Definition
A takeoff technique used when terrain, trees, buildings, or other obstructions lie beyond the departure end of the runway, requiring the airplane to climb at the steepest possible angle after liftoff. The pilot uses the manufacturer's recommended procedure for a maximum-performance climb, typically rotating at the published speed, climbing at V_X (best angle of climb speed) until the obstacle is cleared, then accelerating to V_Y (best rate of climb speed) for the remainder of the climb.
Plain English
A takeoff flown when something tall is in the way past the runway. The pilot lifts off and climbs at the steepest angle the airplane can manage, so it gains the most height in the shortest forward distance, until the obstacle is safely behind and below.
Context Anchor
Seen in takeoff planning, short-field takeoff training, and risk discussions about runways with obstacles near the departure end.
Derivation
Obstacle comes from Latin words meaning something that stands in the way. Clearance means being safely free of something, not touching or striking it. In this term, clearance means safe separation from an object in the takeoff path, not permission from air traffic control.
Why Pilots Care
It directly reduces the chance of striking an obstacle during the most critical low-altitude phase of flight.
Grounding Statement
Picture a runway with trees beyond the far end: the takeoff is not complete just because the wheels leave the ground; the aircraft must also climb high enough to pass safely over the trees.
Intuition Check
Clearance does not mean an ATC clearance here. It means having enough safe space between the aircraft and the obstacle after takeoff.
Example Sentence 1
The strip was bordered by tall pines, so the instructor briefed an obstacle clearance takeoff and a climb at V_X until well above the treeline.
Example Sentence 2
Before every short-field departure the student reviewed the obstacle clearance takeoff numbers from the performance charts.