Misplaced Pages

#27972

30-476: Equivalent foils that move through water are found on hydrofoil power vessels and foiling sailboats that lift out of the water and on submarines that use diving planes to point the boat upwards or downwards, while submerged. Hydrodynamics is the study of foil performance in water. The word "wing" from the Old Norse vængr for many centuries referred mainly to the foremost limbs of birds (in addition to

60-454: A broader set of piloting skills and exposes the aircraft to greater structural stress than for normal flight. In some countries, the pilot must wear a parachute when performing aerobatics. Aerobatic training enhances a pilot's ability to recover from unusual flight conditions, and thus is an element of many flight safety training programs for pilots. While many pilots fly aerobatics for recreation, some choose to fly in aerobatic competitions ,

90-485: A fully aerobatic helicopter, capable of performing loops and rolls, is the Westland Lynx . Most aerobatic manoeuvres involve rotation of the aircraft about its longitudinal (roll) axis or lateral (pitch) axis. Other maneuvers, such as a spin , displace the aircraft about its vertical (yaw) axis. Manoeuvres are often combined to form a complete aerobatic sequence for entertainment or competition. Aerobatic flying requires

120-473: A judged sport. In the early days of flying, some pilots used their aircraft as part of a flying circus to entertain. Maneuvers were flown for artistic reasons or to draw gasps from onlookers. In due course some of these maneuvers were found to allow aircraft to gain tactical advantage during aerial combat or dogfights between fighter aircraft. Aerobatic aircraft fall into two categories—specialist aerobatic, and aerobatic capable. Specialist designs such as

150-516: A large amount of drag. Since even a flat plate can generate lift, a significant factor in foil design is the minimization of drag. An example of this is the rudder of a boat or aircraft. When designing a rudder a key design factor is the minimization of drag in its neutral position, which is balanced with the need to produce sufficient lift with which to turn the craft at a reasonable rate. Other types of foils, both natural and man-made, seen both in air and water, have features that delay or control

180-477: A positive angle of attack to deflect air downward. Symmetrical airfoils have higher stalling speeds than cambered airfoils of the same wing area but are used in aerobatic aircraft as they provide the same flight characteristics whether the aircraft is upright or inverted. Another example comes from sailboats, where the sail is a thin sheet. For flight speeds near the speed of sound ( transonic flight ), specific asymmetrical airfoil sections are used to minimize

210-411: A suitable angle of attack relative to the flow of air past the wing. When this occurs, the wing deflects the airflow downwards, "turning" the air as it passes the wing. Since the wing exerts a force on the air to change its direction, the air must exert a force on the wing, equal in size but opposite in direction. This force arises from different air pressures that exist on the upper and lower surfaces of

240-466: Is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aeroplane" and "acrobatics". Aerobatics are performed in aeroplanes and gliders for training, recreation, entertainment, and sport. Additionally, some helicopters , such as the MBB Bo 105 , are capable of limited aerobatic manoeuvres . An example of

270-634: The Farnborough Airshow in September 1957. Aerobatics are taught to military fighter pilots as a means of developing flying skills and for tactical use in combat. Many aerobatic manoeuvres were indeed developed in military conflicts, e.g. the Immelmann turn or Split S . Aerobatics and formation flying is not limited solely to fixed-wing aircraft; the British Army , Royal Navy , Spanish Air Force and

300-538: The Indian Air Force , among others, have helicopter display teams. All aerobatic manoeuvres demand training and practice to avoid accidents . Accidents due to aerobatic manoeuvres are very rare in competition aerobatics; most of them happen when performing formation flying or stunt flying at very low levels at airshows or air racing . Low-level aerobatics are extremely demanding and airshow pilots must demonstrate their ability before being allowed to gradually reduce

330-912: The Pitts Special , the Extra 200 and 300 , and the Sukhoi Su-26 M and Sukhoi Su-29 aim for ultimate aerobatic performance. This comes at the expense of general purpose use such as touring, or ease of non aerobatic handling such as landing. At a more basic level, aerobatic capable aircraft, such as the Cessna 152 Aerobat or the R2160 Acrobin , can be dual purpose—equipped to carrying passengers and luggage, as well as being capable of basic aerobatic figures. Flight formation aerobatics are flown by teams of up to sixteen aircraft, although most teams fly between four and ten aircraft. Some are state funded to reflect pride in

SECTION 10

#1732837330028

360-412: The armed forces while others are commercially sponsored. Coloured smoke trails may be emitted to emphasise the patterns flown and/or the colours of a national flag. Aerobatic maneuvers flown in a jet-powered aircraft are limited in scope as they cannot take advantage of the gyroscopic forces that a propeller driven aircraft can exploit. Jet-powered aircraft also tend to fly much faster, which increases

390-710: The Olympic games, and are governed by the FAI Aerobatics Commission (CIVA) Competitions start at Primary, or Graduate level (in UK "Beginners") and proceed in complexity through Sportsman (in UK "Standard"), Intermediate and Advanced, with Unlimited being the top competition level. Experienced aerobatic pilots have been measured to pull ±5 g for short periods while unlimited pilots can perform more extreme maneuvers and experience higher g levels -possibly up to +8/−6 g. The limits for positive g are higher than for negative g and this

420-434: The aircraft. Due to safety concerns, the smoke is not a result of combustion but is produced by the vaporization of fog oil into a fine aerosol , achieved either by injecting the oil into the hot engine exhaust or by the use of a dedicated device that can be fitted in any position on the aircraft. The first military aerobatic team to use smoke at will during displays was Fleet Air Arm 702 Squadron " The Black Cats " at

450-642: The architectural aisle). But in recent centuries the word's meaning has extended to include lift producing appendages of insects , bats , pterosaurs , boomerangs , some sail boats and aircraft , or the airfoil on a race car . In nature wings have evolved in dinosaurs, birds , mammals, fish, reptiles and plants as means of locomotion . Various species of penguins and other flighted or flightless water birds such as auks , cormorants , guillemots , shearwaters , eider and scoter ducks and diving petrels are efficient underwater swimmers, and use their wings to propel through water. The design and analysis of

480-499: The flowfield is given by the simplified Navier–Stokes equations , applicable when the fluid is incompressible . And since the effects of the compressibility of air at low speeds is negligible, these simplified equations can be used for airfoils as long as the airflow is substantially less than the speed of sound (up to about Mach 0.3). For hydrofoils at high speeds, of the order of 50 knots (26 m/s) according to Faltinsen, cavitation and ventilation – with air penetrating along

510-464: The fluid flow). If the fluid is a gas , the foil is called an airfoil or aerofoil, and if the fluid is water the foil is called a hydrofoil . A foil generates lift primarily because of its shape and angle of attack . When oriented at a suitable angle, the foil deflects the oncoming fluid, resulting in a force on the foil in the direction opposite to the deflection. This force can be resolved into two components: lift and drag . This "turning" of

540-407: The fluid in the vicinity of the foil creates curved streamlines which results in lower pressure on one side and higher pressure on the other. This pressure difference is accompanied by a velocity difference, via Bernoulli's principle , so for foils generating lift the resulting flowfield about the foil has a higher average velocity on one surface than on the other. A more detailed description of

570-425: The fully limp flexible wing. Domina Jalbert invented flexible un-sparred ram-air airfoiled thick wings. Natural world: Aviation: Sailing: Foil (fluid mechanics) A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift (force generated perpendicular to the fluid flow) is substantially larger than the drag (force generated parallel to

600-460: The height at which they may fly their show. In the EU, flying aerobatics requires special training and a rating. In Canada, no licence is required to perform aerobatics, but to carry passengers during aerobatics a pilot must have at least 10 hours dual flight instruction of aerobatic manoeuvres, or 20 hours of total aerobatic experience. Aerobatic flying competitions are a worldwide phenomenon, rather like

630-437: The lifting ability of a flat plate with span 10 metres and area 10 square metres moving at a speed of 10 m/s at different altitudes and water depths. It uses the lift at an altitude of 11 km as a datum to show how the lift increases with decreasing altitude (increasing air density). It also shows the influence of ground effect and then the effect of increase in density going from air to water. Aerobatic Aerobatics

SECTION 20

#1732837330028

660-437: The onset of lift-induced drag , flow separation , and stall (see Bird flight , Fin , Airfoil , Placoid scale , Tubercle , Vortex generator , Canard (close-coupled), Blown flap , Leading edge slot , Leading edge slats ), as well as Wingtip vortices (see Winglet ). The weight a foil can lift is proportional to its lift coefficient, the density of the fluid, the foil area and its speed squared. The following shows

690-448: The same answers if done correctly. Given a particular wing and its velocity through the air, debates over which mathematical approach is the most convenient to use can be mistaken by those not familiar with the study of aerodynamics as differences of opinion about the basic principles of flight. Wings with an asymmetrical cross-section are the norm in subsonic flight . Wings with a symmetrical cross-section can also generate lift by using

720-416: The size of the figures and the length of time the pilot has to withstand increased g-forces. Jet aerobatic teams often fly in formations, which further restricts the maneuvers that can be safely flown. Aerobatics done at low levels and for an audience is called "stunt flying". To enhance the show effect of aerobatic manoeuvres, smoke is sometimes generated; the smoke allows viewers to see the path travelled by

750-405: The strut from the water surface to the foil – may occur. Both effects may have a substantial influence on the foil's lift. The simplest type of foil is a flat plate. When set at an angle (the angle of attack ) to the flow the plate will deflect the fluid passing over and under it, and this deflection will result in a lift force on the plate. However, while it does generate lift, it also generates

780-401: The top of the wing generates a smaller downward force on the top of the wing than the upward force generated by the higher air pressure on the bottom of the wing. This gives an upward force on the wing. This force is called the lift generated by the wing. The different velocities of the air passing by the wing, the air pressure differences, the change in direction of the airflow, and the lift on

810-524: The very pronounced increase in drag associated with airflow near the speed of sound. These airfoils, called supercritical airfoils , are flat on top and curved on the bottom. Aircraft wings may feature some of the following: Aircraft wings may have various devices, such as flaps or slats, that the pilot uses to modify the shape and surface area of the wing to change its operating characteristics in flight. Besides fixed-wing aircraft , applications for wing shapes include: In 1948, Francis Rogallo invented

840-405: The wing are different ways of describing how lift is produced so it is possible to calculate lift from any one of the other three. For example, the lift can be calculated from the pressure differences, or from different velocities of the air above and below the wing, or from the total momentum change of the deflected air. Fluid dynamics offers other approaches to solving these problems—and all produce

870-451: The wing. Lower-than-ambient air pressure is generated on the top surface of the wing, with a higher-than ambient-pressure on the bottom of the wing. (See: airfoil ) These air pressure differences can be either measured using a pressure-measuring device, or can be calculated from the airspeed] using physical principles —including Bernoulli's principle , which relates changes in air speed to changes in air pressure. The lower air pressure on

900-476: The wings of aircraft is one of the principal applications of the science of aerodynamics , which is a branch of fluid mechanics . The properties of the airflow around any moving object can be found by solving the Navier-Stokes equations of fluid dynamics . Except for simple geometries, these equations are difficult to solve. Simpler explanations can be given For a wing to produce "lift", it must be oriented at

#27972