UA.V.A.K6: Aircraft call signs and registration numbers.

ACS Area V — Operations Task A: Radio Communications Procedures References: ACAdvisory CircularCloseFAA guidance that explains acceptable ways to comply with rules or understand FAA procedures. 107-2; AIMAeronautical Information ManualCloseFAA operational guidance and glossary material used to understand aviation procedures and terminology.; FAAFederal Aviation AdministrationCloseThe U.S. aviation regulator responsible for Part 107 rules, airspace, and pilot certification processes.-H-8083-25; FAAFederal Aviation AdministrationCloseThe U.S. aviation regulator responsible for Part 107 rules, airspace, and pilot certification processes.-G-8082-22

Key Concepts

Correct Use of Aircraft Call Signs

• Always transmit your full aircraft call sign on initial contact. Do not abbreviate it when other aircraft have similar numbers/sounds or identical letters/numbers. Improper use can lead to a pilot executing a clearance meant for someone else—especially when call signs are similar in a holding stack or busy pattern^[2].
• When a controller says “(Identification), change to my frequency 123.4,” this means only the frequency is changing, not the controller. Your initial callup on the new frequency may be abbreviated (e.g., “United Two Twenty-Two on one two three point four”). Comply promptly with frequency changes unless told to switch at a specific time, fix, or altitude; if a specific point is given, keep monitoring the current frequency until then^[2].

Establishing and Maintaining Two-Way Communications

• In Class C airspace, establish two-way radio communications with the ATCAir Traffic ControlCloseThe system that manages controlled airspace, traffic flow, and aircraft separation services. facility providing services before entry and maintain those communications thereafter. Approaching aircraft should give position, altitude, radar beacon code, destination, and request for Class C services. Initiate contact far enough from the boundary to avoid entering before communications are established^[5].
  • If ATCAir Traffic ControlCloseThe system that manages controlled airspace, traffic flow, and aircraft separation services. responds “(aircraft callsign) standby,” communications are established and you may enter Class C. If ATCAir Traffic ControlCloseThe system that manages controlled airspace, traffic flow, and aircraft separation services. replies without using your aircraft identification, communications are not established; do not enter. Be aware of the Class C “Outer Area,” normally 20 NMNautical MileCloseA distance unit used in aviation. One nautical mile is about 1.15 statute miles. from the primary airport, which is procedural and not charted^[5].
• Expect key phraseology tied to your identification. Tower controllers may advise VFRVisual Flight RulesCloseRules for flight using visual reference and minimum weather conditions. aircraft that could be affected by a larger aircraft’s wake with, “CAUTION − WAKE TURBULENCE,” along with the larger aircraft’s position, altitude, and direction. Regardless of warnings, you must adjust operations and flight path to avoid wake encounters^[6].

Registration Numbers and UAS Identity in Broadcasts and Labels

• For standard Remote IDRemote IdentificationCloseRemote ID broadcast requirements for most drones operating in U.S. airspace. unmanned aircraft, the broadcast must include the aircraft’s identity (either a serial number or a session ID), control station latitude/longitude and geometric altitude, unmanned aircraft latitude/longitude and geometric altitude, velocity, a UTC time mark, and emergency status (§ 89.305). The control station location in the message must correspond to the location of the person manipulating the controls, and the time mark must be synchronized with other message elements (§ 89.310)^[8]. Practically, this broadcast functions as your unmanned aircraft’s “on-air” identification and position report, distinct from radio call sign usage.
• Category 2 small unmanned aircraft used for operations over people require a label in English that is legible, prominent, and permanently affixed indicating eligibility to conduct Category 2 operations (§ 107.120). The applicant must also provide remote pilot operating instructions upon sale/transfer that include a system description, allowable modifications, and configuration/mode guidance^[1]. For test purposes, connect “aircraft identification” not only to radio use but also to required physical labeling for certain operational categories.
• Category 1 operations apply to small unmanned aircraft that weigh 0.55 pounds (250 grams) or less at takeoff and throughout flight. Knowing whether your aircraft is at or below 0.55 pounds helps determine its category for operations over people and related identification/labeling expectations^[4].

Radio Equipment, Licenses, and Practical Implications

• VHFVery High FrequencyCloseRadio frequency band used for many aviation communications and broadcasts. aircraft radios operate from 118.0 to 136.975 MHz. Sets are commonly 720- or 760-channel with 0.025 MHz (25 kHz) spacing; VHFVery High FrequencyCloseRadio frequency band used for many aviation communications and broadcasts. is line-of-sight, so higher altitude increases range. No pilot radio license is required for operations within the United States; operating internationally requires a restricted radiotelephone permit. Most U.S.-based general aviation aircraft don’t need a station license domestically; international operations or use of non-VHFVery High FrequencyCloseRadio frequency band used for many aviation communications and broadcasts. radios may require one^[7]. For UASUnmanned Aircraft SystemCloseAn unmanned aircraft plus its control station, communication links, and supporting components. pilots who interface with ATCAir Traffic ControlCloseThe system that manages controlled airspace, traffic flow, and aircraft separation services., understanding where to listen and transmit—and how to properly identify your aircraft on frequency—is essential.