What exactly are these frequency uses mentioned in the FAA's advisory circular on VHF use?

Question

The FAA's document AC 90-50, (currently AC 90-50D) sets forth how the aviation communications frequencies (118.000-136.975) are allocated in the United States. Many of the assignment designations are plain enough, and common to the understanding of pilots, but some designations are outside normal use, for example:

• Aviation Support
• Domestic VHF
• Flight Test Stations
• Flight Inspection Use

Is there a document which provides descriptions of what these designations are and what qualifies as legitimate use of those frequencies?

Answer 1

The FCC is the ultimate authority on radio frequency usage in the US. 47 CFR § 87.5 has the definitions of the aviation services.

Aviation support station. An aeronautical station used to coordinate aviation services with aircraft and to communicate with aircraft engaged in unique or specialized activities. (See subpart K)

Subpark K:

§ 87.319 Scope of service.

Aviation support stations are used for the following types of operations:

(a) Pilot training;
(b) Coordination of soaring activities between gliders, tow aircraft and land stations;
(c) Coordination of activities between free balloons or lighter-than-air aircraft and ground stations;
(d) Coordination between aircraft and aviation service organizations located on an airport concerning the safe and efficient portal-to-portal transit of the aircraft, such as the types of fuel and ground services available; and
(e) Promotion of safety of life and property.

Domestic VHF use is described in § 87.263. In general, these frequencies are used for communicating with aircraft, or between ground stations. There are various restrictions on certain frequencies/ranges, and despite the name, some are allowed for use on international routes.

Back to § 87.5:

Flight test aircraft station. An aircraft station used in the testing of aircraft or their major components.

Flight test land station. An aeronautical station used in the testing of aircraft or their major components.

Flight Inspection is not defined in § 87.5, so it may be the FAA setting these aside for their own use, but these frequencies are used by the FAA for ensuring "the integrity of instrument approaches and airway procedures."