You're inbound to Bozeman (BZN), planning to fly the RNAV (GPS) Y RWY 30 approach. As you brief the approach, your EFB alerts you to a NOTAM: the BZN Runway 30 Approach Light System is out of service. The runway environment might be harder to see so the FAA requires you to increase the minimum flight visibility to land. But how do you know how much to increase it by?
The first question you should ask yourself about an inoperative ALS NOTAM is: What is broken?
Most briefing sources organize NOTAMs in a logical way. For these NOTAMs, review the Airport or Runway tabs for the runway you plan to use. These NOTAMs will describe the specific type of approach light system that is not fully operational, like a MALSR or ALSF 2.
Some NOTAMs only state that the ALS is out of service, so you'll need to check the chart supplement or approach chart to identify the specific type of ALS system. Once you know what is inoperative, use the FAA table or your EFB to determine how your minimums change.
The FAA publishes the INOPERATIVE COMPONENTS OR VISUAL AIDS TABLE to help you adjust minimums for inoperative equipment. Many EFBs, like Garmin Pilot, publish this for quick retrieval under the charts section of each airport or you can find it at the front of the Terminal Procedures Publication (TPP).
The table is divided by approach type and minima category, so your first step is finding which section applies to the approach you're flying.
To use this table:
For ILS, LPV, and GLS approaches with visibility minima of RVR 1800 / 2000 / 2200, the chart directs you to increase the visibility to a specific RVR value. Under part 91 operations you'll need to convert this RVR value to statute miles using the FAA Comparable Values of RVR and Visibility Table to determine your required flight visibility.
You might have learned about the FAA Inoperative Components Table for your instrument written exam, but your EFB can make these adjustments much faster in the cockpit. In Garmin Pilot's SmartCharts, you can select the equipment that is inoperative and it will adjust the values for easier interpretation.
Tip: Adjust the minima during your preflight planning with your NOTAMs so you don't have to spend time reviewing NOTAMs twice.
Let's take a look at how to make the appropriate visibility adjustments with the Inoperative Components Table and an EFB.
The LNAV / VNAV minimum line is 1 1/8 mile of visibility. This is the base value you'll add onto. Using the Inoperative Components Table:
Using the EFB method, open the SmartChart for the RNAV 30 approach, then open the minimums tab. Once there, select the applicable minimums line, and scroll to the bottom to slide ALS (MALSR) to INOP. This automatically increases your visibility to 1 5/8 miles.
Many approaches have limitations and conditional language for inoperative equipment that might affect the way you fly an approach. You may also need to increase the minimum values for an inoperative AutoPilot / Flight Director system or an INOP local altimeter setting.
When operating under part 91, there is no requirement for the reported visibility to be at or above the visibility listed on the approach chart minima in order to start the instrument approach. However, you will need the minimum flight visibility in order to descend below the MDA or DA along with the runway environment in sight, and you must be in a continuous position to make a landing on the intended runway (91.175).
Practically, if the reported visibility is below what's on your approach chart or your adjusted minima, you're probably going to have a hard time seeing the runway environment, and landing from the approach.
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Nicolas is an Airline Pilot & flight instructor. He's worked on projects surrounding aviation safety and marketing. You can reach him at nicolas@boldmethod.com.
