Joining the Circuit: Uncontrolled Aerodromes

The recommended join, step by step

The TC AIM recommends that powered aircraft "approach the traffic circuit from the non-active side" (RAC 4.5.2). The non-active side is the side of the runway opposite the downwind leg. In a left-hand circuit it is on your right as you look down the landing direction.

1. Descend on the non-active side to circuit altitude. "All descents should be made on the non-active side or well clear of the circuit pattern" (RAC 4.5.2).
2. Cross the runway at midfield, level at circuit altitude. This is the midfield crosswind leg. RAC 4.5.2: "plan the descent to cross the runway in level flight at circuit altitude and maintain that altitude until further descent is required for landing."
3. Turn onto downwind, then base and final. All turns are to the left unless the CFS specifies a right-hand circuit.

Arriving from the active side? Cross the aerodrome first. RAC 4.5.2 recommends "that the crossover be accomplished at least 500 ft above the highest circuit altitude in use". With only the 1,000 ft circuit in use, that is 1,500 ft AAE. Then descend on the non-active side and join as above.

Joining straight onto downwind is the alternative, "if the pilot has ascertained that there will be no conflict with other traffic entering the circuit or established within it" (RAC 4.5.2).

These joins are recommendations, not regulations. RAC 4.5.2 says so plainly: "The ICAO SARPs do not prescribe, nor does Transport Canada regulate, circuit entry." What the CARs do require is in the next section.

In the figure, pick the side you arrive from and the circuit direction, and follow the altitude profile.

What the regulation requires

CARs 602.96 applies at or in the vicinity of any aerodrome, controlled or uncontrolled. Paragraphs (f) and (g) of subsection (3), not quoted here, cover the listening watch and the clearance needed at a controlled aerodrome.

Subsection (4) is about flying over an aerodrome, not joining its circuit: unless you are landing or taking off there, stay at or above 2,000 ft over it unless ATC authorizes otherwise.

Circuit altitudes

RAC 4.5.2 gives these altitudes "Unless a specific traffic circuit altitude is published in the CFS entry for the aerodrome or meteorological conditions dictate otherwise":

AAE means above aerodrome elevation. Your altimeter reads ASL, so add the elevation from the CFS: at an aerodrome 1,200 ft ASL, a 1,000 ft circuit is flown at 2,200 ft ASL, and a crossover 500 ft above it is at 2,700 ft ASL or higher.

Powered aeroplanes must give way to gliders (CARs 602.19, as RAC 4.5.2 reminds pilots), and gliders usually cannot hold altitude in the circuit.

Downwind, 45° and straight-in joins

Which other joins are open depends on where the aerodrome is (RAC 4.5.2):

• Not in an MF area, or in an MF area without airport advisory information: approach from the non-active side. Joining on the downwind leg is the alternative once you have ascertained there will be no conflict.
• In an MF area with airport advisory information: "Aircraft could join the circuit pattern straight-in or at a 45˚ angle to the downwind leg or straight-in to the base or final legs". Watch for VFR traffic joining at those points and for IFR straight-in or circling approaches.

In every case, "Straight-in approaches are discouraged whenever there are other aircraft in the traffic circuit, as it may cause a conflict with other aircraft in the circuit and increase the risk of a mid-air collision" (RAC 4.5.2).

Without a radio, the join is fixed by regulation. A VFR aircraft without the required radio may use an aerodrome in an MF area only with a ground station in operation and prior notice given to it, and on arrival it "enters the aerodrome traffic circuit from a position that will require it to complete two sides of a rectangular circuit before turning onto the final approach path" (CARs 602.97(3)(d)).

MF and ATF: the radio calls

An MF area is "Normally" a circle with a 5 NM radius capped at 3,000 ft AAE, but the dimensions and frequency for each aerodrome are published in the CFS under COMM (TC AIM RAC 4.5.1 and 4.5.4). Inside it you must carry a working radio and keep a listening watch on the MF (CARs 602.97(1) and (2)).

Reports are directed to the ground station if one exists and is in operation, and broadcast otherwise (CARs 602.98(2)). TC AIM RAC 4.5.6 gives the two forms: FREDERICTON RADIO for a directed call, FREDERICTON TRAFFIC for a broadcast.

The first call is made five minutes before entering the MF area, not five minutes before landing or 5 NM from the aerodrome. From a normal 5 NM area at 120 kt, that call is about 15 NM from the aerodrome.

An ATF is normally designated for active uncontrolled aerodromes that do not meet the MF criteria. It is normally the UNICOM frequency, or 123.2 MHz where there is no UNICOM (RAC 4.5.5). The same reports "should also be followed" there (RAC 4.5.7). Where an aerodrome has neither an MF nor an ATF, broadcast on 123.2 MHz (RAC 4.5.1).

Continuous circuits and departing

Continuous circuits. After each takeoff, start the crosswind turn "beyond the departure end of the runway and within 300 ft of the circuit altitude", and reach circuit altitude before joining downwind (RAC 4.5.2). For a 1,000 ft circuit, that is no lower than 700 ft AAE. In an MF area, report joining downwind, on final with your intentions, and clear of the runway (CARs 602.102).

Departing. "Aircraft departing the circuit or aerodrome should climb straight ahead on the runway heading up to the circuit traffic altitude before commencing a turn in any direction to an en route heading." A turn back toward the aerodrome waits until you are "at least 500 ft above the highest circuit altitude in use" (RAC 4.5.2).

Where candidates lose marks

• Descend on the non-active side or well clear of the circuit, never over the active side where downwind traffic is.
• Cross the runway level at circuit altitude when joining from the non-active side, not descending.
• The crossover is 500 ft above the highest circuit in use, which is 2,000 ft AAE if a 1,500 ft circuit is in use.
• AAE is above the aerodrome, not above sea level. Add the field elevation before reading your altimeter.
• Left turns are the default. A right-hand circuit applies only where the CFS specifies it or ATC authorizes it (CARs 602.96(3)(c)).
• 45° and straight-in joins are named for MF areas with airport advisory information. Straight-ins are discouraged whenever others are in the circuit.
• The first MF call is five minutes before entering the area, not five minutes from the aerodrome.

Practice

Original questions in the style of the Transport Canada written exams. Tap an answer to see why it is right or wrong.

1. Question 1 of 4

   You arrive on the active side of an uncontrolled aerodrome, elevation 600 ft ASL. Only the 1,000 ft AAE circuit is in use and you must cross the aerodrome before joining. What is the lowest crossover altitude the TC AIM recommends?

   11,600 ft ASL22,100 ft ASL32,600 ft ASL41,500 ft ASL

   Tap an answer to check it.

2. Question 2 of 4

   Joining the circuit from the non-active side of an uncontrolled aerodrome, how does the TC AIM recommend you cross the runway?

   1At least 500 ft above circuit altitude2Descending through circuit altitude3At 500 ft below circuit altitude4In level flight at circuit altitude

   Tap an answer to check it.

3. Question 3 of 4

   You are flying VFR to an uncontrolled aerodrome inside an MF area. When must you make your first report, where circumstances permit?

   1When you are 5 NM from the aerodrome2At least five minutes before your landing3When joining the aerodrome traffic circuit4At least five minutes before entering the MF area

   Tap an answer to check it.

4. Question 4 of 4

   Which statement about the circuit at an uncontrolled aerodrome is correct?

   1All turns are to the left unless the CFS specifies right turns.2Where there is no UNICOM, the ATF is normally 126.7 MHz.3A straight-in approach is always acceptable once it is announced.4The CARs require every aircraft to join at midfield crosswind.

   Tap an answer to check it.

Other topics