Definition
On a precision or approach-with-vertical-guidance instrument approach, the specified altitude or height at which the pilot must decide whether to continue the approach to land or to execute a missed approach. Decision altitude (DA) is referenced to mean sea level (read from the altimeter set to the local altimeter setting). Decision height (DH) is referenced to the height above the touchdown zone or threshold elevation. Continuing below DA/DH requires the required visual references for the runway to be in sight; if they are not, an immediate missed approach must be flown.
Plain English
It's the point on a vertically guided instrument approach where the pilot has to make a go/no-go call. If they can see what they need to see to land, they keep going. If not, they break off the approach and climb away.
Context Anchor
Seen on the profile view of an instrument approach chart, especially on precision approaches and approaches with vertical guidance.
Derivation
Decision speaks to the action required at this point — a choice between landing and going around. Altitude is measured from sea level; height is measured from the runway or touchdown zone. The two terms exist because different approach systems reference the same critical point in different ways.
Why Pilots Care
It is the last safe point to decide whether to land or go around, protecting against controlled flight into terrain when visibility is insufficient.
Grounding Statement
At DA/DH, the choice is simple: see what you need to land safely, or fly the missed approach.
Intuition Check
Do not read “decision” as “the place where you start deciding.” The decision must already be clear at DA/DH: continue only if the required visual references are visible and landing can be made safely; otherwise, go missed. Also, DA is an altitude above sea level, while DH is a height above the runway area.
Example Sentence 1
Approaching DA on the ILS, the captain saw the approach lights, called them in sight, and continued to land.
Example Sentence 2
The published DA/DH for the ILS runway 27 approach is 250 feet MSL.