Obstacle Clearance Altitude/Height

Obstacle clearance altitude/height (OCA/OCH) is the lowest altitude (OCA) or height above the aerodrome elevation (OCH) used in establishing compliance with the appropriate obstacle clearance criteria for an instrument approach procedure. It represents the minimum height at which obstacle clearance can be guaranteed within the protected area for a specific approach.

OCA/OCH vs. MDA/DH

OCA/OCH is the underlying obstacle clearance calculation. MDA or DH is the operationally published minimum, which may be rounded up from OCA/OCH to a publishable value (e.g., to the nearest 10 ft). MDA ≥ OCA. The relationship ensures a safety buffer above the calculated obstacle clearance value.

Related Terms

See also: MDA, Decision Height, Minimum Safe Altitude.