When Can You Descend Below DA or MDA on an Instrument Approach?

Quick Answer

Under 14 CFR 91.175(c), you may descend below DA or MDA only when all three conditions are met: the aircraft is continuously in a position from which a normal-rate descent to landing on the intended runway can be made using normal maneuvers; the flight visibility is at least what the procedure prescribes; and at least one of the specified visual references for the intended runway is distinctly visible and identifiable.

The Three Gates, One at a Time

DPEs test this with a plate on the table and a scenario in motion — "you're at DA and you see something. Can you continue?" The disciplined answer walks all three gates:

1. Position. You must be able to land on the intended runway with normal maneuvers and a normal descent rate. Spotting the runway from a position that would require diving at it fails this gate even with perfect visibility.
2. Flight visibility. At least the visibility prescribed for the procedure — and it is flight visibility, judged from the cockpit, not the reported tower value. The examiner may probe: reported visibility just dropped below minimums inside the FAF — under Part 91 you may continue the approach and land if flight visibility at minimums meets the requirement. Your judgment call, defensible either way, but know whose visibility governs.
3. Visual references. At least one of the items listed in 91.175(c)(3) for the intended runway: the threshold, threshold markings or lights, the REIL, the VASI/PAPI, the touchdown zone or its markings or lights, the runway or runway markings or lights — or the approach light system.

The Approach-Light Asterisk

The approach light system is the reference with a condition attached, and examiners love it: with only the approach lights in sight, you may descend below DA/MDA but not below 100 feet above the touchdown zone elevation — unless the red terminating bars or red side row bars are also distinctly visible. Those red elements exist on ALSF-type systems; see them and you may continue lower. Quote the 100-foot number precisely; "down to about 100 feet" is the kind of imprecision that invites escalation.

DA vs. MDA: the Setup Question

This question usually arrives inside a broader distinction: a DA is a decision altitude on a precision or APV approach — you decide at DA while descending on a glidepath, and some altitude loss during the missed is expected and accounted for. An MDA is a minimum you may not descend below on a nonprecision approach without the 91.175(c) conditions — you level at MDA and hold it to the missed approach point. Blending the two ("I'll dip below MDA a bit like a DA") is an immediate escalation, because the protected surfaces are built differently.

Expect the closing follow-up: none of the references appear by the MAP, or you lose them after descending — execute the missed approach (91.175(e)), fly the published procedure from the plate, and say you would point at it.

The IFR Oral Exam Guide ($24) drills approaches and minimums exactly this way — plate on the table, gate by gate, every number cited — across 269 examiner Q&As and 12 scenario drills in 155 pages aligned to FAA-S-ACS-8C.