not supplied

Development of Slat-gap and Slat-cove Filler Treatments for Noise Reduction Assessment on the High Lift Common Research Model in the NASA LaRC 14x22

Airframe noise is an important issue during the approach and landing phases of flight because engines are throttled back, and airframe sources become an equal or greater contributor to environmental noise. The leading-edge slat component of the high-lift system for transport aircraft has been identified as a prominent source of airframe noise. Noise production mechanisms and potential treatments to mitigate airframe noise have been areas of active research for nearly three decades. Two promising technologies for slat noise reduction are the slat-gap filler (SGF) and slat-cove filler (SCF). Previous work was done using a 2D section of a transport class aircraft wing to demonstrate their feasibility via benchtop and computational models. A wind tunnel test campaign was recently undertaken to test the SGF and SCF technologies in a flight-like environment by installing dynamically scaled treatments on the 10%-scale High-Lift Common Research Model (CRM-HL), which is representative of a commercial twin-aisle transport aircraft. Advancement of the SGF and SCF technologies to overcome challenges of integration with 3D airframe structures, computational simulations of the CRM-HL predicting the aerodynamic and aeroacoustic performance and structural loads, and design of wind tunnel model hardware with features accommodating noise treatments were conducted in parallel. Details of innovations in the SGF and SCF technologies for 3D airframe feasibility will be described. The loads the treatments must sustain in flight and the influence of those loads on the design is also discussed. Finally, the design of wing leading-edge assemblies to treat the 10% CRM-HL with dynamically scaled SGF and SCF components is presented. The treatments were successfully tested in 2020/2021 providing a demonstration of leading-edge noise reduction using components that would allow slat articulation.

airframe noise reduction↗
NASA NTRS1976

Study of the application of advanced technologies to laminar flow control systems for subsonic transports. Volume 1: Summary

A study was conducted to evaluate the technical and economic feasibility of applying laminar flow control to the wings and empennage of long-range subsonic transport aircraft compatible with initial operation in 1985. For a design mission range of 10,186 km (5500 n mi), advanced technology laminar-flow-control (LFC) and turbulent-flow (TF) aircraft were developed for both 200 and 400-passenger payloads, and compared on the basis of production costs, direct operating costs, and fuel efficiency. Parametric analyses were conducted to establish the optimum geometry for LFC and TF aircraft, advanced LFC system concepts and arrangements were evaluated, and configuration variations maximizing the effectiveness of LFC were developed. For the final LFC aircraft, analyses were conducted to define maintenance costs and procedures, manufacturing costs and procedures, and operational considerations peculiar to LFC aircraft. Compared to the corresponding advanced technology TF transports, the 200- and 400-passenger LFC aircraft realized reductions in fuel consumption up to 28.2%, reductions in direct operating costs up to 8.4%, and improvements in fuel efficiency, in ssm/lb of fuel, up to 39.4%. Compared to current commercial transports at the design range, the LFC study aircraft demonstrate improvements in fuel efficiency up to 131%. Research and technology requirements requisite to the development of LFC transport aircraft were identified.

Sturgeon, R. F.↗
NASA NTRS1970

The expanding horizons of air transport

Subsonic and supersonic transport aircraft design, discussing supercritical wing concept, fuel consumption reduction, composite aircraft structures, short haul transports, etc

Kayten, G. G.↗
NASA NTRS1972

Effect of commercial and military performance requirements for transport category aircraft on space shuttle booster design and operation

The effect of two sets of performance requirements, commercial and military, on the design and operation of the space shuttle booster is evaluated. Critical thrust levels are established according to both sets of operating rules for the takeoff, cruise, and go-around flight modes, and the effect on engine requirements determined. Both flyback and ferry operations are considered. The impact of landing rules on potential shuttle flyback and ferry bases is evaluated. Factors affecting reserves are discussed, including winds, temperature, and nonstandard flight operations. Finally, a recommended set of operating rules is proposed for both flyback and ferry operations that allows adequate performance capability and safety margins without compromising design requirements for either flight phase.

Bithell, R. A.↗
NASA NTRS1978

Factors affecting the retirement of commercial transport jet aircraft

A brief historical background of the technology and economics of aircraft replacement and retirement in the prejet era is presented to see whether useful insights can be obtained applicable to the jet area. Significant differences between the two periods were demonstated. Current technological and operational economic perspectives were investigated in detail. Some conclusions are drawn to aircraft retirement policies.

Spencer, F. A.↗
NASA NTRS1979

A computer program for detailed analysis of the takeoff and approach performance capabilities of transport category aircraft

The takeoff and approach performance of an aircraft is calculated in accordance with the airworthiness standards of the Federal Aviation Regulations. The aircraft and flight constraints are represented in sufficient detail to permit realistic sensitivity studies in terms of either configuration modifications or changes in operational procedures. The program may be used to investigate advanced operational procedures for noise alleviation such as programmed throttle and flap controls. Extensive profile time history data are generated and are placed on an interface file which can be input directly to the NASA aircraft noise prediction program (ANOPP).

Foss, W. E., Jr.↗
NASA NTRS1979

Factors affecting the retirement of commercial transport jet aircraft

The historical background of the technology and economics of aircraft replacement and retirement in the prejet era is reviewed in order to determine whether useful insights can be obtained applicable to the jet era. Significant differences between the two periods are noted. New factors are identified and examined. Topics discussed include concern over current policies regarding deregulation, regulatory reform, and retroactive noise regulations; financing and compliance legislation; aging; economic environment and inflation; technological progress; fuel efficiency and cost; and a financial perspective of replacement decisions.

Spencer, F. A.↗
NASA NTRS1980

Transport jet aircraft noise abatement in foreign countries: Growth, structure, impact. Volume 1: Europe, July 1980

The development and implementation of aircraft noise control regulations in various European states are described. The countries include the United Kingdom, France, Switzerland, Federal Republic of Germany, Sweden, Denmark, and the Netherlands. Topics discussed include noise monitoring, airport curfews, land use planning, and the government structure for noise regulation.

Spencer, F. A.↗
NASA NTRS1980

Transport jet aircraft noise abatement in foreign countries: Growth, structure, impact. Volume 2: Pacific basin, August 1980

Noise control measures at the international airports of Hawaii, New Zealand, Australia, Hong Kong, Japan, and Singapore were studied. Factors in noise control, such as government structure are examined. The increasing power of environmental agencies vis-a-vis aviation departments is noted. The following methods of dealing with aircraft noise are examined by type of control: noise at the source control; noise emmission controls, zoning, building codes, subsidies for relocation, insulation, loss in property values, and for TV, radio and telephone interference; and noise-related landing charges.

Spencer, F. A.↗
NASA NTRS1991

An evaluation of flight path management automation in transport category aircraft

A desk-top simulation of a Boeing 757/767 Electronic Flight Instrumentation System (EFIS) and Control Display Unit (CDU) was used in an experiment to compare three modes of communication for the clearance amendment process: standard voice procedures, a textual delivery method, and a graphical delivery method. Eight qualified Boeing 757/767 pilots served as subjects. Each flew nine landing scenarios with three amendments given in each scenario. Both acceptable and unacceptable clearance amendments were presented in order to assess situational awareness. Times for comprehension and execution of the amendment were recorded along with workload ratings, responses to unacceptable amendments, and subjective impressions. The graphical mode was found to be superior in terms of the time measures and subjective ratings. No difference was found between the modes in the ability to detect unacceptable clearances.

Chandra, D.↗