Definition
The departure leg of the standard airport traffic pattern is the straight flight path along the extended runway centerline that begins at takeoff and continues until the pilot turns onto the crosswind leg or, if departing the pattern, continues straight out.
Plain English
It is the straight-ahead climb directly off the runway after liftoff, before any turns are made.
Context Anchor
Seen in standard traffic pattern diagrams and in instructor briefings about what to do immediately after liftoff.
Derivation
Departure' comes from the Old French 'departir,' meaning to leave or go away. 'Leg' is used in aviation to mean one segment of a flight path. Together: the segment of the pattern flown while leaving the runway.
Why Pilots Care
It provides time to establish a positive rate of climb and maintain separation from other traffic before entering the crosswind leg.
Grounding Statement
Picture the airplane lifting off and continuing straight ahead over the runway’s path while it climbs.
Intuition Check
Do not read leg as a body part or as any direction after takeoff. In a traffic pattern, a leg is one specific section of the flight path, and the departure leg is the straight-out section after takeoff.
Example Sentence 1
After liftoff, the pilot climbed straight ahead on the departure leg until reaching pattern altitude before turning crosswind.
Example Sentence 2
The instructor reminded the student to complete the departure leg climb before initiating the crosswind turn.