Definition
The minimum altitude that ensures safe vertical separation from terrain, buildings, towers, trees, and other obstacles along a departure or climb path. After takeoff, the airplane must be climbed to and maintained at or above this altitude until clear of all obstructions in the departure area.
Plain English
The lowest height the airplane needs to reach during the climb to safely pass over anything sticking up from the ground near the airport, such as trees, towers, or buildings.
Context Anchor
Used during takeoff and initial climb, especially when trees, terrain, buildings, or other obstacles are near the departure end of the runway.
Derivation
“Obstruction” comes from a root meaning something built up or placed in the way. “Clearance” here means safe space between the airplane and that thing. Together, the term points to the altitude where the airplane has enough vertical space to pass the obstruction safely.
Why Pilots Care
It directly determines the minimum climb performance needed to depart safely from an airport surrounded by obstacles.
Grounding Statement
Picture taking off toward trees: obstruction clearance altitude is the height where those trees are safely below your flight path.
Intuition Check
Do not confuse “clearance” here with permission from air traffic control. In this term, clearance means physical space above an obstruction.
Example Sentence 1
Before departure, the pilot reviewed the airport diagram and identified the obstruction clearance altitude needed to clear the ridge east of the runway.
Example Sentence 2
The departure procedure listed an obstruction clearance altitude of 1200 feet MSL to keep the aircraft safely above nearby towers.