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I just found this sentence on Wikipedia:

In aviation, some possibly unmanned airports have equipment that let pilots key their VHF radio a number of times in order to request an Automatic Terminal Information Service broadcast, or turn on runway lights.

What kind of airports are unmanned and what other important features do they have, from the perspective of a pilot?

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    $\begingroup$ Welcome to Aviation.SE! This is a very broad topic. We already have a bunch of questions on non-towered airports. Is there something specific you want to know about them? $\endgroup$
    – Bianfable
    Commented Dec 12, 2021 at 12:44
  • $\begingroup$ @Bianfable quite frankly, I left it intentionally broad because I can't really visualise the concept. What I'm looking for is basically the breadth of the conditions in which people choose to create an unmanned airport as opposed to a manned one. $\endgroup$
    – d33tah
    Commented Dec 12, 2021 at 12:49
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    $\begingroup$ Note that Wikipedia's terminology is incorrect; airports without an operational control tower will not have an ATIS, though they might have an AWOS or ASOS broadcast. See my answer here explaining the difference. $\endgroup$
    – randomhead
    Commented Dec 12, 2021 at 16:22
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    $\begingroup$ Welcome to aviation.SE! For context, the US has over 19,000 airports and only 520 have control towers. So non-towered airports are a lot more common than you might think, although obviously if you look at passenger volumes etc. the towered airports are much more visible and important. $\endgroup$
    – Pondlife
    Commented Dec 12, 2021 at 18:11
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    $\begingroup$ As someone who came from HNQ: perhaps the question title could be clarified that this is more about operating airplanes? At first, I thought it's also about passenger/commercial airports that are fully unmanned. $\endgroup$
    – Andrew T.
    Commented Dec 14, 2021 at 3:20

3 Answers 3

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Reasons to leave the airfield unmanned

The common reason is the cost of providing services. For a small airfield without commercial activity, it makes sense to have no control tower and no controller. This is also true for non commercial helipads. Such airfields are known as non-towered or non-controlled airfields, they are not the same, but for the purpose of answering your question, we can consider them as without personnel. Many airfields are only part-time controlled, during day and uncontrolled at night.

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Uncontrolled airfield, source

From Wikipedia:

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.

Pilots will coordinate their activities in the airfield perimeter by announcing what they do, e.g. where they are, or their intent to land, on a common frequency, the common traffic advisory frequency/CTAF in North America, or any other frequency assigned for this purpose.

Non-towered airfields are very common. From AOPA:

Nontowered airports—those not served by an operating air traffic control (ATC) tower—are much more common than towered fields. In fact, nearly 20,000 airports in the United States are nontowered, compared to approximately 500 that have towers.

Remote towers

Some airfields may be remote-controlled, controllers are assigned but are not at the airfield tower. This can be done using cameras and virtual towers. This is the case of London City Airport (EGLC). This is similar to how container cranes in ports can be remotely controlled from low cost centers.

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Remote controller for EGLC, source: NATS

From Wikipedia about a remote virtual tower:

The main benefit of RVT is expected to be cost efficiency. The cost savings originate from the following factors:

  • No need to build and maintain control tower buildings and facilities at the local airports.
  • The building and operational costs of a remote tower and facilities are much lower compared to a traditional tower.
  • More efficient use of human resources (ATCOs and AFISOs), especially by serving multiple airports with medium to low traffic levels from a centralised location.
  • Reduced need to establish and maintain ATM systems locally at the airports. By using data communication networks from the local airport to the remote tower centre, several technical systems can be centralised, hence costs savings are possible. Over 75% of regional airports with fewer than 1 million passengers a year are making a loss.11 These costs could be shared, saving 1.3 million euro per year (in case of Shannon and Cork airports being controlled from Dublin).

Regulation

In the US, FAA regulations (e.g. AC 90-66) apply to these airfields.

See also: Uncontrolled Aerodromes - Procedures at SKYbrary

Pilot activation

On airfields with no personnel (including no remote personnel), some devices may be operated using predetermined schedules or by remote-control by pilots. This includes runway approach and runway lighting, ATIS transmission (including weather information) and navaids.

Remote orders are decoded from the VHF frequency (CTAF) carrier transmission and interruption sequence. Such systems are known as pilot-controlled lighting (PCL), pilot-activated lighting (PAL) or aircraft radio control of aerodrome lighting (ARCAL). From ACAMS, a provider for such remote activation systems:

enter image description here

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  • $\begingroup$ If "everybody" needs to coordinate use of untowered/uncontrolled aerodromes - and there's no dedicated channel for just the specific aerodrome - doesn't that mean a lot of radio chatter and over-talk, at least potentially? $\endgroup$
    – einpoklum
    Commented Dec 14, 2021 at 18:30
  • $\begingroup$ @einpoklum: You're right, it can happen. However there are possibilities to change the frequency. Still such CTAF is used for short blind messages, not for conversations. $\endgroup$
    – mins
    Commented Dec 14, 2021 at 18:38
  • $\begingroup$ @einpoklum isn't that why high-traffic ones aren't uncontrolled? also you may be thinking radio goes an unlimited distance - it does not $\endgroup$ Commented Dec 14, 2021 at 23:35
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Small private airstrips are typically “unmanned”. Many small municipally owned airports are “unmanned”.

These small airports often have no lighting. Many do have lighting and it makes sense to have an automated system for lights or ATIS.

It is mainly an economic decision to have an “unmanned” airport. An airport with little traffic can still operate safely without a control tower and full time staff.

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The more correct term here is an 'untowered' airport. As others have mentioned, untowered airports are by far the majority of all airports, with tens of thousands of them in the U.S. alone. Untowered airports don't have a tower generally because they just don't need one.

There are specific procedures that pilots follow when flying in or out of an untowered airport, including a frequency that pilots use to talk to other pilots flying in and out of that airport, such as for announcing our position and intentions. There is also a specific traffic pattern that aircraft will fly to approach the airport so that other traffic knows where to expect traffic to be. For the lower levels of traffic that are typically present at these airports, these procedures work fine without the need for an air traffic controller with a radar.

I say that the more correct term is 'untowered,' because untowered fields are often not actually unmanned, especially public use ones during the daytime. All of the fields I flew out of during flight training were untowered airports, but all of them had staff on hand during the day, for example, in a Fixed-Base Operator (FBO) office. These are the people who rent the hangars and tie-down parking, sell fuel, and possibly also provide other services such as aircraft rental, flight instruction, aircraft maintenance, and small supply shops for pilots. Many also provide facilities like bathrooms, kitchens, seating areas, etc. for use by pilots. In many (probably most) cases, the FBO is truly unmanned at night, but usually still has some degree of accessibility to pilots flying after hours who need to fuel their aircraft or use other facilities provided by the FBO.

Untowered airports also often provide automated weather reporting services via something like AWOS or and ASOS. Runway lighting is typically controlled by clicking the mic a certain number of times on the radio frequency used by pilots at that airport to talk to each other. The runway lighting system also monitors this frequency and turns on/adjusts the lights based on pilots transmitting those 'codes.' The lights generally turn off again after a certain amount of time passes in order to save energy and lengthen the lifespan of the lights when there's no one needing them.

As far as what types of fields are untowered, these can range from literally just a strip of grass in some pilot's field being used as a private airport to helipads to sea plane bases to public-use airports with runways long enough for medium-sized jets. Pretty much the only types of airports that are usually not untowered are airports with scheduled commercial passenger service, military bases, and unusually busy general aviation airports that have too much traffic to operate safely without air traffic control, such as the GA airports in major metropolitan areas.

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  • $\begingroup$ There are many untowered airports with scheduled passenger airline service. Not on the level of ORD or LHR, of course, but they exist. $\endgroup$
    – randomhead
    Commented Dec 14, 2021 at 22:54
  • $\begingroup$ @randomhead True, though they're much more the exception than the rule. Technically, even Coldfoot, Alaska (population something like 12) could be said to have scheduled service (though it's part 135 instead of 121,) but it's a Piper Navajo with flights cancelled when not needed (or when weather not VFR because there's no radar out there. - haha) Definitely no tower there. $\endgroup$
    – reirab
    Commented Dec 14, 2021 at 23:03

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