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Wake Turbulence and Separation Standards
Tel: +267 3 6882 00 /3913236 Aeronautical Information Services Fax: +267 3913121 P O Box 250 AIC Email: [email protected] Gaborone AFS: FBHQYAYX BOTSWANA 06/11 01 MAR WAKE TURBULENCE AND SEPARATION STANDARDS INTRODUCTION The hazards associated with wake turbulance have long been demonstrated by a number of accidents and incidents. There is at the present time insufficient understanding of the correlation between turbulant wake theory and operational experience to state with an acceptable degree of certainty what weight classifications should be denoted and what separation should be applied between them. In the meantime ICAO has issued guidance material and this forms the basics of procedures being introduced in Botswana with immediate effect. CHARACTERISTICS Wake turbulence vortices are present behind every aircraft, but are particularly severe when generated by large and wide-bodied jet aircraft. These vortices are two counter- rotating cylindrical air masses trailing aft from the aircraft. The vortices are most dangerous to following aircraft during the take-off, initial climb, final approach and landing phases of flight. They tend to drift down, and when close to the ground move sideways from the track of the generating aircraft occasionally rebounding upwards. The characteristics of the wake vortex generated by an aircraft in flight are established initially by factors related to the aircraft gross weight, airspeed, configuration and wingspan. Subsequently, the vortices characteristics are altered and eventually dominated by interactions between the vortices and the ambient atmosphere. The wind,wind shear, turbulence and atmospheric stability affect the motion and decay of a vortex system. Vortex wake generation begins on rotation when the nose wheel lifts off the runway and ends when the nose wheel touches down on landing. -
National Transportation Safety Board Aviation Accident Final Report
National Transportation Safety Board Aviation Accident Final Report Location: IRVINE, CA Accident Number: LAX97FA059 Date & Time: 11/30/1996, 1307 PST Registration: N2TE Aircraft: Morane-Saulnier MS760 II Aircraft Damage: Destroyed Defining Event: Injuries: 3 Fatal Flight Conducted Under: Part 91: General Aviation - Personal Analysis Shortly after takeoff, the pilot radioed the air traffic control tower declaring an emergency and stating his intent to return for landing. He stated that he had taken off with an external boarding ladder attached to the aircraft. Several witnesses reported that the aircraft's downwind leg was too close to the airport causing the aircraft to overshoot the turn to the final approach course, and that the pilot increased the aircraft's bank angle as he tried to align the aircraft with the landing runway. As the aircraft was intercepting the final approach course, it abruptly rolled inverted, the nose dropped, and the aircraft spiraled onto the roof of an industrial building. A Boeing 757 aircraft, landing on the same runway, had passed over the accident site 2 minutes and 17 seconds earlier. The B-757 was cleared to land before the accident aircraft received a takeoff clearance and was on the runway when the pilot declared the emergency and turned downwind. The local controller did not issue a wake turbulence advisory. Experienced MS760 pilots reported that the aircraft will exhibit no adverse performance or safety affects with the boarding ladder attached. Probable Cause and Findings The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain an adequate airspeed margin while maneuvering in a steep banked turn to the landing runway, which resulted in an inadvertent stall/spin. -
Easy Access Rules for Standardised European Rules of the Air (SERA)
Easy Access Rules for Standardised European Rules of the Air (SERA) EASA eRules: aviation rules for the 21st century Rules and regulations are the core of the European Union civil aviation system. The aim of the EASA eRules project is to make them accessible in an efficient and reliable way to stakeholders. EASA eRules will be a comprehensive, single system for the drafting, sharing and storing of rules. It will be the single source for all aviation safety rules applicable to European airspace users. It will offer easy (online) access to all rules and regulations as well as new and innovative applications such as rulemaking process automation, stakeholder consultation, cross-referencing, and comparison with ICAO and third countries’ standards. To achieve these ambitious objectives, the EASA eRules project is structured in ten modules to cover all aviation rules and innovative functionalities. The EASA eRules system is developed and implemented in close cooperation with Member States and aviation industry to ensure that all its capabilities are relevant and effective. Published December 20201 1 The published date represents the date when the consolidated version of the document was generated. Powered by EASA eRules Page 2 of 213| Dec 2020 Easy Access Rules for Standardised European Rules Disclaimer of the Air (SERA) DISCLAIMER This version is issued by the European Aviation Safety Agency (EASA) in order to provide its stakeholders with an updated and easy-to-read publication. It has been prepared by putting together the officially published regulations with the related acceptable means of compliance and guidance material (including the amendments) adopted so far. -
Air Traffic Management for Tiltrotors Questions and Answers
ASS. NAZ. ASSISTENTI E CONTROLLORI DELLA NAVIGAZIONE AEREA ITALIAN AIR TRAFFIC CONTROLLERS’ ASSOCIATION MEMBER OF IFATCA INTERNATIONAL FEDERATION OF AIR TRAFFIC CONTROLLERS’ ASSOCIATIONS AIR TRAFFIC MANAGEMENT FOR TILTROTORS QUESTIONS AND ANSWERS Issue 2 Introduction The history of aviation has seen many technologies developed and matured by the military prior to their introduction into commercial service such as jet propulsion, fly-by-wire flight controls and composite primary structures. Today tiltrotor technology follows a similar path, having been successfully demonstrated by the military for over 10 years in the Bell Boeing V-22, the Leonardo Helicopters AW609 is on the verge of civil certification for commercial use. As the speed, range, and VTOL capability of the V-22 tiltrotor has revolutionized military missions like combat search and rescue, medical evacuation, and long-range ship to shore transportation, so too will the AW609 in commercial SAR, EMS, and offshore oil and gas transportation. The AW609’s use in civil operations will enable true point to point travel and help reduce congestion at busy airports. As the technology and operational regulations are on the horizon1, some questions, remarks or concerns may arise within the Air Traffic Management (ATM) community on how to integrate tiltrotor activities into usual aircraft management and on how to interact with tiltrotor flights. This joint document between Leonardo Helicopters and the Italian Air Traffic Controllers Association ANACNA aims to provide answers to these points. From a Gate-to-Gate perspective this Q&A sheet is divided into the different flight phases: 1. Departure 2. In flight 3. Arrival 4. -
Simulation of Turbulent Flows
Simulation of Turbulent Flows • From the Navier-Stokes to the RANS equations • Turbulence modeling • k-ε model(s) • Near-wall turbulence modeling • Examples and guidelines ME469B/3/GI 1 Navier-Stokes equations The Navier-Stokes equations (for an incompressible fluid) in an adimensional form contain one parameter: the Reynolds number: Re = ρ Vref Lref / µ it measures the relative importance of convection and diffusion mechanisms What happens when we increase the Reynolds number? ME469B/3/GI 2 Reynolds Number Effect 350K < Re Turbulent Separation Chaotic 200 < Re < 350K Laminar Separation/Turbulent Wake Periodic 40 < Re < 200 Laminar Separated Periodic 5 < Re < 40 Laminar Separated Steady Re < 5 Laminar Attached Steady Re Experimental ME469B/3/GI Observations 3 Laminar vs. Turbulent Flow Laminar Flow Turbulent Flow The flow is dominated by the The flow is dominated by the object shape and dimension object shape and dimension (large scale) (large scale) and by the motion and evolution of small eddies (small scales) Easy to compute Challenging to compute ME469B/3/GI 4 Why turbulent flows are challenging? Unsteady aperiodic motion Fluid properties exhibit random spatial variations (3D) Strong dependence from initial conditions Contain a wide range of scales (eddies) The implication is that the turbulent simulation MUST be always three-dimensional, time accurate with extremely fine grids ME469B/3/GI 5 Direct Numerical Simulation The objective is to solve the time-dependent NS equations resolving ALL the scale (eddies) for a sufficient time -
ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY
ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere. -
Hydraulics Manual Glossary G - 3
Glossary G - 1 GLOSSARY OF HIGHWAY-RELATED DRAINAGE TERMS (Reprinted from the 1999 edition of the American Association of State Highway and Transportation Officials Model Drainage Manual) G.1 Introduction This Glossary is divided into three parts: · Introduction, · Glossary, and · References. It is not intended that all the terms in this Glossary be rigorously accurate or complete. Realistically, this is impossible. Depending on the circumstance, a particular term may have several meanings; this can never change. The primary purpose of this Glossary is to define the terms found in the Highway Drainage Guidelines and Model Drainage Manual in a manner that makes them easier to interpret and understand. A lesser purpose is to provide a compendium of terms that will be useful for both the novice as well as the more experienced hydraulics engineer. This Glossary may also help those who are unfamiliar with highway drainage design to become more understanding and appreciative of this complex science as well as facilitate communication between the highway hydraulics engineer and others. Where readily available, the source of a definition has been referenced. For clarity or format purposes, cited definitions may have some additional verbiage contained in double brackets [ ]. Conversely, three “dots” (...) are used to indicate where some parts of a cited definition were eliminated. Also, as might be expected, different sources were found to use different hyphenation and terminology practices for the same words. Insignificant changes in this regard were made to some cited references and elsewhere to gain uniformity for the terms contained in this Glossary: as an example, “groundwater” vice “ground-water” or “ground water,” and “cross section area” vice “cross-sectional area.” Cited definitions were taken primarily from two sources: W.B. -
RASG-MID/6-WP/25 18/05/2017 International Civil Aviation Organization Agenda Item 5
RASG-MID/6-WP/25 18/05/2017 International Civil Aviation Organization Regional Aviation Safety Group - Middle East Sixth Meeting (RASG-MID/6) (Bahrain, 26-28 September 2017) Agenda Item 5: Update from and Coordination with MIDANPIRG WAKE TURBULENCE SEPARATION IN RVSM AIRSPACE (Presented by the Secretariat) SUMMARY This paper presents an overview of the provisions related to Wake Turbulence Separation and addresses the incident that took place between an A380 and CL604 in the RVSM airspace, for the meeting consideration in order to agree on measures that would mitigate the safety risk associated with similar occurrences. Action by the meeting is at paragraph 3. REFERENCES - ATM SG/3 Report - CIR 331 - Doc 4444 - Doc 9426 - Interim Report BFU17-0024-2X 1. INTRODUCTION 1.1 The provisions related to Wake Turbulence Minima are contained in PANS-ATM (ICAO Doc 4444) and detailed characteristics of wake vortices and their effect on aircraft are contained in the Air Traffic Services Planning Manual (ICAO Doc 9426). 1.2 The term “wake turbulence” is used in this context to describe the effect of the rotating air masses generated behind the wing tips of large jet aircraft, in preference to the term “wake vortex” which describes the nature of the air masses. 1.3 Wake vortices are present behind every aircraft, but are particularly severe when generated by a large and wide-bodied jet aircraft. These vortices are two counter-rotating cylindrical air masses trailing aft from the aircraft. The vortices are most dangerous to following aircraft during the take-off, initial climb, final approach and landing phases of flight. -
The Development of Wake Turbulence Re-Categorization in the United States
AIAA 2016-3434 AIAA Aviation 13-17 June 2016, Washington, D.C. 8th AIAA Atmospheric and Space Environments Conference The Development of Wake Turbulence Recategorization in the United States Jillian Cheng1 Engility Corporation, Washington, DC, 20024 and Jeffrey Tittsworth2, Wayne Gallo3, Ashley Awwad4 Federal Aviation Administration, Washington, DC, 20591 This paper describes the background information and provides a status update on a specific aspect of the Federal Aviation Administration (FAA) wake turbulence program known as RECAT (i.e., Recategorization). The fundamental premise of RECAT is that, instead of using the existing FAA Order JO 7110.65 categorical wake turbulence separation minima based on maximum takeoff weight, wake separation can be refined using a more complete set of wake related parameters. This process then leads to a safe reduction of wake turbulence separation minima over those specified in FAA Order JO 7110.65. This paper describes the overall three-phased approach of RECAT, with the ultimate goal of achieving dynamic pairwise separation. Currently, Phase II, or a static pairwise based wake turbulence separation is ready for implementation by the Federal Aviation Administration. The paper describes the analysis approach, including the data sources and severity metrics used in the development of RECAT Phase II. Nomenclature b = wingspan b0 = initial vortex separation Γ = circulation of vortex generated by leading aircraft Γ0 = initial circulation Γ* = non-dimensional circulation T0 = normalized wake age T* = non-dimensional age U = aircraft speed I. Introduction HE demand for safely increasing capacity and efficiency at congested airports increases every year. The main Downloaded by MASSACHUSETTS INST OF TECHNOLOGY on July 12, 2016 | http://arc.aiaa.org DOI: 10.2514/6.2016-3434 Tconstraint on airport throughput is the runway which accommodates only a limited number of flights per unit time. -
Computational Turbulent Incompressible Flow
This is page i Printer: Opaque this Computational Turbulent Incompressible Flow Applied Mathematics: Body & Soul Vol 4 Johan Hoffman and Claes Johnson 24th February 2006 ii This is page iii Printer: Opaque this Contents I Overview 4 1 Main Objective 5 2 Mysteries and Secrets 7 2.1 Mysteries . 7 2.2 Secrets . 8 3 Turbulent flow and History of Aviation 13 3.1 Leonardo da Vinci, Newton and d'Alembert . 13 3.2 Cayley and Lilienthal . 14 3.3 Kutta, Zhukovsky and the Wright Brothers . 14 4 The Navier{Stokes and Euler Equations 19 4.1 The Navier{Stokes Equations . 19 4.2 What is Viscosity? . 20 4.3 The Euler Equations . 22 4.4 Friction Boundary Condition . 22 4.5 Euler Equations as Einstein's Ideal Model . 22 4.6 Euler and NS as Dynamical Systems . 23 5 Triumph and Failure of Mathematics 25 5.1 Triumph: Celestial Mechanics . 25 iv Contents 5.2 Failure: Potential Flow . 26 6 Laminar and Turbulent Flow 27 6.1 Reynolds . 27 6.2 Applications and Reynolds Numbers . 29 7 Computational Turbulence 33 7.1 Are Turbulent Flows Computable? . 33 7.2 Typical Outputs: Drag and Lift . 35 7.3 Approximate Weak Solutions: G2 . 35 7.4 G2 Error Control and Stability . 36 7.5 What about Mathematics of NS and Euler? . 36 7.6 When is a Flow Turbulent? . 37 7.7 G2 vs Physics . 37 7.8 Computability and Predictability . 38 7.9 G2 in Dolfin in FEniCS . 39 8 A First Study of Stability 41 8.1 The linearized Euler Equations . -
Flight-Test Techniques for Wake-Vortex Minimization Studies
FLIGHT-TEST TECHNIQUES FOR WAKE-VORTEX MINIMIZATION STUDIES Robert A. Jacobsen and M. R. Barber* Ames Research Center The flight-test techniques developed for use in the study of wake turbu- lence and used recently in flight studies of wake minimization methods are discussed. Flow visualization has been developed as a technique for qualita- tively assessing minimization methods and is required in flight-test proce- dures for making quantitative measurements. The quantitative techniques are the measurement of the upset dynamics of an aircraft encountering the wake and the measurement of the wake velocity profiles. Descriptions of the instrumen- tation and. the data reduction and correlation methods are given. INTRODUCTION Flight tests have played an important role in the coordinated research program to develop vortex-wake alleviation techniques. The contribution of flight testing to this program lies in three important areas: to verify that the more flexible and less expensive to operate, ground-based research facili- ties are suitable for the development of vortex alleviation devices and tech- niques; to identify, under full-scale conditions, shortcomings of any alleviation technique that might not have been evident in the small-scale test environment; and to assess the operational feasibility of the developed tech- niques. The operational feasibility phase has two facets. The first is the influence of the alleviation device on the operation of the generating air- craft, but this subject is outside the scope of this paper. The second facet is to demonstrate the level of alleviation attained in the oDerationa1 situation. Recent flight experience has emphasized the importance of flight tests in complementing and focusing the research efforts in the ground-based facilities. -
FAA Perspectives on Historical Wake Turbulence R&D to Recent
FAA Perspectives on Historical Wake Turbulence R&D to Recent Operational Implementations James N. Hallocka David C. Burnhamb Frank Y. Wangc 9th AIAA Atmospheric and Space Environments Conference, Denver CO, June 3-9, 2017 Copyright Form C: This material is a work of the U.S. Government and is not subject to copyright protection in the United States.1 Affiliations a Consultant, Retired USDOT Volpe Center, Senior Member AIAA b SCENSI, Former USDOT Volpe Center, Senior Member AIAA c USDOT Volpe Center, Member AIAA 2 5 June 2017 AIAA Denver CO Acknowledgements – FAA Leadership Team • Jeff Tittsworth • Paul Strande • Jillian Cheng • Wayne Gallo • Edward Johnson 3 5 June 2017 AIAA Denver CO Purpose • A major intent of this presentation is to delineate why the many years of Wake Turbulence R&D are finally yielding beneficial operational implementations. • Highlight lessons learned from past R&D. • Going forward – NextGen and Beyond 4 5 June 2017 AIAA Denver CO Some Things to Keep in Mind • Useful to note that wake turbulence separation minima is more than just the well known in-trail separation (FAA JO 7110.65W) CSPR (Closely Spaced Parallel Runways) Intersection Departures Intersecting Runways En-Route vertical separation (ICAO Doc 9574) • Useful to recognize that in the terminal area, FAA has an unique culture of having both VFR and IFR flights Wake separation minima is enforced on approach and at threshold crossings, under IFR Visual approaches can be used in VMC, where pilots can assume wake avoidance responsibility Wake separation