Definition
The vertical and horizontal distance maintained between an aircraft and any terrain, structures, trees, wires, or other obstructions along its flight path, particularly during departure, approach, and landing phases.
Plain English
Keeping enough space between the airplane and anything it could hit — like trees, poles, wires, fences, or buildings — as it climbs out or comes in to land.
Context Anchor
Seen when planning or flying a short-field approach, especially when trees, wires, or rising ground are near the runway end.
Derivation
Obstacle comes from Latin words meaning something that stands in the way. Clearance comes from clear, meaning free or open. Together, the phrase points to keeping the airplane free of anything in its path, not to getting permission from air traffic control.
Why Pilots Care
In short-field operations the aircraft must clear obstacles immediately after liftoff or before touchdown; inadequate clearance is a leading factor in runway-excursion and controlled-flight-into-terrain accidents.
Grounding Statement
On a short-field landing, the goal is to pass the obstacle safely and then touch down close enough to the start of the runway to stop in time.
Intuition Check
Obstacle clearance does not mean an air traffic control clearance. Here, clearance means physical space between the airplane and something it must not hit.
Example Sentence 1
On the short-field approach, the pilot crossed the 50-foot trees with adequate obstacle clearance and touched down within the first third of the runway.
Example Sentence 2
After liftoff the aircraft maintained a steady climb speed that provided the required obstacle clearance before turning crosswind.