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

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