Misplaced Pages

#410589

46-403: The terms are also used metaphorically in business and elsewhere about circumstances where progress is made harder (headwind) or easier (tailwind). In aeronautics , a headwind is favorable in takeoffs and landings because an airfoil moving into a headwind is capable of generating greater lift than the same airfoil moving through tranquil air, or with a tailwind, at equal ground speed . As

92-613: A meridian travels approximately one minute of geographic latitude in one hour. The length of the internationally agreed nautical mile is 1 852  m . The US adopted the international definition in 1954, having previously used the US nautical mile ( 1 853 .248 m ). The UK adopted the international nautical mile definition in 1970, having previously used the UK Admiralty nautical mile ( 6 080  ft or 1 853 .184 m ). (* = approximate values) The speeds of vessels relative to

138-482: A controlled amount of the substance. Francesco Lana de Terzi measured the pressure of air at sea level and in 1670 proposed the first scientifically credible lifting medium in the form of hollow metal spheres from which all the air had been pumped out. These would be lighter than the displaced air and able to lift an airship . His proposed methods of controlling height are still in use today; by carrying ballast which may be dropped overboard to gain height, and by venting

184-452: A distance in nautical miles on a chart can easily be measured by using dividers and the latitude scales on the sides of the chart. Recent British Admiralty charts have a latitude scale down the middle to make this even easier. Speed is sometimes incorrectly expressed as "knots per hour", which would mean "nautical miles per hour per hour" and thus would refer to acceleration . Prior to 1969, airworthiness standards for civil aircraft in

230-470: A four-person screw-type helicopter, have severe flaws. He did at least understand that "An object offers as much resistance to the air as the air does to the object." ( Newton would not publish the Third law of motion until 1687.) His analysis led to the realisation that manpower alone was not sufficient for sustained flight, and his later designs included a mechanical power source such as a spring. Da Vinci's work

276-470: A heading of 060 in the above-mentioned example. Aeronautics Aeronautics is the science or art involved with the study, design , and manufacturing of air flight -capable machines, and the techniques of operating aircraft and rockets within the atmosphere . While the term originally referred solely to operating the aircraft, it has since been expanded to include technology, business, and other aspects related to aircraft. The term " aviation "

322-584: A lifting gas, though practical demonstration awaited a gas-tight balloon material. On hearing of the Montgolfier Brothers' invitation, the French Academy member Jacques Charles offered a similar demonstration of a hydrogen balloon. Charles and two craftsmen, the Robert brothers, developed a gas-tight material of rubberised silk for the envelope. The hydrogen gas was to be generated by chemical reaction during

368-423: A result, aviators and air traffic controllers commonly choose to take off or land in the direction of a runway that will provide a headwind. Aircraft carriers usually turn into the wind during takeoffs and landings, and may increase their own speed. While on take-off and landing, headwinds are good because they allow the aircraft to use a shorter runway, in flight, however, headwinds are bad because they reduce

414-465: A standard nautical chart using Mercator projection , the horizontal (East–West) scale varies with latitude. On a chart of the North Atlantic, the scale varies by a factor of two from Florida to Greenland. A single graphic scale , of the sort on many maps, would therefore be useless on such a chart. Since the length of a nautical mile, for practical purposes, is equivalent to about a minute of latitude,

460-497: Is 14.40 {\displaystyle 14.40} metres per knot. Although the unit knot does not fit within the SI system, its retention for nautical and aviation use is important because the length of a nautical mile , upon which the knot is based, is closely related to the longitude / latitude geographic coordinate system . As a result, nautical miles and knots are convenient units to use when navigating an aircraft or ship. On

506-450: Is felt strongly by cyclists. It decreases the speed and increases the advantage of drafting , i.e. riding closely together in groups. This can affect tactics in road bicycle racing . The comedian Jacob Haugaard made a pointedly absurd campaign promise of more tailwind on bicycle paths when he successfully ran as an independent in the 1994 Danish parliamentary election . Cycling in Denmark

SECTION 10

#1732883993411

552-418: Is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction . Rocket engines push rockets forwards simply by throwing their exhaust backwards extremely fast. Rockets for military and recreational uses date back to at least 13th-century China . Significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry

598-416: Is said to have 7.5 knots of crosswind and 13 knots of headwind on runway 06, or 13 knots of tailwind on runway 24. Aircraft usually have maximum tailwind and crosswind components which they cannot exceed. If the wind is at eighty degrees or above it is said to be full-cross. If the wind exceeds 100 degrees it is common practice to takeoff and land from the opposite end of the runway, it has

644-491: Is sometimes used interchangeably with aeronautics, although "aeronautics" includes lighter-than-air craft such as airships , and includes ballistic vehicles while "aviation" technically does not. A significant part of aeronautical science is a branch of dynamics called aerodynamics , which deals with the motion of air and the way that it interacts with objects in motion, such as an aircraft. Attempts to fly without any real aeronautical understanding have been made from

690-421: Is the art or practice of aeronautics. Historically aviation meant only heavier-than-air flight, but nowadays it includes flying in balloons and airships. Aeronautical engineering covers the design and construction of aircraft, including how they are powered, how they are used and how they are controlled for safe operation. A major part of aeronautical engineering is aerodynamics , the science of passing through

736-433: Is very popular. Tailwinds and headwinds are commonly measured in relation to the speed of vehicles — commonly air and watercraft — as well as in running events — particularly sprints up to 200 metres where athletes run in the same or mostly same direction and wind assistance from a tailwind above two metre per second is not allowed in records. This limit also applies to long jump and triple jump . Pilots calculate

782-462: Is widely acknowledged as the founder of modern aeronautics. He was first called the "father of the aeroplane" in 1846 and Henson called him the "father of aerial navigation." He was the first true scientific aerial investigator to publish his work, which included for the first time the underlying principles and forces of flight. In 1809 he began the publication of a landmark three-part treatise titled "On Aerial Navigation" (1809–1810). In it he wrote

828-517: The International Civil Aviation Organization list the knot as permitted for temporary use in aviation, but no end date to the temporary period has been agreed as of 2024 . Until the mid-19th century, vessel speed at sea was measured using a chip log . This consisted of a wooden panel, attached by line to a reel, and weighted on one edge to float perpendicularly to the water surface and thus present substantial resistance to

874-456: The Rozière. The principle was to use the hydrogen section for constant lift and to navigate vertically by heating and allowing to cool the hot air section, in order to catch the most favourable wind at whatever altitude it was blowing. The balloon envelope was made of goldbeater's skin . The first flight ended in disaster and the approach has seldom been used since. Sir George Cayley (1773–1857)

920-430: The fluids in which they travel (boat speeds and air speeds ) can be measured in knots. If so, for consistency, the speeds of navigational fluids ( ocean currents , tidal streams , river currents and wind speeds ) are also measured in knots. Thus, speed over the ground (SOG; ground speed (GS) in aircraft) and rate of progress towards a distant point (" velocity made good ", VMG) can also be given in knots. Since 1979,

966-977: The ground speed of an aircraft requires the calculation of the head or tailwind. Assume: A = Angle of the wind origin from the direction of travel {\displaystyle A={\text{Angle of the wind origin from the direction of travel}}} W S = The measured total wind speed {\displaystyle WS={\text{The measured total wind speed}}} C W = Crosswind {\displaystyle CW={\text{Crosswind}}} T W = Tailwind {\displaystyle TW={\text{Tailwind}}} H W = Headwind {\displaystyle HW={\text{Headwind}}} Then C W = sin ⁡ ( A ) ⋅ W S {\displaystyle CW=\sin(A)\cdot WS} H W = cos ⁡ ( A ) ⋅ W S {\displaystyle HW=\cos(A)\cdot WS} For example, if

SECTION 20

#1732883993411

1012-541: The sailing master 's dead reckoning and navigation . This method gives a value for the knot of 20 + 1 ⁄ 4 inches per second or 1.85166 kilometres per hour. The difference from the modern definition is less than 0.02%. Derivation of knots spacing: 1   kn = 1852   m/h = 0.5144   m/s {\displaystyle 1~{\textrm {kn}}=1852~{\textrm {m/h}}=0.5144~{\textrm {m/s}}} , so in 28 {\displaystyle 28} seconds that

1058-407: The "flying man". He was the first person to make well-documented, repeated, successful flights with gliders , therefore making the idea of " heavier than air " a reality. Newspapers and magazines published photographs of Lilienthal gliding, favourably influencing public and scientific opinion about the possibility of flying machines becoming practical. His work lead to him developing the concept of

1104-526: The Headwind or Tailwind Component and the Crosswind Component of local wind before takeoff. The direction of wind at a runway is measured using a windsock and the speed by an anemometer , often mounted on the same post. Headwind and Tailwind are opposite interpretations of the wind component which is parallel to the direction of travel, while Crosswind represents the perpendicular component. Determining

1150-508: The Italian explorer Marco Polo described the Chinese techniques then current. The Chinese also constructed small hot air balloons, or lanterns, and rotary-wing toys. An early European to provide any scientific discussion of flight was Roger Bacon , who described principles of operation for the lighter-than-air balloon and the flapping-wing ornithopter , which he envisaged would be constructed in

1196-652: The United States Federal Aviation Regulations specified that distances were to be in statute miles, and speeds in miles per hour. In 1969, these standards were progressively amended to specify that distances were to be in nautical miles, and speeds in knots. The following abbreviations are used to distinguish between various measurements of airspeed : The indicated airspeed is close to the true airspeed only at sea level in standard conditions and at low speeds. At 11 000  m ( 36 000  ft), an indicated airspeed of 300 kn may correspond to

1242-405: The air becomes compressed, typically at speeds above Mach 1. Transonic flow occurs in the intermediate speed range around Mach 1, where the airflow over an object may be locally subsonic at one point and locally supersonic at another. A rocket or rocket vehicle is a missile , spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine . In all rockets, the exhaust

1288-544: The air. With the increasing activity in space flight, nowadays aeronautics and astronautics are often combined as aerospace engineering . The science of aerodynamics deals with the motion of air and the way that it interacts with objects in motion, such as an aircraft. The study of aerodynamics falls broadly into three areas: Incompressible flow occurs where the air simply moves to avoid objects, typically at subsonic speeds below that of sound (Mach 1). Compressible flow occurs where shock waves appear at points where

1334-606: The earliest times, typically by constructing wings and jumping from a tower with crippling or lethal results. Wiser investigators sought to gain some rational understanding through the study of bird flight. Medieval Islamic Golden Age scientists such as Abbas ibn Firnas also made such studies. The founders of modern aeronautics, Leonardo da Vinci in the Renaissance and Cayley in 1799, both began their investigations with studies of bird flight. Man-carrying kites are believed to have been used extensively in ancient China. In 1282

1380-475: The filling process. The Montgolfier designs had several shortcomings, not least the need for dry weather and a tendency for sparks from the fire to set light to the paper balloon. The manned design had a gallery around the base of the balloon rather than the hanging basket of the first, unmanned design, which brought the paper closer to the fire. On their free flight, De Rozier and d'Arlandes took buckets of water and sponges to douse these fires as they arose. On

1426-413: The first scientific statement of the problem, "The whole problem is confined within these limits, viz. to make a surface support a given weight by the application of power to the resistance of air." He identified the four vector forces that influence an aircraft: thrust , lift , drag and weight and distinguished stability and control in his designs. He developed the modern conventional form of

Headwind and tailwind - Misplaced Pages Continue

1472-476: The fixed-wing aeroplane having a stabilising tail with both horizontal and vertical surfaces, flying gliders both unmanned and manned. He introduced the use of the whirling arm test rig to investigate the aerodynamics of flight, using it to discover the benefits of the curved or cambered aerofoil over the flat wing he had used for his first glider. He also identified and described the importance of dihedral , diagonal bracing and drag reduction, and contributed to

1518-434: The future. The lifting medium for his balloon would be an "aether" whose composition he did not know. In the late fifteenth century, Leonardo da Vinci followed up his study of birds with designs for some of the earliest flying machines, including the flapping-wing ornithopter and the rotating-wing helicopter . Although his designs were rational, they were not based on particularly good science. Many of his designs, such as

1564-400: The gas contained in a second, inner ballonet. On 19 September 1784, it completed the first flight of over 100 km, between Paris and Beuvry , despite the man-powered propulsive devices proving useless. In an attempt the next year to provide both endurance and controllability, de Rozier developed a balloon having both hot air and hydrogen gas bags, a design which was soon named after him as

1610-463: The ground speed of the aircraft, which requires more fuel to get to the destination. Conversely, tailwinds are bad on take-off and landing, but are good in flight. In sailing , a headwind may make forward movement difficult, and necessitate tacking into the wind. In motor vehicles , wind can affect fuel consumption and top speed but is usually ignored by the driver who chooses the speed from speed limits and road conditions. In cycling , headwind

1656-459: The knot is kn . The same symbol is preferred by the Institute of Electrical and Electronics Engineers ( IEEE ), while kt is also common, especially in aviation, where it is the form recommended by the International Civil Aviation Organization ( ICAO ). The knot is a non- SI unit. The knot is used in meteorology , and in maritime and air navigation. A vessel travelling at 1 knot along

1702-512: The lifting containers to lose height. In practice de Terzi's spheres would have collapsed under air pressure, and further developments had to wait for more practicable lifting gases. From the mid-18th century the Montgolfier brothers in France began experimenting with balloons. Their balloons were made of paper, and early experiments using steam as the lifting gas were short-lived due to its effect on

1748-743: The modern wing. His flight attempts in Berlin in the year 1891 are seen as the beginning of human flight and the " Lilienthal Normalsegelapparat " is considered to be the first air plane in series production, making the Maschinenfabrik Otto Lilienthal in Berlin the first air plane production company in the world. Otto Lilienthal is often referred to as either the "father of aviation" or "father of flight". Other important investigators included Horatio Phillips . Aeronautics may be divided into three main branches, Aviation , Aeronautical science and Aeronautical engineering . Aviation

1794-516: The most common type of rocket and they typically create their exhaust by the combustion of rocket propellant . Chemical rockets store a large amount of energy in an easily released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks. Knot (unit) The knot ( / n ɒ t / ) is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.151 mph or 0.514 m/s ). The ISO standard symbol for

1840-525: The other hand, the manned design of Charles was essentially modern. As a result of these exploits, the hot air balloon became known as the Montgolfière type and the gas balloon the Charlière . Charles and the Robert brothers' next balloon, La Caroline , was a Charlière that followed Jean Baptiste Meusnier 's proposals for an elongated dirigible balloon, and was notable for having an outer envelope with

1886-493: The paper as it condensed. Mistaking smoke for a kind of steam, they began filling their balloons with hot smoky air which they called "electric smoke" and, despite not fully understanding the principles at work, made some successful launches and in 1783 were invited to give a demonstration to the French Académie des Sciences . Meanwhile, the discovery of hydrogen led Joseph Black in c.  1780 to propose its use as

Headwind and tailwind - Misplaced Pages Continue

1932-410: The understanding and design of ornithopters and parachutes . Another significant invention was the tension-spoked wheel, which he devised in order to create a light, strong wheel for aircraft undercarriage. During the 19th century Cayley's ideas were refined, proved and expanded on, culminating in the works of Otto Lilienthal . Lilienthal was a German engineer and businessman who became known as

1978-427: The water moving around it. The chip log was cast over the stern of the moving vessel and the line allowed to pay out. Knots tied at a distance of 47  feet 3  inches (14.4018  m ) from each other, passed through a sailor's fingers, while another sailor used a 30-second sand-glass (28-second sand-glass is the currently accepted timing) to time the operation. The knot count would be reported and used in

2024-1046: The wind is at 09015 that means the wind is currently from heading 090 degrees with a speed of 15  knots and the aircraft is taking-off from runway 24; having heading of 240. The pilot prefers the runway side with less than 90 difference from wind direction, in this case Runway 06; heading 060. Here, A = 30 ∘ {\displaystyle A=30^{\circ }} . Crosswind = sin ⁡ [ 30 ∘ ] ⋅ 15 k n o t s ≈ 7.5 k n o t s {\displaystyle {\text{Crosswind}}=\sin[30^{\circ }]\cdot 15{\mathsf {knots}}\approx 7.5{\mathsf {knots}}} Headwind = cos ⁡ [ 30 ∘ ] ⋅ 15 k n o t s ≈ 13 k n o t s {\displaystyle {\text{Headwind}}=\cos[30^{\circ }]\cdot 15{\mathsf {knots}}\approx 13{\mathsf {knots}}} The aircraft

2070-443: Was lost after his death and did not reappear until it had been overtaken by the work of George Cayley . The modern era of lighter-than-air flight began early in the 17th century with Galileo 's experiments in which he showed that air has weight. Around 1650 Cyrano de Bergerac wrote some fantasy novels in which he described the principle of ascent using a substance (dew) he supposed to be lighter than air, and descending by releasing

2116-577: Was the enabling technology of the Space Age , including setting foot on the Moon . Rockets are used for fireworks , weaponry, ejection seats , launch vehicles for artificial satellites , human spaceflight and exploration of other planets. While comparatively inefficient for low speed use, they are very lightweight and powerful, capable of generating large accelerations and of attaining extremely high speeds with reasonable efficiency. Chemical rockets are

#410589