DOCSLIB.ORG

NCAR-TN/EDD-74 the Measurement of Air Velocity and Temperature

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
NCAR-TN/EDD-74 the Measurement of Air Velocity and Temperature NCAR-TN/EDD-74 /-o /2 The Measurement of Air Velocity and Temperature Using the NCAR Buffalo Aircraft Measuring Systemi , -L/ D. H. LENSCHOW , /' June 1972 NATIONAL CENTER FOR ATMOSPHERIC RESEARCH /4ol /AJ Boulder, Colorado iii PREFACE Several years ago it was recognized that the development of iner- tial navigation systems for aircraft would make possible more accurate measurements of air velocity than were previously possible. Combining this improvement in measurement capability with the mobility of air- craft results in a very powerful tool for investigating a variety of atmospheric problems--from measurements of eddy fluxes of heat, mois- ture, and momentum within a few tens of meters of the earth's surface to measurements of lee wave structure several kilometers above the surface. The development of the measuring system on NCAR's Buffalo aircraft is a joint effort of NCAR and the Desert Research Institute (DRI), Reno, Nevada. At NCAR, both the Research Aviation Facility and the Laboratory of Atmospheric Science have contributed to its development. DRI's par- ticipation is under the direction of J. Telford. This report does not discuss measurements from all the sensors on the aircraft. Other sensors include a microwave refractometer (from which humidity fluctuations can be obtained), a dew-point hygrometer, an electrochemical ozone sensor, and a variometer (rate-of-climb sensor). Furthermore, the measurements and methods of measurements discussed here are not to be considered complete or absolute. Not only do the sensors change as new and better ways of measuring become available, but in- flight comparisons with other aircraft and with ground-based sensors and wind tunnel and laboratory tests will continue to shed new light on pres- ent methods for making airborne measurements. v CONTENTS Preface ................... ........... iii List of Figures .......................... vii 1. INTRODUCTION .................... 1 2. BASIC VELOCITY EQUATIONS ................... 4 3. USE OF THE INERTIAL PLATFORM ................. 9 4. AIR SENSING ................. 22 5. CONCLUSION ............. ........ 32 Appendix ............................ 35 References ................ 38 vii FIGURES 1. Flow measurement sensors mounted on the nose boom of the NCAR de Havilland Buffalo aircraft ............ 2 2. Spectra of vertical and lateral acceleration of the air sensing probe mounted on the end of the Buffalo nose boom . .................. ...... 3 3. Coordinate systems used in deriving the equations for calculating the air velocity components ........... 6 4. Airplane attitude angles and axes used in equations for calculating the air velocity components ......... 8 5. Block diagram of an inertial navigation system ..... 9 6. Velocity errors in an inertial navigation system ....... 14 7. Position errors in an inertial navigation system ... .... 15 8. Position and velocity errors after four flights, each of about 6-hr duration ............. .... 17 9. Block diagram of an inertial barometric vertical velocity and altitude measuring system ............ 18 10. Spectra of pressure altitude and inertial altitude and the coherence of these variables with 34 degrees of freedom . .. 20 11. Response of the Rosemount thermometer to a step-function change in temperature .................... 31 12. Comparison of the output of an unprotected resistance-wire thermometer with the Rosemount thermometer .......... 31 1 1. INTRODUCTION This report describes methods used to measure air velocity and temperature from an aircraft and their application to the measuring system on the NCAR Buffalo aircraft. The main components of this system are: * An inertial navigation system (Litton Industries, Inc., Model LN-15D) that provides measurements of airplane acceleration, velocity, position, and angles of attitude. The stabilized platform of the iner- tial navigation system is located inside the Buffalo's laminated fiber glass nose boom. * An air sensing probe (shown in Fig. 1) that provides measure- ments of angles of attack and sideslip, pitot-static pressure, and tem- perature. The probe is mounted 5 m forward of the airplane nose on a hollow steel tube. The steel tube is supported by the fiber glass nose boom, and the tube's after end is rigidly attached to the outer case of the inertial navigation system platform. Shock and vibration isolators, mounted between the steel tube and the outer fiber glass boom, insulate the platform and probe from aircraft vibrations. The spectra of verti- cal and lateral probe acceleration during a flight (Fig. 2) indicate that the natural vibration frequency of the probe is about 8 Hz, with harmonics at 16 and 24 Hz. Recently, the outer boom has been stiffened, but the effect of this modification on the probe's vibration spectra has not yet been determined. * A second pitot-static tube that provides measurements of both static pressure and pitot-static pressure. This pitot tube, which is free to align itself parallel to the airstream, is mounted 2 m forward of one of the wing tips. In the following sections the equations used to calculate the air velocity components from the inertial system and air sensing probe mea- surements are derived, use and limitations of the inertial navigation platform are discussed, methods used to calculate true airspeed and static temperature are presented, and errors in measurement and their effect on the calculated atmospheric variables are discussed. Fig. 1 Flow measurement sensors mounted on the nose boom of the NCAR de Havilland Buffalo aircraft. 3 10-' -)N II I 0I(1) '4. '~ II 5 I II I10 - - II LJ 4 Fig. 210------ Spectra0.1 of vertical and Ilateral accelerationI-I10 of the air sensing100 probeO.I moun Late endI of the Buffalo nose10 boom. 100 FREQUENCY (Hz) Fig. 2 Spectra of vertical and lateral acceleration of the air sensing probe mounted on the end of the Buffalo nose boom. 4 2. BASIC VELOCITY EQUATIONS The derivation of the air velocity equations closely follows Axford (1968). However, several changes were made in terminology and coordi- nate systems to conform to standard aeronautical engineering usage (Etkin, 1959) for the aircraft coordinate system and to standard iner- tial navigation (Kayton and Fried, 1969) and meteorological usage for the air velocity in the local earth coordinate system. The velocity of the air with respect to the earth, v = iu + jv + kw, is obtained by adding the velocity of the aircraft with respect to the earth, vp, and the velocity of the air with respect to the aircraft, v If all the measurements are made at the same point, we have v = v + v (2-1) p a The components of v are measured with sensors mounted on the aircraft, a usually on a boom forward of the aircraft to reduce as much as possible the measurable effects of the distortion of the airflow by the aircraft. The components of v are obtained from integrated accelerometer outputs p on an inertial navigation system or from a radiation transmitting and sensing device such as a doppler radar or radar altimeter. If the aircraft velocity is obtained from integrated accelerometer measurements, the velocity is measured in an inertial frame of reference. If we convert to an earth-based coordinate system, we obtain dv - a - (- + W ) x v + g (2-2) dt p e p -e -a- - - where a is the measured acceleration, t and t are the angular veloci- e p ties of the earth and platform, respectively, and g is the gravitational acceleration (which includes the centripetal acceleration). Since the accelerometers may not be located near the air velocity sensors, the 5 * + -0 term Q x R, where Q is the angular acceleration of the aircraft, and + P + + P R = iX + jY + kZ is the distance from the accelerometers to the air ve- locity sensors, must be added to Eq. (2-2). Thus, Eq. (2-1) can be com- bined with the integral of Eq. (2-2) and rewritten as v = v +[a - (u+ + x v + dt + x R = v + v + x R (2-3) a ep p p a p p In the general case, the measured components of v and v may not be in the local earth coordinate system. The air sensors, for example, are usually rigidly connected to the aircraft fuselage, or in the case of the Buffalo, rigidly connected to the inertial navigation system. Therefore, it is necessary to know the angles between the coordinates of the measuring systems and the local earth coordinates. The measured ve- locity components can then be rotated by means of the appropriate angu- lar transformation to the local earth coordinate system. The inertial system on the Buffalo is stabilized along the local earth axes so the rotation angles of the platform gimbals are equivalent to the aircraft attitude angles. From the inside platform gimbal outward, i.e., from the stabilized accelerometer and gyro cluster outward to the aircraft frame, the order of the rotations is as follows: first, a rotation l about the z-axis of the earth coordinate system; second, a rotation 6 about the y"-axis, which is the y-axis rotated in the horizontal plane by the angle i; and third, a rotation ( about the x'-axis, which is the x-axis in the aircraft coordinate system. The aircraft axes are shown in Fig. 3; a right-handed angular rotation is positive. The symbols and axes have been defined to correspond to standard aerodynamic conventions (Etkin, 1959). 6 / x / -/' Xi "' (a) x\( East (a) Aircraft Axes (b) Intermediate Local Earth Axes V.^y^^^/>~~~~/\^~ ~(c) Inertial Platform (Meteorological) Axes Fig. 3 Coordinate systems used in deriving the equations for calculat- ing the air velocity components. In matrix notation, the transformation of the air velocity from aircraft (x',y',z') to platform (x,y,z) coordinates [same as (b) coordi- nates in Fig. 3] is given by [uil [T i [u ] (2-4) where cosi -sin 0 cos9 0 sine 1 0 0 T . = sini cosi 0 -(2-5)0 1 0 0cos -sin) 0 0 1 -sine 0 cos9 0 sin) cos) cosicose -sinicos4 + cosJsinesin4 sinisin) + cosisinOcos4 sinpcose cosicos) + sinsinessinj sinisinecosI - cosisinJ (2-6) -sine cosesin4 coseco s The terms of Q x R must also be transformed to the local earth P coordinate system.
Load more

Recommended publications
  • CESSNA WING TIPS - EMPENNAGE TIPS CESSNA WING TIPS These Wing Tip Kits Consist of a Left and Right Hand Drooped Fiberglass Wing Tip
    CESSNA WING TIPS - EMPENNAGE TIPS CESSNA WING TIPS These wing tip kits consist of a left and right hand drooped fiberglass wing tip. These wing tips are better than those manufactured by Cessna because they are made of fiberglass rather than a royalite type material, that bends and CM cracks after a short time on the aircraft. The superior epoxy rather than polyester fiberglass is used. Epoxy fiberglass has major advantages over a royalite type material; It is approximately six timesstronger and twelve times stiffer, it resists ultraviolet light and weathers better, and it keeps its chemical composition intact much longer. With all these advantages, they will probably be the last wingtips that will ever have to be installed on the aircraft. Should these wing tips be damaged through some unforeseen circumstances, they are easily repairable due to their fiberglass construc- tion. These kits are FAA STC’d and manufactured under a FAA PMA authority. The STC allows you to install these WP modern drooped wing tips, even if your aircraft was not originally manufactured with this newer, more aerodynamically efficient wingtip. *Does not include the Plate lens. Plate lens must be purchased separately. **Kits includes the left hand wing tip, right hand wing tip, hardware, and the plate lens Cessna Models Kit No.** Price Per Kit All 150, A150, 152, A152, 170A & B, P172, 175, 205 &L19, 172, 180, 185 for model year up through 1972.182, 206 for 05-01526 . model year up through 1971, 207 from 1970 and up (219-100) ME 05-01545 172, R172K(172XP), 172RG, 180, 185 for model year 1973 and up, 182, 206 for model year 1972 and up.
    [Show full text]
  • Aircraft Winglet Design
    DEGREE PROJECT IN VEHICLE ENGINEERING, SECOND CYCLE, 15 CREDITS STOCKHOLM, SWEDEN 2020 Aircraft Winglet Design Increasing the aerodynamic efficiency of a wing HANLIN GONGZHANG ERIC AXTELIUS KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES 1 Abstract Aerodynamic drag can be decreased with respect to a wing’s geometry, and wingtip devices, so called winglets, play a vital role in wing design. The focus has been laid on studying the lift and drag forces generated by merging various winglet designs with a constrained aircraft wing. By using computational fluid dynamic (CFD) simulations alongside wind tunnel testing of scaled down 3D-printed models, one can evaluate such forces and determine each respective winglet’s contribution to the total lift and drag forces of the wing. At last, the efficiency of the wing was furtherly determined by evaluating its lift-to-drag ratios with the obtained lift and drag forces. The result from this study showed that the overall efficiency of the wing varied depending on the winglet design, with some designs noticeable more efficient than others according to the CFD-simulations. The shark fin-alike winglet was overall the most efficient design, followed shortly by the famous blended design found in many mid-sized airliners. The worst performing designs were surprisingly the fenced and spiroid designs, which had efficiencies on par with the wing without winglet. 2 Content Abstract 2 Introduction 4 Background 4 1.2 Purpose and structure of the thesis 4 1.3 Literature review 4 Method 9 2.1 Modelling
    [Show full text]
  • Module-7 Lecture-29 Flight Experiment
    Module-7 Lecture-29 Flight Experiment: Instruments used in flight experiment, pre and post flight measurement of aircraft c.g. Module Agenda • Instruments used in flight experiments. • Pre and post flight measurement of center of gravity. • Experimental procedure for the following experiments. (a) Cruise Performance: Estimation of profile Drag coefficient (CDo ) and Os- walds efficiency (e) of an aircraft from experimental data obtained during steady and level flight. (b) Climb Performance: Estimation of Rate of Climb RC and Absolute and Service Ceiling from experimental data obtained during steady climb flight (c) Estimation of stick free and fixed neutral and maneuvering point using flight data. (d) Static lateral-directional stability tests. (e) Phugoid demonstration (f) Dutch roll demonstration 1 Instruments used for experiments1 1. Airspeed Indicator: The airspeed indicator shows the aircraft's speed (usually in knots ) relative to the surrounding air. It works by measuring the ram-air pressure in the aircraft's Pitot tube. The indicated airspeed must be corrected for air density (which varies with altitude, temperature and humidity) in order to obtain the true airspeed, and for wind conditions in order to obtain the speed over the ground. 2. Attitude Indicator: The attitude indicator (also known as an artificial horizon) shows the aircraft's relation to the horizon. From this the pilot can tell whether the wings are level and if the aircraft nose is pointing above or below the horizon. This is a primary instrument for instrument flight and is also useful in conditions of poor visibility. Pilots are trained to use other instruments in combination should this instrument or its power fail.
    [Show full text]
  • How to Make My Air Glide S Work Properly
    How to make my Air Glide S work properly Originally written by Horst Rupp. Many thanks to Richard Frawley who edited and retranslated this article into proper English. 2014/11/21. The basic prerequisite for the Air Glide S, in particular the AHRS part, to work properly so that the extraneous ‘noise’ (gusts, wind shifts, perturbations etc) can be removed is to ensure that it is set up correctly. The instrument is very sensitive and the installation needs to be done in a way that ensures that only the correct inputs are being sensed. Most legacy instrument installations take all pressures from probes at the rudder fin. And most unfortunately, many of them use the total energy (TE) pressure from the fin to feed in parallel a mass-measurement variometer with a capacity flask (in Germany mostly a Winter) and a pressure sensor probe variometer such as the Air Glide S (no capacity flask). There are many publications indicating the deterioration (mostly damping) of the pressure sensor probe measurements by the stream of air mass in and out of the capacity flask. So, it is obviously a somewhat bad idea to do that to your Air Glide S. This interference with a mass measuring instruments is certainly not compliant with the above mentioned basic prerequisite. Fortunately, the Air Glide S can be compensated by total pressure (called electronic compensation as opposed to TE compensation). This is a new feature of the Air Glide S arriving with V 1.1. Total pressure and TE pressure carry more or less (depends on quality of probe) the same information - but for the sign : Total pressure is static pressure PLUS pitot pressure, TE pressure is static pressure MINUS pitot pressure (probe compensation factor (~)-1).
    [Show full text]
  • Richard Lancaster [email protected]
    Glider Instruments Richard Lancaster [email protected] ASK-21 glider outlines Copyright 1983 Alexander Schleicher GmbH & Co. All other content Copyright 2008 Richard Lancaster. The latest version of this document can be downloaded from: www.carrotworks.com [ Atmospheric pressure and altitude ] Atmospheric pressure is caused ➊ by the weight of the column of air above a given location. Space At sea level the overlying column of air exerts a force equivalent to 10 tonnes per square metre. ➋ The higher the altitude, the shorter the overlying column of air and 30,000ft hence the lower the weight of that 300mb column. Therefore: ➌ 18,000ft “Atmospheric pressure 505mb decreases with altitude.” 0ft At 18,000ft atmospheric pressure 1013mb is approximately half that at sea level. [ The altimeter ] [ Altimeter anatomy ] Linkages and gearing: Connect the aneroid capsule 0 to the display needle(s). Aneroid capsule: 9 1 A sealed copper and beryllium alloy capsule from which the air has 2 been removed. The capsule is springy Static pressure inlet and designed to compress as the 3 pressure around it increases and expand as it decreases. 6 4 5 Display needle(s) Enclosure: Airtight except for the static pressure inlet. Has a glass front through which display needle(s) can be viewed. [ Altimeter operation ] The altimeter's static 0 [ Sea level ] ➊ pressure inlet must be 9 1 Atmospheric pressure: exposed to air that is at local 1013mb atmospheric pressure. 2 Static pressure inlet The pressure of the air inside 3 ➋ the altimeter's casing will therefore equalise to local 6 4 atmospheric pressure via the 5 static pressure inlet.
    [Show full text]
  • [email protected] C/ Fruela, 6 Fax: +34 91 463 55 35 28011 Madrid (España) Notice
    CICIAIAIACAC COMISIÓN DE INVESTIGACIÓN DE ACCIDENTES E INCIDENTES DE AVIACIÓN CIVIL Report IN-015/2019 Incident involving a BOEING B-737-524, registration LY-KLJ, at the Getafe Air Base (Madrid) on 5 April 2019 GOBIERNO MINISTERIO DE ESPAÑA DE TRANSPORTES, MOVILIDAD Y AGENDA URBANA Edita: Centro de Publicaciones Secretaría General Técnica Ministerio de Transportes, Movilidad y Agenda Urbana © NIPO: 796-20-128-4 Diseño, maquetación e impresión: Centro de Publicaciones COMISIÓN DE INVESTIGACIÓN DE ACCIDENTES E INCIDENTES DE AVIACIÓN CIVIL Tel.: +34 91 597 89 63 E-mail: [email protected] C/ Fruela, 6 Fax: +34 91 463 55 35 http://www.ciaiac.es 28011 Madrid (España) Notice This report is a technical document that reflects the point of view of the Civil Aviation Accident and Incident Investigation Commission (CIAIAC) regarding the circumstances of the accident object of the investigation, and its probable causes and consequences. In accordance with the provisions in Article 5.4.1 of Annex 13 of the International Civil Aviation Convention; and with articles 5.5 of Regulation (UE) nº 996/2010, of the European Parliament and the Council, of 20 October 2010; Article 15 of Law 21/2003 on Air Safety and articles 1., 4. and 21.2 of Regulation 389/1998, this investigation is exclusively of a technical nature, and its objective is the prevention of future civil aviation accidents and incidents by issuing, if necessary, safety recommendations to prevent from their reoccurrence. The investigation is not pointed to establish blame or liability whatsoever, and it’s not prejudging the possible decision taken by the judicial authorities.
    [Show full text]
  • Study of the Pilot's Attention in the Cabin During the Flight Auxiliary Devices Such As Variometer, Turn Indicator with Crosswise Or Other
    Journal of KONES Powertrain and Transport, Vol. 25, No. 3 2018 ISSN: 1231-4005 e-ISSN: 2354-0133 DOI: 10.5604/01.3001.0012.4309 STUDY OF THE PILOT’S ATTENTION IN THE CABIN DURING THE FLIGHT Mirosław Adamski, Mariusz Adamski, Ariel Adamski Polish Air Force Academy, Department of Aviation Dywizjonu 303 Street 35, 08-521 Deblin, Poland tel.: +48 261 517423, fax: +48 261 517421 e-mail: [email protected] [email protected], [email protected] Andrzej Szelmanowski Air Force Institute of Technology Ksiecia Boleslawa Street 6, 01-494 Warsaw, Poland tel.: +48 261 851603, fax: +48 261 851646 e-mail: [email protected] Abstract The pilot, while performing certain tasks or being in the battlefield environment works in a time lag. He is forced to properly interpret the information and quickly and correctly take action. Therefore, the instruments in the cabin should be arranged in such a way that they are legible and the operator have always-easy access to them. Due to the dynamics of the aircraft and the time needed to process the information by the pilot, a reaction delay occurs, resulting in the plane flying in an uncontrolled manner even up to several hundred meters. This article discusses the VFR and IFR flight characteristics, the pilot’s attention during flight, cabin ergonomics, and the placement of on-board instruments having a significant impact on the safety of the task performed in the air. In addition, tests have been carried out to determine exactly what the pilot’s eye is aimed at while completing the aerial task.
    [Show full text]
  • Wing Tip.Qxd
    WINGTIP COUPLING AT 15,000 FEET Dangerous Experiments by C.E. “Bud” Anderson ingtip coupling evolved from an invention by Dr. Richard Vogt, a German scientist who emigrated to W the U.S. after WW II. The basic con- cept involved increasing an aircraft’s range by attaching two “free-floating,” fuel-carrying aerodynamic panels to the wingtips. This could be accomplished without undue struc- tural weight penalties as long as the panels were free to articulate and support themselves with their own aerodynamic lift. The panels would increase the basic wing configuration’s aspect ratio and would therefore significantly reduce induced drag; the “free” extra fuel car- ried by this more efficient wing would consid- erably increase an aircraft’s range. Soon, other logical uses of this unusual concept became apparent: for example, two escort fighters might be carried along “free” on a large bomber without sacrificing its range. To be feasible, the wingtip extensions, But there was also the problem of how such fuel-carrying extensions could be handled on the ground. How would they be supported without airflow to or panels, whatever they were, would have to hold them up?—perhaps by the use of a retractable outrigger landing gear, but what about runway width requirements? And—the big question—what about be kept properly aligned, preferably by a sim- the stability and control problems that might be induced by such a configura- ple and automatic flight-control system. tion; would the extensions be easy to control? Many questions are also immedi- 64 FLIGHT JOURNAL The second wingtip-coupling experiment involved an ETB-29A and two EF-84Bs (photo courtesy of Peter M.
    [Show full text]
  • Fast 49 Airbus Technical Magazine Worthiness Fast 49 January 2012 4049July 2007
    JANUARY 2012 FLIGHT AIRWORTHINESS SUPPORT 49 TECHNOLOGY FAST AIRBUS TECHNICAL MAGAZINE FAST 49 FAST JANUARY 2012 4049JULY 2007 FLIGHT AIRWORTHINESS SUPPORT TECHNOLOGY Customer Services Events Spare part commonality Ensuring A320neo series commonality 2 with the existing A320 Family AIRBUS TECHNICAL MAGAZINE Andrew James MASON Publisher: Bruno PIQUET Graham JACKSON Editor: Lucas BLUMENFELD Page layout: Quat’coul Biomimicry Cover: Radio Altimeters When aircraft designers learn from nature 8 Picture from Hervé GOUSSE ExM Company Denis DARRACQ Authorization for reprint of FAST Magazine articles should be requested from the editor at the FAST Magazine e-mail address given below Radio Altimeter systems Customer Services Communications 15 Tel: +33 (0)5 61 93 43 88 Correct maintenance practices Fax: +33 (0)5 61 93 47 73 Sandra PREVOT e-mail: [email protected] Printer: Amadio Ian GOODWIN FAST Magazine may be read on Internet http://www.airbus.com/support/publications ELISE Consulting Services under ‘Quick references’ ILS advanced simulation technology 23 ISSN 1293-5476 Laurent EVAIN © AIRBUS S.A.S. 2012. AN EADS COMPANY Jean-Paul GENOTTIN All rights reserved. Proprietary document Bruno GUTIERRES By taking delivery of this Magazine (hereafter “Magazine”), you accept on behalf of your company to comply with the following. No other property rights are granted by the delivery of this Magazine than the right to read it, for the sole purpose of information. The ‘Clean Sky’ initiative This Magazine, its content, illustrations and photos shall not be modified nor Setting the tone 30 reproduced without prior written consent of Airbus S.A.S. This Magazine and the materials it contains shall not, in whole or in part, be sold, rented, or licensed to any Axel KREIN third party subject to payment or not.
    [Show full text]
  • TOTAL ENERGY COMPENSATION in PRACTICE by Rudolph Brozel ILEC Gmbh Bayreuth, Germany, September 1985 Edited by Thomas Knauff, & Dave Nadler April, 2002
    TOTAL ENERGY COMPENSATION IN PRACTICE by Rudolph Brozel ILEC GmbH Bayreuth, Germany, September 1985 Edited by Thomas Knauff, & Dave Nadler April, 2002 This article is copyright protected © ILEC GmbH, all rights reserved. Reproduction with the approval of ILEC GmbH only. FORWARD Rudolf Brozel and Juergen Schindler founded ILEC in 1981. Rudolf Brozel was the original designer of ILEC variometer systems and total energy probes. Sadly, Rudolph Brozel passed away in 1998. ILEC instruments and probes are the result of extensive testing over many years. More than 6,000 pilots around the world now use ILEC total energy probes. ILEC variometers are the variometer of choice of many pilots, for both competition and club use. Current ILEC variometers include the SC7 basic variometer, the SB9 backup variometer, and the SN10 flight computer. INTRODUCTION The following article is a summary of conclusions drawn from theoretical work over several years, including wind tunnel experiments and in-flight measurements. This research helps to explain the differences between the real response of a total energy variometer and what a soaring pilot would prefer, or the ideal behaviour. This article will help glider pilots better understand the response of the variometer, and also aid in improving an existing system. You will understand the semi-technical information better after you read the following article the second or third time. THE INFLUENCE OF ACCELERATION ON THE SINK RATE OF A SAILPLANE AND ON THE INDICATION OF THE VARIOMETER. Astute pilots may have noticed when they perform a normal pull-up manoeuvre, as they might to enter a thermal; the TE (total energy) variometer first indicates a down reading, whereas the non-compensated variometer would rapidly go to the positive stop.
    [Show full text]
  • Commercial Aircraft Performance Improvement Using Winglets
    Nikola N. Gavrilović Commercial Aircraft Performance Graduate Research Assistant Improvement Using Winglets University of Belgrade Faculty of Mechanical Engineering Aerodynamic drag force breakdown of a typical transport aircraft shows Boško P. Rašuo that lift-induced drag can amount to as much as 40% of total drag at Full Professor cruise conditions and 80-90% of the total drag in take-off configuration. University of Belgrade Faculty of Mechanical Engineering One way of reducing lift-induced drag is by using wing-tip devices. By applying several types of winglets, which are already used on commercial George S. Dulikravich airplanes, we study their influence on aircraft performance. Numerical Full Professor investigation of five configurations of winglets is described and Florida International University preliminary indications of their aerodynamic performance are provided. Department of Mechanical and Materials Engineering, Miami, Florida, USA Moreover, using advanced multi-objective design optimization software an optimal one-parameter winglet configuration was detrmined that Vladimir Parezanović simultaneously minimizes drag and maximizes lift. Researcher Institute PPRIME, CNRS UPR3346 Poitiers, France Keywords: Winglet, Bionics, Computational fluid dynamics, Drag reduction, Lift-induced drag, Optimization 1. INTRODUCTION of soaring birds and their use of tip feathers to control flight, continued on the quest to reduce induced drag The main motivation for using wingtip devices is and improve aircraft performance and further develop reduction of lift-induced drag force. Environmental the concept of winglets in the late 1970s [4]. This issues and rising operational costs have forced industry research provided a fundamental knowledge and design to improve efficiency of commercial air transport and approach required for extremely attractive option to this has led to some innovative developments for improve aerodynamic efficiency of civilian aircraft, reducing lift-induced drag.
    [Show full text]
  • Chapter 12 Design of Control Surfaces
    Aileron Design Chapter 12 Design of Control Surfaces From: Aircraft Design: A Systems Engineering Approach Mohammad Sadraey 792 pages September 2012, Hardcover Wiley Publications 12.4.1. Introduction The primary function of an aileron is the lateral (i.e. roll) control of an aircraft; however, it also affects the directional control. Due to this reason, the aileron and the rudder are usually designed concurrently. Lateral control is governed primarily through a roll rate (P). Aileron is structurally part of the wing, and has two pieces; each located on the trailing edge of the outer portion of the wing left and right sections. Both ailerons are often used symmetrically, hence their geometries are identical. Aileron effectiveness is a measure of how good the deflected aileron is producing the desired rolling moment. The generated rolling moment is a function of aileron size, aileron deflection, and its distance from the aircraft fuselage centerline. Unlike rudder and elevator which are displacement control, the aileron is a rate control. Any change in the aileron geometry or deflection will change the roll rate; which subsequently varies constantly the roll angle. The deflection of any control surface including the aileron involves a hinge moment. The hinge moments are the aerodynamic moments that must be overcome to deflect the control surfaces. The hinge moment governs the magnitude of augmented pilot force required to move the corresponding actuator to deflect the control surface. To minimize the size and thus the cost of the actuation system, the ailerons should be designed so that the control forces are as low as possible.
    [Show full text]