MDA (Minimum Descent Altitude)
Minimum Descent Altitude (MDA)
Definition
The Minimum Descent Altitude (MDA) is the lowest altitude, expressed in feet above mean sea level (MSL), to which an aircraft may descend on a non-precision instrument approach without having the required visual references for landing in sight. The MDA is designed to provide a safe vertical buffer above obstacles until a missed approach is initiated or a landing is made.
Purpose
- Ensure obstacle clearance during the final segment of a non-precision approach
- Define the limit of descent without visual contact with the runway
- Support decision-making between continuing visually or executing a missed approach
Where MDA Applies
- Non-precision approaches (e.g., VOR, NDB, RNAV (LNAV), LOC)
- Circling approaches, where maneuvering to a runway other than that aligned with the approach is required
- Visual segments after some RNAV or step-down approaches
Key Characteristics
| Attribute | Description |
|---|---|
| Published on approach charts | Specified for each aircraft category (A–D) |
| Not a decision altitude | Descent must stop at or before reaching MDA |
| Time or distance-based missed approach | Must initiate go-around at MAPt if visual contact not established |
| Obstacle clearance built-in | Usually ~295 ft above highest obstacle within protected area |
MDA vs. Decision Altitude (DA)
| Feature | MDA | DA (Precision Approach) |
|---|---|---|
| Used on | Non-precision approaches | Precision approaches (e.g., ILS) |
| Descent profile | Step-down to altitude, then level | Continuous descent to DA |
| Action at minimum | Must not descend below until visual | Must initiate missed approach immediately if no visual |
| Go-around point | After reaching MAPt (Missed Approach Point) | At DA |
Example Phraseology
- “Minimum descent altitude 1,200 feet.”
- “Holding MDA until missed approach point.”
- “No contact at MDA, going around.”
Visual Reference Required to Continue Below MDA
You may descend below MDA only when:
- ✅ The runway environment is clearly in sight (e.g., runway lights, markings, threshold)
- ✅ You can make a normal descent and landing
- ✅ Visibility is equal to or better than the required minimums
Pilot Tips
- ✅ Begin level-off early to avoid busting MDA
- ✅ Use altitude callouts and checklists during final approach
- ✅ Practice MDA scenarios in LearnATC's non-precision modules
- ✅ Always know your aircraft category and refer to the correct minima column on the approach chart
Related Terms
- Missed Approach Point (MAPt) – the point at which you must decide to land or go around
- OCH (Obstacle Clearance Height) – used in calculating MDA
- Circling MDA – higher minima used when circling to a different runway
