TOWER CONTROLLER

Approved by George Enciu, vACC Director

Created by Teodor G Petrică, OPS

1. Position overview

The tower is generally responsible for all movements on the runways and within the control zone (CTR). It also determines the direction of operation at the airport. Different or additional tasks are described in the respective airport SOP.

In addition to the safe handling of air traffic, it is particularly important to work efficiently when there is a high volume of traffic, as is often the case on the network at the moment! The pilot principle also applies here: "Safe, orderly and expeditious", i.e. first and foremost safe, but immediately afterwards orderly and smoothly (efficient).

2. Tasks

2.1. Setting the Operation Direction

The tower determines which runway is used at an airport. This is primarily determined by the prevailing wind (direction and strength), which can be determined using METAR and TAF. If local peculiarities must be taken into account (e.g. maximum tailwind components for a runway). For instance, the maximum tailwind component at LROP is 7 knots; at LRTR is 12 knots.

Aircraft prefer to take off and land against the wind. The name of the runway indicates the direction in which it is pointing according to the heading. Runway 08L in Bucharest Otopeni therefore points 079° towards the east. The opposite direction, runway 26R, is rotated by 180° and points 259°, which is approximately towards the west. The wind direction in the METAR indicates the direction from which the wind is coming. If the wind is coming from 260° (west), for example, runway 26R is used to be able to take off and land with a headwind. If the wind is not coming directly from the direction in which a runway is pointing, the one where the headwind component is greatest is used.

The active runway(s) are published via the ATIS, whenever this station is available.

Remarks

The operating direction should not be confused with the operating mode.

The operating mode is a term that describes how the selected runways are controlled. Each airfield has a variety of options. In addition to standard operation, an airfield can be operated for Low Visibility Operations (LVO), for example, in order to maintain flight operations even in bad weather.

At larger airfields with parallel runways, there are several possible ways of using them. Under certain conditions, the runways can be used in "Parallel Dependent", in which, for example, radar separation from the parallel runway must be maintained on the approach.

2.2. Taxi Movements in the Runway Area

The main area where a Tower service is runway. Tower is authorized to issue clearances for taxiing (lineup), crossing, backtracking, and finally taking off and landing. It is always important to maintain correct runway separation. In addition to a standard lineup clearance, a conditional clearance can also be used to optimize frequency efficiency. If the runway is immediately clear for departure, the lineup clearance can be skipped, and a direct takeoff clearance can be issued (see below).

2.3. Establishing the Sequence

The tower typically receives departing aircraft from the Ground controller in a random sequence, usually just before reaching the holding point of the active runway. If another runway must be crossed on the way to the active runway, the handover can occur earlier.

In air traffic control, the "first come, first served" principle generally applies. This means that the first aircraft at the runway is allowed to take off first. However, the tower may deviate from this principle to minimize average delay.

The arrival sequence, on the other hand, is predetermined for IFR traffic as the aircraft in the final approach are handed over by the Approach controller, and the Tower cannot alter this sequence. However, the Tower has authority over VFR traffic and can, for example, determine which VFR aircraft should fit into which IFR gap. Additionally, the Tower can establish a landing sequence for multiple VFR aircraft.

2.4. Clearance for Takeoffs and Landings

The most well-known clearances in the tower area are takeoff and landing clearances. Here, too, the rules for runway separation must be ensured. In the S2 training, the practice of not withholding a takeoff or landing clearance is also noteworthy. If necessary and conditions are met, reduced runway separation can be applied.

Takeoffs must also be timed so that either radar separation, wake turbulence separation, or a certain minimum spacing is ensured in the air. For more details, refer to the paragraph "Separation in the Tower Area" below.

At most airports, a separate transfer of communication is necessary once the aircraft is airborne.

An arriving aircraft can be cleared to land as soon as no other aircraft has a clearance for the same runway and runway separation is ensured.

2.5. Handling Missed Approaches

A missed approach or go-around can be initiated either by the controller or the pilot. As a Tower controller, it is important not to panic in such situations. The procedure for handling a missed approach is described below.

First of all, a controller must assume that a pilot can make a missed approach at any time up to and including touchdown! There must always be a plan B in the event of a missed approach.

From the controller's point of view, a missed approach should not be handled hectically, even in stressful situations, but rather according to a clear plan. These steps are now explained in detail:

1. Instruct a missed approach (only if initiated by the controller)
   • Since an instructed missed approach is usually safety-critical, the controller should raise their voice on the frequency and give a clearly audible ROT123 go around, if necessary twice in a row
   • A reason should be given briefly and concisely (e.g. ROT123 go around, traffic on runway)

or

1. Acknowledge missed approach (only if initiated by the pilot)

   • When the pilot reports that they is about to go around, this should be acknowledged with a ROT456, Roger. The instruction to fly the published missed approach is not necessary, as this is part of the approach procedure for which the pilot has been cleared
   • Since the first few seconds after initiating a missed approach are very stressful in the cockpit, especially in the one-person VATSIM cockpit, no further radio messages should be sent to the pilot - with the exception of instructions relevant to separation (see point 2).

2. If necessary, ensure/establish traffic information + staggering

   • In most cases, a pilot can fly the standard missed approach procedure. However, if the missed approach comes close to another aircraft - regardless of whether separation is always present or not - a traffic information should be given

3. Coordination with Approach / other stations

   • Every missed approach must be coordinated with the approach controller (if online). Verbal coordination should always be preferred, as pure labeling often gets lost in the tag.

4. Ask the pilot why and send them away

   • If the reason for the missed approach was not obvious (e.g. because it was instructed by the controller), the pilot should be asked (HYS109, report the reason for the missed approach). The reason may be relevant for other air traffic (e.g. wind shears - this information should definitely be passed on to subsequent pilots) or it may be of a technical nature (e.g. problems with the engine, landing gear, etc.), which means that the aircraft should be treated as a priority for the next approach / in an emergency situation as an emergency.
   • As soon as the aircraft is free of conflict with all other traffic and some time has passed since the missed approach was initiated, the aircraft is sent away to the approach controller.

5. Pass on reason to APP

   • As mentioned above, there can be many reasons for a missed approach, which are also important for the approach controller to know. Therefore, the reason should be passed on to the APP controller so that he does not have to ask the pilot again unnecessarily

2.6. Control of VFR Traffic Within the Control Zone

The Tower controller is responsible for the entry and exit of VFR traffic into and out of the control zone, issuing the necessary clearances. Since VFR traffic is not subject to mandatory separation from each other, traffic information must be provided if two aircraft are approaching each other. Additionally, the Tower has the ability to delay VFR traffic within the control zone as needed, using methods such as holding patterns, extending the downwind leg, or establishing a landing sequence. The Tower also clears VFR traffic for various training approaches, such as low approaches or touch-and-go.

All aspects of VFR handling are covered in the "VFR Operations" chapter below.

2.7. Monitoring Separation

IFR traffic must be separated from other IFR traffic within the control zone. Therefore, the Tower is responsible for ensuring separation between two IFR aircraft, including departures, arrivals, and missed approaches relative to other traffic.

For departures, the tower controls the timing of takeoff clearances to ensure aircraft are properly separated.

Approach controllers hand over arriving aircraft in a way that typically does not require the tower controller to intervene. However, there may be instances where a pilot unexpectedly reduces speed early, causing the following aircraft to close the gap. In such cases, the Tower must monitor separation and, if necessary, instruct a go-around to maintain safe distances.

In the event of a missed approach, the Tower must also ensure separation from other aircraft. For detailed information on separation in the Tower area, refer to the "Separation in Tower Area" paragraph below.

3. Separation in the Tower Area

As a tower, you are responsible for the departure sequence and the distances between departures. It will certainly take a while until you develop a feeling for how long you have to wait between two departures to get the desired distance.

Between two departures that require staggering, you must now calculate the largest value from:

• Radar separation (generally 3 NM): Radar separation is therefore always the minimum between two IFR aircraft.
• Wake Vortex Separation (4 - 8 NM): Depending on the category of wake turbulence, you also have to take wake turbulence separation into account.
• Departure Spacing (individual values): Sometimes local procedures require more distance than the spacing actually requires. One example is departures on the same SIDs: An additional requirement for departure spacing at most airports is that identical SIDs in a row need at least 5 NM.

While separation always describes the absolute minimum, spacing is a value that is always greater than or equal to the gradation minimum and includes an optional surcharge.

Expressed mathematically: Spacing = minimum gradation + optional surcharge

In individual cases, the Approach or Centre controller can also specify departure spacing if the airspace is very full. In this case, an MDI (minimum departure interval), usually expressed in minutes, can also be imposed. For example, if it says MDI SOKRU 6 Minutes, the Tower controller can only allow all departures to SOKRU to take off with an interval of 6 minutes.

Always consider the different speeds during takeoff. If you have a C150 in front and an B744 behind on a different SID, you could theoretically do 3 NM. It should be logical that this makes no sense, as the B744 flies at least twice as fast as the Cessna light traffic and therefore at 3 NM a separation violation occurs shortly afterwards. In such cases (rear departure significantly faster than front departure) it is advisable to let the fast traffic take off as number 1 and thus reverse the departure sequence.

Handling the approaches for you as a tower controller is quickly explained. You receive the approaching aircraft from the approach controller approximately 8 - 12 NM from the runway. If you have approaching traffic on your frequency, you should give them clearance to land as quickly as possible. If an approach is coming and you have no departing traffic, you should give them clearance to land directly on the initial call. The pilot must have received their landing clearance before crossing 1 NM final at the latest. If they does not have clearance there, a go-around will take place independently.

The Approach controller is responsible for the separation between approaches until the runway threshold is crossed.

If two approaches are so close that there is a risk of a separation violation, you must instruct one of the aircraft (usually the one behind) to make a missed approach before the separation violation occurs. In addition, traffic information about the traffic in question can be useful.

3.1. Radar Separation

The following table provides an overview of the radar separation obligation:

In other words, there is a radar separation obligation between:

• all flights in airspace A and (B - does not apply in Romania)
• IFR to IFR in airspace C, (D and E - does not apply in Romania)
• IFR to VFR (and vice versa) in airspace C
• Special VFR to IFR in the control zone

The following vertical separation must be applied between two aircraft subject to separation:

The following lateral separation must be applied between two aircraft subject to separation:

Formation flights must be spaced 1 NM further than the required minimum distance from other traffic. Two formation flights must be spaced 2 NM further than the required minimum distance from each other.

3.2. Wake Vortex Separation

Wake turbulence separation is used in areas where wake turbulence is expected.

• Between aircraft with separation obligation (see radar separation ), if::
• an aircraft is directly behind an aircraft flying ahead at the same altitude or less than 1000ft below

• an aircraft directly behind another aircraft, at its 6 o'clock position, crossing at the same altitude or less than 1000 ft below

• Between aircraft in the approach or departure phase of the flight when:

• an aircraft is directly behind an aircraft flying ahead at the same altitude or less than 1000ft below
• an aircraft directly behind another aircraft, at its 6 o'clock position, crossing at the same altitude or less than 1000 ft below
• both aircraft use the same runway or parallel runways less than 760m apart
• the aircraft use intersecting or parallel runways (separated by 760m or more) and one aircraft traverses the flight path of the aircraft ahead at the same altitude or less than 1000ft

Wake turbulence separation does not apply in the following cases:

• incoming VFR flights
• approaching IFR flights conducting a visual approach, have reported the aircraft ahead in sight and have been instructed to follow it and maintain separation

In these cases, a wake turbulence warning (CAUTION WAKE TURBULENCE) must be issued.

1. Departure phase A VFR flight is in the departure phase between take-off and
2. to reach 1000ft above airfield level or
3. to achieve horizontal flight or

4. to enter the (right) downwind approach

5. Approach phase A VFR flight is in the approach phase when it is at or below 1000ft above airfield level and until landing:

6. has flown into the traffic pattern or part of it or
7. has begun the final descent within a control zone

3.2.1. Wake turbulence categories

For this purpose, aircraft are divided into four wake turbulence categories (WTC) according to their maximum take-off mass (MTOM).

Of course, you don't need to know how heavy each aircraft is. In the flight plan, you will always find the corresponding WTC next to the aircraft type.

3.2.2. Separation Minimum Values

Wake vortex separation can be created either distance-based or time-based. Distance-based wake vortex separation is usually used. However, there are also situations in which this is not possible, which is why time-based wake vortex separation is used.

Distance based

Time based

With time-based wake turbulence separation, a distinction is made between the separation values ​​of departing and approaching aircraft.

A distinction is also made between a take-off from a taxiway junction or the full length of the runway. For a take-off on a crossing runway, the values ​​for a take-off from a taxiway junction generally apply. The scaling value increases by one minute each time.

In contrast to distance-based wake turbulence gradation, time-based wake turbulence gradation does not have a gradation value between heavy-heavy.

Aircraft taking off

Approaching aircraft

4. VFR Operations

TBA

5. Coordination

5.1. Coordination with Ground Controller

Under normal circumstances, all aircraft take-off in the full length of the runway. However, in some situations, some planes may take-off from an intersection with the runway, for this reason, the TWR must be informed by the GND that a certain plane will take off from an intersection.

5.2. Coordination with Approach Controller

Prior to releasing an aircraft for departure, the TWR controller must coordinate with the APP controller. This is typically done using the format CALLSIGN SID where the TWR controller informs the APP controller of the aircraft’s call sign and Standard Instrument Departure (SID) route. The APP controller then has several options:

1. Release the Traffic: The APP controller approves the departure without any additional constraints.
2. Release with Constraints: The APP controller may approve the departure but with specific constraints, such as altitude restrictions or heading adjustments to manage traffic flow.
3. Not Release the Traffic: The APP controller can deny the release if the traffic conditions do not permit a safe departure at that moment.

All departures that are set to enter the Terminal Maneuvering Area (TMA) are subject to this approval request. This internal coordination is done verbally to ensure clarity and immediate reply.

In the event of a missed approach or go-around, the TWR controller must promptly inform the APP controller. This allows the APP controller to make necessary adjustments to the approach sequence and manage the traffic flow accordingly.

The APP controller can also coordinate special requests with the TWR controller for go-arounds or initial climb clearances. This is particularly important if the traffic flow is expected to be higher than usual. For example, during peak hours or special events, traffic management might require different handling compared to normal daily operations.

If there are special traffic flow requirements, the APP controller may request the TWR controller to implement specific procedures for certain flights. These could include:

1. Go-Around Procedures: Special instructions for aircraft that need to execute a go-around to ensure they are safely re-integrated into the approach sequence.

2. Initial Climb Clearance: Adjusting the initial climb clearance for departing aircraft to manage vertical separation and ensure efficient use of airspace.

This coordination ensures that both controllers are aligned on the traffic management plan and can respond swiftly to changing conditions, maintaining safety and minimizing delays.

6. Phraseology

TBA

Last update: 2024-06-23