Vertical Speed

This article describes the use of vertical speed (rates of climb and descend) by air traffic controllers to control the traffic flow and solve conflicts. It describes the general procedures, typical applications and associated risks. It also gives some advice on the use of this method by air traffic controllers. Note that any part of this article is not intended to act as or replace any existing local procedures.

Description

In order to facilitate a safe and orderly flow of traffic, aircraft may be instructed to adjust rate of climb or rate of descent. Vertical speed adjustments should be limited to those necessary to establish and/or maintain a desired separation minimum. Instructions involving frequent changes of climb/descent rates should be avoided.

Climbing/descending aircraft may be instructed to maintain a specified rate of climb/descend, a rate of climb/descent equal to or greater than a specified value or a rate of climb/descent equal to or less than a specified value.

An aircraft may be instructed to expedite climb or descent as appropriate to or through a specified level, or may be instructed to reduce its rate of climb or rate of descent.

Aircraft must be advised when a rate of climb/descent restriction is no longer required. The flight crew must inform the ATC unit concerned if unable, at any time, to comply with a specified rate of climb or descent.

Phraseology

The vertical speed clearance may be a part of a vertical clearance or a separate one. It specifies the required rate of climb/descent, usually in feet per minute and may also contain:

• upper or lower limit of the vertical speed, if applicable. The phrases "or greater" and "or less" are used in this case. If no limit is specified, then the aircraft is expected to maintain an exact vertical speed.
• a condition, if applicable (e.g. until passing a level or a point)
• further information (e.g. reason for the restriction, e.g. traffic, special use area, etc.)

PRE078 climb FL 370 at 1000 feet per minute or greater until passing FL 360 due crossing traffic.

Typical Uses

Accomodation of climb requests
Separation of departing and arriving traffic
Descending arriving aircraft below the overflying traffic
Vertical sequencing, i.e. establishing and maintaining vertical separation between two (or more) climbing or two (or more) descending aircraft
Corrective action (e.g. when the unrestricted vertical speed is considered insufficient)