Browse Topic: Stall

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Hydrodynamic Drives TerminologyJ641_201912 (Current)12/02/2019
Since the torque converter and fluid coupling are commonly used components of automatic transmissions in industry, the SAE appointed a committee to standardize terminology, test procedure, data recording, design symbols, and so forth, in this field. The following committee recommendations will facilitate a clear understanding for engineering discussions, comparisons, and the preparation of technical papers. The recommended usages represent the predominant practice or the acceptable practice. Where agreement is not complete, alternates have been included for clarification. EXAMPLE: Two systems of blade angle designations are described. Consequently, when a blade angle is specified, the system should be designated. This SAE Recommended Practice deals only with the physical parts and dimensions and does not attempt to standardize the design considerations, such as the actual fluid flow angle resulting from the physical blade shape.
Automatic Transmission and Transaxle Committee
Separating-Reattaching Flows Over an Iced Airfoil2019-01-194606/10/2019
Delayed Detached Eddy Simulations (DDES) of separating-reattaching flows on the suction side of an ice-contaminated airfoil were conducted. A single-section straight-wing NACA23012 airfoil with leading-edge ice was studied. The geometry represents a realistic glaze horn-ice contamination obtained during the icing test campaigns described in [1], which has aerodynamic data for comparison. The three-dimensional transient flow behavior was simulated using the open-source flow solver OVERFLOW, version 2.2l [2] developed by NASA Langley Research Center. Configurations at three angles of attack that exhibit unsteady flow behavior starting with the bursting angle were examined at Mach number of 0.18 and Reynolds number of 1.8x106. As the stall angle was approached the aerodynamic performance parameters displayed large-scale unsteadiness where periods of attached and separated flows were observed. The time-averaged results show good agreement with the aerodynamic test data. The calculated
Oztekin, Ezgi, Riley, James
Experimental Aerodynamic Simulation of Glaze Ice Accretion on a Swept Wing2019-01-198706/10/2019
Aerodynamic assessment of icing effects on swept wings is an important component of a larger effort to improve three-dimensional icing simulation capabilities. An understanding of ice-shape geometric fidelity and Reynolds and Mach number effects on iced-wing aerodynamics is needed to guide the development and validation of ice-accretion simulation tools. To this end, wind-tunnel testing was carried out for 8.9% and 13.3% scale semispan wing models based upon the Common Research Model airplane configuration. Various levels of geometric fidelity of an artificial ice shape representing a realistic glaze-ice accretion on a swept wing were investigated. The highest fidelity artificial ice shape reproduced all of the three-dimensional features associated with the glaze ice accretion. The lowest fidelity artificial ice shapes were simple, spanwise-varying horn ice geometries intended to represent the maximum ice thickness on the wing upper surface. The results presented in this paper show
Broeren, Andy P., Potapczuk, Mark G., Lee, Sam, Woodard, Brian S., Bragg, Michael B., Smith, Timothy G.
Numerical and Experimental Second Law Analysis of a Low Thickness High Chamber Wing Profile2018-01-195510/30/2018
This paper presents a coupled numerical and experimental study of an unconventional wing profile such as cp-180-050-gn (Cambered plate C = 18% T = 5% R = 0.78). This wing profile deals with low speeds. It is not currently used on any aircraft model. Otherwise, it presents interesting performances that can be exploited for the design of low-speed STOL or VTOL aircraft by mean of the very high lift that it can generate and can fit with different uses such as VAWT, cyclorotors drones, which are designed explicitly for low-speed operations. After a preliminary CFD assessment of the wing a complete experimental characterisation also at high angles of attack has been performed. The excellent agreement between CFD and experiments has allowed producing a complete analysis of the behaviour of the wing profile both before and after stall conditions. This study has the objective of analysing the viability of such an unconventional wing in traditional or over-stalling conditions. A complete
Trancossi, Michele, Sharma, Shivesh
Benefits of Using Encoders to Improve Step Motor System PerformanceTBMG-2899806/01/2018
Step motors are widely used in automation due to their high resolution, precision positioning, minimal control electronics, and low cost. As an open loop system, traditional step motors are driven without the need for sensors to feed information back to a controller; however, the open loop configuration of step motors has challenges.
A Computational and Experimental Investigation into the Effects of Debris on an Inverted Double Wing in Ground Effect2018-01-072604/03/2018
Cars in several motor sports series, such as Formula 1, make use of multi-element front wings to provide downforce. These wings also provide onset flows to other surfaces that generate downforce. These elements are highly loaded to maximise their performance and are generally operating close to stall. Rubber debris, often known as marbles, created from the high slip experienced by the soft compound tyres can become lodged in the multiple elements of a front wing. This will lead to a reduction in the effectiveness of the wing over the course of a race. This work will study the effect of such debris, both experimentally and numerically, on an inverted double element wing in ground effect at representative Reynolds numbers. The wing was mounted at two different ride heights above a fixed false-floor in the Loughborough University wind tunnel and the effect of debris blockage modelled by closing sections of the gap between elements with tape. The reduction in downforce compared to the
Corfield, Emma, Hodgson, Graham, Garmory, Andrew
Experimental Study of Dielectric Barrier Discharge Driven Duct Flow for Propulsion Applications in Unmanned Aerial Systems2017-01-206309/19/2017
The dielectric barrier discharge (DBD) has been studied significantly in the past two decades for its applications to various aerodynamic problems. The most common aerodynamic applications have been stall/separation control and boundary layer modification. Recently several researchers have proposed utilizing the DBD in various configurations to act as viable propulsion systems for micro and nano aerial vehicles. The DBD produces stable atmospheric-pressure non-thermal plasma in a thin sheet with a preferred direction of flow. The plasma flow, driven by electrohydrodynamic body forces, entrains the quiescent air around it and thus develops into a low speed jet on the order of 10-1 to 101 m/s. Several researchers have utilized DBDs in an annular geometric setup as a propulsion device. Other researchers have used them to alter rectangular duct flows and directional jet devices. This study investigates 2-D duct flows for applications in micro plasma thrusters. The DBD actuators are located
Browning, Patrick, Shambaugh, Bryan, Dygert, Joseph
A First Principles Based Approach for Dynamic Modeling of Turbomachinery2016-01-199509/20/2016
As the cost and complexity of modern aircraft systems increases, emphasis has been placed on model-based design as a means for reducing development cost and optimizing performance. To facilitate this, an appropriate modeling environment is required that allows developers to rapidly explore a wider design space than can cost effectively be considered through hardware construction and testing. This wide design space can then yield solutions that are far more energy efficient than previous generation designs. In addition, non-intuitive cross-coupled subsystem behavior can also be explored to ensure integrated system stability prior to hardware fabrication and testing. In recent years, optimization of control strategies between coupled subsystems has necessitated the understanding of the integrated system dynamics. To this end, a dynamic vapor cycle modeling toolset known as the AFRL Transient Thermal Management and Optimization (ATTMO) toolset was developed to address two-phase flow
McCarthy, Patrick, Niedbalski, Nicholas, McCarthy, Kevin, Walters, Eric, Cory, Joshua, Patnaik, Soumya
Experimental Investigation on a 3D Wing Section Hosting Multiple SJAs for Stall Control Purpose2015-01-245309/15/2015
Flow control over aerodynamic shapes in order to achieve performance enhancements has been a lively research area for last two decades. Synthetic Jet Actuators (SJAs) are devices able to interact actively with the flow around their hosting structure by providing ejection and suction of fluid from the enclosed cavity containing a piezo-electric oscillating membrane through dedicated orifices. The research presented in this paper concerns the implementation of zero-net-mass-flux SJAs airflow control system on a NACA0015, low aspect ratio wing section prototype. Two arrays with each 10 custom-made SJAs, installed at 10% and 65% of the chord length, make up the actuation system. The sensing system consists of eleven acoustic pressure transducers distributed in the wing upper surface and on the flap, an accelerometer placed in proximity of the wing c.g. and a six-axis force balance for integral load measurement. A dSPACE™ hardware connected to the software environment Matlab/Simulink® and
Andreoli, Danilo, Cassaro, Mario, Battipede, Manuela, Ahmadi, Goodarz, Marzocca, Piergiovanni
Tailplane with Positive Camber for Reduced Elevator Hinge Moment2015-01-256609/15/2015
The Learjet 85 is a business jet with an unpowered manual elevator control and is designed for a maximum dive Mach number of 0.89. During the early design, it was found that the stick force required for a 1.5g pull-up from a dive would exceed the limit set by FAA regulations. A design improvement of the tailplane was initiated, using 2D and 3D Navier-Stokes CFD codes. It was discovered that a small amount of positive camber could reduce the elevator hinge moment for the same tail download at high Mach numbers. This was the result of the stabilizer forebody carrying more of the tail download and the elevator carrying less. Consequently, the elevator hinge-moment during recovery from a high-speed dive was lower than for the original tail. Horizontal tails are conventionally designed with zero or negative camber since a positive camber can have adverse effects on tail stall and drag. The tailplane sections for the Learjet 85 were tailored to minimize these adverse effects while achieving
Chandrasekharan, Reuben, Iarocci, Nick, Vafa, Sherry, Akel, Iyad
Nonlinear Slender Beam-Wise Schemes for Structural Behavior of Flexible UAS Wings2015-01-246209/15/2015
The innovative highly flexible wings made of extremely light structures, yet still capable of carrying a considerable amount of non- structural weights, requires significant effort in structural simulations. The complexity involved in such design demands for simplified mathematical tools based on appropriate nonlinear structural schemes combined with reduced order models capable of predicting accurately their aero-structural behaviour. The model presented in this paper is based on a consistent nonlinear beam-wise scheme, capable of simulating the unconventional aeroelastic behaviour of flexible composite wings. The partial differential equations describing the wing dynamics are expanded up to the third order and can be used to explore the effect of static deflection imposed by external trim, the effect of gust loads and the one of nonlinear aerodynamic stall. As to provide a rationale evaluation of the important nonlinear contributions in aeroelastic wing simulations, the aeroelastic
Bruni, Claudia, Cestino, Enrico, Frulla, Giacomo, Marzocca, Piergiovanni
Study of Unmanned Supersonic Aircraft Configuration2014-36-019309/30/2014
The aim of this work is to present the preliminary performance studies of the unmanned, lightweight (less than 10 kg), supersonic research aircraft. The studies comprise the typical mission for the aircraft's first supersonic version, based on the aerodynamic, thrust, and mass characteristics presented in a previous work. The aircraft, named as “Pohox”, is an Unmanned Air Vehicle, or “UAV”, and is intended to be the flying test bed for a multi cycle engine capable to provide thrust in subsonic, transonic and supersonic regimes. Different tools have been developed to perform the analysis. In the analysis, different flight paths are considered in order to provide insights in terms of fuel consumption, altitude and speed gain. Aircraft ‘excess power’ diagrams have been generated, to provide guidance for the definition of the flight paths to be analyzed. Drag dependency with Mach number is considered in the analysis. In addition, two important regions in the Aircraft's altitude versus
Barbosa, Luciano Magno Frágola, Maciel, Francelle Maria Oliveira, de Barros, José Eduardo Mautone
Hydrodynamic Drives TerminologyJ641_201206 (Historical)06/04/2012
Since the torque converter and fluid coupling are commonly used components of automatic transmissions in industry, the SAE appointed a committee to standardize terminology, test procedure, data recording, design symbols, and so forth, in this field. The following committee recommendations will facilitate a clear understanding for engineering discussions, comparisons, and the preparation of technical papers. The recommended usages represent the predominant practice or the acceptable practice. Where agreement is not complete, alternates have been included for clarification. This SAE Recommended Practice deals only with the physical parts and dimensions and does not attempt to standardize the design considerations, such as the actual fluid flow angle resulting from the physical blade shape.
Automatic Transmission and Transaxle Committee
Real-Time Flight Envelope Monitoring SystemTBMG-1278202/01/2012
The objective of this effort was to show that real-time aircraft control-surface hinge-moment information could be used to provide a robust and reliable prediction of vehicle performance and control authority degradation. For a given airfoil section with a control surface — be it a wing with an aileron, rudder, or elevator — the control-surface hinge moment is sensitive to the aerodynamic characteristics of the section. As a result, changes in the aerodynamics of the section due to angle-of-attack or environmental effects such as icing, heavy rain, surface contaminants, bird strikes, or battle damage will affect the control surface hinge moment. These changes include both the magnitude of the hinge moment and its sign in a time-averaged sense, and the variation of the hinge moment with time. The current program attempts to take the real-time hinge moment information from the aircraft control surfaces and develop a system to predict aircraft envelope boundaries across a range of
Tactile Robotic Topographical Mapping Without Force or Contact SensorsTBMG-270204/01/2008
A method of topographical mapping of a local solid surface within the range of motion of a robot arm is based on detection of contact between the surface and the end effector (the fixture or tool at the tip of the robot arm). The method was conceived to enable mapping of local terrain by an exploratory robot on a remote planet, without need to incorporate delicate contact switches, force sensors, a vision system, or other additional, costly hardware. The method could also be used on Earth for determining the size and shape of an unknown surface in the vicinity of a robot, perhaps in an unanticipated situation in which other means of mapping (e.g., stereoscopic imaging or laser scanning with triangulation) are not available.
Free-to-Roll Testing of Airplane Models in Wind TunnelsTBMG-241511/01/2007
A free-to-roll (FTR) test technique and test rig make it possible to evaluate both the transonic performance and the wing-drop/rock behavior of a high-strength airplane model in a single wind-tunnel entry. The free-to-roll test technique is a single degree-of-motion method in which the model is free to roll about the longitudinal axis. The rolling motion is observed, recorded, and analyzed to gain insight into wing-drop/rock behavior.
Reverse-Tangent Injection in a Centrifugal CompressorTBMG-218009/01/2007
Injection of working fluid into a centrifugal compressor in the reverse tangent direction has been invented as a way of preventing flow instabilities (stall and surge) or restoring stability when stall or surge has already commenced. If not suppressed, such instabilities interrupt the smooth flow of the working fluid and, in severe cases of surge, give rise to pressure and flow oscillations that can be strong enough to damage the compressor
Wireless Communication-The Link Between the Rolling Lan and the Rest of the World98C01610/19/1998
Over the past years many have been predicting various dramatic changes in the vehicle including automatic route guidance, the office in the vehicle, and the auto PC. There are a number of factors which need to come together before significant momentum can develop toward realizing any of these predictions. This paper enumerates these factors and explores the current state and possible evolution of each. While each of these factors could stall progress, the linchpin is likely to be wireless communication. The current state of wireless and its capabilities going forward are examined in depth.
Janc, Robert V.
Lock Up Times in Mechanical Diode Type One Way Clutches95105402/01/1995
The Mechanical Diode (MD) one way clutch is a positive locking mechanism. During lock up, steel struts are interposed between locking features on the facing surfaces of two disks. The movement of struts into a lock position as a shaft motion reversal is attempted is of interest in assessing the reliability of the one-way clutch. This paper presents the results of a study which predicts strut movement into lock position by examining the forces on the strut at each stage of the locking action and the response of the strut mass and surrounding fluid to these forces. Locking action is found to occur in a few microseconds with typical component sizes and lubricants.
Fitz, Frank
The Research on Quasi-Three-Dimensional Flow Design of Hydrodynamic Torque Converter Blades91270111/01/1991
In this paper, a quasi-three-dimensional design method of torque converter blade is presented, and a turbine example is designed. In addition, a new way that three-dimensional flow field calculation is added into traditional blade design is given and the judge rule of flow field is presented. The blade system of a Chinese made YB 300 torque converter has been redesigned with the aid of the new way, and its performance has been improved. The experiment shows that the maximum efficiency has been raised from original 84. 7% to 86%, with other factors such as stall torque ratio and so on unchanged or a little better.
Ma, Wenxing, Luo, BangJie, Wu, Shurong
Advanced Flight Control For The Fokker 10088137310/01/1988
The Automatic Flight Control and Augmentation System (AFCAS), recently certified on the Fokker F28 - Mk0100, provides this aircraft with a full flight regime autoflight system including CAT IIIb autoland capability and a fully integrated autothrottle. The FCS-1000, developed jointly by Rockwell International and the Fokker Aircraft Company, is based upon a classical triplex architecture interfaced with dual electromechanical servos. Additional new features designed to decrease the flight crew's workload in critical flight phases and to achieve a higher level of flight safety include: ultimate aircraft speed protection functions (i.e. an Engine Out Driftdown profile), coupled Windshear Escape, and a new Flight Mode Annunciation philosophy.
LaForge, L.G., van Gent, A.H.
PDS (Porsche Dynamic Slip Control Clutch)-A New Inter-Axle Coupling Device for 4WD-Cars88069802/01/1988
The PDS (Porsche Dynamic Slip-Control) is a new coupling system designed specifically for the conversion of FWD vehicles into 4WD. It was designed by PORSCHE working under a contract from UNI-CARDAN, a big European manufacturer of driveline components. The system is very suitable for mid-size cars with front/transverse engine location. Requiring no inter-axle differential, only a hang-on power-take-off from the front axle differential housing or gearbox is necessary. Although it is a relatively simple system, the PDS offers the traction and acceleration capability of a center-differential outfit. Improvements were found in cornering stability and starting under adverse road conditions. The report includes description of function, test-results of the pre-development phase, calculations of the vehicle handling characteristics and gives an overview of the further development potential of this 4WD system.
Müller, Robert, Witte, Lothar
A 2000 Ton Crawler/Transporter for Operation in Prudhoe Bay, Alaska86120509/01/1986
Recently designed and fabricated in Kennewick, Washington, a pair of 2000 ton capacity crawler/transporters has been used in moving refinery modules to permanent installations on Alaska's North Slope. Vehicle design features include four corner chain-driven, track driving sprockets (tumblers), resilient track roller suspensions, elevating load platform (hereinafter “bolsters”), dynamic braking, diesel/torque converter power, automatic lubrication and electro-pneumatic controls. Four independent power units provide 14 00 horse-power per crawler and over two million pounds of drawbar pull at converter stall. Weighing 300 tons, the pin-connected crawler dissembles for highway transport into loads of under 95,000 pounds.
Crane, Tom, Stemp, Randy
Application of the Vortex-Lattice Method to High-Angle-of-Attack Subsonic Aerodynamics85181710/01/1985
The vortex-lattice method for general, unsteady, incompressible aerodynamics is described. This method can treat multiple lifting surfaces operating in close proximity, fully accounting for interference. It is not limited by planform, camber, twist, or maneuver as long as separation occurs only along known lines and vortex bursting does not occur near one of the lifting surfaces. Steady flows can be treated efficiently as special cases of uniform motion. Several examples are presented as a partial illustration of the range of problems that can be treated. These include steady and unsteady flows over rectangular and delta wings, a numerical simulation of the wingrock phenomenon, and steady and unsteady interference among two canards and a wing. In the numerical simulation of wingrock, the equation governing the motion of a delta wing mounted on a free-to-roll sting is integrated numerically by a predictor-corrector method with the aerodynamic roll moment being supplied by the vortex
Mook, Dean T., Nayfeh, Ali H.
A Parametric Evaluation of Supersonic STOVL85117006/01/1985
This paper describes the results of a study to evaluate parametric variations to a single engine short-takeoff vertical-landing fighter/attack aircraft design. The variables considered involved thrust vectoring, thrust degradation, maximum lift, and other changes to determine the impact on short-takeoff performance, but subject to a vertical-landing capability. The results indicate that there are certain parameters that have a significant effect on short-field performance. Also, the optimal control strategies for transitions from a short-takeoff to forward flight and from forward flight to hover are determined. The results have applicability beyond the configuration evaluated.
Kidwell, George H., Rapp, David C.
Control System Techniques for Improved Departure/Spin Resistance for Fighter Aircraft79108302/01/1979
The paper summarizes some fundamental information on control system effects on controllability of highly-maneuverable aircraft at high angles of attack and techniques for enhancing fighter aircraft departure/spin resistance using control system design. The discussion includes: (a) a brief review of pertinent high angle-of-attack phenomena including aerodynamics, inertia coupling, and kinematic coupling; (b) effects of conventional stability augmentation systems at high-α; (c) high-α control system concepts designed to enhance departure/spin resistance; and (d) the outlook for applications of these concepts to future fighters, particularly those designs which incorporate relaxed static stability.
Nguyen, Luat T.
Engine Selection Problems for Jet Powered Ultra STOL70026602/01/1970
This paper discusses the effect of engine size and cycle on two types of Ultra STOL aircraft. One type, a powered lift plus deflected cruise thrust vehicle, is analyzed to determine the effect of wing loading, cruise engine, lift engine thrust loading, number of lift engines, cruise engine bypass ratio, and turbine inlet temperature on airplane gross weight and cost at a 1000-ft field length. The other type, a conventional nondeflected thrust airplane, is analyzed to determine the effect of wing loading, thrust loading, engine bypass ratio, and turbine inlet temperature on airplane gross weight and cost at field lengths from 1000-2000 ft. Results of this analysis indicate that powered lift aircraft are not cost competitive unless field lengths of less than 1000 ft are considered.
Axelson, D. H., Upton, G. G.
Devices for Stick Free Stability68020204/03/1968
Longitudinal stability design requirements usually call for a pull force on the control wheel of increasing magnitude as the speed is reduced from trim to a speed slightly above the stall speed. Whether or not an airplane can meet this requirement depends upon its stick-free stability and the characteristics of the elevator hinge. Control force stability can be produced even though control position stability does not exist. The most powerful method for improving control force stability is by means of the double bungee in conjunction with an adjustable stabilizer or adjustable trimming tab. The simplest device consists of the single downspring. This paper discusses the uses and limitations of various types of devices in producing control free stability. The present generation of light aircraft is subject to nonlinear hinge moment and pitching moment variations at high power and low air speed. The author demonstrates a typical unstable wheel force regime, and shows by analysis a simple
Wible, Richard
Aircraft Integrated Data Systems as a Flight Operations Tool68067102/01/1968
A new use of an aircraft integrated system has been developed, which provides a method of improving flying safety and operating efficiency. Data recorded in flight are processed on a ground-based digital computer, and instances of operation outside established operational envelopes are identified. Positive information is available to guide corrective action directed toward improving training programs, operating procedures, or performance by individual crewmen.
Seawell, William T.
A New Variable Speed Permanent Magnet D-C Motor66036502/01/1966
This paper discusses a new high efficiency variable speed permanent magnet (PM) d-c electric motor designed for initial use in windshield wiper assemblies on 1967 passenger cars. It traces the development from the basic two-speed, three-brush PM motor to the more sophisticated variable speed unit. Laboratory test data are used to compare performance of a variable speed wire-wound design and a two-speed PM motor with the new variable speed PM unit. Evolution of the needed circuitry is discussed and illustrated. The importance of using a diode in the circuit is stressed as the key to success in the high efficiency variable speed PM development.
Purdy, James A., Diello, William, Perry, Donald S.
Dynamic Measurements of Forward Gas Expulsion during High Speed Stall of Jet Engines65084002/01/1965
Dynamic measurements taken in a length of pipe mounted in front of a full-scale engine which was intentionally stalled at high corrected speed clearly demonstrate that gases hot enough to stall adjacent engines are expelled forward for a considerable distance. As a consequence, the isolation length of the inlet duct and the provision of adequate stall margin is required to assure compatible inlet flow conditions in clustered engine installations.
Alford, J. S., Victor, I. W.
Control and Flight Characteristics of Commercial Supersonic Transport Aircraft64002001/01/1964
The paper outlines some considerations for design engineers concerning the handling qualities of commercial supersonic transport aircraft, as well as a review of some more important stability requirements. It concludes with a recommended test for obtaining the flight handling qualities required for airline operation, which will assure the meeting of the economic demands of the business.
Flower, Scott
Centerline Thrust for Twin Engine Aircraft64043801/01/1964
This paper compares the controllability and performance of the conventional twin and centerline thrust (CLT) twin after an engine failure during take-off. The CLT concept offers, for the first time, controllability down to stall speed with one engine inoperative. In addition, it reduces by 50% the total engine out take-off distance over a 50 ft obstacle. These advantages are significant to all users of twin engine airplanes, and they are almost essential for the safety of pilots flying relatively low powered twins out of short fields.
Thompson, W. D.
All Mechanical Primary Flight Control System for VTOL/STOL Aircraft62048101/01/1962
This paper describes the development of a mechanism for the conversion of a human pilot's control stick or pedal displacement commands into differentiated output power commands or any desired sum or combination of the displacement command and successive differentiations. By this means the pilot's task of controlling a VTOL airplane during the VTOL phases of flight is reduced to where ordinary piloting technique is adequate.
Morris, William B.
The Supersonic Transport: Pilot Views on Operational Goals, Handling Characteristics, and Related Subjects61034001/01/1961
Moss, W. W., Gannett, J. R., Patten, P. H.
JET POWERPLANT REQUIREMENTS FOR VTOL59023601/01/1959
HEWSON, C. T.
CONTROL APPROACHES TO SOLUTION OF COMPRESSOR STALL56028601/01/1956
The control of compressor stall and surge is one of the most difficult problems confronting the control engineer today. Three modes of stall control are presented: (1) the scheduling, or open loop, control now in use on most gas turbine engines, (2) the closed loop control using compressor parameters which synthesize the stall boundary, and (3) the closed loop control using an incipient stall ‘sensor’. The use of a closed loop control which uses synthesizing stall parameters may partially solve some of the present problems, such as variations in physical properties of fuel. However, there is a great incentive to develop a means for detecting incipient stall and surge in order to aid in reducing the development time for future supersonic, high altitude gas turbine engines.
GEBHARDT, W. A., BODEMULLER, R.
ARE WE GAINING ON THE COMPRESSOR STALL PROBLEM?55018401/01/1955
GARDNER, ALFRED J.
Hydra-Matic Transmission52021501/01/1952
IN this paper, the author tells briefly of the history of the Hydra-matic, of some of the features that have made for its success, and of the improvements that have just appeared or are about to appear in the transmission. The latter include a new type of reverse and a new variable-capacity vane type of pump.
Herndon, Walter B.
Safety In Performance Operating Rules50011701/01/1950
MALOY, R. B.
LONGITUDINAL CONTROL SYSTEM FOR HIGH-SPEED AIRCRAFT48018101/01/1948
A SET of feeler elevators or “feelevators” added to regular spring-tab elevators can lessen the effect of airspeed on the ratio of stick force to airplane normal acceleration. The author develops an equation for computing the stick force per g of normal acceleration with a spring-tab and feelevator arrangement, and applies the equation to a large, high-speed fighter. Plotted results show that, with the feelevator, the stick force required at high speeds to move the elevator is great enough so that the pilot will not accidentally set the elevators for dangerously large accelerations. Yet at low speeds, a reasonably small stick force is enough to control the elevators.
WENDT, HAROLD O.
General discussion of factors relative to selected stall speed regulations for transport airplanes45007601/01/1945
Vanik, M. F.
SPECULATIONS on AIRWORTHINESS and OPERATING REGULATIONS44014701/01/1944
THE wartime interruption in the building of civil aircraft is a good period for making a skeptical re-examination of regulations as they now exist, to decide what shape future regulations should take. Now is the time for proposing changes, especially fundamental ones, if they are found desirable. The past 20 years have seen a general trend away from arbitrary methods of airworthiness regulations to more rational ones. This trend will continue, Mr. Warner believes, dealing in the next few years with the establishment of rational relationships between design requirements and operating conditions. It will concern the length to which we should go in replacing rigid requirements by flexible ones, leaving an opportunity of fitting the characteristics of the equipment to the particular purpose for which it is to be used. Mr. Warner considers the question of whether design and operating requirements should be so interwoven that no aircraft can ever be used in an unsafe fashion without
WARNER, EDWARD
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