In aviation, a non-towered airport is an airport without a control tower, or air traffic control (ATC) unit. The vast majority of the world's airports are non-towered.[ citation needed ] In the United States, there are close to 20,000 non-towered airports compared to approximately 500 airports with control towers. [1] Airports with a control tower without 24/7 ATC service follow non-towered airport procedures when the tower is closed but the airport remains open, for example at night. [2]
At non-towered airports, instead of receiving instructions from an air traffic controller, aircraft pilots follow recommended operations and communications procedures for operating at an airport without a control tower. The exact procedures vary from country to country, but they may include standard arrival and departure procedures, as well as a common communications phraseology by radio transmissions over a common frequency. For example, a common traffic advisory frequency (CTAF) is recommended for radio communication and is used in the United States, Canada, New Zealand and Australia. [3]
Non-towered airports may lie inside or underneath controlled airspace. In that case, some or all aircraft arriving and departing require clearances from a remote air traffic control unit, such as terminal or center control, even though there is no control tower managing landings and takeoffs. Pilots may be able to obtain those clearances by radio, by phone, or through a company dispatcher or local flight service station; in some cases, departing aircraft (IFR or VFR) take off and level out below the floor of controlled airspace, then radio for a clearance before climbing further. Some countries establish low-altitude VFR corridors for non-towered airports in large urban areas so that VFR arrivals and departures can avoid controlled airspace altogether. [4]
Some countries, such as Canada and Norway, use mandatory frequency airports (MF) or mandatory traffic advisory airports (MTAF), which operate like towered airports in some ways: the radio operators (typically a flight service station) still issue only advisories, but aircraft are required to make radio contact with the ground station before operating in the airport's control zone.
Many non-towered airports have radio to ground operations such as UNICOM to assist aircraft arriving, departing, or maneuvering on the ground. These radio operators such as from fixed-base operators have no authority to give aircraft clearances or instructions, but they can issue advisories to let them know about weather conditions, runway conditions, traffic, and other concerns.
A mobile airport traffic control tower (MATCT) is a temporary tower in an area with an immediate increase in air traffic density. This may be due to wildfire suppression operations carrying out aerial firefighting. [5]
For special events such as fly-ins, temporary towers may operate for only several days each year at fields that are otherwise non-towered. Temporary towers may operate out of an existing airport building, an RV, or even simply a chair (with a portable transmitter and binoculars). [6] [7]
When the traffic volume at an airport gets too high for safe and efficient operations, or when the mix of aircraft types and speeds becomes too large, an airport may be considered for a tower. However, it is also necessary to find the money to construct a building and pay the controllers' salaries; in some cases aviation regulations or local opposition may prevent establishment of the unit. [8]
Hazards are created by failure to use radios to report positions and intentions when operating within the airspace, which can lead to collisions between aircraft unaware of each other. In 1996, an incoming United Express Flight 5925 collided with a King Air aircraft, which failed to report its intent to take off on a common traffic advisory frequency at non-towered Quincy Airport in Illinois. Some pilots fail to use the correct runway at non-towered airports.
In aviation, instrument flight rules (IFR) is one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other is visual flight rules (VFR).
In aviation, visual flight rules (VFR) are a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minima, i.e. in visual meteorological conditions (VMC), as specified in the rules of the relevant aviation authority. The pilot must be able to operate the aircraft with visual reference to the ground, and by visually avoiding obstructions and other aircraft.
Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organize and expedite the flow of air traffic, and provide information and other support for pilots. In some countries, ATC plays a security or defensive role, or is operated by the military.
The Federal Aviation Regulations (FARs) are rules prescribed by the Federal Aviation Administration (FAA) governing all aviation activities in the United States. The FARs comprise Title 14 of the Code of Federal Regulations (CFR). A wide variety of activities are regulated, such as aircraft design and maintenance, typical airline flights, pilot training activities, hot-air ballooning, lighter-than-air aircraft, man-made structure heights, obstruction lighting and marking, model rocket launches, commercial space operations, model aircraft operations, Unmanned Aircraft Systems (UAS) and kite flying. The rules are designed to promote safe aviation, protecting pilots, flight attendants, passengers and the general public from unnecessary risk.
An airfield traffic pattern is a standard path followed by aircraft when taking off or landing while maintaining visual contact with the airfield.
Airspace is the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere. It is not the same as aerospace, which is the general term for Earth's atmosphere and the outer space in its vicinity.
The world's navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. Most nations adhere to the classification specified by the International Civil Aviation Organization (ICAO) and described below, though they might use only some of the classes defined below, and significantly alter the exact rules and requirements. Similarly, individual nations may also designate special use airspace (SUA) with further rules for reasons of national security or safety.
A flight service station (FSS) is an air traffic facility that provides information and services to aircraft pilots before, during, and after flights, but unlike air traffic control (ATC), is not responsible for giving instructions or clearances or providing separation. They do, however, relay clearances from ATC for departure or approaches. The people who communicate with pilots from an FSS are referred to as flight service specialists.
Canadian airspace is the region of airspace above the surface of the Earth within which Canada has jurisdiction. It falls within a region roughly defined as either the Canadian land mass, the Canadian Arctic or the Canadian archipelago, and areas of the high seas. Airspace is managed by Transport Canada and detailed information regarding exact dimensions and classification is available in the Designated Airspace Handbook which is published every fifty-six days by Nav Canada.
Special visual flight rules are a set of aviation regulations under which a pilot may operate an aircraft. It is a special case of operating under visual flight rules (VFR).
The Canada Flight Supplement (CFS) is a joint civil/military publication and is a supplement of the Aeronautical Information Publication. It is the nation's official airport directory. It contains information on all registered Canadian and certain Atlantic aerodromes and certified airports.
An airport surveillance radar (ASR) is a radar system used at airports to detect and display the presence and position of aircraft in the terminal area, the airspace around airports. It is the main air traffic control system for the airspace around airports. At large airports it typically controls traffic within a radius of 60 miles (96 km) of the airport below an elevation of 25,000 feet. The sophisticated systems at large airports consist of two different radar systems, the primary and secondary surveillance radar. The primary radar typically consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace surrounding the airport. It detects the position and range of aircraft by microwaves reflected back to the antenna from the aircraft's surface. The secondary surveillance radar consists of a second rotating antenna, often mounted on the primary antenna, which interrogates the transponders of aircraft, which transmits a radio signal back containing the aircraft's identification, barometric altitude, and an emergency status code, which is displayed on the radar screen next to the return from the primary radar.
An airport with a mandatory frequency (MF), mandatory traffic advisory frequency (MTAF) or air/ground radio (A/G) is an airport which does not have a control tower but still requires arriving and departing aircraft to communicate with other aircraft or a radio operator on a published frequency.
A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist in identifying them on air traffic control radar. Collision avoidance systems have been developed to use transponder transmissions as a means of detecting aircraft at risk of colliding with each other.
The United States airspace system's classification scheme is intended to maximize pilot flexibility within acceptable levels of risk appropriate to the type of operation and traffic density within that class of airspace – in particular to provide separation and active control in areas of dense or high-speed flight operations.
In United States aviation, a special flight rules area (SFRA) is a region in which the normal regulations of flight do not apply in whole or in part, especially regulations concerning airspace classification, altitude, course, and speed restrictions, and the like.
ATC Zero is an official term used by the U.S. Federal Aviation Administration (FAA) that means the FAA is unable to safely provide the published ATC services within the airspace managed by a specific facility. The term is always used in conjunction with a facility reference. FAA ATC facilities include Air Route Traffic Control Centers (ARTCC); Terminal Radar Control facility (TRACON), Air Traffic Control Tower (ATCT), Flight Service Stations (FSS), or the Air Traffic Control System Command Center (ATCSCC). The term is defined in FAA Order JO 1900.47, Air Traffic Control Operational Contingency Plans. It is one of three designations used by the FAA to describe degraded operations and invoke operational contingency plans.
The National Airspace System (NAS) is the airspace, navigation facilities and airports of the United States along with their associated information, services, rules, regulations, policies, procedures, personnel and equipment. It includes components shared jointly with the military. It is one of the most complex aviation systems in the world, and services air travel in the United States and over large portions of the world's oceans.
On August 8, 2009, at 11:53 a.m. (15:53 UTC), nine people died when a tour helicopter and a small private airplane collided over the Hudson River near Frank Sinatra Park in Hoboken, New Jersey, United States. The aircraft were in an area known as the "Hudson River VFR Corridor", which extends from the surface of the river to altitudes of 800 to 1,500 ft at various locations along the Hudson River in the immediate area of New York City. Within this corridor, aircraft operate under visual flight rules (VFR), under which the responsibility to see and avoid other air traffic rests with the individual pilots rather than with the air traffic controller.
A contact approach is an approach available to aircraft operating on an instrument flight rules (IFR) flight plan, where the pilot may deviate from the published instrument approach procedure (IAP) and proceed to the destination airport by visual reference to the surface. It is similar to a visual approach, except that the pilot is not required to have the destination airport nor the preceding aircraft in sight at all times during the approach, and the visibility requirements are less stringent.