Definition
Required obstacle clearance (ROC) is the minimum vertical distance an aircraft must remain above obstacles along a published instrument flight procedure segment, built into the procedure design to ensure safe terrain and obstacle separation when the aircraft flies the procedure as charted.
Plain English
ROC is the buffer of empty air the procedure designers build in between your aircraft and anything sticking up from the ground. As long as you fly the procedure correctly, that buffer is already there.
Context Anchor
Seen in instrument departure and obstacle departure procedure discussions, especially when explaining climb requirements after takeoff.
Derivation
“Clearance” here comes from the idea of being clear of something, meaning safely free from contact or conflict. In this term, it means physical space above obstacles, not permission from air traffic control.
Why Pilots Care
It guarantees safe vertical separation from terrain and structures when visibility is low or during instrument flight.
Grounding Statement
On an instrument departure, ROC is the planned vertical margin between the climbing airplane and nearby obstacles.
Intuition Check
Do not read “clearance” here as ATC permission. ROC means required physical separation from obstacles.
Example Sentence 1
On a standard departure, the required obstacle clearance is provided as long as the pilot maintains at least the published climb gradient.
Example Sentence 2
The pilot confirmed the ROC was sufficient before beginning the climb on instruments.