Aviation Safety Letter 3/2004

VFR En-route Altitude

by Daniel Morissette. This article is an authorized translation of an article originally published in the January-February 2004 issue of the magazine Aviation Québec.

When giving taxi clearance at a controlled airport, the ground controller often asks what the altitude in flight or the initial altitude in flight will be. Once in flight, and out of the area, the pilot will request, on occasion, to change their cruising altitude.

The pilot may choose their VFR altitude, depending on if they remain in the appropriate class of airspace, notwithstanding the Canadian Aviation Regulations (CARs).

The VFR pilot is responsible for choosing an appropriate altitude for their flight. Air traffic control (ATC) may impose certain restrictions in certain airspaces, for example, in a control area. Example: "No higher than.no lower than." Specific altitudes will be assigned or approved in a class C airspace for improved safety, and to facilitate the exchange and flow of traffic.

Why does the controller want to know your cruising altitude when you are taxiing? They really want to know your intentions so that they can plan their traffic. If you would like to climb to 6 500 ft, they may anticipate a potential conflict with an aircraft arriving on landing. They could order the arriving aircraft to enter the control area at 3 000 ft or higher, and order you to not climb higher than 2 500 ft in the area, until the two aircraft are able to see each other, or until they have passed each other. However, if you would like to fly at only 1 500 ft, the controller's strategy will surely be different.

In VFR flight, outside class C or D airspaces — that is to say in class E or G airspace — you do not require clearance, but must comply with visual flight rules and the CARs on cruising altitudes (see CAR 602.34). However, if you would like to continue with radar surveillance while it is still available, advise the controller of your changes in altitude, and remain on the frequency until you are advised that the radar surveillance is ending, or you advise the controller that you no longer require the service. It has happened in the past that a pilot calls the area control centre (ACC) for radar surveillance and, after having been identified by the controller, leaves the frequency without warning the controller, and never calling back. In this case, the controller was trying in vain to inform the pilot of traffic.

Once you are out of the control area and/or in class C or D airspace, your altitude is at your discretion. It is the pilot's responsibility, if not using radar surveillance, to advise their intentions and changes in altitude on the appropriate frequencies.

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