Flying An ILS To Minimums And What The Approach Lights Actually Tell You At Decision Height

Flying an ILS to Category I minimums means arriving at a decision height of 200 feet above the touchdown zone with visibility as low as half a mile (or an RVR of about 2,400 feet) and deciding, in an instant, whether to land or go missed. Under FAR 91.175, you may only continue below decision height if you have the required flight visibility, the aircraft is positioned for a normal landing, and you can see at least one specific visual reference for the runway. The approach lights are usually the first thing you see - but seeing only the approach lights carries a critical limitation that stops your descent at 100 feet.

What an ILS Actually Gives You

The Instrument Landing System (ILS) provides two guidance signals. The localizer supplies left-and-right guidance aligned with the runway centerline. The glideslope supplies up-and-down guidance along a beam angled at roughly three degrees down to the touchdown zone.

Fly the intersection of those two signals and the system walks you down a wire in the sky, straight to the pavement. A full ILS - a Category I approach - typically takes you to a 200-foot decision height with visibility as low as 1/2 mile or an RVR of 2,400 feet.

That number, 200 feet, is the one that matters. At decision height you make a decision: you either have what the regulations require to continue, or you go around. There is no third option.

What You Must See to Descend Below Decision Height

Under 14 CFR 91.175, you cannot descend below decision height unless three conditions are true at the same time:

You have the required flight visibility for that approach.
The aircraft is in a position to make a normal landing using normal maneuvers.
You can see and identify at least one of a specific list of visual references for that runway.

That third condition is the one pilots memorize. The full list of visual references that count:

The approach light system (with the limitation described below)
The threshold
The threshold markings
The threshold lights
The runway end identifier lights (REIL)
The visual glideslope indicator (VASI or PAPI)
The touchdown zone or touchdown zone markings
The touchdown zone lights
The runway or runway markings
The runway lights

See at least one of those, meet the visibility, and be positioned to land normally, and you are legal to continue. See nothing usable, and you fly the miss.

The Approach Light Rule That Trips Pilots Up

The approach light system is the long trail of bright lights leading up to the runway threshold, out in front of the pavement. On a full system it can stretch well over 2,000 feet from the threshold, and when you break out at minimums it is very often the first thing that resolves out of the murk - not the runway, the lights.

Here is the catch. If the approach lights are the only thing you can see, the regulation allows you to descend only to 100 feet above the touchdown zone elevation - no lower - unless you can also see something more definitive.

What counts as more definitive? The red terminating bars or the red side row bars of the approach light system. Or, by the time you reach that 100-foot gate, the runway itself, its markings, the threshold, or the touchdown zone coming into view.

So picture it in the real airplane. At 200 feet: gray, then a smear of light - the approach lights. Good. You keep descending, but the ground is rising to meet you. At 100 feet you need more than the light bar alone. You need the red terminating bars, the threshold, the runway markings, or the touchdown zone - something that says the runway is right there.

Why the Regulation Is the Floor, Not the Goal

The regulation tells you the minimum you must have to legally continue. It does not tell you the approach is a good idea. There is a real difference between legally breaking out and comfortably breaking out.

The transition at minimums - going from heads-down on the instruments to the visual picture outside, in a second or two, at 200 feet, in reduced visibility - is one of the highest-workload moments in all of flying.

This matters most for pilots who rarely fly approaches to actual minimums. Most real-world instrument flying breaks out comfortably high - 1,000 to 1,500 feet - with plenty of time. The true ragged-edge minimums approach is a perishable skill that gets rusty fast.

How to Fly a Minimums Approach Well

Brief the approach lights specifically. Don’t just note the decision altitude and the missed approach. Know what approach lighting the runway has. A full system with red terminating bars gives you options down to 100 feet; a runway with minimal or no approach lighting does not. That changes your whole picture of what breakout will look like.

Decide before you get there. The word decision is in decision height for a reason. Know before you reach that altitude that if you arrive without the references, you are going around. No debate at 200 feet, no ducking under, no leaning forward to squint for the runway. The pilots who get hurt are the ones who arrive at minimums undecided and try to negotiate with the weather.

Keep flying the airplane through the transition. When the lights appear, the temptation is to fixate and chase the visual, dropping your instrument scan entirely. Ease into the visual picture while keeping the airplane stable, on speed, and on path. The airplane doesn’t know you saw the lights - it still needs to be flown.

Practice the go-around at least as often as the landing. With a safety pilot or instructor, fly under the hood down to minimums. The missed approach off a real minimums breakout - powering up, cleaning up, and transitioning back to instruments right at the ground - is arguably harder than the landing. Fly it until it’s boring.

Why This Matters for Pilots

A well-flown ILS to minimums is precision under pressure: trust in the system, trust in your training, and the discipline to make one clean decision at exactly the right moment. Those approach lights rising out of the gray are a reward - but only if you earned the right to see them by flying everything before them exactly right. Read the picture correctly and you land; read it wrong, or see nothing you can use, and you fly the miss.

Key Takeaways

A Category I ILS brings you to a 200-foot decision height with visibility as low as 1/2 mile or RVR 2,400 feet.
FAR 91.175 requires three things to descend below decision height: required flight visibility, a position for a normal landing, and at least one approved visual reference.
If the approach lights are the only reference in sight, you may descend to just 100 feet above touchdown zone elevation - no lower - until you see the red terminating/side row bars or the runway environment.
Decide to go around before reaching minimums; never negotiate with the weather at 200 feet.
Minimums approaches and the associated missed approach are perishable skills - practice both regularly with a safety pilot or instructor.