What is Flight Level (FL) ?

Vertical positioning of aircraft when at or below the transition altitude is expressed in terms of altitude whereas such positioning at or above the transition level is in terms of flight levels.

Note: While passing through the transition layer, vertical positioning is expressed in terms of altitude when descending, and in terms of flight level when ascending. Flight level 0 (zero) is located at the atmosphere pressure level of 1013.2 hectopascals. Consecutive flight levels are separated by 500 feet.

What is RVSM?

RVSM is a concept introduced by ICAO in 1982 and adopted in various parts of the world between 1997 to 2005 which resulted in reduction in the requirement of minimum vertical separation between aircrafts above FL290 to FL 410 (included) from 2,000 feet to 1,000 feet.

Why RVSM was introduced?

The main reasons behind implementation of RVSM are :

  • A theoretical doubling of the airspace capacity, between FL290 and FL410; and
  • The opportunity for aircraft to operate at closer to the optimum flight levels resulting in lesser fuel consumption.

This program basically depends on the serviceability of specified aircraft equipment and the existence of appropriate operating procedures to ensure that the risk of loss of separation is no greater than it would be outside RVSM airspace.

Within RVSM airspace (between FL290 and FL410 inclusive) the vertical separation minimum is:

  • 1000ft (300m) between RVSM-approved aircraft group, and
  • 2000ft (600m) between non-RVSM approved aircraft group and any other aircraft operating within RVSM airspace.
  • 2000ft (600m) between non-RVSM aircraft operating as general air traffic (GAT) and any other aircraft within RVSM airspace.

Approval for aircrafts operating in RVSM

(a) The applicant for authorization is required to submit the appropriate data package for aircraft approval. The package must consist of at least the following:
1. An identification of the RVSM aircraft group or the nongroup aircraft.
2. A definition of the RVSM flight envelopes applicable to the subject aircraft.
3. Documentation that establishes compliance with the applicable RVSM aircraft requirements.
4. The conformity tests used to ensure that aircraft approved with the data package meet the RVSM aircraft requirements.

(b) Altitude-keeping equipment:
1. The aircraft must be equipped with two operational independent altitude measurement systems.
2. The aircraft must be equipped with at least one automatic altitude control system that controls the aircraft altitude.
3. The aircraft must be equipped with an altitude alert system that signals an alert when the altitude displayed to the flight crew deviates from the selected altitude.

Authorization Procedures

(i) Periodic inspections, functional flight tests, and maintenance and inspection procedures, with acceptable maintenance practices, for ensuring continued compliance with the RVSM aircraft requirements.
(ii) A quality assurance program for ensuring continuing accuracy and reliability of test equipment used for testing aircraft to determine compliance with the RVSM aircraft requirements.
(iii) Validation and Demonstration: The operator must provide evidence that:
a. It is capable to operate and maintain each aircraft or aircraft group for which it applies for approval to operate in RVSM airspace.
b. Each pilot has an adequate knowledge of RVSM requirements, policies, and procedures.

Note: Each operator requesting a clearance to operate within RVSM airspace shall correctly annotate the flight plan filed with air traffic control with the status of the operator and aircraft with regard to RVSM approval. Each operator shall verify RVSM applicability for the flight planned route through the appropriate flight planning information sources.

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