Changing Levels

Question 1

When may aircraft be instructed to climb or descent to a level previously occupied by another aircraft?

Answer 1

Provided that:

Vertical separation already exists

The vacating aircraft is proceeding to a level that will maintain vertical separation; and

Either:

A) the controller observes that the vacating aircraft had left the level, or

B) the pilot has reported vacating the level.

Question 2

What should be taken into account when changing levels?

Answer 2

If turbulence exists, delay until vacating aircraft known to be at or through level separated by required minimum

Exercise caution when instructing to climb and descend. Consideration shall be given to fact that aircraft may climb and descend at markedly different rates and if necessary, additional measures such as specifying maximum or minimum descent rate for each aircraft shall be applied to ensure separation is maintained.

Particularly when aircraft concerned in same holding pattern.

Pilots in direct communication with each other may with their concurrence be instructed to maintain a specified vertical separation between aircraft during climb or descent.

Question 3

How may aircraft be instructed to change level?

Answer 3

At a specified time place or rate