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At least 37 records · Page 2

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NASA NTRS1954

The Effect of Blunt-Trailing-Edge Modifications on the High-Speed Stability and Control Characteristics of a Swept-Wing Fighter Airplane

An investigation was conducted on a 35 deg swept-wing fighter airplane to determine the effects of several blunt-trailing-edge modifications to the wing and tail on the high-speed stability and control characteristics and tracking performance. The results indicated significant improvement in the pitch-up characteristics for the blunt-aileron configuration at Mach numbers around 0.90. As a result of increased effectiveness of the blunt-trailing-edge aileron, the roll-off, customarily experienced with the unmodified airplane in wings-level flight between Mach numbers of about 0.9 and 1.0 was eliminated, The results also indicated that the increased effectiveness of the blunt aileron more than offset the large associated aileron hinge moment, resulting in significant improvement in the rolling performance at Mach numbers between 0.85 and 1.0. It appeared from these results that the tracking performance with the blunt-aileron configuration in the pitch-up and buffeting flight region at high Mach numbers was considerably improved over that of the unmodified airplane; however, the tracking errors of 8 to 15 mils were definitely unsatisfactory. A drag increment of about O.OOl5 due to the blunt ailerons was noted at Mach numbers to about 0.85. The drag increment was 0 at Mach numbers above 0.90.

Sadoff, Melvin↗

NASA NTRS1955

Measurement and Analysis of Wing and Tail Buffeting Loads on a Fighter Airplane

The buffeting loads measured on the wing and tail of a fighter airplane during 194 maneuvers are given in tabular form, along with the associated flight conditions. Measurements were made at altitudes of 30,000 to 10,000 feet and at speeds up to a Mach number of 0.8. Least-squares methods have been used for a preliminary analysis of the data. The agreement between the results of this analysis and the loads measured in stalls is sufficiently good to suggest the examination of the buffeting of other airplanes on the same basis.

Huston, Wilber B↗

NASA NTRS1959

A Flight Investigation of the Low-Speed Handling Qualities of a Tailless Delta-Wing Fighter Airplane

Carrier landing-approach studies of a tailless delta-wing fighter airplane disclosed that approach speeds were limited by ability to control altitude and lateral-directional characteristics. More detailed flight studies of the handling-qualities characteristics of the airplane in the carrier-approach configuration documented a number of factors that contributed to the adverse comments on the lateral-directional characteristics. These were: (1) the tendency of the airplane to roll around the highly inclined longitudinal axis, so that significant sideslip angles developed in the roll as a result only of kinematic effects; (2) reduction of the rolling response to the ailerons because of the large dihedral effect in conjunction with the kinematically developed sideslip angles; and (3) the onset of rudder lock at moderate angles of sideslip at the lowest speeds with wing tanks installed. The first two of the factors listed are inseparably identified with this type of configuration which is being considered for many of the newer designs and may, therefore, represent a problem which will be encountered frequently in the future. The results are of added significance in the demonstration of a typical situation in which extraneous factors occupy so much of the pilot's attention that his capability of coping with the problems of precise flight-path control is reduced, and he accordingly demands a greater speed margin above the stall to allow for airspeed fluctuations.

White, Maurice D.↗

NASA NTRS1983

An aerodynamic assessment of various supersonic fighter airplanes based on Soviet design concepts

The aerodynamic, stability, and control characteristics of several supersonic fighter airplane concepts were assessed. The configurations include fixed-wing airplanes having delta wings, swept wings, and trapezoidal wings, and variable wing-sweep airplanes. Each concept employs aft tail controls. The concepts vary from lightweight, single engine, air superiority, point interceptor, or ground attack types to larger twin-engine interceptor and reconnaissance designs. Results indicate that careful application of the transonic or supersonic area rule can provide nearly optimum shaping for minimum drag for a specified Mach number requirement. Through the proper location of components and the exploitation of interference flow fields, the concepts provide linear pitching moment characteristics, high control effectiveness, and reasonably small variations in aerodynamic center location with a resulting high potential for maneuvering capability. By careful attention to component shaping and location and through the exploitation of local flow fields, favorable roll-to-yaw ratios may result and a high degree of directional stability can be achieved.

Spearman, M. L.↗

NASA NTRS2006

Predicting Tail Buffet Loads of a Fighter Airplane

Buffet loads on aft aerodynamic surfaces pose a recurring problem on most twin-tailed fighter airplanes: During maneuvers at high angles of attack, vortices emanating from various surfaces on the forward parts of such an airplane (engine inlets, wings, or other fuselage appendages) often burst, immersing the tails in their wakes. Although these vortices increase lift, the frequency contents of the burst vortices become so low as to cause the aft surfaces to vibrate destructively. Now, there exists a new analysis capability for predicting buffet loads during the earliest design phase of a fighter-aircraft program. In effect, buffet pressures are applied to mathematical models in the framework of a finite-element code, complete with aeroelastic properties and working knowledge of the spatiality of the buffet pressures for all flight conditions. The results of analysis performed by use of this capability illustrate those vibratory modes of a tail fin that are most likely to be affected by buffet loads. Hence, the results help in identifying the flight conditions during which to expect problems. Using this capability, an aircraft designer can make adjustments to the airframe and possibly the aerodynamics, leading to a more robust design.

Moses, Robert W.↗

NASA NTRS1972

Investigation of an automatic spin prevention system for fighter airplanes

An investigation was conducted to evaluate the effectiveness of an automatic spin-prevention system for current fighter airplanes as a first step in determining the feasibility of such a system. The concept makes use of the components of the conventional flight-control system with the addition of control logic to monitor angle of attack, yaw rate, and normal acceleration. Analytical techniques were used to study the system concept applied to three representative fighter configurations, and model flight tests were employed to evaluate a prototype system on a representative fighter configuration. Emphasis was placed on the development of the control logic required. A discussion of possible implementations of the system concept is presented. Results of the investigation indicated that a relatively simple system (with full control authority) was effective in preventing the developed spins of the fighter configurations considered and that the system design is dependent on the stall and spin characteristics of the particular airplane.

Gilbert, W. P.↗

NASA NTRS1977

Aerodynamic characteristics of supersonic fighter airplane configurations based on Soviet design concepts

The aerodynamic, stability, and control characteristics of several supersonic fighter airplane concepts are examined. The configurations, which are based on Soviet design concepts, include fixed-wing aircraft having delta wings, swept wings, and trapezoidal wings, and a variable wing-sweep aircraft. Each concept employs aft tail controls. The concepts vary from lightweight, single-engine, air superiority, point interceptor, or ground attack types to larger twin-engine interceptor and reconnaissance designs. Analytical and experimental results indicate that careful application of the transonic or supersonic area rule can provide nearly optimum shaping for minimum drag for a specified Mach number requirement. In addition, through the proper location of components and the exploitation of interference flow fields, the concepts provide linear pitching moment characteristics, high control effectiveness, and reasonably small variations in aerodynamic center location with a resulting high potential for maneuvering capability.

Spearman, M. L.↗

NASA NTRS1983

Determination of aerodynamic parameters of a fighter airplane from flight data at high angles of attack

A procedure for the estimation of airplane model structure and parameters is applied to data from a modern fighter airplane operating within an angle of attack range of 5 to 60 deg. The paper briefly describes the airplane, flight and wind tunnel data available, and the estimation method. The results presented contain basic longitudinal characteristics of the airplane and the estimates of aerodynamic parameters in the yawing-moment equations. These estimates are obtained from small and large amplitude maneuvers. Because the latter set of data was not suitable for airplane identification, some of the large amplitude maneuvers were joined together and then partitioned into subsets according to the values of angle of attack. Each subset was then analyzed as a separate data set. Most of the estimated parameters and functions are in good agreement with the wind tunnel measurements. The estimated lateral parameters in the model equations also demonstrate good prediction capabilities.

Klein, V.↗

NASA NTRS1959

Lift and Drag of a Swept-Wing Fighter Airplane at Transonic and Supersonic Speeds

A flight investigation was made of the lift and drag of a sweptwing fighter airplane in the basic configuration and in a slats-locked-closed configuration over a Mach number range from about 0.63 to about 1.44. At a nominal lift coefficient of 0.1 negligible drag-coefficient difference existed between the two configurations over a comparable Mach number and altitude range. For the basic configuration at zero lift the supersonic drag level was about three times as great as the subsonic drag level, which was about 0.01, whereas the drag-due-to-lift factor increased about 137 percent over the test Mach number range. At comparable Mach numbers the high-altitude data produced a larger lift-curve slope and showed a more pronounced variation of lift-curve slope in the transonic region than did the low-altitude data. For the high-altitude data the lift-curve slope at a Mach number of 1.44 was approximately 62 percent of the value at a Mach number of 0.9.

SWEPT WING↗

NASA NTRS1949

An Apparatus for Varying Effective Dihedral in Flight with Application to a Study of Tolerable Dihedral on a Conventional Fighter Airplane

An apparatus for varying effective dihedral in flight by means of servo actuation of the ailerons in response to sideslip angle is described. The results of brief flight tests of the apparatus on a conventional fighter airplane are presented and discussed. The apparatus is shown to have satisfactory simulated a wide range of effective dihedral under static and dynamic conditions. The effects of a small amount of servo lag are shown to be measurable when the apparatus is simulating small negative values of dihedral. However, these effects were not considered by the pilots to give the airplane an artificial feel. The results of an investigation employing the apparatus to determine the tolerable (safe for normal fighter operation) range of effective dihedral on the test airplane are presented.

Kauffman, William M↗

NASA NTRS1959

The Effect of Lower Surface Spoilers on the Transonic Trim Change of a Wind-Tunnel Model of a Fighter Airplane Having a Modified Delta Wing

In an attempt to find an aerodynamic means of counteracting the transonic trim change of a fighter airplane, lower surface spoilers were tested on a 0.055-scale wind-tunnel model. The Mach number range of the tests was 0.8 to 1.2 at Reynolds numbers of approximately 4 million. Although the spoilers produced a moderate decrease in the trim change at low altitudes, they also produced a large increase in drag. Pressure-distribution tests with external fuel tanks showed large pressure changes on the lower surface of the wing due to the tanks.

Robinson, Robert C.↗

NASA NTRS1946

Analysis of Effect of Rolling Pull-Outs on Wing and Aileron Loads of a Fighter Airplane

An analysis was made to determine the effect of rolling pull-out maneuvers on the wing and aileron loads of a typical fighter airplane, the P-47B. The results obtained indicate that higher loads are imposed upon wings and ailerons because of the rolling pull-out maneuver, than would be obtained by application of the loading requirements to which the airplane was designed. An increase of 102 lb or 15 percent of wing weight would be required if the wing were designed for rolling pull-out maneuver. It was also determined that the requirements by which the aileron was originally designed were inadequate.

AIRFOILS - NACA 65-410 - ORDINATES LOW-DRAG (BLOWE↗

NASA NTRS1976

Simulator study of the effectiveness of an automatic control system designed to improve the high-angle-of-attack characteristics of a fighter airplane

A piloted, fixed-base simulation was conducted to study the effectiveness of some automatic control system features designed to improve the stability and control characteristics of fighter airplanes at high angles of attack. These features include an angle-of-attack limiter, a normal-acceleration limiter, an aileron-rudder interconnect, and a stability-axis yaw damper. The study was based on a current lightweight fighter prototype. The aerodynamic data used in the simulation were measured on a 0.15-scale model at low Reynolds number and low subsonic Mach number. The simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative combat maneuvering. Results of the investigation show the fully augmented airplane to be quite stable and maneuverable throughout the operational angle-of-attack range. The angle-of-attack/normal-acceleration limiting feature of the pitch control system is found to be a necessity to avoid angle-of-attack excursions at high angles of attack. The aileron-rudder interconnect system is shown to be very effective in making the airplane departure resistant while the stability-axis yaw damper provided improved high-angle-of-attack roll performance with a minimum of sideslip excursions.

Gilbert, W. P.↗

NASA NTRS1961

Large-Angle Motion Tests, Including Spins, of A Free-Flying Radio-Controlled 0.13-Scale Model of A Twin Jet Swept Wing Fighter Airplane

An investigation has been conducted with a free-flying radio-controlled 0.15-scale model of a twin-jet swept-wing fighter airplane to determine the tendency of this design to enter spins and to evaluate the nature of the spin obtained from post-stall motions. The test results indicate that it may be difficult to obtain a developed spin on the airplane, particularly the flat-type spin. Two types of erect developed spins will be possible; one will be flat and fast rotating from which recovery may not be obtained and the other will be steeper and oscillatory from which recoveries will be satisfactory. Controls will be effective for satisfactory termination of the post-stall gyrations obtained. The recommended recovery technique from both post-stall gyrations and developed spins will be movement of the rudder to oppose the yawing rotation and simultaneous movement of the ailerons to with the rotation (stick right when turning to the right). When recovery is imminent, the stick should be moved longitudinally to neutral. It is recommended that the spin not be allowed to develop fully on this airplane. The developed-spin results obtained in the investigation were in good agreement with spin-tunnel results.

Sanger M Burk, Jr↗

NASA NTRS1979

Effects of spanwise blowing on two fighter airplane configurations

The NASA Langley Research Center has recently conducted an investigation to determine the effects of spanwise blowing on two configurations representative of current fighter airplanes. This research examined not only the longitudinal, or performance, effects but was especially oriented toward determining the lateral-directional effects, particularly in the stall/departure angle of attack range. The wind tunnel tests included measurement of static and forced-oscillation aerodynamic data, visualization of the airflow changes over the wing created by the spanwise blowing and free flight model tests. Effects of blowing rate, chordwise location of the blowing ports, asymmetric blowing, and the effects of blowing on the effectiveness of conventional aerodynamic controls were investigated.

Anglin, E. L.↗

NASA NTRS1953

A Flight Study of the Effects on Tracking Performance of Changes in the Lateral-oscillatory Characteristics of a Fighter Airplane

A study of the effects of variations in lateral-oscillatory characteristics on air-to-air tracking performance has been made, using a conventional, propeller-driven fighter airplane equipped with servo devices for varying these characteristics in flight. Tracking runs were made both in smooth air and in simulated rough air. The lateral-oscillation period, damping, and roll coupling were varied over wide ranges during the investigation.

GUSTS, TURBULENCE↗

NASA NTRS1972

Supersonic aerodynamic damping and oscillatory stability in pitch and yaw fro a model of a variable-sweep fighter airplane with twin vertical tails

Wind-tunnel measurements of the aerodynamic damping and oscillatory in pitch and yaw for a 1/22-scale model of a proposed carrier-based variable-sweep fighter airplane have been made by using a small-amplitude forced-oscillation technique. Tests were made with a wing leading-edge sweep angle of 68 deg at angles of attack from about -1.5 deg to 15.6 deg at a Mach number of 1.60 and at angles of attack from about -3 deg to 21 deg at Mach numbers of 2.02 and 2.36. The results of the investigation indicate that the basic configuration has positive damping and positive oscillatory stability in pitch for all test conditions. In yaw, the damping is generally positive except near an angle of attack of 0 deg at a Mach number of 1.60. The oscillatory stability in yaw is positive except at angles of attack above 16 deg at Mach numbers of 2.02 and 2.36. The addition of external stores generally causes increases in both pitch and yaw damping. The oscillatory stability in pitch is reduced throughout the angle-of-attack range by the addition of the external stores. The effect of adding stores on the oscillatory stability in yaw is a function of angle of attack and Mach number. The effect of changing horizontal-tail incidence on the pitch parameters is also very dependent on angle of attack and Mach number.

Kilgore, R. A.↗

NASA NTRS1974

Exhaust-nozzle characterisitcs for a twin-jet variable-wing-sweep fighter airplane model at Mach numbers to 2.2

A wind-tunnel investigation has been conducted to determine the exhaust-nozzle aerodynamic and propulsive characteristics for a twin-jet variable-wing-sweep fighter airplane model. The powered model was tested in the Langley 16-foot transonic tunnel and in the Langley 4-foot supersonic pressure tunnel at Mach numbers to 2.2 and at angles of attack from about minus 2 to 6 deg. Compressed air was used to simulate the nozzle exhaust flow at values of jet total-pressure ratio from approximately 1 (jet off) to about 21. Effects of configuration variables such as speed-brake deflection, store installation, and boundary-layer thickness on the the nozzle characteristics were also investigated.

Reubush, D. E.↗