AIM - RAC 1. 7 ATC Clearances, Instructions and Information

Whenever an ATC clearance is received and accepted by the pilot, compliance shall be
made with the clearance. If a clearance is not acceptable, the pilot should immediately
inform ATC of this fact since acknowledgement of the clearance alone will be taken
by a controller as indicating acceptance. For example, upon receiving a clearance for
takeoff, the pilot should acknowledge the clearance and take off without undue delay
or, if not ready to take off at that particular time, inform ATC of his or her intentions,
in which case the clearance may be changed or cancelled.

A pilot shall comply with an ATC instruction that is directed to and received by the
pilot, provided the safety of the aircraft is not jeopardized.

A clearance will be identified by the use of some form of the word “clear” in its
contents. An instruction will always be worded in such a manner as to be readily
identified, although the word “instruct” will seldom be included. Pilots shall comply
with and acknowledge receipt of all ATC instructions directed to and received by them
(CAR 602.31).

CAR 602.31 permits pilots to deviate from an ATC instruction or clearance in order to
follow TCAS/ACAS resolution advisories. Pilots responding to a resolution advisory
shall advise the appropriate ATC unit of the deviation as soon as practicable and shall
expeditiously return to the last ATC clearance received and accepted, or the last ATC
instruction received and acknowledged prior to the resolution advisory manoeuvre.
Aircraft manoeuvres conducted during a resolution advisory should be kept to the
minimum necessary to satisfy the resolution advisory. For more information on TCAS/
ACAS, see RAC 12.15.2.

ATC is not responsible for the provision of IFR separation to an IFR aircraft which
carries out a TCAS or an ACAS resolution advisory manoeuvre until one of the
following conditions exist:

(a)             the aircraft has returned to the last ATC clearance received and accepted, or last
                 ATC instruction received and acknowledged prior to the resolution advisory; or

(b)             an alternate ATC clearance or instruction has been issued.

TCAS or ACAS does not alter or diminish the pilot-in-command’s responsibility to
ensure safe flight. Since TCAS/ACAS does not respond to aircraft which are not
transponder-equipped or aircraft with a transponder failure, TCAS/ACAS alone does
not ensure safe operation in every case. The services provided by ATC units are not
predicated upon the availability of TCAS or ACAS equipment in an aircraft.
It should be remembered that control is predicated on known air traffic only and, when
complying with clearances or instructions, pilots are not relieved of the responsibility
for practising good airmanship.

A clearance or instruction is only valid WHILE IN CONTROLLED AIRSPACE.
Pilots crossing between controlled and uncontrolled airspace should pay close
attention to the terrain and obstacle clearance requirements.
ATS personnel routinely inform pilots of conditions, observed by others or by
themselves, which may affect flight safety and are beyond their control. Examples of
such conditions are observed airframe icing and bird activity. These are meant solely
as assistance or reminders to pilots and are not intended in any way to absolve the pilot
of the responsibility for the safety of the flight.