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Transport Canada - Aviation Safety Letter Airmanship rules supreme in the circuit - ISSUE 4/2009

Airmanship rules supreme in the circuit - ISSUE 4/2009

It’s much safer for everyone if we all follow the same procedures for joining the circuit at uncontrolled aerodromes. The Transport Canada Aeronautical Information Manual (TC AIM) states:

“...aircraft should approach the traffic circuit from the upwind side...Alternatively once the pilot has ascertained without any doubt that there will be no conflict with other traffic entering the circuit or traffic established within the circuit, the pilot may also join the circuit on the downwind leg (Figure 4.6).”

I don’t like this statement because it seems to imply that conflicts with other traffic are only a concern when joining the circuit straight onto the downwind leg. This is clearly wrong. Every time I read this (and look at Figure 4.6), I wonder if it means that we can join the circuit from the upwind side even if there will be a conflict. I certainly doubt that is the intent of the TC AIM.

So what do the Canadian Aviation Regulations (CARs) say? Here are the four most applicable regulations for this discussion, found in CARs 602.19 and 602.96, about right of way and operating an aircraft on, or in the vicinity of, an aerodrome (controlled or not). These are my words, not the CARs.

  • When two aircraft are converging at approximately the same altitude, the pilot-in-command of the aircraft that has the other on its right shall give way—CAR 602.19(2)
  • Before landing or taking off, the pilot must be satisfied that there will be no risk of collision with other aircraft or vehicles and that the aerodrome is suitable for his intended operation—CAR 602.96(2)
  • The pilot must observe the traffic circuit so as to avoid a collision—CAR 602.96(3)(a)
  • The pilot must conform to, or avoid, the circuit made by other aircraft operating at the airport—CAR 602.96(3)(b)

The CARs do not state that one must join the circuit from the upwind side, or on the downwind leg, or from anywhere in particular; nor do the CARs relieve pilots entering or established in the circuit of their right-of-way obligations under CAR 602.19(2).

Nowhere in the CARs does it say that traffic established in the circuit can ignore the right-of-way rules; still, the CARs do require all pilots to avoid collisions in spite of who has the right of way.

Therefore, according to the CARs, pilots joining a standard left-hand circuit from the upwind side or on crosswind who see traffic on the downwind, that is, on their right, should give way in accordance with CAR 602.19(2). If, on the other hand, the aerodrome has a right-hand circuit, then the pilot on downwind will have any traffic arriving from the upwind side on his right. If there is a risk of collision in this situation, again according to CAR 602.19(2), the pilot joining from the upwind side has the right of way over traffic already on downwind.

Needless to say, pilots should do their utmost to avoid joining a right-hand circuit in such a situation, and forcing their fellow pilot already established in downwind to give way. In fact, pilots should avoid joining any circuit at the upwind entry if there is any possibility of a conflict, no matter if it’s a right or left pattern.

The statement in the TC AIM about avoiding conflicts when joining the circuit on the downwind leg must apply equally to all situations when joining the circuit, not just joining on the downwind leg. The CARs clearly require us to observe the traffic circuit so as to avoid a collision, and require us to conform to, or avoid, the circuit made by other aircraft operating at the airport. It further requires that we ensure that we will not risk collision with other traffic, no matter how one chooses to join the circuit.

On a related note, pilots doing circuits should give way to traffic joining straight onto the downwind by extending their climb straight out a little farther from the airport for separation. If there is traffic on downwind and they turn crosswind, they risk collision with that traffic (thereby contravening CAR 602.19). I believe it is better to climb straight out farther from the aerodrome for separation than it is to ultimately extend the downwind leg far past the airport because of traffic ahead. A case study which illustrates the perils of extending the downwind leg too far is the midair collision at Mascouche, Que., in December 1997 (read it at aviation/1997/a97q0250/a97q0250.asp). The 5.8-mi. downwind leg by the Cessna 150 stretched outside the aerodrome’s five-mile zone. Good airmanship suggests we follow the circuit-joining procedures as laid-out in the TC AIM, but perhaps the wording should be fixed to reflect more closely the CARs. We are better off if we all follow the recommended procedures, as it is better to know what the other pilot is likely to do and vice versa.

Michael Shaw
Captain COPA Flight 8
Ottawa, Ont.

Thank you for writing to us. Your comments are appreciated and will be considered in an upcoming revision of the TC AIM. —Ed.


This article was published by Transport Canada in TP 185E -. Reprinted with permission

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