AERONAUTICAL INFORMATION CIRCULAR 27/08
CHANGES TO ATC PHRASEOLOGY FOR ALTITUDE ASSIGNMENT

Introduction
The International Civil Aviation Organization (ICAO) publishes standard aviation terms and phrases for use worldwide in the Procedures for Air Navigation Services—Air Traffic Management (PANS-ATM), Document 4444. For the most part, the use of standard terms and phraseology in Canada by air traffic control (ATC) is consistent with those published by ICAO. However, the phraseology currently used by Canadian ATC when issuing altitude instructions is often not in accordance with that recommended by ICAO.
Intention of Circular

The intention of this circular is to inform pilots that NAV CANADA, in its continuing effort to harmonize with international standards and procedures, will be implementing use of the ICAO recommended phraseology when issuing altitude instructions.

1. Climb/Descend/Maintain
Currently, air traffic controllers in Canada routinely use the term MAINTAIN [altitude] when instructing an aircraft to change altitude as well as when instructing an aircraft to maintain the present altitude. Since MAINTAIN [altitude] is internationally understood to mean “remain at” [altitude], this could cause confusion among foreign pilots who might believe that they are at the wrong altitude when instructed to remain at an altitude different from their present altitude. In the near future, NAV CANADA will withdraw use of the term MAINTAIN for altitude change instructions and replace it with the ICAO standard phraseology, CLIMB TO or DESCEND TO [altitude]. The term MAINTAIN [altitude] will continue to be used to indicate maintenance of a level. The phraseology CLIMB TO AND MAINTAIN or DESCEND TO AND MAINTAIN [altitude] might also be used by ATC when considered appropriate.

2. Continue Climb/Descent To, Stop Climb/Descent At
There is currently no phraseology specified in NAV CANADA’s ATC Manual of Operations for amending the assigned altitude of an aircraft that is climbing or descending. The ICAO standard phraseology CONTINUE CLIMB or CONTINUE DESCENT TO [altitude] and STOP CLIMB or STOP DESCENT AT [altitude] will soon be introduced for use by Canadian air traffic controllers for this purpose. Should the climb or descent of an aircraft be interrupted by an instruction to STOP CLIMB or DESCENT AT [altitude], further clearance from ATC must be obtained before resuming climb or descent.

3. When Ready Climb/Descend To
The phraseology AT YOUR/PILOT’S DISCRETION when used by ATC in Canada has mixed meanings. In the case of the uncontrolled movements around an airport, such as push back on the apron or during landing and takeoff from uncontrolled areas, it is used to indicate that the action to be taken is at the “pilot’s responsibility.” In the case of VHF direction-finding service (VDF) cloud breaking procedures, air traffic controllers are required to advise the pilot “that descent into cloud is at the discretion of the pilot,” also indicating that the action is taken at the responsibility of the pilot.

While NAV CANADA’s current ATC Manual of Operations does not specify use of the term AT PILOT’S DISCRETION for altitude change, the term is used by air traffic controllers to indicate that the altitude change is to be commenced at the “pilot’s convenience.” The meaning of the phrase AT PILOT’S DISCRETION as specified in the U.S. Federal Aviation Administration (FAA) Airman’s Information Manual differs from that published in Transport Canada’s Aeronautical Information Manual (AIM). Although this is not the interpretation in Canada, it appears that pilots who fly frequently in the United States sometimes mistakenly assume that the phrase cancels all altitude crossing requirements such as those required in a Standard Terminal Arrival Procedure. Additionally, the phrase is not always understood by foreign pilots and may be difficult to pronounce for those whose first language is not English.

ICAO recommends that the phrase WHEN READY be used to indicate that an altitude change or other action is to be commenced at a time convenient to the pilot. Since this phrase is concise, internationally understood, and less likely to be misinterpreted, WHEN READY will become the standard NAV CANADA phrase as well.

WHEN READY, if used in conjunction with an altitude assignment, means that ATC has offered the pilot the option of starting climb or descent whenever the pilot wishes. Pilots may temporarily level off at any intermediate altitude; however, once an altitude has been vacated, the pilot may not return to that altitude because ATC may have reassigned it to another aircraft. Pilots are expected to advise ATC of any temporary level-off at any intermediate altitude. Compliance with any assigned or published altitude crossing restriction is required unless specifically cancelled by ATC.

Date of Implementation
These phraseology changes will be implemented by NAV CANADA effective 17 July 2008 and included in a future revision to the Transport Canada AIM.

Jerricho wrote:I was of the impression that "pilot's discretion" in the US allowed for leveling off at intermediate altitudes. Can't remember where I read that.

WHEN READY, if used in conjunction with an altitude assignment, means that ATC has offered the pilot the option of starting climb or descent whenever the pilot wishes. Pilots may temporarily level off at any intermediate altitude; however, once an altitude has been vacated, the pilot may not return to that altitude because ATC may have reassigned it to another aircraft. Pilots are expected to advise ATC of any temporary level-off at any intermediate altitude.

(b) If the phrase “at pilot’s discretion” is used in conjunction with an altitude clearance, the change of altitude may be initiated when the pilot decides. When the change is initiated, the pilot should advise ATC. Pilots may temporarily level off at any intermediate altitude; however, pilots should advise ATC of any temporary level-off at any intermediate altitude. Vertical navigation is at the pilot’s discretion; however, adherence to assigned or published altitude crossing restrictions and speeds is mandatory (CAR 602.31 Compliance with Air Traffic Control Instructions and Clearances) unless otherwise cleared. [MEAs are not considered restrictions; however, pilots are expected to remain at or above MEAs].

the_professor wrote:Dave T wrote:
I think we have a better chance of an increase in safety this way than we do expecting poor english pilots to learn more english.



Yes, the best solution to this problem is to simply lower the bar.

If only life were that simple...