Reduced vertical separation minimum (RVSM) is the reduction, from 2,000 feet to 1,000 feet, of the standard vertical separation required between aircraft flying between

flight level In aviation and aviation meteorology, a flight level (FL) is an aircraft's altitude at standard air pressure, expressed in hundreds of feet. The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25 hPa ...

290 (29,000 ft) and flight level 410 (41,000 ft). Expressed in the International System of Units (SI), it is the reduction, from 600 m to 300 m, of required vertical separation of aircraft between altitudes 8,850 and 12,500 m. This reduction in vertical separation minimum therefore increases the number of aircraft that can fly in a particular volume of controlled airspace.

Historical background

In 1958 the standard vertical separation of aircraft in controlled airspace was set at 1,000

feet The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made ...

from

ground level Ground level may refer to: * Earth's surface * Storey of a building/structure on (level with) the ground; also called the "ground floor" * Ground Level, Australian band * "Ground Level", a song by Stereo MCs from the album ''Connected'' See als ...

sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardise ...

290, and at 2,000 feet above flight level 290. The larger minimum separations at higher altitudes was necessary because the accuracy of

altimeter An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. The m ...

s, used to determine altitude by measuring air pressure, decreases with height. Efforts to reduce this separation above flight level 290 began almost immediately, but doing so without compromising safety required improvements in altimeters and other equipment, due in part to inherent difficulties in accurately determining and maintaining aircraft altitudes and, therefore, the actual vertical distance between aircraft. It was not until the 1990s that

air data computer An air data computer (ADC) or central air data computer (CADC) computes altitude, vertical speed, air speed, and Mach number from pressure and temperature inputs. It is an essential avionics component found in modern aircraft. This computer, rath ...

s (ADCs), altimeters, and

autopilot An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...

systems became sufficiently accurate to safely reduce the vertical separation minimum.

Implementation

Between 1997 and 2005 RVSM was implemented in all of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

North Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in ...

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...

and North America,

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

, and over the North Atlantic,

South Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

, and

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

s. The North Atlantic implemented initially in March 1997 at flight levels 330 through 370. The entire western hemisphere implemented RVSM FL290–FL410 on January 20, 2005. Africa implemented it on September 25, 2008. The

People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

implemented metric RVSM on 21 November 2007. But the

Hong Kong Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China (abbr. Hong Kong SAR or HKSAR), is a city and special administrative region of China on the eastern Pearl River Delta i ...

FIR continued to use flight levels in feet. The

Russian Federation Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...

implemented RVSM and flight levels in feet on November 17, 2011. However, in some FIRs, meters are still in use below transition level.

Requirements

Only aircraft with specially certified altimeters and autopilots may fly in RVSM airspace, otherwise the aircraft must fly lower or higher than the airspace, or seek special exemption from the requirements. Additionally, aircraft operators (airlines or corporate operators) must receive specific approval from the aircraft's state of registry to conduct operations in RVSM airspace. Non RVSM approved aircraft may transit through RVSM airspace provided they are given continuous climb/descent throughout the designated airspace, and 2,000 ft vertical separation is provided at all times between the non-RVSM flight, and all others for the duration of the climb/descent. "State aircraft", which includes aircraft used in military, customs and police service, are exempted from the requirement to be RVSM approved. Participating states have been requested, however, to adapt their state aircraft for RVSM approval, to the extent possible, and especially those aircraft used for general air traffic (GAT). Equipment Requirements: * 2 Independent Altitude Measuring Systems * SSR (secondary surveillance radar) Altitude Reporting Transponder * Altitude Alert System * Autopilot * Flight Crew Approved Training Program / OpSpecs Approval

References

External links

Altimetry System Error (ASE) and its effects on operations in RVSM airspaceFAA article promoting the new ruleRVSM on SkybraryUse of Trailing Cones for RVSM Certification
Air traffic control 1997 introductions Altitudes in aviation

Historical background

Implementation

Requirements

See also

References

Further reading

External links