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 290 (29,000 ft) and flight level 410 (41,000 ft). Expressed in the

International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...

(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 Controlled airspace is airspace of defined dimensions within which air traffic control (ATC) services are provided. The level of control varies with different classes of airspace. Controlled airspace usually imposes higher weather minimums tha ...

Historical background

In 1958 the standard vertical separation of aircraft in

was set at 1,000 feet 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 also ...

or sea level to flight level 290, and at 2,000 feet above flight level 290. The larger minimum separations at higher altitudes was necessary because the accuracy of altimeters, 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 computers (ADCs), altimeters, and autopilot systems became sufficiently accurate to safely reduce the vertical separation minimum.

Implementation

Between 1997 and 2005 RVSM was implemented in all of Europe, North Africa, Southeast Asia and

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, South America, and over the

North 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 and ...

, South Atlantic, and Pacific Oceans. 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 implemented metric RVSM on 21 November 2007. But the Hong Kong

FIR Firs (''Abies'') are a genus of 48–56 species of evergreen coniferous trees in the family (biology), family Pinaceae. They are found on mountains throughout much of North America, North and Central America, Europe, Asia, and North Africa. The ...

continued to use flight levels in feet. The Russian Federation implemented RVSM and flight levels in feet on November 17, 2011. However, in some FIRs, meters are still in use below

transition 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 ...

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 A general officer is an officer of high rank in the armies, and in some nations' air forces, space forces, and marines or naval infantry. In some usages the term "general officer" refers to a rank above colonel."general, adj. and n.". OED On ...

(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