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At least 487 records · Page 27

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NASA NTRS1923

The tail plane

This report deals with the calculation of the equilibrium, statistical stability, and damping of the tail plane. The author has simplified the present theory of longitudinal stability for the particular purpose of obtaining one definite coefficient characteristics of the effect of the tail plane. This coefficient is obtained by substituting certain aerodynamic characteristics and some dimensions of the airplane in a comparatively simple mathematical expression. Care has been taken to confine all aerodynamical information necessary for the calculation of the coefficient to the well-known curves representing the qualities of the wing section. This is done by making use of the present results of modern aerodynamics. All formulas and relations necessary for the calculation are contained in the paper. They give in some cases only an approximation of the real values. An example of calculation is added in order to illustrate the application of the method. The coefficient indicates not only whether the effect of the tail plane is great enough, but also whether it is not too great. It appears that the designer has to avoid a certain critical length of the fuselage, which inevitably gives rise to periodical oscillations of the airplane. The discussion also shows the way and in what direction to carry out experimental work.

Munk, Max M↗

NASA NTRS1993

Linear stability of streamwise developing longitudinal vortices

The linear stability of numerical solutions to the quasicylindrical equations of motion for swirling flows is investigated. Initial conditions are derived from Batchelor's similarity solution for a trailing line vortex. The stability calculations are performed using a 2nd-order accurate finitedifference scheme on a staggered grid with the accuracy of the computed eigenvalues enhanced through Richardson extrapolation. The streamwise development of both viscous and inviscid instability modes is discussed for low and high swirl cases. The effect of adverse and favorable pressure gradients on the viscous stability of a longitudinal vortex is also investigated.

Spall, Robert E.↗

NASA NTRS1980

Comparison of Space Shuttle Orbiter low-speed static stability and control derivatives obtained from wind-tunnel and approach and landing flight tests

Tests were conducted in the 8 foot transonic pressure tunnel to obtain wind tunnel data for comparison with static stability and control parameters measured on the space shuttle orbiter approach and landing flight tests. The longitudinal stability, elevon effectiveness, lateral directional stability, and aileron effectiveness derivatives were determined from the wind tunnel data and compared with the flight test results. The comparison covers a range of angles of attack from approximately 2 deg to 10 deg at subsonic Mach numbers of 0.41 to 0.56. In general the wind tunnel results agreed well with the flight test results, indicating the wind tunnel data is applicable to the design of entry vehicles for subsonic speeds over the angle of attack range studied.

Freeman, D. C., Jr.↗

NASA NTRS1976

The stability and control of tailless airplanes, 19 August 1944

In the present state of the design of tailless airplanes, it appears that: (1) Sweepback affords a method of supplying tail length for directional and longitudinal stability and control and allows the utilization of a high-lift flap but introduces undersirable tip stalling tendencies that must be overcome before the advantages of sweepback can be realized. (2) The damping in pitching appears to have little effect on the longitudinal behavior of the airplane provided the static margin is never permitted to become negative. (3) The directional stability must be as great as for conventional airplanes if the same requirements regarding satisfactory stability and control characteristics are to be adhered to. (4) The influence of the lateral resistance and the damping in yawing on the flying qualities is somewhat obscure.

Donlan, C. J.↗

NASA NTRS1979

Piloted simulator investigation of helicopter control systems effects on handling qualities during instrument flight

An exploratory piloted simulation was conducted to investigate the effects of the characteristics of helicopter flight control systems on instrument flight handling qualities. This joint FAA/NASA study was motivated by the need to improve instrument flight capability. A near-term objective is to assist in updating the airworthiness criteria for helicopter instrument flight. The experiment consisted of variations of single-rotor helicopter types and levels of stability and control augmentation systems (SCAS). These configurations were evaluated during an omnirange approach task under visual and instrument flight conditions. The levels of SCAS design included a simple rate damping system, collective decoupling plus rate damping, and an attitude command system with collective decoupling. A limited evaluation of stick force versus airspeed stability was accomplished. Some problems were experienced with control system mechanization which had a detrimental effect on longitudinal stability. Pilot ratings, pilot commentary, and performance data related to the task are presented.

Forrest, R. D.↗

NASA NTRS1979

Wind tunnel tests of four flexible wing ultralight gliders

The aerodynamic lift, drag, and pitching moment characteristics of four full scale, flexible wing, ultralight gliders were measured in the settling chamber of a low speed wind tunnel. The gliders were tested over a wide range of angle of attack and at two different velocities. Particular attention was devoted to the lift and pitching moment behavior at low and negative angles of attack because of the potential loss of longitudinal stability of flexible wing gliders in this regime. The test results were used to estimate the performance and longitudinal control characteristics of the gliders.

Ormiston, R. A.↗

NASA NTRS1953

Investigation of the Low-Speed Stability and Control Characteristics of a 1/10-Scale Model of the Convair YF-102 Airplane in the Langley Free-Flight Tunnel

An investigation of the low-speed, power-off stability and control characteristics of a 1/10-scale model of the Convair YF-102 airplane has been made in the Langley free-flight tunnel. The model was flown over a lift-coefficient range from 0.5 to the stall in its basic configuration and with several modifications involving leading-edge slats and increases in vertical-tail size. Only relatively low-altitude conditions were simulated and no attempt was made to determine the effect of freeing the controls. The longitudinal stability characteristics of the model were considered satisfactory for all conditions investigated. The lateral stability characteristics were considered satisfactory for the basic configuration over the speed range investigated except near the stall, where large values of static directional instability caused the model to be directionally divergent. The addition of leading-edge slats or an 8-percent increase in vertical-tail area increased the angle of attack at which the model became directionally divergent. The use of leading-edge slats in combination with a 40-percent increase in vertical-tail size eliminated the directional divergence and produced satisfactory stability characteristics through the stall. The longitudinal and lateral control characteristics were generally satisfactory. Although the adverse sideslip characteristics for the model were considered satisfactory over the angle-of-attack range, analysis indicates that the adverse sideslip characteristics of the airplane may be objectionable at high angles of attack.

Johnson, Joseph L., Jr.↗

NASA NTRS1952

Free-Flight-Tunnel Investigation of the Dynamic Stability and Control Characteristics of a Chance Vought F7U-3 Airplane in Towed Flight

As part of a program to determine the feasibility of using a fighter airplane as a parasite in combination with a Consolidated Vultee RB-36 for long-range reconnaissance missions (project FICON), an experimental investigation has been made in the Langley free-flight tunnel to determine the dynamic stability and control characteristics of a 1/17.5-scale model of a Chance Vought F7U-3 airplane in several tow configurations. The investigation consisted of flight tests in which the model was towed from a strut in the tunnel by a towline and by a direct coupling which provided complete angular freedom. The tests with the direct coupling also included a study of the effect of spring restraint in roll in order to simulate approximately the proposed full-scale arrangement in which the only freedom is that permitted by the flexibility of the launching and retrieving trapeze carried by the-bomber. For the tow configurations in which a towline was used (15 and 38 feet full scale), the model had a very unstable lateral oscillation which could not be controlled. The stability was also unsatisfactory for the tow configuration in Which the model was coupled directly to the strut with complete angular freedom. When spring restraint in roll was added, however, the stability was satisfactory. The use of the yaw damper which increased the damping in yaw to about six times the normal value of the model appeared to have no appreciable effect on the lateral oscillations in the towline configurations, but produced a slight improvement in the case of the direct coupling configurations. The longitudinal stability was satisfactory for those cases in which the lateral stability was good enough to permit study of longitudinal motions.

Grana, David C.↗

NASA NTRS1948

Experimental investigation of the aerodynamic effects of distributed spanwise blowing on a fighter configuration

The results of wind tunnel tests at NASA Langley targeted at the performance and configurational characteristics of 0.1 and 0.13 scale model spanwise blowing (SWB) jet wing concepts are reported. The concept involves redirection of engine compressor bleed air to provide SWB at the fuselage-wing juncture near the wing leading edge. The tests covered the orientation of the outer panel nozzles, the effects of SWB operation on the performance of leading and trailing edge flaps and the effects of SWB on lateral stability. The trials were run at low speeds and angles of attack from 24-45 deg (landing). Both lift and longitudinal stability improved with the SWB, stall and leading edge vortex breakdown were delayed and performance increased with the SWB rate. Lateral stability was degraded below 20 deg angle of attack while instabilities were delayed above 20 deg due to roll damping.

Huffman, J. K.↗

NASA NTRS1999

Additional Development and Systems Analyses of Pneumatic Technology for High Speed Civil Transport Aircraft

In the Task I portion of this NASA research grant, configuration development and experimental investigations have been conducted on a series of pneumatic high-lift and control surface devices applied to a generic High Speed Civil Transport (HSCT) model configuration to determine their potential for improved aerodynamic performance, plus stability and control of higher performance aircraft. These investigations were intended to optimize pneumatic lift and drag performance; provide adequate control and longitudinal stability; reduce separation flowfields at high angle of attack; increase takeoff/climbout lift-to-drag ratios; and reduce system complexity and weight. Experimental aerodynamic evaluations were performed on a semi-span HSCT generic model with improved fuselage fineness ratio and with interchangeable plain flaps, blown flaps, pneumatic Circulation Control Wing (CCW) high-lift configurations, plain and blown canards, a novel Circulation Control (CC) cylinder blown canard, and a clean cruise wing for reference. Conventional tail power was also investigated for longitudinal trim capability. Also evaluated was unsteady pulsed blowing of the wing high-lift system to determine if reduced pulsed mass flow rates and blowing requirements could be made to yield the same lift as that resulting from steady-state blowing. Depending on the pulsing frequency applied, reduced mass flow rates were indeed found able to provide lift augmentation at lesser blowing values than for the steady conditions. Significant improvements in the aerodynamic characteristics leading to improved performance and stability/control were identified, and the various components were compared to evaluate the pneumatic potential of each. Aerodynamic results were provided to the Georgia Tech Aerospace System Design Lab. to conduct the companion system analyses and feasibility study (Task 2) of theses concepts applied to an operational advanced HSCT aircraft. Results and conclusions from these experimental evaluations are presented herein, as are recommendations for further development and follow-on investigations. Also provided as an Appendix for reference are the basic results from the previous pneumatic HSCT investigations.

Englar, Robert J.↗

NASA NTRS1947

Stick-Fixed Stability and Control Characteristics of the Consolidated Vultee Model 240 Airplane as Estimated from Tests of a 0.092-Scale Powered Model

Estimates of the static stick-fixed stability and control characteristics of the Consolidated Vultee model 240 airplane are presented in this report. The estimates are based on tests of a 0.092-scale powered model in the 10-foot wind tunnel of the Guggenheim Aeronautical Laboratory of the California Institute of Technology. Results of the analysis are evaluated in terms of the Army specifications for stability and control characteristics which are more specific and, in general, equal to or more rigid than the Civil Aeronautics Administration requirements. The stick-fixed stability and control characteristics of the Consolidated Vultee model 240 were found to be satisfactory except for the following: 1) Marginal longitudinal stability in the landing approach (flaps 30 deg, 50% minimum continuous power) with aft center of gravity (31% M.A.C.); 2) Marginal rudder control to hold zero sideslip in a climb after take-off with asymmetric power (flaps 30 deg, left engine inoperative, right engine delivering take-off power) with maximum rudder throw limited to +/- 18 deg; 3) Marginal dihedral effect with flaps 40 deg and engines delivering maximum continuous power.

McCullough, George B.↗

NASA NTRS1949

Investigation of Stability and Control Characteristics of a 1/10-scale Model of a Canadian Tailless Glider in the Langley Free-flight Tunnel

An investigation of the stability and control characteristics of a 1/10-scale model of a Canadian tailless glider has been conducted in the 10 Langley free-flight tunnel. The glider designated the N.R.L. tailless glider has a straight center section and outboard panels sweptback 43 deg. along the leading edge of the wing. The aspect ratio is 5.83 and the taper ratio is 0.323. From the results of the investigation and on the basis of comparison with higher-scale static tests of the National Research Council of Canada, it is expected that the longitudinal stability of the airplane will be satisfactory with flap up but unsatisfactory near the stall with flap down. The airplane is expected to have unsatisfactory lateral stability and control characteristics in the design configuration with either flap up or flap down. The model flights showed very low damping of the lateral oscillation. Increasing the vertical-tail area improved the lateral stability, and it appeared that a value of the directional-stability parameter C(sub n beta) of at least 0.002 per degree would probably be necessary for satisfactory lateral flying characteristics. A comparison of the calculated dynamic lateral stability characteristics of the N.R.L. tailless glider with those of a conventional-type sweptback airplane having a similar wing plan form and about the same inclination of the principal longitudinal axis of inertia showed that the tailless glider had poorer lateral stability because of the relatively larger radius of gyration in roll and the smaller damping-in-yaw factor C(sub nr).

Johnson, Joseph L.↗

NASA NTRS1984

Wind-Tunnel Investigation of an Advanced General Aviation Canard Configuration

Wind-tunnel tests of a model of an advanced canard configuration designed for general aviation were conducted in the Langley 30- by 60-Foot Tunnel. The objective of the tests was to determine the aerodynamic stability and control characteristics of the configuration for a large range of angles of attack and sideslip at several power conditions. Analysis of the aerodynamic data indicates significant effects of power and of center-of-gravity location. For forward center-of-gravity locations, the configuration had extremely stall-resistant stability and control characteristics. For aft center-of-gravity locations and high-power conditions, the combined effects of increased pitch control and reduced longitudinal stability overpowered the stall resistance provided by the canard, which led to a high-angle-of-attack, deep-stall trim condition. Other aspects of the aerodynamic characteristics studied include the following: flow-visualization study, effect of negative angles of attack, lateral-directional characteristics, and comparison of the stall characteristics with another canard configuration.

Chambers, J. R.↗

NASA NTRS1946

Comparison of Wind-Tunnel and Flight Measurements of Stability and Control Characteristics of a Douglas A-26 Airplane

Tests in Langley pressure tunnel of model XA-26 bomber were compared with those of A-26B (twin-engine attack bomber) and showed that static longitudinal stability, indicated by elevator-fixed neutral points, and variation of elevator deflection in straight and turning flight were good. Airplane possessed improved stability at low speeds which was attributed to pronounced stalling at root of production wing. At rudder-force reversal at speeds higher than those in flight tests, agreement in rudder-fixed and rudder-free static directional stability was good. Hinge moment obtained at zero sideslip was satisfactory for determining aileron forces in sideslip.

SIDESLIPPING - DOUGLAS A-26↗

NASA NTRS1973

Computer Programs for Calculating and Plotting the Stability Characteristics of a Balloon Tethered in a Wind

Computer programs for calculating the stability characteristics of a balloon tethered in a steady wind are presented. Equilibrium conditions, characteristic roots, and modal ratios are calculated for a range of discrete values of velocity for a fixed tether-line length. Separate programs are used: (1) to calculate longitudinal stability characteristics, (2) to calculate lateral stability characteristics, (3) to plot the characteristic roots versus velocity, (4) to plot the characteristic roots in root-locus form, (5) to plot the longitudinal modes of motion, and (6) to plot the lateral modes for motion. The basic equations, program listings, and the input and output data for sample cases are presented, with a brief discussion of the overall operation and limitations. The programs are based on a linearized, stability-derivative type of analysis, including balloon aerodynamics, apparent mass, buoyancy effects, and static forces which result from the tether line.

Bennett, R. M.↗

NASA NTRS1974

Study of the single body yawed-wing aircraft concept

Areas relating to the development and improvement of the single-fuselage, yawed-wing transonic transport concept were investigated. These included: (1) developing an alternate configuration with a simplified engine installation;(2) determining a structural design speed placard that would allow the engine-airframe match for optimum airplane performance; and (3) conducting an aeroelastic stability and control analysis of the yawed-wing configuration with a flexible wing. A two-engine, single-fuselage, yawed-wing configuration was developed that achieved the Mach 1.2 design mission at 5560 km (3000 nmi) and payload of 18,140 kg (40,000 lb) with a gross weight of 217,700 kg (480,000 lb). This airplane was slightly heavier than the aft-integrated four-engine configuration that had been developed in a previous study. A modified structural design speed placard, which was determined, resulted in a 6% to 8% reduction in the gross weight of the yawed-wing configurations. The dynamic stability characteristics of the single-fuselage yawed-wing configuration were found to be very dependent on the magnitude of the pitch/roll coupling, the static longitudinal stability, and the dihedral effect.

Kulfan, R. M.↗

NASA NTRS1999

Preliminary Results of the 1.5% TCA (Modular) Controls Model in the NASA Langley UPWT

To summarize the significant highlights in this report: (1) Data quality, determined by multiple repeat runs performed on the TCA baseline configuration, and long-term repeatability, determined by comparing baseline Reference H data from this test to a previous test, have been shown to be good. (2) The longitudinal stability of the TCA is more non-linear than for the Reference H, and while it is similar at normal lift values, the TCA has considerably more pitch-up at higher lift. (3) Longitudinal control effectiveness of the TCA is similar to the Reference H and the ratio of elevator effectiveness to horizontal tail effectiveness is approximately 0.3. 4) The directional stability of the TCA is improved relative to Reference H at higher angles-of attack. The chine is effective for improving directional stability. (5) The directional control effectiveness 'of the TCA rudder is the same as that of the Reference H rudder at low angles-of-attack, after taking factors, such as number of rudder panels deflected and vertical tail volume into account. However, rudder effectiveness was shown to be reduced at higher angles-of-attack. (6) The lateral stability was shown to be reduced relative to the Reference H, which may be beneficial at low speeds for alleviating lateral control saturation. (7) Lateral control effectiveness for the TCA was shown to be similar to the Reference H for negative trailing-edge flap deflections and was reduced by approximately 25% for positive trailing-edge flap deflections.

Kubiatko, Paul↗

NASA NTRS1999

Preliminary Results of the 1.5% TCA (Modular) Controls Model in the NASA Langley UPWT

Kubiatko, Paul↗