Definition
The lowest altitude, depicted on approach charts, that provides the required obstacle clearance for an aircraft being radar vectored by ATC. It is the floor below which a controller will not assign altitudes when vectoring an aircraft within a defined area on or near an instrument approach.
Plain English
The lowest altitude a controller is allowed to send you down to when they are steering you with radar. It guarantees you stay safely above terrain and obstacles in that area.
Context Anchor
Used in instrument flying and radar assistance when altitude assignments must keep an aircraft above terrain and obstacles.
Derivation
Terrain comes from Latin words meaning land or earth. Obstacle comes from a Latin word meaning something that stands in the way. Minimum means the smallest allowed amount, and altitude means height. Together, the phrase points to the lowest height that still clears the land and anything sticking up from it.
Why Pilots Care
Maintains required separation to prevent controlled flight into terrain when pilots receive radar guidance.
Grounding Statement
Picture this altitude as a hard floor drawn above the highest terrain and obstacles in the area, with a required safety cushion built in.
Intuition Check
Do not read “minimum” as “recommended” or “comfortable.” Here it means the lowest altitude that still preserves the required obstacle-protection margin.
Example Sentence 1
The controller kept us at 3,000 feet on the vector because that was the terrain/obstacle clearance minimum altitude for that sector.
Example Sentence 2
The pilot maintained the terrain/obstacle clearance minimum altitude throughout the radar-assisted segment.