TRAFFIC PATTERN- The traffic flow that is prescribed for aircraft landing at, taxiing on, or taking off from an airport. The components of a typical traffic pattern are upwind leg, crosswind leg, downwind leg, base leg, and final approach. 

a. Upwind Leg- A flight path parallel to the landing runway in the direction of landing. 

b. Crosswind Leg- A flight path at right angles to the landing runway off its upwind end. 

c. Downwind Leg- A flight path parallel to the landing runway in the direction opposite to landing. The downwind leg normally extends between the crosswind leg and the base leg. 

d. Base Leg- A flight path at right angles to the landing runway off its approach end. The base leg normally extends from the downwind leg to the intersection of the extended runway centerline. 

e. Final Approach- A flight path in the direction of landing along the extended runway centerline. The final approach normally extends from the base leg to the runway. An aircraft making a straight-in approach VFR is also considered to be on final approach. 

(See STRAIGHT-IN APPROACH VFR.) 

(See TAXI PATTERNS.) 

(See ICAO term AERODROME TRAFFIC CIRCUIT.) 

(Refer to 14 CFR Part 91.) 

(Refer to AIM.) 

TRAFFIC SITUATION DISPLAY (TSD)- TSD is a computer system that receives radar track data from all 20 CONUS ARTCCs, organizes this data into a mosaic display, and presents it on a computer screen. The display allows the traffic management coordina- tor multiple methods of selection and highlighting of individual aircraft or groups of aircraft. The user has the option of superimposing these aircraft positions over any number of background displays. These background options include ARTCC boundaries, any stratum of en route sector boundaries, fixes, airways, military and other special use airspace, airports, and geopolitical boundaries. By using the TSD, a coordinator can monitor any number of traffic situations or the entire systemwide traffic flows. 

TRAJECTORY- A EDST representation of the path an aircraft is predicted to fly based upon a Current Plan or Trial Plan. 

(See EN ROUTE DECISION SUPPORT TOOL.) 

TRAJECTORY MODELING- The automated pro- cess of calculating a trajectory. 

TRAJECTORY OPTIONS SET (TOS)- A TOS is an electronic message, submitted by the operator, that is used by the Collaborative Trajectory Options Program (CTOP) to manage the airspace captured in the traffic management program. The TOS will allow the operator to express the route and delay trade-off options that they are willing to accept. 

TRANSFER OF CONTROL- That action whereby the responsibility for the separation of an aircraft is transferred from one controller to another. 

(See ICAO term TRANSFER OF CONTROL.) 

TRANSFER OF CONTROL [ICAO]- Transfer of responsibility for providing air traffic control service. 

TRANSFERRING CONTROLLER- A controller/ facility transferring control of an aircraft to another controller/facility. 

(See ICAO term TRANSFERRING UNIT/CONTROLLER.) 

## TRANSFERRING FACILITY - 

(See TRANSFERRING CONTROLLER.) 

TRANSFERRING UNIT/CONTROLLER [ICAO]- Air traffic control unit/air traffic controller in the process of transferring the responsibility for providing air traffic control service to an aircraft to the next air traffic control unit/air traffic controller along the route of flight. 

Note: See definition of accepting unit/controller. 

## TRANSITION- 

a. The general term that describes the change from one phase of flight or flight condition to another; e.g., transition from en route flight to the approach or transition from instrument flight to visual flight. 

b. A published procedure (DP Transition) used to connect the basic DP to one of several en route airways/jet routes, or a published procedure (STAR Transition) used to connect one of several en route airways/jet routes to the basic STAR. 

(Refer to DP/STAR Charts.) 

TRANSITION POINT- A point at an adapted number of miles from the vertex at which an arrival aircraft would normally commence descent from its en route altitude. This is the first fix adapted on the arrival speed segments. 

