Air Traffic Control Tower

Introduction:

  • Airport Traffic Control Towers provide for a safe, orderly, and expeditious flow of traffic in the vicinity of an airport
    • When the responsibility is delegated, towers also provide for the separation of Instrument Flight Rules aircraft in the terminal areas
  • This flow of traffic begins with the flow of information to pilots through clearance delivery
  • If clearance delivery services are not available at a particular airport, pilots will contact ground control for the same
  • Once with ground control, pilots may request taxi instructions to route to the designated runway or other destinations on the airport
  • Assuming takeoff, pilots contact tower control for a takeoff clearance
  • Other Services may exist under visual and instrument flight rules, to include tower enroute control to streamline procedures in congested airspace
  • Think you've got a solid understanding of air traffic control towers? Don't miss the air traffic control tower quiz below, and topic summary

Tower Construction:

  • Air Traffic Control Tower Airport Diagram
    Air Traffic Control Tower Airport Diagram
  • Air Traffic Controllers (ATC) for a local airport generally reside in an Air Traffic Control Tower (ATCT)
  • Air Traffic Control Towers are structures tall enough to provide a visual reference to controllers in the terminal environment
  • It is noteworthy that the control tower may also consist of several structures beneath or adjacent to the physical tower
  • Although usually a prominent feature, the tower's location is also labeled on airport diagrams [Figure 1]
  • Air Traffic Control Tower Airport Diagram
    Air Traffic Control Tower Airport Diagram

Clearance Delivery:

  • Clearance delivery is established at busy airports to facilitate the delivery of flight instructions without congesting the ground frequency
    • Where clearance delivery is not a dedicated frequency, ground control absorbs this function
  • Clearance delivery has no control function and is used solely as the name implies, for the delivery of clearances
  • Clearance Delivery Frequency:

    • Clearance delivery frequencies can be found in the U.S. Chart Supplement as well as several online sources such as Airnav.com
  • What is a clearance?

    • An ATC clearance is an authorization for an aircraft to proceed under specified conditions within controlled airspace
    • Clearances are issued based on a prediction of known traffic and known physical airport conditions
      • A clearance is not an authorization to deviate from any rule, regulation, or minimum altitude nor to conduct unsafe operations of an aircraft
    • Reading back a clearance implies acceptance unless you reject it and give a reason in favor of receiving an amended clearance
  • Obtaining a Clearance:

    • Pilots generally obtain their clearance by contacting clearance delivery or ground before engine start
    • They may, however, be obtained in the air, using the same procedures as on the ground (although, with a departure control frequency)
    • Before calling for a clearance, however, pilots must listen to the Automated Terminal Informatino Service or Automated Surface Observing System (ASOS)/Automated Weather Observing System (AWOS) to receive local weather/NOTAMs as well as the information code
    • The complexity of the radio call depends upon if the pilot is departing under Visual Flight Rules (VFR) or Instrument Flight Rules (IFR)
    • Visual Flight Rules:

      • Pilot: "[Agency], [Callsign], [Location], [ATIS/ASOS/AWOS Code] [Request]"
      • Pilot: "Danbury Clearance, Cessna One Seven Two Seven Victor at Arrow, Information Alpha, VFR to the west, requesting 4,500"
    • Instrument Flight Rules:

      • Pilot: "[Agency] clearance, [Callsign] with [ATIS/ASOS/AWOS Code], IFR to [Destination] on request" OR simply "[Agency] clearance, [Callsign] IFR to [Destination]"
      • ATC: "[Callsign], I have your clearance, advise when ready to copy"
      • Pilot: "[Callsign], ready to copy"
      • ATC: "Cessna One Seven Two Seven Victor, is cleared to Navy Pensacola via direct Montgomery, Pecan, Valdosta, Tallahassee, then as filed. Maintain runway heading for vectors on course. Climb to and maintain one zero thousand. Expect flight level two seven zero ten minutes after takeoff. Contact Meridian Departure Control on two seven six point four. Squawk four seven one zero. The reason for the change of flight plan is a line of a severe thunderstorm in the vicinity of Jacksonville""
    • If operating at an airfield that does not have an organic clearance delivery, then the clearance, control information, or a response to a request for information originated by an ATC facility and relayed to the pilot through an air-to-ground communication station will be prefixed with: "ATC clears," "ATC advises," or "ATC requests"
    • See also: 7 Ways To Pick Up Your IFR Clearance At A Non-Towered Airport
    • Uncontrolled Airport Considerations:

      • At an uncontrolled field, if a clearance is required, you may:
        1. Depart VFR and contact Terminal Radar Approach ControL (TRACON)/Air Route Traffic Control Center (ARTCC) while VFR airborne
        2. Use the Ground Communication Outlet (GCO) connection to Air Traffic - If the GCO only connects to Flight Service, contact Air Traffic via the telephone number provided
        3. Frequencies are found in the Chart Supplement U.S.
        4. Remote Communications Outlet (RCO) frequency for Flight Service or Remote Transmit Receive Outlet (RTR) frequency for Air Traffic
          • To use an RCO/RTR, contact FSS on a VOR with voice capability: "Danbury Radio, Cessna one-seven-two-seven-victor at Danbury Airport, Delta, X-ray, Romeo, one one twenty-two point six"
          • Upon acknowledgment from FSS, request the clearance by providing your location, your request (IFR clearance), your destination, and your planned runway (think possible departure procedure assignment), and when you'd like to depart (think release and clearance void times)
        5. Telephone Flight Service Station (FSS) clearance/delivery number
    • Air Traffic Control may read clearances quickly, leading to missing a segment
      • Don't try to make something up, be clear before your workload begins to increase and ask ATC to repeat the missed segment
  • Clearance Items:

    • Clearances are issued in a standardized format, recalled with the acronym: "CRAFT:"
    • Clearance Limit:

      • A clearance limit will authorize flight to a point, be it an airport of fix
        • Many airports and associated Navigation Aids (NAVAIDs) are collocated with the same name and/or identifier, requiring care to ensure a clear understanding of the clearance limit
      • When the clearance limit is the airport of intended landing, the clearance should contain the airport name followed by the word "airport"
        • "Cleared to [Airport]"
      • When the clearance limit is a NAVAID, intersection, or waypoint and the type is known, the clearance should contain type
        • "Cleared to [Fix], expect further clearance in three zero minutes"
      • At some locations, a short-range clearance procedure is utilized whereby air traffic control issues the clearance to a fix within or just outside of the terminal area, and pilots are advised of the frequency on which they will receive the long-range clearance direct from the center controller
    • Departure Instructions:

      • Where the volume of traffic warrants, departure procedures are issued to separate a departure from other air traffic in the terminal area
        • "Maintain runway heading for vectors on course" or
        • "Cleared to Teterboro Airport via the Bangor Three Departure, then as filed"
    • Route of Flight:

      • Usually air traffic control issues, clearances for the altitude or flight level, and route filed by the pilot
        • Due to traffic conditions, it may be necessary for ATC to specify an altitude or flight level or route different from that requested by the pilot
        • Flow patterns have been established in certain congested areas or between congested areas whereby traffic capacity
          • These flow patterns increase traffic capacity
          • Information on these flow patterns is available in offices where preflight briefings are available or where flight plans are accepted
      • When required, air traffic clearances include data to assist pilots in identifying radio reporting points
        • "via direct Montgomery, Pecan, Valdosta, Tallahassee, then as filed"
      • It is the responsibility of pilots to notify ATC immediately if their navigation equipment cannot receive the type of signals they must utilize to comply with their clearance
        • ATC issues clearances per the filed flight plan suffix
    • Altitude Data:

      • ATC nomrally issues clearances for the altitude or flight level filed by the pilot
      • The altitude or flight level instructions in an ATC clearance normally require the pilot to "maintain" the altitude or flight level at which the flight will operate when in controlled airspace
        • "Climb to and maintain one zero thousand"
      • When possible, if the altitude assigned is different from the altitude requested by the pilot, ATC will inform the pilot when to expect climb or descent clearance or to request altitude change from another facility
        • "Expect flight level two-seven-zero ten minutes after takeoff"
      • If not given the desired altitude before crossing the boundary of the ATC facility's area, the pilot should reinitiate the request with the next facility
      • ATC may use the term "cruise" instead of "maintain" to assign a block of airspace to a pilot from the minimum IFR altitude up to and including the altitude specified in the cruise clearance
        • The pilot may level off at any intermediate altitude within this block of airspace
        • Climb/descent within the block is at the discretion of the pilot
        • However, once the pilot starts descent and verbally reports leaving an altitude in the block, the pilot may not return to that altitude without additional ATC clearance
    • Departure Frequency:

      • ATC advises pilots of the frequency on which they will receive the long-range clearance direct from the center controller
        • "Contact Meridian Departure Control on two seven six point four"
    • Transponder Code:

      • Transponder codes are assigned to link your aircraft to your assigned route/flight plan
        • "Squawk four seven one zero"
      • Learn more about the transponder and codes here
    • Holding Instructions:

      • Whenever cleared to a fix other than the destination airport (clearance limit), and delays are expected, it is the responsibility of the ATC controller to issue complete holding instructions (unless the pattern is charted), an EFC time, and the best estimate of any additional en route/terminal delay
        • If the holding pattern is charted and the controller doesn't issue complete holding instructions, the pilot must hold as depicted on the appropriate chart
        • When the pattern is charted, the controller may omit all holding instructions except the charted holding direction and the statement "AS PUBLISHED," e.g., "HOLD EAST AS PUBLISHED"
        • Controllers must always issue complete holding instructions when pilots request them
      • If no holding pattern is charted and holding instructions have not been issued, the pilot should ask ATC for holding instructions before reaching the fix
        • This procedure will eliminate the possibility of an aircraft entering a holding pattern other than that desired by ATC
        • If unable to obtain holding instructions before reaching the fix (due to frequency congestion, stuck microphone, etc.), hold in a standard pattern on the course on which you approached the fix and request further clearance as soon as possible
          • In this event, the altitude/flight level of the aircraft at the clearance limit will be protected
          • Separation is provided, as required
      • If still awaiting a clearance beyond the fix when the aircraft is 3 minutes or less from a clearance limit, the pilot must start a speed reduction so that the aircraft will cross the fix, initially, at or below the maximum holding speed
      • When no delay is expected, the controller should issue a clearance beyond the fix as soon as possible and, whenever possible, at least 5 minutes before the aircraft reaches the clearance limit
      • Pilots should report to ATC the time and altitude/flight level at which the aircraft reaches the clearance limit and report leaving the clearance limit
      • In the event of a two-way communications failure, pilots shall comply with Title 14 of the Code of Federal Regulations (CFR) Section 91.185
  • IFR Clearances Off Uncontrolled Airports:

    • Pilots departing on an IFR flight plan should consult the Chart Supplement U.S. to determine the frequency or telephone number to use to contact clearance delivery. On initial contact, pilots should advise that the flight is IFR and state the departure and destination airports
    • Air traffic facilities providing clearance delivery services via telephone will have their telephone number published in the Chart Supplement U.S. of that airport's entry. This same section may also contain a telephone number to use for cancellation of an IFR flight plan after landing
    • Except in Alaska, pilots of MEDEVAC flights may obtain their clearance by calling 1-877-543-4733
  • Pilot Responsibility upon Clearance Issuance:

    • Record ATC Clearance:

      • When conducting an IFR operation, make a written record of your clearance
      • The specified conditions which are a part of your air traffic clearance may be somewhat different from those included in your flight plan
      • Additionally, ATC may find it necessary to ADD conditions, such as particular departure route
      • The very fact that ATC specifies different or additional conditions means that other aircraft are involved in the traffic situation
    • Clearance/Instruction Readback:

      • Pilots of airborne aircraft should read back those parts of ATC clearances and instructions containing altitude assignments, vectors, or runway assignments as a means of mutual verification
      • The read-back of the "numbers" serves as a double check between pilots and controllers and reduces the kinds of communications errors that occur when a number is either "misheard" or is incorrect
        • Include the aircraft identification in all read-backs and acknowledgments to help controllers determine that the correct aircraft received the clearance or instruction. The requirement to include aircraft identification in all read-backs and acknowledgments becomes more important as frequency congestion increases and when aircraft with similar call signs are on the same frequency
          • "Climbing to Flight Level three three zero, United Twelve" or "November Five Charlie Tango, roger, cleared to land runway nine left"
        • Read back altitudes, altitude restrictions, and vectors in the same sequence given in the clearance or instruction
        • Altitudes contained in charted procedures, such as departure procedures, instrument approaches, etc., should not be read back unless the controller specifically requests them
        • Initial read back of a taxi, departure, or landing clearance should include the runway assignment, including left, right, center, etc. if applicable
    • It is the responsibility of the pilot to accept or refuse the clearance issued
  • Types of Clearances:

    • Amended Clearance:

      • Amendments to an initial clearance are issued when necessary to resolve conflicts between aircraft
        • This may come in the form of a new route, holding, or change altitude before reaching the point where standard separation from other IFR traffic would no longer exist
      • A pilot may wish an explanation of the handling of the flight at the time of occurrence; however, controllers are not able to take time from their immediate control duties, nor can they afford to overload the ATC communications channels to furnish explanations
        • Pilots may obtain an explanation by directing a letter or telephone call to the chief controller of the facility involved
      • Pilots have the privilege of requesting a different clearance from that which ATC has issued if they feel that they have information that would make another course of action more practicable or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued
        • An example might be avoiding weather the pilot sees ahead, but ATC has not yet warned them about
    • Coded Departure Route:

      • Coded Departure Routes (CDRs) provide air traffic control a rapid means to reroute departing aircraft when the filed route is constrained by either weather or congestion
      • It consists of eight-character designator that represents a route of flight
        • The first three alphanumeric characters represent the departure airport
        • Characters four through six represent the arrival airport
        • The overlying ARTCC chooses the last two
          • Example: PITORDN1 is Pittsburgh to Chicago
      • CDRs are updated every 56 days
      • General aviation customers who wish to participate in the program may now enter "CDR Capable" in the remarks section of their flight plan
        • When entering "CDR Capable" into the remarks section of the flight plan, the general aviation customer communicates to ATC the ability to decode the current CDR into a flight plan route and the willingness to fly a different route than filed
    • Special VFR Clearances:

  • Adherence to Clearance:

    • Once receiving a clearance from air traffic under either visual or instrument flight rules, the pilot-in-command of the aircraft must not deviate from the provisions thereof unless receiving an amended clearance
    • The addition of a VFR or other restriction; i.e., climb or descent point or time, crossing altitude, etc., does not authorize a pilot to deviate from the route of flight or any other provision of the ATC clearance
    • When ATC issues a clearance or instruction, pilots must to promptly execute its provisions upon receipt
    • Turns:

      • When a heading is assigned or ATC requests a turn, pilots must promptly initiate the turn, complete the turn, and maintain the new heading unless issued additional instructions
        • ATC: "Cessna One Seven Two Seven Victor, turn left heading two-seven-zero"
    • Climbs and Descents:

      • Pilots must commence descent upon receipt of the clearance and descend at the suggested rates until reaching the assigned altitude of 6,000 feet
        • "United Four Seventeen, descend and maintain six-thousand"
    • "Pilot's Discretion:"

      • The term "AT PILOT'S DISCRETION" included in the altitude information of an ATC clearance means that ATC has offered the pilot the option to start climb or descent when the pilot wishes, is authorized to conduct the climb or descent at any rate, and to level off at any intermediate altitude as desired temporarily
        • However, once the aircraft has vacated an altitude, it may not return to that altitude
      • When ATC has not used the term "AT PILOT'S DISCRETION" nor imposed any climb or descent restrictions, pilots should initiate climb or descent promptly on the acknowledgment of the clearance
        • Descend or climb at an optimum rate to 1,000 feet above or below the assigned altitude, and then attempt to descend or climb at a rate of between 500 and 1,500 fpm until reaching the assigned altitude
        • If at any time the pilot is unable to climb or descend at a rate of at least 500 feet a minute, advise ATC
      • If the altitude information of an ATC DESCENT clearance includes a provision to "CROSS [fix] AT" or "AT OR ABOVE/BELOW [Altitude]," how the descent complies with the crossing altitude is at the pilot's discretion
        • This authorization to descend at the pilot's discretion is only applicable to that portion of the flight to which the crossing altitude restriction applies, and the pilot must comply with the crossing altitude as a provision of the clearance
        • Any other clearance in which pilot execution is optional will so state "AT PILOT'S DISCRETION"
          • "United Four Seventeen, descend at pilot's discretion, maintain six thousand"
            • The pilot is authorized to conduct descent within the context of the term at the pilot's discretion as described above
          • "United Four Seventeen, cross Lakeview V-O-R at or above Flight Level two zero zero, descend and maintain six thousand"
            • The pilot is authorized to conduct descent at the pilot's discretion until reaching Lakeview VHF Omni-Directional Receiver (VOR) and must comply with the clearance provision to cross the Lakeview VOR at or above FL 200. After passing Lakeview VOR, the pilot must descend at the suggested rates until reaching the assigned altitude of 6,000 feet
          • "United Four Seventeen, cross Lakeview V-O-R at six thousand, maintain six thousand"
            • The pilot is authorized to conduct descent at the pilot's discretion, however, they must comply with the clearance provision to cross the Lakeview VOR at 6,000 feet
          • "United Four Seventeen, descend now to Flight Level two-seven-zero, cross Lakeview V-O-R at or below one zero thousand, descend and maintain six thousand"
            • Promptly execute and complete descent to FL 270 upon receipt of the clearance. After reaching FL 270, the pilot may descend "at pilot's discretion" until reaching Lakeview VOR. The pilot must comply with the clearance provision to cross Lakeview VOR, at or below 10,000 feet. After Lakeview VOR the pilot is expected to descend at the suggested rates until reaching 6,000 feet
          • "United Three Ten, descend now and maintain Flight Level two four zero, pilot's discretion after reaching Flight Level two eight zero"
            • The pilot must commence descent upon receipt of the clearance and descend at the suggested rates until reaching FL 280. At that point, the pilot is authorized to continue the descent to FL 240 "at pilot's discretion"
    • "Immediately:"

      • ATC, in certain situations, will include the word "IMMEDIATELY" in a clearance or instruction to impress the urgency of an imminent situation, and expeditious compliance by the pilot is expected and necessary for safety
        • ATC: "Cessna One Seven Two Seven Victor, turn left to two seven zero immediately"
          • The pilot must initiate a left turn as quickly as possible consistent with safety
    • Deviating From a Clearance:

      • In accordance with FAR 91.123, pilots are permitted to deviate from a clearance under three conditions:
        • An amended clearance is obtained;
        • An emergency exists, or;
        • The deviation is in response to a traffic alert and collision avoidance system resolution advisory
      • If ATC issues a clearance that would cause a pilot to deviate from a rule or regulation, or in the pilot's opinion, would place the aircraft in jeopardy, IT IS THE PILOT'S RESPONSIBILITY TO REQUEST CLARIFICATION AND/OR AN AMENDED CLEARANCE
        • Similarly, if a pilot prefers to follow a different course of action, such as make a 360° turn for spacing to follow traffic when established in a landing or approach sequence, land on a different runway, takeoff from a different intersection, takeoff from the threshold instead of an intersection, or delay operation, THE PILOT IS EXPECTED TO INFORM ATC ACCORDINGLY
        • When the pilot requests a different course of action, however, the pilot is expected to cooperate to preclude disruption of traffic flow or creation of conflicting patterns
        • The pilot must use the appropriate aircraft call sign to acknowledge all ATC clearances, frequency changes, or advisory information
      • Each pilot who deviates from an ATC clearance in response to a Traffic Alert and Collision Avoidance System resolution advisory must notify ATC of that deviation as soon as possible
      • In case emergency authority is used to deviate from provisions of an ATC clearance, the pilot-in-command must notify ATC as soon as possible and obtain an amended clearance. In an emergency that does not result in a deviation from the rules prescribed in 14 CFR Part 91 but which requires ATC to give priority to an aircraft, the pilot of such aircraft must, when requested by ATC, make a report within 48 hours of such emergency to the manager of that ATC facility
      • The guiding principle is that the last ATC clearance has precedence over the previous ATC clearance. When amending the route or altitude in a previously issued clearance, the controller will restate applicable altitude restrictions. If altitude to maintain is changed or restated, whether before departure or while airborne, and previously issued altitude restrictions are omitted, those altitude restrictions are canceled, including departure procedures and STAR altitude restrictions. For example:
        • A departure flight receives a clearance to the destination airport to maintain FL 290. The clearance incorporates a DP, which has certain altitude crossing restrictions. Shortly after takeoff, the flight receives a new clearance changing the maintaining FL from 290 to 250. If the altitude restrictions are still applicable, the controller restates them
        • A departing aircraft is cleared to cross Fluky Intersection at or above 3,000 feet, Gordonville VOR at or above 12,000 feet, maintain FL 200. Shortly after departure, the altitude to be maintained is changed to FL 240. If the altitude restrictions are still applicable, the controller issues an amended clearance as follows: "cross Fluky Intersection at or above three thousand, cross Gordonville V-O-R at or above one two thousand, maintain Flight Level two four zero"
        • An arriving aircraft is cleared to the destination airport via V45 Delta VOR direct; the aircraft is cleared to cross Delta VOR at 10,000 feet and maintain 6,000 feet. Before Delta VOR, the controller issues an amended clearance as follows: "turn right heading one eight zero for vector to runway three six I-L-S approach, maintain six thousand"
          • Because the altitude restriction "cross Delta V-O-R at 10,000 feet" was omitted from the amended clearance, it is no longer in effect
      • Pilots of turbojet aircraft equipped with afterburner engines should advise ATC before takeoff if they intend to use afterburning during their climb to the enroute altitude. Often, the controller may be able to plan traffic to accommodate a high-performance climb and allow the aircraft to climb to the planned altitude without restriction
      • If ATC issues an "expedite" climb or descent clearance, and the altitude to maintain is subsequently changed or restated without an expedite instruction, the expedite instruction is canceled. Expedite climb/descent normally indicates to the pilot to use the best rate of climb/descent without requiring an exceptional change in aircraft handling characteristics. Normally controllers will inform pilots of the reason for an instruction to expedite

Ground Control:

  • Ground control provides control of movement aircraft or vehicles through taxi instructions on the airport surface area
  • Issues information on-ramp service, hazardous ground conditions, fueling operations
  • Air Carrier Ops:
    • Should contact before starting engines, to receive engine start time, taxi and/or clearance information
  • Relays clearance:
    • If clearance delivery is not available, ground will obtain and relay as well as provide ATIS information is unavailable
  • Ground is responsible for the ATIS
  • Listen here (requires flash)
  • Issued with receipt of new official weather on the hour or when conditions change and warrant an update
  • When talking to FSS over a VOR broadcasting ATIS, ATIS will be interrupted
  • "Have the numbers" means you have only received wind, altimeter, and runway (WAR)
  • Important to check before takeoff and contracting approach inbound

Tower Control:

  • Tower control is responsible for aircraft on the active runway departing or landing, and all aircraft airborne within the designated airspace
  • Line Up and Wait:

    • Line Up and Wait (LUAW), formerly called "position and hold," is an ATC procedure designed to position an aircraft onto the runway for an imminent departure. The ATC instruction "LINE UP AND WAIT" is used to instruct a pilot to taxi onto the departure runway and line up and wait
      • Tower: "N234AR Runway 24L, line up and wait"
    • This ATC instruction is not an authorization to takeoff. In instances where the pilot has been instructed to line up and wait and has been advised of a reason/condition (wake turbulence, traffic on an intersecting runway, etc.) or the reason/condition is clearly visible (another aircraft that has landed on or is taking off on the same runway), and the reason/condition is satisfied, the pilot should expect an imminent takeoff clearance, unless advised of a delay. If you are uncertain about any ATC instruction or clearance, contact ATC immediately
    • If a takeoff clearance is not received within a reasonable amount of time after clearance to line up and wait, contact ATC
      • It could be due to a stuck mic or maybe a spacing requirement
      • Aircraft: Cessna 234AR holding in position Runway 24L
      • Aircraft: Cessna 234AR holding in position Runway 24L at Bravo
    • FAA analysis of accidents and incidents involving aircraft holding in position indicates that two minutes or more elapsed between the time the instruction was issued to line up and wait and the resulting event (land-over or go-around). Pilots should consider the length of time that they have been holding in position whenever they HAVE NOT been advised of any expected delay to determine when it is appropriate to query the controller
      • Reference advisory Circulars 91-73A, Part 91 and Part 135 Single-Pilot Procedures during Taxi Operations, and 120-74A, Parts 91, 121, 125, and 135 Flightcrew Procedures during Taxi Operations for more
    • Situational awareness during line up and wait operations is enhanced by monitoring ATC instructions/clearances issued to other aircraft. Pilots should listen carefully if another aircraft on frequency has a similar call sign and pay close attention to communications between ATC and other aircraft. If you are uncertain of an ATC instruction or clearance, query ATC immediately. Take care not inadvertently to execute a clearance/instruction for another aircraft
    • Pilots should be especially vigilant when conducting line up and wait operations at night or during reduced visibility conditions. They should scan the runway's full length and look for aircraft on final approach or landing roll out when taxiing onto a runway. Contact ATC anytime there is a concern about a potential conflict
    • When two or more runways are active, aircraft may be instructed to "LINE UP AND WAIT" on two or more runways. When multiple runway operations are being conducted, it is important to listen closely to your call sign and runway. Be alert for similar sounding call signs and acknowledge all instructions with your call sign. When you are holding in position and are unsure if the takeoff clearance was for you, ask ATC before you begin takeoff roll. ATC prefers that you confirm a takeoff clearance rather than mistake another aircraft's clearance for your own
    • When ATC issues intersection "line up and wait" and takeoff clearances, the intersection designator will be used. If ATC omits the intersection designator, call ATC for clarification
      • ATC: "[Callsign], [Runway], at [Location], line up and wait"
      • Aircraft: "Cherokee 234AR, Runway 24L at November 4, line up and wait"
    • Suppose landing traffic is a factor during line up and wait operations. In that case, ATC will inform the aircraft in position of the closest traffic within six flying miles requesting a full-stop, touch-and-go, stop-and-go, or an unrestricted low approach to the same runway. Pilots should take care to note the position of landing traffic. ATC will also advise the landing traffic when an aircraft is authorized to "line up and wait" on the same runway
      • Tower: "Cessna 234AR, Runway 24L, line up and wait. Traffic a Boeing 737, six-mile final"
      • Tower: "Delta 1011, continue, traffic a Cessna 210 holding in position Runway 24L"
    • ATC will normally withhold landing clearance to arrival aircraft when another aircraft is in position and holding on the runway
    • Never land on a runway occupied by another aircraft, even if a landing clearance was issued. Do not hesitate to ask the controller about the traffic on the runway and be prepared to execute a go-around
    • Always clarify any misunderstanding or confusion concerning ATC instructions or clearances. Advise ATC immediately if there is any uncertainty about the ability to comply with any instructions
  • Air Traffic Control Tower Services:

    • ATCT control runway traffic, issuing takeoff and landing clearances
      • They contain the "tower controller" who is responsible for aircraft on the active runway and anything airborne with the designated airspace
      • Additionally, "Ground" and "Clearance Delivery" personnel are physically located in the tower and are responsible for issuing clearances and controlling movement on the ground up to the switch to tower
    • Provides airport advisory information to arriving flights in the absence of ATIS
    • Will keep the pilot informed of the latest reported weather and actual field conditions such as current ceiling, runway visibility, surface winds, and runway conditions
  • Communications:

    • On departure, when given a clearance, be sure to read back all altitudes, headings, and frequencies
    • ATC: "[Callsign] climb and maintain [Heading], switch [Facility] departure"

VFR/IFR Flights:

  • A pilot departing VFR, either intending to or needing to obtain an IFR clearance en route, must be aware of the position of the aircraft and the relative terrain/obstructions
  • When accepting a clearance below the Minimum Enroute Aaltitude (MEA)/Minimum IFR Altitude (MIA)/Minimum Vector Altitude (MVA)/Off-Route Obstruction Clearance Altitude (OROCA), pilots are responsible for their terrain/obstruction clearance until reaching the MEA/MIA/MVA/OROCA
    • OROCA is an off-route altitude that provides obstruction clearance with a 1,000-foot buffer in non-mountainous terrain areas and a 2,000-foot buffer in designated mountainous areas within the U.S. This altitude may not provide signal coverage from ground-based navigational aids, air traffic control radar, or communications coverage
  • If unable to maintain terrain/obstruction clearance, advise the controller and state intentions

Tower Enroute Control:

  • Tower Enroute Control, or TEC, is an ATC program to provide a service to aircraft proceeding to and from metropolitan areas
    • It links designated Approach Control Areas by a network of identified routes made up of the existing airway structure of the National Airspace System
  • The FAA initiated an expanded TEC program to include as many facilities as possible
  • The program intends to provide an overflow resource in the low altitude system, which would enhance ATC services
  • A few facilities have historically allowed turbojets to proceed between certain city pairs, such as Milwaukee and Chicago, via tower en route, and these locations may continue this service
    • However, the expanded TEC program will be applied, generally, for non-turbojet aircraft operating at and below 10,000 feet
  • The program is entirely within the approach control airspace of multiple terminal facilities
    • Essentially, it is for relatively short flights
  • Participating pilots are encouraged to use TEC for flights of two hours duration or less
    • If longer flights are planned, extensive coordination may be required within the multiple complex which could result in unanticipated delays
  • Pilots requesting TEC are subject to the same delay factor at the destination airport as other aircraft in the ATC system
    • Departure and en route delays may occur depending upon individual facility workload
    • When a major metropolitan airport is incurring significant delays, pilots in the TEC program may want to consider an alternative airport experiencing no delay
  • There are no unique requirements upon pilots to use the TEC program
    • Normal flight plan filing procedures will ensure proper flight plan processing
    • Pilots should include the acronym "TEC" in the remarks section of the flight plan when requesting tower en route control
  • All approach controls in the system may not operate up to the maximum TEC altitude of 10,000 feet
  • IFR flight may be planned to any satellite airport in proximity to the major primary airport via the same routing
  • Some advantages include abbreviated filing procedures and reduced traffic separation requirements
  • TEC is dependent upon the ATC's workload, and the procedure varies among locales
  • For more information visit: PilotMag - Tower Enroute Control

Air Traffic Control Tower Knowledge Quiz:

Conclusion:

  • A clearance is an instruction; however, the pilot-in-command is directly responsible for and is the final authority as to, the operation of that aircraft
    • A clearance is therefore not an authorization to deviate from any rule, regulation, or minimum altitude nor to conduct unsafe operation of the aircraft
  • If requiring an IFR departure clearance at an uncontrolled airfield, you can obtain one through departure control on the ground, if within 30 minutes of the filed departure time
  • All three positions may be manned by separate controllers, or in the case of low traffic hours or non-busy airports, the same person
    • IFR flight plans should be filed at least 30 minutes before your estimated departure time to preclude possible delay in receiving a release time
    • Non-scheduled operations at and above FL 230 should be filed at least 4 hours before the estimated time of departure
  • Ground control and clearance delivery are often the same at average to small-sized airports, often operated by the same person, to provide appropriate clearance and taxi instructions before handed off to the Air Traffic Control Tower
    • Unless otherwise advised by the tower, remain on that frequency during taxiing and run-up, then change to local control frequency when ready to request takeoff clearance
    • When in receipt of a clearance, expect taxi instructions to quickly follow as the controller is likely to have the ready to minimize radio transmissions
  • While clearances can be relayed when at a non-towered remote location, they can also be received directly by calling the ARTCC, which services the area
  • Air Traffic Control Towers can provide other services, such as to furnish Braking Action Reports and Advisories
  • They exist when traffic requirements demand and subsequently designated the airspace as either Class B, class C, or class D depending on the level of congestion and services required/provided
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