When can you actually descend below minimums?
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Reaching minimums is the part of an approach everybody briefs. Leaving them is the part that gets rushed — usually at the exact moment workload is highest and the runway environment is somewhere ahead in the murk.
The rule is 14 CFR 91.175(c), and it is worth knowing that it sets three conditions, all of which must hold before you go below DA or MDA:
- The aircraft is continuously in a position from which a normal descent to a landing on the intended runway can be made at a normal rate, using normal manoeuvres.
- Flight visibility is at least what the approach prescribes.
- At least one of the listed visual references is distinctly visible and identifiable — the approach light system, threshold, threshold markings or lights, REIL, VASI, touchdown zone, touchdown zone markings or lights, or the runway and its markings or lights.
The one most often forgotten is the qualifier on the approach lights: with the ALS as your only reference, you may not go below 100 feet above touchdown zone elevation unless the red terminating bars or red side row bars are also distinctly visible.
From the right seat: the condition students most often miss is the first one, because it is the only one that is a judgement rather than a number. Visibility and visual references are things you check. "Continuously in a position for a normal descent at a normal rate" is a thing you have to decide — and it is the one that quietly rules out the dive-and-drive save at the last second.
Fifteen minutes, and worth it before your next IPC.