40 Fun Facts About Aerodynamics

Which feature of a golf ball's cover lets it fly much farther than a perfectly smooth ball would?

Dimples stir the air hugging the ball into turbulence, so it clings longer and leaves a narrower wake behind. Golfers first noticed that nicked, worn balls flew truer than smooth new ones.

Which bird's beak was the model for the streamlined front of Japan's 500 Series Shinkansen bullet train?

The kingfisher's beak shape, copied on the train's front, cut energy use by about 15 percent and made the train quieter.

Which bird of prey folds back its wings and tail to dive on other birds at over 200 miles per hour?

The peregrine falcon is often called the fastest animal on the planet, and one bird was recorded diving at 242 miles per hour.

Which racket sport uses a feathered projectile so stable that it always flips to fly cork-first?

Badminton's shuttlecock is a high-drag cone of about 16 feathers, designed to slow down very quickly. However it is struck, it turns to travel base-first.

Which Aboriginal Australian throwing tool has wing-shaped arms that make it curve back to the thrower?

A boomerang's arms work like spinning wings, each generating lift as it turns. The oldest surviving Aboriginal one, found in a South Australian peat bog, dates to about 10,000 BC.

Which tree's winged seeds, nicknamed helicopters or whirlybirds, spin like rotor blades as they fall?

Maple seeds autorotate: the single wing spins as it drops, which lets the wind carry the seed farther from its parent tree.

Which British-French airliner used a slender delta wing to cruise at twice the speed of sound?

Concorde flew so fast that its fuselage heated up and stretched by as much as 30 centimetres in flight, shrinking back as it cooled.

Which American test pilot first flew faster than sound, in a rocket plane he named Glamorous Glennis?

Chuck Yeager made the flight with two ribs broken in a riding fall two nights earlier. A friend sawed off a broom handle so he could lever the hatch shut.

Which seabird, with the longest wingspan of any living bird, can soar for hours without flapping?

The snowy albatross, one of the wandering albatrosses, has wings spanning up to 3.7 metres and glides 22 metres forward for every metre it drops.

Which thunder-like noise from faster-than-sound aircraft led to bans on routine supersonic flights over land?

A sonic boom is not a single bang at the moment a jet passes the speed of sound. It trails the aircraft for the whole supersonic flight, like a carpet of noise unrolling beneath it.

Which brothers steered their early aircraft by twisting the wingtips with cables, a technique called wing warping?

The Wright brothers borrowed the idea from birds, which Wilbur saw twisting their wingtips to keep balance, and they went on to patent it.

Which test facility, first built in Britain in 1871, lets engineers study airflow around a stationary scale model?

A wind tunnel lets forces measured on a small model be scaled up to the full-size aircraft. Francis Wenham built the first enclosed one decades before powered flight.

Whose third law of motion explains how a wing that pushes air downward is pushed upward in return?

Isaac Newton's third law says every action has an equal and opposite reaction, so the air a wing turns downward shoves back up on the wing as lift.

Which of the four forces of flight comes from a propeller or jet engine pushing air backward?

Thrust drives an aircraft forward and has to beat drag before the plane can speed up. A rocket makes it the same way, by hurling hot exhaust gas out behind.

What steady speed, about 120 miles per hour for a belly-down skydiver, is reached when drag balances gravity?

Terminal velocity rises when a skydiver pulls in their limbs. Competition speed skydivers falling head-down reach about 150 metres per second, nearly triple the belly-down figure.

Which device on the rear of many sports cars is named for disrupting unfavourable airflow over the body?

A spoiler does what its name says: it spoils air movement that would otherwise cause lift or turbulence. Many road-car versions are fitted mainly for looks.

Which wind direction do pilots prefer for takeoff because it adds lift without adding ground speed?

A headwind means air is already flowing over the wings before the plane moves, so it lifts off in a shorter distance. Aircraft carriers turn into the wind for the same reason.

Which skydiver became the first person to fall faster than sound, after jumping from a balloon 24 miles up?

Felix Baumgartner reached an estimated 843.6 miles per hour over New Mexico in 2012, then opened his parachute for the last two and a half kilometres.

Which British Second World War fighter had elliptical wings, a shape that keeps induced drag low?

The Spitfire's designers chose the ellipse because the wing had to be thin for speed yet deep enough near the body to house the wheels and guns.

Which tactic do cyclists, stock car drivers and speed skaters use when they tuck in close behind a rival?

Drafting works because the leader punches a hole in the air, leaving a slipstream of lower resistance behind. It can even save the leader a little energy.

Which sudden loss of lift strikes a wing tilted beyond its critical angle of attack, typically about 15 degrees?

A stall has nothing to do with an engine stopping, and it can happen at any airspeed. Even a glider with no engine at all can do it.

Which streamlined shape creates almost 30 times less drag than a flat plate in the same airflow?

An airfoil has a drag coefficient of about 0.045, against 1.28 for a flat plate facing the flow. Even a bullet shape, at 0.295, drags several times harder.

Which Swiss mathematician gives his name to the principle that a faster-moving fluid has lower pressure?

Daniel Bernoulli published the idea in his 1738 book Hydrodynamica. Leonhard Euler turned it into the equation engineers use today fourteen years later.

Which Austrian physicist, who photographed shock waves around bullets, has a famous speed ratio named after him?

Ernst Mach and his son Ludwig captured the shadows of the invisible waves with schlieren photography. The ratio of an object's speed to the speed of sound now carries his name.

Which word describes flight above roughly five times the speed of sound, a regime reached by the X-15 rocket plane?

Hypersonic flow gets so hot that air molecules break apart and lose electrons, changing the chemistry of the gas around the vehicle.

Which hinged wing surfaces, which replaced wing warping by about 1915, work as a pair to make an aircraft roll?

Ailerons take their name from the French for little wing, a term also used for the tips of a bird's wings that steer it in flight.

Which high-lift panels do pilots lower from the wings to shorten an airliner's takeoff and landing distances?

Flaps add lift at low speed but also add drag, which is why they are retracted as soon as the aircraft no longer needs them.

Which near-vertical tips fitted to many airliners save fuel by weakening the vortices that trail behind?

Winglets were developed by NASA engineer Richard Whitcomb after the 1973 oil crisis sent fuel costs soaring. They typically improve a jet's fuel efficiency by 4 to 6 percent.

What name do engineers give to the push that a Formula One car's upside-down wings exert on its tyres?

Downforce is lift used in reverse. Engineers call the extra cornering grip it gives aerodynamic grip, as opposed to the mechanical grip that comes from tyres and suspension.

Which baseball pitch is thrown with almost no spin, so that it flutters unpredictably on its way to the batter?

A knuckleball swerves because the ball's raised stitching drags unevenly on the air as it slowly turns. Even catchers struggle to hold on to it.

Which phenomenon, named after a German physicist, makes a spinning ball swerve off a straight path through the air?

The Magnus effect is behind a bending soccer free kick, a baseball curveball and a golfer's slice. Engineers have even used it to propel ships with spinning rotors.

Which American suspension bridge, nicknamed Galloping Gertie, twisted itself apart in 1940, months after opening?

The Tacoma Narrows deck had bucked in the wind ever since it was built, which is how workers came to nickname it. A 40-mile-per-hour wind finally tore it apart.

On an aircraft wing that is producing lift, which part has the fastest airflow and the lowest air pressure?

The upper surface carries faster, lower-pressure air, but not because that air must rejoin the air below at the same instant: that popular 'equal transit time' story is false.

Which German pioneer, known as the flying man, made over 2,000 glider flights before a fatal crash in 1896?

Otto Lilienthal steered by shifting his body beneath the wings, much as hang glider pilots do, and shaped his designs after studying how storks fly.

Which probe, invented by a French engineer studying aqueducts, do aircraft use to measure their airspeed?

The Pitot tube dates from 1732 and took its modern form in 1858. Ice blocking one was a contributing factor when Air France Flight 447 crashed into the Atlantic.

Which thin sheet of slowed air beside a wing's skin did Ludwig Prandtl first describe in Heidelberg in 1904?

The boundary layer is where the stickiness of air slows the flow next to the skin, producing the skin friction that holds every aircraft back.

Which Yorkshire baronet, sometimes called the father of aviation, identified the four forces that act on an aircraft?

George Cayley set out the idea of the modern aeroplane in 1799: a fixed-wing machine with separate systems for lift, propulsion and control.

Which Hungarian-born scientist gives his name to the 100-kilometre line often used to mark the edge of space?

Theodore von Kármán calculated a lower ceiling than the line named after him: about 84 kilometres, above which an aeroplane would have to fly fast enough to melt.

Which Victorian engineer's name is on the number that predicts when smooth airflow will turn turbulent?

Osborne Reynolds popularised the number in 1883, but the idea came from George Stokes in 1851 and it was only named for Reynolds in 1908.

Which name is given to a small wing mounted ahead of the main wing, as on the Saab Viggen jet fighter?

Canard is French for duck, a name that arose because the 1906 Santos-Dumont 14-bis was said to look like a duck with its neck stretched out in flight.