Getting Started
Why This Matters
Radio Comms Protocols
As a remote pilot, you may not be landing on runways or requesting fuel services, but you’re still sharing airspace with manned aircraft, especially around non-towered airports and private fields. These locations don’t have control towers guiding every plane, so pilots rely on radio frequencies to self-coordinate.
That means you, as a drone pilot, need to know:
- What frequencies are being used
- What’s being said
- And how to stay safely out of the way
Even if you’re just monitoring (not transmitting), knowing the difference between CTAF, UNICOM, and MULTICOM gives you the ability to anticipate aircraft movement, avoid airspace conflicts, and stay compliant under Part 107.
Lesson Focus
Understanding CTAF, UNICOM, and MULTICOM
In this lesson, you’ll learn:
- What UNICOM is and when to use it.
- How to tell when to use CTAF vs. UNICOM.
- What MULTICOM is, and when it’s used as a fallback frequency.
- How to interpret and monitor these frequencies as a drone pilot so you can stay situationally aware and avoid interfering with crewed aircraft traffic.
About
Communication Frequencies
for Non-Towered Airports
UNICOM Frequency
Communicate with Ground Personnel when no ATC and no CTAF
Used for:
- Communicating with airfield ground services
- Pilot-to-pilot announcements when no CTAF is present
Definition:
UNICOM stands for Universal Communications and is primarily used at non-towered airports or private fields to communicate with ground-based personnel to announce their position and intentions.
Reasons a Drone Pilot Would Use UNICOM:
Used when no CTAF
As an sUAS pilot, you won’t usually transmit on UNICOM unless you’re trained and authorized to do so. But listening to the frequency can help you avoid midair conflicts.
As an sUAS pilot a few scenarios you’d use UNICOM are as follows:
To monitor manned aircraft traffic:
- If you’re flying near a non-towered airport, you can tune into the UNICOM frequency to listen for traffic announcements.
- This gives you a heads-up when a plane is approaching or departing so you can clear out, land, or stay safely away.
To communicate with ground personnel (if needed):
- If you’re working on a commercial project near a private airfield or rural airport, and you need to request permission to fly near their traffic pattern or coordinate for safety reasons (like asking when they’re not flying), UNICOM might be the only way to reach someone on the ground.
When UNICOM is functioning as CTAF:
- At some airports, UNICOM is used in place of CTAF for pilots to announce their positions and intentions. Listening in on this helps you understand where planes are flying, especially important when operating an sUAS within a few miles of an airport.
Dual Use:
If Both CTAF and UNICOM Exist:
Choosing Between CTAF and UNICOM
Radio Comm Standards
At some non-towered airports, both CTAF and UNICOM are available. In this case, the frequency is usually the same—but the purpose of each is slightly different. This setup allows pilots to stay coordinated in the air and on the ground—even without a dedicated tower or multiple radio communication channels.
Here’s how to proceed;:
- CTAF:
- Use CTAF to announce your position and intentions in the air to serve as pilot-to-pilot communication. This helps other pilots in the area know where you are and what you plan to do—like entering the pattern with your sUAS.
- UNICOM:
- Use UNICOM to talk to ground personnel, such as requesting fuel, parking guidance, or other services once you’ve landed.
- NO CTAF:
- If there is no designated CTAF, pilots will use UNICOM for both purposes.
In this case, UNICOM becomes a dual-purpose frequency, handling both air traffic announcements and ground service communication.
Quick Review
- CTAF: Used by pilots to coordinate traffic and announce their positions/intentions.
- UNICOM: Used to talk to ground services (e.g., refueling, parking).
- If only UNICOM is available, it’s used for both air traffic coordination and ground services.
MULTICOM
MULTICOM
Used when no CTAF or UNICOM
Used when:
- There’s no ATC, no CTAF, and no UNICOM—typically at small or remote airstrips.
Definition:
- MULTICOM is a designated common-use frequency (typically 122.9 MHz) for general aviation communication in areas where no other frequency has been assigned.
In remote locations, such as rural or remote airfields, there is often limited infrastructure and no control tower, CTAF, or UNICOM.
In these situations, MULTICOM provides a way for pilots to communicate with other pilots or ground services. Similarly, at private airports or small airfields with little to no air traffic control or communication services through CTAF or UNICOM, MULTICOM solves this problem.
122.9 MHz
Standard MULTICOM frequency:
To make things as simple as possible MULITICOM uses a Standard frequency across the nation and across all airports, unless otherwise states. That frequency is 122.9 MHz.
Example:
- You’re documenting wildlife near a private backcountry airstrip with no tower and no listed frequency. A plane announces:
- “Springfield traffic, Piper Cub 39A, entering left downwind for Runway 18—Springfield.”
- They’re using MULTICOM 122.9 MHz as a stand-in for UNICOM and CTAF.
Situational Overview:
Which Frequency to Use When
| Situation | Frequency to Use |
|---|---|
| ATC available | Use ATC |
| CTAF only | CTAF |
| CTAF + UNICOM present | Use CTAF for air traffic, UNICOM for ground services |
| No CTAF, but UNICOM present | Use UNICOM for air traffic and ground services |
| No CTAF or UNICOM | Use MULTICOM (typically 122.9 MHz) |
