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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Study of aircraft in intraurban transportation systems

A systems analysis was conducted to define the technical economic and operational characteristics of an aircraft transportation system for short-range intracity commutor operations. The analysis was for 1975 and 1985 in the seven county, Detroit, Michigan area. STOL and VTOL aircraft were studied in sizes from 40 to 120 passengers. The preferred vehicle for the Detroit area was the deflected slipstream STOL. Since the study was parametric in nature, it is applicable to generalization, and it was concluded that a feasible intraurban air transportation system could be developed in many viable situations.

Stout, E. G.↗
NASA NTRS1972

Study of short haul high-density V/STOL transportation systems, volume 1

The relative advantages of STOL aircraft concepts were examined by simulating the operations of a short haul high-density intercity STOL system set in two arenas, the California corridor and the Chicago-Detroit-Cleveland triangle, during the 1980 time period. The study was constrained to the use of three aircraft concepts designated as the deflected slipstream turboprop, externally blown flap, and augmentor wing turbofan configurations. The projected demographic, economic, travel demand, and travel characteristics of the representative arenas were identified. The STOL airline operating scenarios were then formulated and through the use of the aerospace modal split simulation program, the traveler modal choices involving alternative STOL concepts were estimated in the context of the total transportation environment for 1980. System combinations that presented the best potential for economic return and traveler acceptance were then identified for each STOL concept.

Solomon, H. L.↗
NASA NTRS1972

Program plan to develop airworthiness standards for STOL aircraft

A program plan to develop criteria for airworthiness standards for STOL transport aircraft is presented. Initially, three different STOL concepts are to be examined with a goal to arrive at a generalized set of standards. The Breguet 941 deflected-slipstream STOL has been initially evaluated on a piloted motion simulator and in flight. Confidence in establishing criteria for airworthiness standards for STOL transport aircraft has been obtained from these studies.

Cayot, J. E.↗
NASA NTRS1972

Optimum performance of static propellers and rotors.

A criterion for the optimum performance of static propellers and hovering helicopter rotors is developed. Numerical results are presented for the optimum radial distributions of circulation and inflow at the propeller disk and relating the optimum power coefficient and the figure of merit to the thrust coefficient. It is shown that the present theory, which fully accounts for the effect of slipstream rotation, predicts optimum distributions of circulation and inflow that differ significantly from those based on approximate methods.

Wu, J. C.↗
NASA NTRS1973

STOL aircraft flight and landing area considerations.

One proposed solution to the total short-haul transportation system problem is to use existing low-wing-loading turbopropeller STOL aircraft. Deflected slipstream turboprop aircraft have also been considered for early STOL service. Aspects of current aircraft research are discussed together with the NASA research aircraft, field length and aircraft performance considerations, crosswind landings, crosswind reducing fences, elevated STOL ports, a guaranteed friction STOL runway, and problems of runway containment.

Riebe, J. M.↗
NASA NTRS1974

The effect of wind tunnel wall interference on the performance of a fan-in-wing VTOL model

A fan-in-wing model with a 1.07-meter span was tested in seven different test sections with cross-sectional areas ranging from 2.2 sq meters to 265 sq meters. The data from the different test sections are compared both with and without correction for wall interference. The results demonstrate that extreme care must be used in interpreting uncorrected VTOL data since the wall interference may be so large as to invalidate even trends in the data. The wall interference is particularly large at the tail, a result which is in agreement with recently published comparisons of flight and large scale wind tunnel data for a propeller-driven deflected-slipstream configuration. The data verify the wall-interference theory even under conditions of extreme interference. A method yields reasonable estimates for the onset of Rae's minimum-speed limit. The rules for choosing model sizes to produce negligible wall effects are considerably in error and permit the use of excessively large models.

Heyson, H. H.↗
NASA NTRS1974

An Analytical Investigation of Wing-Jet Interaction

The aerodynamic interaction between the wing and an inviscid jet with Mach number nonuniformity is formulated by using a two-vortex-sheet model for the jet. One of the vortex sheets accounts for the induced jet flow and the other the induced outer flow. No additional source distribution is needed for the jet at an angle of attack. The above problem is solved by satisfying the jet and wing tangency and the jet pressure-continuity conditions and using a quasi vortex lattice method for computing the induced flow field. The latter method is derived through theoretical consideration by properly accounting for singularities present in the equations and possesses the same simplicity and generality as the conventional vortex lattice method but has a better rate of numerical convergence. The resulting system of algebraic equations is solved by Purcell's vector method. The numerical formulation is first applied to the wing-slipstream interaction problem. Results for one centered-jet configuration are compared with those predicted by some existing theories.

Lan, E. C.↗
NASA NTRS1975

Optimum performance and potential flow field of hovering rotors

Rotor and propeller performance and induced potential flowfields were studied on the basis of a rotating actuator disk concept, with special emphasis on rotors hovering out of ground effect. A new theory for the optimum performance of rotors hovering OGE is developed and presented. An extended theory for the optimum performance of rotors and propellers in axial motion is also presented. Numerical results are presented for the optimum distributions of blade-bound circulation together with axial inflow and ultimate wake velocities for the hovering rotor over the range of thrust coefficient of interest in rotorcraft applications. Shapes of the stream tubes and of the velocities in the slipstream are obtained, using available methods, for optimum and off-optimum circulation distributions for rotors hovering in and out of ground effect. A number of explicit formulae useful in computing rotor and propeller induced flows are presented for stream functions and velocities due to distributions of circular vortices over axi-symmetric surfaces.

Wu, J. C.↗
NASA NTRS1975

Time-dependent transonic flow solutions for axial turbomachinery

Three-dimensional unsteady transonic flow through an axial turbomachine stage is described in terms of a pair of two-dimensional formulations pertaining to orthogonal surfaces, namely, a blade-to-blade surface and a hub-to-casing surface. The resulting systems of nonlinear, inviscid, compressible equations of motion are solved by an explicit finite-difference technique. The blade-to-blade program includes the periodic interaction between rotor and stator blade rows. Treatment of the boundary conditions and of the blade slipstream motion by a characteristic type procedure is discussed in detail. Harmonic analysis of the acoustic far field produced by the blade row interaction, including an arbitrary initial transient, is outlined. Results from the blade-to-blade program are compared with experimental measurements of the rotating pressure field at the tip of a high-speed fan. The hub-to-casing program determines circumferentially averaged flow properties on a meridional plane. Blade row interactions are neglected in this formulation, but the force distributions over the entire blade surface for both the rotor and stator are obtained. Results from the hub-to-casing program are compared with a relaxation method solution for a subsonic rotor. Results are also presented for a quiet fan stage which includes transonic flow in both the rotor and stator and a normal shock in the stator.

Erdos, J.↗
NASA NTRS1976

Flight test evaluation of a method to determine the level flight performance propeller-driven aircraft

A procedure is developed for deriving the level flight drag and propulsive efficiency of propeller-driven aircraft. This is a method in which the overall drag of the aircraft is expressed in terms of the measured increment of power required to overcome a corresponding known increment of drag. The aircraft is flown in unaccelerated, straight and level flight, and thus includes the effects of the propeller drag and slipstream. Propeller efficiency and airplane drag are computed on the basis of data obtained during flight test and do not rely on the analytical calculations of inadequate theory.

Cross, E. J., Jr.↗
NASA NTRS1976

Energy consumption characteristics of transports using the prop-fan concept

The fuel saving and economic potentials of the prop-fan high-speed propeller concept were evaluated for twin-engine commercial transport airplanes designed for 3333.6 km range, 180 passengers, and Mach 0.8 cruise. A fuel saving of 9.7% at the design range was estimated for a prop-fan airplane having wing-mounted engines, while a 5.8% saving was estimated for a design having the engines mounted on the aft body. The fuel savings and cost were found to be sensitive to the propeller noise level and to aerodynamic drag effects due to wing-slipstream interaction. Uncertainties in these effects could change the fuel savings as much as + or - 50%. A modest improvement in direct operating cost (DOC) was estimated for the wing-mounted prop-fan at current fuel prices. This improvement could become substantial in the event of further relative increases in the price of oil. The improvement in DOC requires the achievement of the nominal fuel saving and reductions in propeller and gearbox maintenance costs relative to current experience.

Source record↗
NASA NTRS1977

A study of commuter airplane design optimization

Problems of commuter airplane configuration design were studied to affect a minimization of direct operating costs. Factors considered were the minimization of fuselage drag, methods of wing design, and the estimated drag of an airplane submerged in a propellor slipstream; all design criteria were studied under a set of fixed performance, mission, and stability constraints. Configuration design data were assembled for application by a computerized design methodology program similar to the NASA-Ames General Aviation Synthesis Program.

Roskam, J.↗
NASA NTRS1978

Shock capturing finite-difference and characteristic reference plane techniques for the prediction of three-dimensional nozzle-exhaust flowfields

This report summarizes work accomplished under Contract No. NAS1-12726 towards the development of computational procedures and associated numerical. The flow fields considered were those associated with airbreathing hypersonic aircraft which require a high degree of engine/airframe integration in order to achieve optimized performance. The exhaust flow, due to physical area limitations, was generally underexpanded at the nozzle exit; the vehicle afterbody undersurface was used to provide additional expansion to obtain maximum propulsive efficiency. This resulted in a three dimensional nozzle flow, initialized at the combustor exit, whose boundaries are internally defined by the undersurface, cowling and walls separating individual modules, and externally, by the undersurface and slipstream separating the exhaust flow and external stream.

Dash, S.↗
NASA NTRS1978

Fuel saving potential of Mach 0.8 twin engine prop-fan transports

The fuel saving and economic potentials of the prop-fan high-speed propeller concept have been evaluated for twin-engine commercial transport airplanes designed for 3333.6 km range, 180 passengers, and Mach 0.8 cruise. A fuel saving of 9.7% at the design range was estimated for a prop-fan aircraft having wing-mounted engines, while a 5.8% saving was estimated for a design having the engines mounted on the aft body. The fuel savings and cost were found to be sensitive to the propeller noise level and to aerodynamic drag effects due to wing-slipstream interaction. Uncertainties in these effects could change the fuel savings as much as plus or minus 50%. A modest improvement in direct operating cost was estimated for the wing-mounted prop-fan at current fuel prices.

Davenport, F. J.↗
NASA NTRS1979

Flight test evaluation of an RAF high altitude partial pressure protective assembly

A partial pressure suit was evaluated during tests in an F-104 and F-15 as a protective garment for emergency descents. The garment is an pressure jerkin and modified anti-g suit combined with an oronasal mask. The garment can be donned and doffed at the aircraft to minimize thermal buildup. The oronasal mask was favored by the pilots due to its immobility on the face during high g-loading. The garment was chosen to provide optimum dexterity for the pilot, which is not available in a full pressure suit, while protecting the pilot at altitudes up to 18,288 meters, during a cabin decompression, and subsequent aircraft descent. During cabin decompressions in the F-104 and F-15, cabin pressure altitude was measured at various aircraft angles of attack, Mach numbers, and altitudes to determine the effect of the aerodynamic slipstream on the cabin altitude.

Ashworth, G. R.↗
NASA NTRS1979

Summary of past experience in natural laminar flow and experimental program for resilient leading edge

The potential of natural laminar flow for significant drag reduction and improved efficiency for aircraft is assessed. Past experience with natural laminar flow as reported in published and unpublished data and personal observations of various researchers is summarized. Aspects discussed include surface contour, waviness, and smoothness requirements; noise and vibration effects on boundary layer transition, boundary layer stability criteria; flight experience with natural laminar flow and suction stabilized boundary layers; and propeller slipstream, rain, frost, ice and insect contamination effects on boundary layer transition. The resilient leading edge appears to be a very promising method to prevent leading edge insect contamination.

Carmichael, B. H.↗
NASA NTRS1979

Full-scale wind-tunnel investigation of an Ayres S2R-800 Thrush Agricultural Airplane

This paper summarizes the significant results of recent full-scale wind tunnel tests at the NASA-Langley Research Center of the Ayres S2R-800 Thrush Agricultural Aircraft. The purpose of the tests was to provide fundamental aerodynamic, performance, and stability and control information of the airplane and dispersal equipment; and to study near-field wake interaction characteristics behind the aircraft. The aerodynamic tests included the use of a propeller thrust-torque balance to measure the efficiency of the propeller in the presence of the engine and to provide data for determining slipstream interference effects and slip-stream drag.

Johnson, J. L., Jr.↗