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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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At least 217 records · Page 12

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NASA NTRS1979

Examination of the flap-lag stability of rigid articulated rotor blades

A critical examination of flap-lag stability of a centrally hinged, spring-restrained rigid blade in both hover and forward flight is presented. Several differences in the equations of motion for blade flap-lag stability in the existing literature are identified. A rigorous and systematic development of these equations for a rigid articulated blade in forward flight shows the existence of some linear aerodynamic coupling terms associated with blade steady-state flapping and lagging in the perturbation equations. The differences identified are shown to be associated with whether or not the lag hinge flaps with the blade. The implications of these differences on stability are examined, and it is shown that the pitch-lag coupling terms associated with a hinge arrangement in which the lag hinge flaps with the blade have a marked influence on flap-lag stability, depending on the system parameters.

Kaza, K. R. V.↗

NASA NTRS1978

Flap survey test of a combined surface blowing model: Flow measurements at static flow conditions

The Combined Surface Blowing (CSB) V/STOL lift/propulsion system consists of a blown flap system which deflects the exhaust from a turbojet engine over a system of flaps deployed at the trailing edge of the wing. Flow measurements consisting of velocity measurements using split film probes and total measure surveys using a miniature Kiel probe were made at control stations along the flap systems at two spanwise stations, the centerline of the nozzle and 60 percent of the nozzle span outboard of the centerline. Surface pressure measurements were made in the wing cove and the upper surface of the first flap element. The test showed a significant flow separation in the wing cove. The extent of the separation is so large that the flow into the first flap takes place only at the leading edge of the flap. The velocity profile measurements indicate that large spanwise (3 dimensional) flow may exist.

Fukushima, T.↗

NASA NTRS1981

On the generation of side-edge flap noise

A theory is proposed for estimating the noise generated at the side edges of part span trailing edge flaps in terms of pressure fluctuations measured just in-board of the side edge of the upper surface of the flap. Asymptotic formulae are developed in the opposite extremes of Lorentz contracted acoustic wavelength large/small compared with the chord of the flap. Interpolation between these limiting results enables the field shape and its dependence on subsonic forward flight speed to be predicted over the whole frequency range. It is shown that the mean width of the side edge gap between the flap and the undeflected portion of the airfoil has a significant influence on the intensity of the radiated sound. It is estimated that the noise generated at a single side edge of a full scale part span flap can exceed that produced along the whole of the trailing edge of the flap by 3 dB or more.

Howe, M. S.↗

NASA NTRS1981

Effectiveness of leading-edge vortex flaps on 60 and 75 degree delta wings

A series of wind tunnel tests were run on 60 and 75 deg sweep delta wings to examine the effectiveness of leading-edge vortex flaps. Tests results showed that leading-edge vortex flaps are effective in giving large increases in lift-to-drag ratio and decreases in drag over a wide range of angle of attack. Tests on inverted flaps on the 60 deg delta wing showed substantial increases in lift and drag and may indicate a possibility of using inverted flaps on delta wings in the landing portion of flight. The 60 deg data were compared with that for a 75 deg sweep delta wing confirming that leading-edge vortex flap effectiveness is stronger as sweep is increased. Pitching moment effects due to vortex flaps use were also examined.

Marchman, J. F., III↗

NASA NTRS1982

On the generation of side-edge flap noise

A theory is proposed for estimating the noise generated at the side edges of part span trailing edge flaps in terms of pressure fluctuations measured just in-board of the side edge on the upper surface of the flap. Asymptotic formulas are developed in the opposite extremes of Lorentz contracted acoustic wavelength large/small compared with the chord of the flap. Interpolation between these limiting results enables the field shape and its dependence on subsonic forward flight speed to be predicted over the whole frequency range. It is shown that the mean width of the side edge gap between the flap and the undeflected portion of the airfoil has a significant influence on the intensity of the radiated sound. The results indicate that the noise generated at a single side of a full scale part span flap can exceed that produced along the whole of the trailing edge of the flap by 3 dB or more.

Howe, M. S.↗

NASA NTRS1982

Analysis, design, and test of a graphite/polyimide Shuttle orbiter body flap segment

For future missions, increases in Space Shuttle orbiter deliverable and recoverable payload weight capability may be needed. Such increases could be obtained by reducing the inert weight of the Shuttle. The application of advanced composites in orbiter structural components would make it possible to achieve such reductions. In 1975, NASA selected the orbiter body flap as a demonstration component for the Composite for Advanced Space Transportation Systems (CASTS) program. The progress made in 1977 through 1980 was integrated into a design of a graphite/polyimide (Gr/Pi) body flap technology demonstration segment (TDS). Aspects of composite body flap design and analysis are discussed, taking into account the direct-bond fibrous refractory composite insulation (FRCI) tile on Gr/Pi structure, Gr/Pi body flap weight savings, the body flap design concept, and composite body flap analysis. Details regarding the Gr/Pi technology demonstration segment are also examined.

Graves, S. R.↗

NASA NTRS1987

Wind-tunnel free-flight investigation of a 0.15-scale model of the F-106B airplane with vortex flaps

An investigation to determine the effects of vortex flaps on the flight dynamic characteristics of the F-106B in the area of low-speed, high-angle-of-attack flight was undertaken on a 0.15-scale model of the airplane in the Langley 30- by 60-Foot Tunnel. Static force tests, dynamic forced-oscillation tests, as well as free-flight tests were conducted to obtain a data base on the flight characteristics of the F-106B airplane with vortex flaps. Vortex flap configurations tested included a full-span gothic flap, a full-span constant-chord flap, and a part-span gothic flap.

Yip, Long P.↗

NASA NTRS1988

Validation of a pair of computer codes for estimation and optimization of subsonic aerodynamic performance of simple hinged-flap systems for thin swept wings

Extensive correlations of computer code results with experimental data are employed to illustrate the use of linearized theory attached flow methods for the estimation and optimization of the aerodynamic performance of simple hinged flap systems. Use of attached flow methods is based on the premise that high levels of aerodynamic efficiency require a flow that is as nearly attached as circumstances permit. A variety of swept wing configurations are considered ranging from fighters to supersonic transports, all with leading- and trailing-edge flaps for enhancement of subsonic aerodynamic efficiency. The results indicate that linearized theory attached flow computer code methods provide a rational basis for the estimation and optimization of flap system aerodynamic performance at subsonic speeds. The analysis also indicates that vortex flap design is not an opposing approach but is closely related to attached flow design concepts. The successful vortex flap design actually suppresses the formation of detached vortices to produce a small vortex which is restricted almost entirely to the leading edge flap itself.

Carlson, Harry W.↗

NASA NTRS1992

Blade-mounted trailing edge flap control for BVI noise reduction

Numerical procedures based on the 2-D and 3-D full potential equations and the 2-D Navier-Stokes equations were developed to study the effects of leading and trailing edge flap motions on the aerodynamics of parallel airfoil-vortex interactions and on the aerodynamics and acoustics of the more general self-generated rotor blade vortex interactions (BVI). For subcritical interactions, the 2-D results indicate that the trailing edge flap can be used to alleviate the impulsive loads experienced by the airfoil. For supercritical interactions, the results show the necessity of using a leading edge flap, rather than a trailing edge flap, to alleviate the interaction. Results for various time dependent flap motions and their effect on the predicted temporal sectional loads, differential pressures, and the free vortex trajectories are presented. For the OLS model rotor, contours of a BVI noise metric were used to quantify the effects of the trailing edge flap on the size and directivity of the high/low intensity noise region(s). Average reductions in the BVI noise levels on the order of 5 dB with moderate power penalties on the order of 18 pct. for a four bladed rotor and 58 pct. for a two bladed rotor were obtained.

Hassan, A. A.↗

NASA NTRS1992

Flight test operations using an F-106B research airplane modified with a wing leading-edge vortex flap

Flight tests of an F-106B aircraft equipped with a leading-edge vortex flap, which represented the culmination of a research effort to examine the effectiveness of the flap, were conducted at the NASA Langley Research Center. The purpose of the flight tests was to establish a data base on the use of a wing leading-edge vortex flap as a means to validate the design and analysis methods associated with the development of such a vortical flow-control concept. The overall experiment included: refinements of the design codes for vortex flaps; numerous wind tunnel entries to aid in verifying design codes and determining basic aerodynamic characteristics; design and fabrication of the flaps, structural modifications to the wing tip and leading edges of the test aircraft; development and installation of an aircraft research instrumentation system, including wing and flap surface pressure measurements and selected structural loads measurements; ground-based simulation to assess flying qualities; and finally, flight testing. This paper reviews the operational aspects associated with the flight experiment, which includes a description of modifications to the research airplane, the overall flight test procedures, and problems encountered. Selected research results are also presented to illustrate the accomplishments of the research effort.

Dicarlo, Daniel J.↗

NASA NTRS1992

In-flight surface-flow measurements on a subsonic transport high-lift flap system

As part of a multiphased program for subsonic transport high-lift flight research, flight tests were conducted on the Transport Systems Research Vehicle (B737-100 aircraft) at the NASA Langley Research Center, to obtain detailed flow characteristics of the high-lift flap system for correlation with computational and wind-tunnel investigations. Pressure distributions, skin friction, and flow-visualization measurements were made on a triple-slotted flap system for a range of flap deflections, chord Reynolds numbers (10 to 21 million), and Mach numbers (0.16 to 0.36). Experimental test results are given for representative flap settings indicating flow separation on the fore-flap element for the largest flap deflection. Comparisons of the in-flight flow measurements were made with predictions from available viscous multielement computational methods modified with simple-sweep theory. Computational results overpredicted the experimentally measured pressures, particularly in the case involving separation of the fore lap, indicating the need for better modeling of confluent boundary layers and three-dimensional sweep effects.

Yip, Long P.↗

NASA NTRS1931

The Effect of Slots and Flaps on the Lift and Drag of the Mcdonnell Airplanes Determined in Flight

This note contains the results of flight test conducted by the National Advisory Committee for Aeronautics on a low-wing monoplane equipped with leading-edge slots extending over the entire wing and flaps extending only to the ailerons, to find their effect on the lift and drag characteristics of the airplane. Curves are given showing the lift and drag characteristics of the airplane for the following conditions of the slots and flaps neutral; slots closed and flaps down; and slots open and flaps down. In addition, the high and low speed in level flight and the climbing characteristics are given. The results show that the slots used alone increase the maximum lift coefficient 54 per cent; the flaps alone increase it 38 per cent; and the slots and flaps in combination decrease the landing speed from 60 to 43 m.p.h.; increase the speed range of the airplane 40 per cent; and increase the glide angle at landing speed 4.2 degrees.

Soule, Hartley A↗

NASA NTRS1937

Full-scale Wind-tunnel and Flight Test of a Fairchild 22 Airplane Equipped with a Zap Flap and Zap Ailerons

A wing equipped with a Zap flap and Zap ailerons was tested on a Fairchild 22 airplane in the full-scale wind tunnel and in flight to determine the effect of the flaps and ailerons on the performance and the control characteristics of the airplane. The flaps were 0.30 of the wing chord and 0.83 of the wing span. Two sets of ailerons having equal areas but different proportions were tested, one set being 0.56 of the semispan and 0.18 of the chord and the other set being 0.46 of the semispan and 0.22 of the chord. The wind-tunnel tests showed that, when the ailerons and horizontal tail surfaces were removed, the flaps increased the maximum lift coefficient from 1.48 to 2.39. In flight, the fully deflected flaps decreased the minimum speed from 48.2 to 38.8 miles per hour. The take-off and landing distances were both reduced by the flaps. The wind-tunnel tests showed the ailerons to increase the drag coefficient, at a lift coefficient and Reynolds Number corresponding to the high speed of the airplane, from 0.0432 to 0.0498 and 0.0514, the 0.46 semispan ailerons giving the highest drag. In the flight tests both sets of ailerons were found to give satisfactory rolling action in the normal-flight range. They required relatively large stick forces for their operation, however, and the variation of the forces with aileron deflection was not linear.

Dearborn, C H↗

NASA NTRS1940

Tests of a Gust-alleviating Flap in the Gust Tunnel

Tests were made to determine the effectiveness of a long-period dynamically overbalanced flap in reducing airplane accelerations due to atmospheric gusts. For two gust shapes, one gust velocity, one forward velocity, and one wing loading, a series of flights was made with the flap locked and was then repeated with the flap free to operate. The records were evaluated by routine methods. The results indicate that the flap reduced the maximum acceleration increment 39 percent for a severe gust but with a representative gust shape (a sharp-edge gust), the reduction was only 3 percent. The results also indicate that the flap tended to reduce the longitudinal stability of the airplane. Computations made of the effectiveness and the action of the flap were in good agreement with the experimental results.

Donely, Philip↗

NASA NTRS1939

Tests of an N.A.C.A. 23012 Airfoil with a slotted deflector flap

Section aerodynamic characteristics of a large-chord N.A.C.A. 23012 airfoil with a slotted deflector flap were obtained in the N.A.C.A. 7- by 10-foot wind tunnel. The characteristics of an N.A.C.A. slotted flap and of a simple split flap are included for comparison. The slotted deflector flap was found to have a somewhat lower maximum lift coefficient and somewhat higher drag at high lift coefficients than the N.A.C.A. slotted flap. The high drag of the open slot with the deflector flap neutral indicates that the slot should be closed for this condition.

House, R O↗

NASA NTRS1958

Exploratory Wind-Tunnel Investigation to Determine the Lift Effects of Blowing over Flaps from Nacelles Mounted Above the Wing

An exploratory wind-tunnel investigation has been made to determine the lift effects of blowing from nacelles over the upper surface of flaps on a model having a delta wing of aspect ratio 3. Several flap conditions were examined. High-pressure air was blown from an external-pipe arrangement supported above the wing to simulate jet-engine exhaust. The jet momentum- coefficient range was from 0 to 3.0 and the model angle of attack was 0 deg. The results of this limited investigation show that values of jet circulation lift coefficient larger than the Jet reaction were produced with blowing over flaps from nacelles mounted above the wing. 'I!heuse of double slotted flaps with the gap unsealed between the flaps and wing had a large detrimental effect on the lift capabilities. With these gaps sealed, larger lift coefficients were obtained when fantails were added to the nacelles. The longitudinal trim problems created by large diving moments were similar to those encountered with other jet-augmented-flap systems

Riebe, John M↗

NASA NTRS1938

Pressure Distribution Over Airfoils with Fowler Flaps

Report presents the results of tests made of a Clark y airfoil with a Clark y Fowler flap and of an NACA 23012 airfoil with NACA Fowler flaps. Some of the tests were made in the 7 by 10-foot wind tunnel and others in the 5-foot vertical wind tunnel. The pressures were measured on the upper and lower surfaces at one chord section both on the main airfoils and on the flaps for several angles of attack with the flaps located at the maximum-lift settings. A test installation was used in which the model was mounted in the wind tunnel between large end planes so that two-dimensional flow was approximated. The data are given in the form of pressure-distribution diagrams and as plots of calculated coefficients for the airfoil-and-flap combinations and for the flaps alone.

Wenzinger, Carl J↗

NASA NTRS1939

Design charts for predicting downwash angles and wake characteristics behind plain and flapped wings

Equations and design charts are given for predicting the downwash angles and the wake characteristics for power-off conditions behind plain and flapped wings of the types used in modern design practice. The downwash charts cover the cases of elliptical wings and wings of taper ratios 1, 2, 3, and 5, with aspect ratios of 6, 9, and 12, having flaps covering 0, 40, 70, and 100 percent of the span. Curves of the span load distributions for all these cases are included. Data on the lift and the drag of flapped airfoil sections and curves for finding the contribution of the flap to the total wing lift for different types of flap and for the entire range of flap spans are also included. The wake width and the distribution of dynamic pressure across the wake are given in terms of the profile-drag coefficient and the distance behind the wing. A method of estimating the wake position is also given. The equations and charts are based on theory that has been shown in a previous report to be in agreement with experiment.

Silverstein, Abe↗