Reduced Vertical Separation Minima or Minimum (RVSM) is an aviation term used to define the decrease of the standard vertical separation prerequisite among aircraft flying between FL290 (29,000 ft.)and FL410 (41,000 ft) inclusive, from 2,000 feet to 1,000 feet (or between 8,850 metres and 12,500 metres from 600 metres to 300 metres). It then rises the number of aircraft that can securely fly in a specific capacity of airspace.
Generally, standard vertical separation is 1,000 feet above ground to FL290, and 2,000 feet from FL290 to FL410. It is because the precision of the pressure altimeter lowers with height. Nowadays, Air Data Computers (ADCs) jointly with altimeters have developed to be more precise and autopilots more clever at keeping a set level. Thus, the 2,000 feet separation became too much for some modern aircrafts. That is why ICAO planned to reduce to 1,000 feet.
In the USA, RVSM is called as the Domestic Reduced Vertical Separation Minimum (DRVSM) (Wikipedia, 20121).
RVSM was introduced in North Africa, South America, Southeast Asia, North America, all of Europe and over the Pacific Oceans, South Atlantic and North Atlantic from 1997 to 2005. First, the North Atlantic introduced between FL330 and FL370 in March 1997. On 24 January 2002, RVSM of 1,000 feet separation was introduced by all European and North African countries. Russian Federation introduced Flight Levels and RVSM in feet on 17 November 2011. However, meters are still used below transition level. China and Mongolia implemented RVSM in metres.
RVSM offers six more cruising levels from FL 290 to FL 410, significantly reducing in-flight delays and fuel costs (Wikipedia, 20121).
|RVSM Airspace (image embedded from EuroControl on 10 August 2012)|
In RVSM airspace, only airplanes with specially qualified autopilots and altimeters can fly. Other airplanes should fly below or above the airspace, or seek out exceptional exclusion from the requirements. In addition, airlines must have particular endorsement from the aircraft's State of registry in order to fly in RVSM airspace. 2,000 feet vertical separation is constantly provided between the RVSM flights and non-RVSM flights, and all others during the climb/descent.
State aircraft which includes military, police service and customs aircraft are excluded from the requirement to be RVSM approved (Wikipedia, 20121).
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- This Wikipedia page provides more details about this occurrence.