The flight levels these days are awfully crowded with corporate jet traffic, airliners, and now even the new very light jets. All this traffic means congestion and delays are more commonplace than anyone wishes them to be. One method used to reduce this congestion and inherent delays in some flight levels is called RVSM, or reduced vertical separation minimums.
Previously the flight levels had a vertical separation of 2,000 feet between aircraft. By reducing this to 1,000 feet, the capacity of the domestic airspace in North America essentially doubled. Beginning at FL290 and extending up
to and including FL410, RVSM covers the entire domestic United States, Canada, Mexico, and throughout Europe and Asia.
By reducing the vertical separation to 1,000 feet, the capacity of the domestic airspace in North America is essentially doubled.
A few of the proponents that allowed RVSM to become a reality were technological advancements in traffic avoidance and barometric altimeters. Higher sensitivity in altimeters proved to be reliable enough to reduce the separation safely to 1,000 feet.
Specifically the advent and broad use of air data computers—the proliferation of traffic collision avoidance equipment and vast improvements in the technology that drives it. In the near future, advances in air traffic control will provide even better display and control of aircraft that will likely further reduce separation minimums, such as next generation technology ADS-B (automatic dependent surveillance broadcast).
Certain equipment requirements must be met prior to entering RVSM airspace, unless a specific waiver is granted. Two primary altimeters, autopilot, altitude hold with an altitude alerter, and a mode C transponder are required. Depending on aircraft certification, an installed and operable TCAS system may also be required. Along with aircraft equipment, aircrew training is also required for operation inside of RVSM airspace.
While operating in RVSM airspace, it is important to not overshoot assigned altitudes because of the reduced separation. When approaching a cleared flight level, vertical speed should be restrained between 500 to 1,000 feet per minute and not exceed 1,500 feet per minute.
At no time should the aircraft be allowed to deviate more than 150 feet from an assigned flight level without manual intervention. These feet per minute (fpm) tolerances and strict level-off requirements stem not only from separation standards but also help prevent undesired TCAS resolution advisories.
For the purpose of precision altitude keeping, the autopilot should be used to capture assigned altitudes and during level flight unless turbulence or aircraft re-trimming require otherwise.
Coupled with the technology and the training required, RVSM is a safe and effective way to reduce congestion and increase capacity for the valuable airways of the sky.
