"Closed traffic" is a request GA pilots regularly make at controlled (towered) airports in the US to request a clearance to fly a "closed" pattern around the airport (takeoff, crosswind, downwind, base, final, land, repeat) for takeoff and landing practice. Every pilot is exposed to this pattern in training and will utilize it hundreds, thousands, of times to hone in his/her skills during his/her aviation career. This is not a pattern you would see an airliner perform unless it had to abort a landing and go around, but even then that is a special case with different interactions. GA pilots use this traffic pattern in training, it's not unusual to have a handful of GA aircraft buzzing around a class D or non-towered airport flying in closed traffic while mixing in with regular traffic. Closed traffic is discouraged at Class C (in the US) and higher airports, but it is not unusual to see it at these airports as well. At a towered airport, a pilot can practice communications while at it because he/she is interacting with the tower controller several times each loop and each time around may present different interactions depending on how busy the airport is as the controller does his best to juggle all the birds within his airspace simultaneously. Doing this "pattern work" is not only absolutely necessary in training but It can also be more fun and challenging than flying from point A to point B and may not require you to leave the airspace of your own or nearby airport.
The Simple Development Case:
1) Pilot requests a clearance for "closed traffic" when ready for takeoff.
2) Pilot takes off and flies the pattern announcing his position when midfield on downwind.
3) ATC grants landing clearance with the "option" (explained later).
4) Repeat steps 2-3 until ready for a "full stop" landing.
The Harder Development Case:
Same as the simple case but with the additional possibility of closed traffic requests while inbound, and the added complexity of ATC having to juggle (control the sequence) of pattern traffic as well as regular inbound and outbound traffic.
THE DETAILS:
There are 2 ways in which a pilot typically enters into a closed traffic pattern: While already at the practice airport or during his approach to that airport.
Making a Closed Traffic Request While Still on the Ground:
For pilots already at the airport the request is typically made just before receiving takeoff clearance while holding short of the designated departure runway. The interaction would typically go something like this:
Request:
[Agency tower][Callsign], Holding short [runway], ready for takeoff, request closed traffic.
Readback:
Cleared for takeoff, runway [runway] [Callsign]
Occasionally, depending on ATC workload or other circumstances (eg, too many airplanes already in the pattern) the request may be denied or the pilot is given the option to initiate his request from an alternate (less busy) runway, typically the request is approved.
Once the airplane has departed it will fly a short upwind leg, turn 90 deg. crosswind (following the established pattern direction for the runway or as modified by tower), downwind and level off at about 1000 ft AGL, base, final, landing, and repeat. If the airport has radar the tower controller will generally issue a landing clearance by the time the airplane reaches midfield on the downwind leg. Occasionally, the controller may be too busy and the clearance may be delayed in which case the pilot would gently remind the controller of his position by the time he is broadside the numbers on the downwind leg. If the clearance does not come before reaching the base turning point, pilot continues to fly downwind until it does. A delayed clearance would typically be due to other arriving traffic or some other complication. Such interaction would go something like this:
[Agency tower][Callsign], Downwind
To which the controller, depending on traffic load and other factors permitting, would typically respond:
[Callsign][Agency tower], Cleared for the option, Runway [runway]. (giving the pilot the option to do a full stop landing, stop and go, touch and go, or missed approach). This is the most open clearance a pilot would receive and is the one that pilots normally expect by default.
Readback:
Cleared for the option, runway [runway], [Callsign]
If the controller cannot accommodate an "optional" landing he will let the pilot know what the expectation is when he issues the landing clearance. For example, there may be other arriving traffic in close proximity and only a "touch and go" or a "full stop" landing can be approved at that moment. Many variations are possible.
Other times, in order to make life easier for himself but still grant the pilot the "option" the controller might direct the pilot to do an "extended downwind" and sneak him/her somewhere with the inbound traffic, or place him at the tail end of it as follows:
[Callsign][Agency tower], Extend downwind, will call your base.
Readback:
Extend downwind, you call my base, [Callsign]
In this instance, the pilot continues flying downwind parallel to the runway until he is called to enter base:
[Callsign][Agency tower], Turn to base following white Cessna on final.
Readback:
Turn base following white Cessna. Looking for traffic, [Callsign]
Once the pilot identifies and can visually follow the indicated traffic he waits for it to pass him on final and lets the controller know that he has the traffic in sight, then proceeds to turn to base and final. This interaction would go something like this:
[Agency tower][Callsign], Traffic in sight, turning base.
Instants later, the clearance for landing arrives:
[Callsign][Agency tower], Number 2 behind white Cessna on final, Cleared for the option, runway [runway]
Radback:
Number 2 behind traffic, Cleared for the option, runway [runway], [Callsign]
Now the pilot has an "option" landing clearance and is also approved to subsequently remain in the pattern. He would do his landing, takeoff, and repeat the sequence above as many times as desired or permitted by ATC, each time around dealing with the particular circumstances of the moment.
Another situation that may arise is if another airplane or object is occupying the runway in which case the controller would issue a missed approach and go around:
[Callsign][Agency tower], negative, please execute go around.
Readback:
Wilco, executing go around, [Callsign]
When the pilot has had his fill of pattern work for the day he would, out of courtesy, inform the controller that he is calling it quits and wants the next landing to be a "full stop." This puts the controller on notice that he will be making a regular landing and taxiing to a ground destination:
[Agency tower][Callsign], This will be a full stop. (after receiving his landing clearance)
Controller may or may not acknowledge.
===
Making a Closed Traffic Request While Inbound:
Another way to enter into "closed traffic" is on approach to the airport when requesting the landing clearance:
[Agency tower][Callsign], 10 miles NW, landing, request option for pattern work [Weatherinfo]
To which he might receive a directive such as:
[Callsign][Agency tower], proceed direct runway [runway], report 2 mile final.
[Callsign][Agency tower], report 2 mile base runway [runway]. (pilot expected to fly to base first and report 2 miles out)
[Callsign][Agency tower], report on the 45 runway [runway]. (pilot expected to enter the landing pattern on the "45" and report once on it.
Readback:
Proceed direct runway [runway], report 2 mile final, [Callsign]
Report 2 mile base runway [runway], [Callsign]
Report on the 45 runway [runway], [Callsign]
===
Development suggestions:
There are many other possible circumstances and communication interactions that might arise while in closed traffic but this covers the most common ones. For this reason and considering that closed traffic pattern work is typically only done by GA pilots, it would not be unreasonable to limit closed traffic under ATC control to Class D airports (for US) only. These are typically small, controlled (towered) municipal airports. The reason for this is that there is just too much traffic at larger or international airports for this type of interaction to be efficiently covered by ATC and is discouraged, and in some cases prohibited. At other larger airports, closed traffic would be directed to alternative less busy runways. "Pattern work" can also be done at uncontrolled (non-towered) airports but obviously there is no ATC interaction at those airports, only CTAF reporting and pilot-to-pilot interactions. At most uncontrolled airports in the US, radio communications is not even a requirement, it is mostly a courtesy extended to other pilots when approaching, departing, taxiing, or entering and maintaining closed traffic. In the latter case, the pilot announces his position at each leg around the pattern informing others of his intentions.
Initially, for development in AutoATC it would be reasonable to limit ATC interactions to the simplest situations such as at small towered airports with no other approaching traffic, thus requiring only the most basic directives (i.e., entering the pattern (ground or inbound), a downwind position update, and "option" landing clearance). Everything else could be added as resources permit.
Background:
"Closed traffic" is a request GA pilots regularly make at controlled (towered) airports in the US to request a clearance to fly a "closed" pattern around the airport (takeoff, crosswind, downwind, base, final, land, repeat) for takeoff and landing practice. Every pilot is exposed to this pattern in training and will utilize it hundreds, thousands, of times to hone in his/her skills during his/her aviation career. This is not a pattern you would see an airliner perform unless it had to abort a landing and go around, but even then that is a special case with different interactions. GA pilots use this traffic pattern in training, it's not unusual to have a handful of GA aircraft buzzing around a class D or non-towered airport flying in closed traffic while mixing in with regular traffic. Closed traffic is discouraged at Class C (in the US) and higher airports, but it is not unusual to see it at these airports as well. At a towered airport, a pilot can practice communications while at it because he/she is interacting with the tower controller several times each loop and each time around may present different interactions depending on how busy the airport is as the controller does his best to juggle all the birds within his airspace simultaneously. Doing this "pattern work" is not only absolutely necessary in training but It can also be more fun and challenging than flying from point A to point B and may not require you to leave the airspace of your own or nearby airport.
The Simple Development Case:
1) Pilot requests a clearance for "closed traffic" when ready for takeoff. 2) Pilot takes off and flies the pattern announcing his position when midfield on downwind. 3) ATC grants landing clearance with the "option" (explained later). 4) Repeat steps 2-3 until ready for a "full stop" landing.
The Harder Development Case:
Same as the simple case but with the additional possibility of closed traffic requests while inbound, and the added complexity of ATC having to juggle (control the sequence) of pattern traffic as well as regular inbound and outbound traffic.
THE DETAILS:
There are 2 ways in which a pilot typically enters into a closed traffic pattern: While already at the practice airport or during his approach to that airport.
Making a Closed Traffic Request While Still on the Ground:
For pilots already at the airport the request is typically made just before receiving takeoff clearance while holding short of the designated departure runway. The interaction would typically go something like this:
Request: [Agency tower][Callsign], Holding short [runway], ready for takeoff, request closed traffic.
Affirmative ATC response: [Callsign][Agency tower], Cleared for takeoff, runway [runway], closed traffic approved.
Readback: Cleared for takeoff, runway [runway] [Callsign]
Occasionally, depending on ATC workload or other circumstances (eg, too many airplanes already in the pattern) the request may be denied or the pilot is given the option to initiate his request from an alternate (less busy) runway, typically the request is approved.
Once the airplane has departed it will fly a short upwind leg, turn 90 deg. crosswind (following the established pattern direction for the runway or as modified by tower), downwind and level off at about 1000 ft AGL, base, final, landing, and repeat. If the airport has radar the tower controller will generally issue a landing clearance by the time the airplane reaches midfield on the downwind leg. Occasionally, the controller may be too busy and the clearance may be delayed in which case the pilot would gently remind the controller of his position by the time he is broadside the numbers on the downwind leg. If the clearance does not come before reaching the base turning point, pilot continues to fly downwind until it does. A delayed clearance would typically be due to other arriving traffic or some other complication. Such interaction would go something like this:
[Agency tower][Callsign], Downwind
To which the controller, depending on traffic load and other factors permitting, would typically respond:
[Callsign][Agency tower], Cleared for the option, Runway [runway]. (giving the pilot the option to do a full stop landing, stop and go, touch and go, or missed approach). This is the most open clearance a pilot would receive and is the one that pilots normally expect by default.
Readback: Cleared for the option, runway [runway], [Callsign]
If the controller cannot accommodate an "optional" landing he will let the pilot know what the expectation is when he issues the landing clearance. For example, there may be other arriving traffic in close proximity and only a "touch and go" or a "full stop" landing can be approved at that moment. Many variations are possible.
Other times, in order to make life easier for himself but still grant the pilot the "option" the controller might direct the pilot to do an "extended downwind" and sneak him/her somewhere with the inbound traffic, or place him at the tail end of it as follows:
[Callsign][Agency tower], Extend downwind, will call your base.
Readback: Extend downwind, you call my base, [Callsign]
In this instance, the pilot continues flying downwind parallel to the runway until he is called to enter base:
[Callsign][Agency tower], Turn to base following white Cessna on final.
Readback: Turn base following white Cessna. Looking for traffic, [Callsign]
Once the pilot identifies and can visually follow the indicated traffic he waits for it to pass him on final and lets the controller know that he has the traffic in sight, then proceeds to turn to base and final. This interaction would go something like this:
[Agency tower][Callsign], Traffic in sight, turning base.
Instants later, the clearance for landing arrives: [Callsign][Agency tower], Number 2 behind white Cessna on final, Cleared for the option, runway [runway]
Radback: Number 2 behind traffic, Cleared for the option, runway [runway], [Callsign]
Now the pilot has an "option" landing clearance and is also approved to subsequently remain in the pattern. He would do his landing, takeoff, and repeat the sequence above as many times as desired or permitted by ATC, each time around dealing with the particular circumstances of the moment.
Another situation that may arise is if another airplane or object is occupying the runway in which case the controller would issue a missed approach and go around:
[Callsign][Agency tower], negative, please execute go around.
Readback: Wilco, executing go around, [Callsign]
When the pilot has had his fill of pattern work for the day he would, out of courtesy, inform the controller that he is calling it quits and wants the next landing to be a "full stop." This puts the controller on notice that he will be making a regular landing and taxiing to a ground destination:
[Agency tower][Callsign], This will be a full stop. (after receiving his landing clearance)
Controller may or may not acknowledge.
===
Making a Closed Traffic Request While Inbound:
Another way to enter into "closed traffic" is on approach to the airport when requesting the landing clearance:
[Agency tower][Callsign], 10 miles NW, landing, request option for pattern work [Weatherinfo]
To which he might receive a directive such as:
[Callsign][Agency tower], proceed direct runway [runway], report 2 mile final. [Callsign][Agency tower], report 2 mile base runway [runway]. (pilot expected to fly to base first and report 2 miles out) [Callsign][Agency tower], report on the 45 runway [runway]. (pilot expected to enter the landing pattern on the "45" and report once on it.
Readback: Proceed direct runway [runway], report 2 mile final, [Callsign] Report 2 mile base runway [runway], [Callsign] Report on the 45 runway [runway], [Callsign]
=== Development suggestions:
There are many other possible circumstances and communication interactions that might arise while in closed traffic but this covers the most common ones. For this reason and considering that closed traffic pattern work is typically only done by GA pilots, it would not be unreasonable to limit closed traffic under ATC control to Class D airports (for US) only. These are typically small, controlled (towered) municipal airports. The reason for this is that there is just too much traffic at larger or international airports for this type of interaction to be efficiently covered by ATC and is discouraged, and in some cases prohibited. At other larger airports, closed traffic would be directed to alternative less busy runways. "Pattern work" can also be done at uncontrolled (non-towered) airports but obviously there is no ATC interaction at those airports, only CTAF reporting and pilot-to-pilot interactions. At most uncontrolled airports in the US, radio communications is not even a requirement, it is mostly a courtesy extended to other pilots when approaching, departing, taxiing, or entering and maintaining closed traffic. In the latter case, the pilot announces his position at each leg around the pattern informing others of his intentions.
Initially, for development in AutoATC it would be reasonable to limit ATC interactions to the simplest situations such as at small towered airports with no other approaching traffic, thus requiring only the most basic directives (i.e., entering the pattern (ground or inbound), a downwind position update, and "option" landing clearance). Everything else could be added as resources permit.