Decision Altitude (DA)
Definition
Decision Altitude (DA) is the specified altitude (MSL) on a precision or APV (Approach with Vertical Guidance) instrument approach at which the pilot must make a decision: either continue the approach and land if required visual references are in sight, or initiate a missed approach if they are not. It is also referred to as Decision Height (DH) when measured above runway threshold elevation (AGL).
DA is used with approaches like ILS, LPV, LNAV/VNAV, and RNP AR.
Purpose
- Define the point of decision-making during a precision approach
- Ensure obstacle clearance while providing vertical guidance to the runway
- Improve approach safety by establishing a strict, no-delay go-around trigger if landing is not assured
When DA Applies
DA vs. MDA
| Feature | Decision Altitude (DA) | Minimum Descent Altitude (MDA) |
|---|---|---|
| Approach type | Precision/APV | Non-precision |
| Action required | Immediate go-around at DA if no visual contact | May level off at MDA and wait until MAPt |
| Descent profile | Continuous descent | Step-down, level-off |
| Published as | Altitude or height (DA or DH) | Altitude (MDA) |
| Missed approach trigger | At altitude | At Missed Approach Point (MAPt) |
Visual Reference Requirement
To continue below DA, the pilot must have:
- ✅ The runway environment in sight (lights, markings, threshold, etc.)
- ✅ A normal, stabilized approach path to land
- ✅ Sufficient visibility per approach minimums