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When Can You Descend Below Minimums On Your Next Instrument Approach?

Boldmethod

When you're flying an instrument approach, you can go all the way down to the published minimums without seeing a thing (except clouds).

But what do you need to go below minimums and land?

According to FAR 91.175(c), there are three requirements:

  • You must always be able to make a descent to landing on the intended runway using normal maneuvers and a normal descent rate,
  • The flight visibility (that you observe) must meet or exceed the minimums published for the approach, and
  • You must be able to distinctly identify one of the approved visual references for the runway (often called the "runway environment")
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So What Do You Need To See On Your Approach To Go Below Minimums?

You can group the runway visual references that the FARs refer to in two main groups:

1) The ones that let you descend down to 100' above the touchdown zone elevation (TDZE).
2) The ones that let you land.

So first off, what gets you down to 100' above the touchdown zone? Here are some examples:

What Gets You Down To 100' Above The Touchdown Zone?

If you can see the white approach light system and nothing else, you can descend down to 100' above touchdown zone elevation, regardless of the type of approach you're flying (even if it's a non-precision approach). But at the 100' point, you need other visual references to go lower.

So what would you be looking for on those approach light systems? Here are some examples of what you'd see to go down to 100' above the touchdown zone.

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What Gets You Down To The Runway?

So what gets your wheels on the pavement? If you see any of these references, you can descend down to the runway and land:

  • The approach light systems' red terminating bars or red side row bars (used on ALSF-1 and ALSF-2 systems)
  • The runway threshold
  • The threshold lights
  • The runway end identifier lights (they're the flashing strobes on the corners of the runway's approach threshold)
  • The visual approach slope indicator (this includes both VASIs and PAPIs)
  • The touchdown zone or touchdown zone markings
  • The touchdown zone lights
  • The runway or runway markings
  • The runway lights

That's a lot to remember, so here's a picture to better explain what you're looking for:

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How Do You Know What Lights To Look For?

When you look at your approach chart, you'll see the lights listed in two places. The top of the chart shows the type of approach lighting system for your approach runway. In this case, KTKI has a MALSR on Runway 18.

The second spot you can look is the airport diagram. Not only does it have the approach light system, it also tells you the type of runway lighting. In this case, runway 18 has high-intensity runway lights (HIRL).

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Time To Get Some Practice...

Whether you're instrument rated not, it never hurts to get some practical experience recognizing runway lights.

The next time you're at a pilot controlled airport, use CTAF to turn up the lights. And if you're at a tower controlled airport and it isn't too busy, ask tower to turn the lights on - they're usually happy to do so.

The more familiar you are with the lights you're looking for, the easier it is to pick them out of the soup when you're down to minimums on your instrument approach.

Colin Cutler

Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at colin@boldmethod.com.

Images Courtesy:

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