Definition
The vertical and lateral clearance maintained between an aircraft and terrain, vegetation, buildings, towers, antennas, wires, and other physical objects on or rising from the surface. In instrument flight, this clearance is built into published procedures, minimum altitudes, and ATC-assigned altitudes so that an aircraft flying the procedure correctly remains safely above and clear of all charted obstacles.
Plain English
Keeping the aircraft a safe distance away from anything it could hit on the ground, including hills, trees, towers, and tall buildings.
Context Anchor
Seen in instrument procedures, minimum altitude discussions, obstacle clearance, approaches, departures, and any situation where the pilot may not be able to see terrain or structures outside.
Why Pilots Care
Prevents collisions with terrain or structures when visual references are unavailable or unreliable.
Intuition Check
Do not read separation as simply “not touching.” In aviation, separation means a planned safety margin from obstacles, not barely clearing them. Also, obstacles are not only buildings or towers; hills, trees, and terrain count too.
Example Sentence 1
Flying the published minimum en route altitude guarantees separation from natural and manmade obstacles along that airway segment.
Example Sentence 2
Radar vectors are assigned at the minimum vectoring altitude to provide separation from natural and manmade obstacles.