According to the International Civil Aviation Organization, a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a natural surface. Runways, as well as taxiways and ramps, are sometimes referred to as “tarmac,” though few runways are built using tarmac. Runway lengths are now given in meters worldwide, except in North America where feet are used. In 1916, in a World War I war effort context, the first concrete-paved runway was built in Clermont-Ferrand in France, allowing local company Michelin to manufacture Bréguet Aviation military aircraft. In January 1919, aviation pioneer Orville Wright underlined the need for "distinctly marked and prepared landing places, the preparing of the surface of reasonably flat ground an expensive undertaking there would be a continuous expense for the upkeep." Runways are named by a number between 01 and 36, the magnetic azimuth of the runway's heading in decadegrees. This heading differs from true north by the local magnetic declination.

A runway numbered 09 points east, runway 18 is south, runway 27 points west and runway 36 points to the north. When taking off from or landing on runway 09, a plane is heading around 90°. A runway can be used in both directions, is named for each direction separately: e.g. "runway 15" in one direction is "runway 33" when used in the other. The two numbers differ by 18. For clarity in radio communications, each digit in the runway name is pronounced individually: runway one-five, runway three-three, etc.. A leading zero, for example in "runway zero-six" or "runway zero-one-left", is included for all ICAO and some U. S. military airports. However, most U. S. civil aviation airports drop the leading zero. This includes some military airfields such as Cairns Army Airfield; this American anomaly may lead to inconsistencies in conversations between American pilots and controllers in other countries. It is common in a country such as Canada for a controller to clear an incoming American aircraft to, for example, runway 04, the pilot read back the clearance as runway 4.

In flight simulation programs those of American origin might apply U. S. usage to airports around the world. For example, runway 05 at Halifax will appear on the program as the single digit 5 rather than 05. If there is more than one runway pointing in the same direction, each runway is identified by appending left and right to the number to identify its position —for example, runways one-five-left, one-five-center, one-five-right. Runway zero-three-left becomes runway two-one-right. In some countries, regulations mandate that where parallel runways are too close to each other, only one may be used at a time under certain conditions. At large airports with four or more parallel runways, some runway identifiers are shifted by 1 to avoid the ambiguity that would result with more than three parallel runways. For example, in Los Angeles, this system results in runways 6L, 6R, 7L, 7R though all four runways are parallel at 69°. At Dallas/Fort Worth International Airport, there are five parallel runways, named 17L, 17C, 17R, 18L, 18R, all oriented at a heading of 175.4°.

An airport with only three parallel runways may use different runway identifiers, such as when a third parallel runway was opened at Phoenix Sky Harbor International Airport in 2000 to the south of existing 8R/26L — rather than confusingly becoming the "new" 8R/26L it was instead designated 7R/25L, with the former 8R/26L becoming 7L/25R and 8L/26R becoming 8/26. Runway designations may change over time because Earth's magnetic lines drift on the surface and the magnetic direction changes. Depending on the airport location and how much drift occurs, it may be necessary to change the runway designation; as runways are designated with headings rounded to the nearest 10°, this affects some runways sooner than others. For example, if the magnetic heading of a runway is 233°, it is designated Runway 23. If the magnetic heading changes downwards by 5 degrees to 228°, the runway remains Runway 23. If on the other hand the original magnetic heading was 226°, the heading decreased by only 2 degrees to 224°, the runway becomes Runway 22.

Because magnetic drift itself is slow, runway designation changes are uncommon, not welcomed, as they require an accompanying change in aeronautical charts and descriptive documents. When runway designations do change at major airports, it is changed at night as taxiway signs need to be changed and the huge numbers at each end of the runway need to be repainted to the new runway designators. In July 2009 for example, London Stansted Airport in the United Kingdom changed its runway designations from 05/23 to 04/22 during the night. For fixed-wing aircraft, it is advantageous to perform takeoffs and landings into the wind to reduce takeoff or landing roll and reduce the ground speed needed to attain flying speed. Larger airports have several runways in different directions, so that one can be selected, most n

Three Way

Three Way is a 2004 neo-noir crime thriller film directed by Scott Ziehl and starring Dominic Purcell, Joy Bryant, Ali Larter, Desmond Harrington, Dwight Yoakam, Gina Gershon. The plot, based on Gil Brewer's pulp novel Wild To Possess, concerns a kidnapping plot; the film was released with titles 3-way and Three Way Split. The film starts in San Diego. Lew finds out, he finds both of them dead in the bed. He fears that the police would suspect him because he has had a bad past, so he dumps the bodies and his gun in the sea along with his boat, he leaves for a new life. Lew gets a new girlfriend Rita. One evening while erecting a signboard on the side of a road, he overhears Isobel and Ralph discussing the kidnapping and murder plot of Ralph's wife Florence, he soon plots his own plan to pinch the ransom. At the same time, brother of the man Lew's wife had affair with, comes following Lew thinking that Lew murdered his brother. Ralph keeps her in a boat. Lew takes Florence away from the boat, he phones Ralph anonymously, threatening to call police unless he cuts him in for half the ransom money.

Ralph agrees. Ralph and Isobel suspect that it is Florence who has some accomplice of her own and is blackmailing them. Lew sends Rita to get the money from Ralph, but Lew's plans turns awry when Herbert kills Florence. When Rita comes back she shoots him dead, she finds that the money she brought from Ralph is fake. Lew goes to Ralph to ask them about the real money. In the meanwhile Rita tips the police. Soon police comes and arrests Lew and Isobel. Lew is released on the verdict of Rita. Dominic Purcell as Lewis'Lew' Brookbank Joy Bryant as Rita Caswell Ali Larter as Isobel Delano Desmond Harrington as Ralph Hagen Dwight Yoakam as Herbert Claremont Gina Gershon as Florence DeCroix Hagen Roxana Zal as Janice Brookbank Dan Martin as Patrolman Three Way on IMDb

Affinity laws

The affinity laws for pumps/fans are used in hydraulics, hydronics and/or HVAC to express the relationship between variables involved in pump or fan performance and power. They apply to pumps and hydraulic turbines. In these rotary implements, the affinity laws apply both to axial flows; the laws are derived using the Buckingham π theorem. The affinity laws are useful as they allow prediction of the head discharge characteristic of a pump or fan from a known characteristic measured at a different speed or impeller diameter; the only requirement is that the two pumps or fans are dynamically similar, the ratios of the fluid forced are the same. It is required that the two impellers' speed or diameter are running at the same efficiency. Law 1. With impeller diameter held constant: Law 1a. Flow is proportional to shaft speed: Q 1 Q 2 = 1 Law 1b. Pressure or Head is proportional to the square of shaft speed: H 1 H 2 = 2 Law 1c. Power is proportional to the cube of shaft speed: P 1 P 2 = 3 Law 2. With shaft speed held constant: Law 2a.

Flow is proportional to the cube of the impeller diameter: Q 1 Q 2 = 3 Law 2b. Pressure or Head is proportional to the square of the impeller diameter: H 1 H 2 = 2 Law 2c. Power is proportional to the fifth power of the impeller diameter: P 1 P 2 = 5 where Q is the volumetric flow rate D is the impeller diameter N is the shaft rotational speed H is the pressure or head developed by the fan/pump P is the shaft power; these laws assume that the pump/fan efficiency remains constant i.e. η 1 = η 2, exactly true, but can be a good approximation when used over appropriate frequency or diameter ranges. The exact relationship between speed and efficiency depends on the particulars of the individual fan or pump design. Product testing or computational fluid dynamics become necessary if the range of acceptability is unknown, or if a high level of accuracy is required in the calculation. Interpolation from accurate data is more accurate than the affinity laws; when applied to pumps the laws work well for constant diameter variable speed case but are less accurate for constant speed variable impeller diameter case.

For radial flow centrifugal pumps, it is common industry practice to reduce the impeller diameter by "trimming", whereby the outer diameter of a particular impeller is reduced by machining to alter the performance of the pump. In this particular industry it is common to refer to the mathematical approximations that relate the volumetric flow rate, trimmed impeller diameter, shaft rotational speed, developed head, power as the "affinity laws"; because trimming an impeller changes the fundamental shape of the impeller, the relationships shown in Law 2 cannot be utilized in this scenario. In this case the industry looks to the following relationships, a better approximation of these variables when dealing with impeller trimming. With shaft speed held constant and for small variations in impeller diameter via trimming: The volumetric flow rate varies directly with the trimmed impeller diameter: Q 1 Q 2 = 1 The pump developed head (the