What is the technical difference between Unicom and Multicom? ... I would like a source.
Unicom
Title 47: Telecommunication
PART 87—AVIATION SERVICES
Subpart G—Aeronautical Advisory Stations (Unicoms)
§ 87.213 Scope of service.
(a) An aeronautical advisory station (unicom) must provide service to any aircraft station upon request and without discrimination. A unicom must provide impartial information concerning available ground services.
(b)(1) Unicom transmissions must be limited to the necessities of safe and expeditious operation of aircraft such as condition of runways, types of fuel available, wind conditions, weather information, dispatching, or other necessary information. At any airport at which a control tower, control tower remote communications outlet station (RCO) or FAA flight service station is located, unicoms must not transmit information pertaining to the conditions of runways, wind conditions, or weather information during the hours of operation of the control tower, RCO or FAA service station.
(2) On a secondary basis, unicoms may transmit communications which pertain to the efficient portal-to-portal transit of an aircraft, such as requests for ground transportation, food or lodging.
(3) Communications between unicoms and air carrier must be limited to the necessities of safety of life and property.
(4) Unicoms may communicate with aeronautical utility stations and ground vehicles concerning runway conditions and safety hazards on the airport when neither a control tower nor FAA flight service station is in operation.
(c) Unicoms must not be used for air traffic control (ATC) purposes other than to relay ATC information between the pilot and air traffic controller. Relaying of ATC information is limited to the following:
(1) Revisions of proposed departure time;
(2) Takeoff, arrival or flight plan cancellation time;
(3) ATC clearances, provided a letter of agreement is obtained from the FAA by the licensee of the unicom.
[53 FR 28940, Aug. 1, 1988, as amended at 55 FR 30464, July 26, 1990]
Multicom
Title 47: Telecommunication
PART 87—AVIATION SERVICES
Subpart H—Aeronautical Multicom Stations
§ 87.237 Scope of service.
(a) The communications of an aeronautical multicom station (multicom) must pertain to activities of a temporary, seasonal or emergency nature involving aircraft in flight. Communications are limited to directing or coordinating ground activities from the air or aerial activities from the ground. Air-to-air communications will be authorized if the communications are directly connected with the air-to-ground or ground-to-air activities described above. Multicom communications must not include those air/ground communications provided for elsewhere in this part.
(b) If there is not unicom and an applicant is unable to meet the requirements for a unicom license, the applicant will be eligible for a multicom license.
(1) The multicom license becomes invalid when a unicom is established at the landing area.
(2) Multicoms must not be used for ATC purposes other than the relay of ATC information between the pilot and air traffic controller. Relaying of ATC information is limited to the following:
(i) Revisions of proposed departure time;
(ii) Takeoff, arrival flight plan cancellation time;
(iii) ATC clearances, provided a letter of agreement is obtained from the FAA by the licensee of the multicom.
(3) Communications by a multicom must be limited to the safe and expeditious operation of private aircraft, pertaining to the conditions of runways, types of fuel available, wind conditions, weather information, dispatching or other information. On a secondary basis, multicoms may transmit communictions which pertain to efficient portal-to-portal transit of an aircraft such as requests for ground transportation, food or lodging.
