2.3 Control of Communications

Control means who runs the exchange

“Control of communications” is not the same as aircraft command for flight path, and it is not the same as message priority. Priority decides which type of message may preempt others. Control decides which station directs the order of work on the channel: when to talk, which frequency to use, how long to continue, and when to suspend. RIC-21 §4.3 sets clear default rules and equally clear exceptions for distress and urgency.

Rule 1 — Aircraft comply with the ground station (normal operations)

In communications between aeronautical ground stations and aircraft stations, the aircraft station shall comply with instructions given by the ground station in all matters relating to:

• the order and time of transmission;
• the choice of frequency; and
• the duration and suspension of communications.

In plain language: when you are talking to tower, ground, terminal, centre, a flight service station, or “Ottawa Radio” type facilities, the ground station sequences you. If they say “standby,” you standby. If they say “go ahead on tower frequency 122.1,” you change and answer there. If they suspend communications, you stop transmitting on that exchange as instructed.

Why ground control is the default

Ground stations manage many aircraft on shared frequencies. Central sequencing prevents two aircraft from transmitting at once, keeps working frequencies organized, and matches traffic flow to controller or radio-operator workload. The ROC-A exam expects you to accept this hierarchy for normal ops.

Critical exception — distress and urgency

The compliance rule does not apply in cases of distress or urgency communications. In those cases, control lies with the station initiating the priority call.

That means:

• The aircraft (or other station) that starts a MAYDAY or PAN PAN exchange controls that priority traffic for control purposes under §4.3.
• Ground stations still provide essential services, but they do not use ordinary sequencing rules to block or re-time distress/urgency initiations the way they would a routine call.
• This aligns with priority levels 1 and 2 in §4.1: life-safety traffic must not be delayed by routine control mechanics.

Exam phrasing to watch: “Who controls communications in a distress situation?” → the station initiating the distress (priority) call—not automatically the tower simply because it is a ground station.

Rule 2 — Who is in charge of the aircraft station

RIC-21 states: the operation of an aircraft station is under the control of the pilot or another person in charge of the station.

Implications:

• Radio operation on the aircraft is a responsibility assigned to the pilot-in-command or the person designated in charge of the station—not a free-for-all for every occupant with a headset.
• Students and passengers may be allowed to practice only under that control framework; the legal control still rests with the pilot or person in charge.
• For multi-crew aircraft, procedures may designate who keys the mic, but the RIC-21 statement remains: control of the station sits with the pilot or person in charge.

Rule 3 — Ground retains control with aircraft; between aircraft, the called station controls

RIC-21 draws a clean distinction:

Aircraft-to-aircraft control

When one aircraft calls another, the called aircraft controls the exchange. That prevents the calling aircraft from forcing a frequency or long monologue on a busy peer. The called station can accept the proposed working frequency or assign a different one.

Working frequency agreement (RIC-21 procedure)

If the station called agrees with the calling station, it transmits an indication that from that moment it will listen on the working frequency or channel announced by the calling station.

If the station called does not agree on the working frequency or channel, it transmits an indication of the working frequency or channel to be used instead.

So: proposal by caller → acceptance or counter-assignment by the station that has control (ground, or the aircraft being called).

Official RIC-21 examples (learn the pattern)

(a) Ground station calling an aircraft — ground has control

PIPER CHARLIE FOXTROT X-RAY QUEBEC QUEBEC
THIS IS
OTTAWA RADIO
GO AHEAD ON TOWER FREQUENCY ONE TWO TWO DECIMAL ONE
OVER

Teaching point: Ottawa Radio (ground) directs the aircraft to the working frequency (122.1). The aircraft is expected to comply.

(b) Aircraft calling a ground station — ground still has control

OTTAWA RADIO
THIS IS
PIPER CHARLIE FOXTROT X-RAY QUEBEC QUEBEC
ON FREQUENCY ONE TWO TWO DECIMAL ONE
OVER

Teaching point: Even though the aircraft initiates the call, control remains with the ground station in normal ground–air work. The aircraft states the frequency it is on so the ground station can manage the contact; the aircraft does not “take control” merely by calling first.

(c) One aircraft to another — the aircraft being called has control

CESSNA CHARLIE FOXTROT X-RAY QUEBEC TANGO
THIS IS
PIPER CHARLIE FOXTROT X-RAY QUEBEC QUEBEC
ON FREQUENCY ONE ONE NINE DECIMAL SEVEN
OVER
PIPER CHARLIE FOXTROT X-RAY QUEBEC QUEBEC
THIS IS
CESSNA CHARLIE FOXTROT X-RAY QUEBEC TANGO
CHANGE TO SEARCH AND RESCUE FREQUENCY ONE TWO THREE DECIMAL SIX
OUT

Teaching point: Piper calls Cessna on 119.7, but Cessna (the called station) directs a change to SAR frequency 123.6. That is control by the station being called.

Integrating control with other §4 rules

• Priority (§4.1): A ground station can sequence routine traffic, but distress/urgency still outrank everything; initiating stations control those priority calls.
• Privacy (§4.2): Control procedures do not authorize public disclosure of protected communications.
• Interference (§4.4): You must not interrupt another station except for higher-priority traffic—control is not a licence to walk over ongoing communications without a priority basis.

Common exam scenarios

Scenario 1. Tower says “Standby.” You want to pass company traffic. Correct action: comply—order/time of transmission is controlled by the ground station.

Scenario 2. You declare PAN PAN. Who controls that urgency exchange under §4.3? You (the initiating station), not ordinary ground sequencing rules.

Scenario 3. Aircraft A calls Aircraft B and proposes 122.8. Aircraft B wants 123.6. Who decides? Aircraft B (being called).

Scenario 4. Student asks whether the first station to speak always controls. Answer: No. Between air and ground, ground normally controls even if the aircraft called first. Between aircraft, the called station controls. In distress/urgency, the initiator controls.

Study checklist

1. List the three subject matters of ground instructions: order/time, frequency, duration/suspension.
2. State the distress/urgency exception: initiating station controls.
3. State aircraft station responsibility: pilot or person in charge.
4. Contrast ground–air vs air–air control.
5. Reconstruct the Ottawa Radio / Piper / Cessna examples: who assigned 122.1, who stated 122.1 when calling, who ordered 123.6.

Mastering control prevents both exam errors and real-world frequency chaos—especially at uncontrolled fields where pilots must still apply air-to-air control logic correctly when coordinating with other aircraft.