Altimeter Setting and Standard Pressure Region

Altimeter Setting Region

The altimeter setting region is an airspace of defined dimensions below 18,000 feet ASL within which the following altimeter setting procedures apply:

Departure – Prior to takeoff, the pilot shall set the aircraft altimeter to the current altimeter setting of that aerodrome or, if that altimeter setting is not available, to the elevation of the aerodrome.
En route – During flight the altimeter shall be set to the current altimeter setting of the nearest station along the route of flight or, where such stations are separated by more than 150 NM, the nearest station to the route of flight.
Arrival – When approaching the aerodrome of intended landing the altimeter shall be set to the current aerodrome altimeter setting, if available.

Standard Pressure Region

The standard pressure region includes all airspace over Canada at or above 18,000 feet ASL (the high-level airspace), and all low-level airspace that is outside of the lateral limit of the altimeter setting region. Within the standard pressure region the following flight procedures apply:

General – Except as otherwise indicated below, no person shall operate an aircraft within the standard pressure region unless the aircraft altimeter is set to standard pressure, which is 29.92 inches of mercury.
Departure – Prior to takeoff the pilot shall set the aircraft altimeter to the current altimeter setting of that aerodrome or, if the altimeter setting is not available, to the elevation of that aerodrome. Immediately prior to reaching the flight level at which flight is to be conducted, the altimeter shall be set to standard pressure (29.92 inches of mercury). If the planned cruising flight level is above FL 180, resetting the altimeter to 29.92 inches of mercury at 18,000 feet ASL is acceptable.
Arrival – Prior to commencing descent with the intention to land, the altimeter shall be set to the current altimeter setting of the aerodrome of intended landing, if available. However, if a holding procedure is conducted, the altimeter shall not be set to the current aerodrome altimeter setting until immediately prior to descending below the lowest flight level at which the holding procedure is conducted. Pilots of aircraft descending from cruising flight levels above FL 180 may reset altimeters to the current altimeter setting of the aerodrome of intended landing when approaching FL 180 provided no holding or cruise level flight below FL 180 is to be made or anticipated.

Transition

Except as otherwise authorized by ATC, aircraft progressing from one region to another shall make the change in the altimeter setting while within the standard pressure region prior to entering, or after leaving, the altimeter setting region.

If the transition is to be made into the altimeter setting region while in level cruising flight, the pilot should obtain the current altimeter setting from the nearest station along the route of flight as far as practical before reaching the point at which the transition is to be made. When climbing from the altimeter setting region into the standard pressure region, pilots shall set their altimeters to standard pressure immediately after entering the standard pressure region. When descending into the altimeter setting region, pilots shall set their altimeters to the appropriate station altimeter setting immediately prior to descending into the altimeter setting region. Normally, the pilot will receive the appropriate altimeter setting as part of the ATC clearance prior to descent. If it is not incorporated in the clearance, it should be requested by the pilot.

**Altimeter Setting and Standard Pressure Regions**
^{_{Transport Canada – Aeronautical Information Manual}}

References

AIM RAC 2.10 Altimeter Setting Region
AIM RAC 2.11 Standard Pressure Region
CAR 602.35 Altimeter Setting and Operating Procedures in the Altimeter Setting Region
CAR 602.36 Altimeter Setting and Operating Procedures in the Standard Pressure Region
CAR 602.37 Altimeter Setting and Operating Procedures in Transition between Regions