Landing under IFR

"You should know the previous airliner went missed" - What an instrument student doesn't want to hear from ATC

An instrument approach procedure (IAP) is designed to get you low enough clear the weather and land safely. But what else should a good instrument pilot know? Well, there are a few regulations that dictate precisely how you're supposed to behave. Let's take a look.

Under IFR, landings are dictated by 14 CFR 91.175. Like every good regulation, it starts by stating the obvious. That is, if you need to use an approach due to adverse weather conditions, you must use a published instrument procedure.

Obviously, to do that, you must be a current instrument-rated pilot under an instrument flight plan or an instrument student with a qualified instructor receiving training.

How low can you go? Can you go down low?

Get it? Get it? If you don't, watch this. Minimums dictate how low you're legally allowed to go in order to hopefully be in a good position to land (else, execute the missed approach). Note that you can interrupt an approach at whatever altitude/height. Moreover, if you reach Visual Meteorological Conditions (VMC) conditions prior to reaching minimums, you can obviously adjust your flight path for a stable landing (or joining the pattern, facilitating other aircraft, etc.).

The FAA regulates clearly what minimums you must use. Specifically, you must use the highest of these three options 91.175(b):

• (b)(1) is fairly straightforward. Use the minimums written on the chart.

• (b)(2) states that if the PIC has prescribed minimums, you must abide by them (this is typically a limitation for specific air-carriers (part 121 airliners, part 135 charters, etc.). It won't affect the basic part 91 pilot like you and me.

• (b)(3) essentially says you can only use minimums for the equipment you have on board. If your airplane does not have Wide Area Augmentation System (WAAS), you cannot descend to LPV minimums.

Descending below minimums

In order to descend below minimums (DA/DH or MDA), three conditions must be met [91.175(c)]:

1. You are in a good position to land with a stabilized descent;

2. The visibility is no lower than the one prescribed by the IAP;

3. You have at least one visual reference in sight.

The first two are easy. The third is two-part. It lists 10 items that could be used as a visual reference. I say it's two part because the first item provides you with the first visual reference and also says that if you have the Approach Lighting System (ALS) in sight, you can descend to 100 ft above the touch down zone elevation (TDZE) as published on the chart. So if you see the ALS, you can go lower to help you reach one of the 10 visual reference.

The 10 visual reference are reported below with the respective graphic (thank you Boldmethod...). Note how the first is actually part of the ALS itself. This is why the regulation covers both the descent to 100 ft and the first visual reference in the same paragraph.

Visual Reference	Graphic
1) ALS red terminating bars or the red side row bars
2) The runway threshold (sometimes referred to as the piano keys)
3) The runway threshold markings
4) The green runway threshold lights
5) The stroboscopic runway end identifier lights (REIL)
6) The visual glideslope indicator (PAPI or VASI)
7) The touchdown zone or touchdown zone markings
8) The touchdown zone lights
9) The runway or runway markings (in essence, the runway itself)
10) The runway lights (that run along the runway edge)

Landing under IFR or canceling in-air

We learned what you need in order to land after an instrument approach preocedure. However, a brief discussion is necessary regarding your IFR flight plan.

Towered Airport

If you land at a towered field, ATC will cancel your IFR flight plan automatically, so it's very easy to manage. The radar loses your signal and removes you from the National Airspace System (NAS). Easy and worry-free.

Un-towered Airport

If you land at an un-towered field, ATC will ask you on final "Advise IFR cancellation in the air or on the ground through the GCO". Two things can happen:

1. You decide to cancel IFR in the air with them and proceed under VFR;

2. You keep flying under IFR until you reach the ground. On the ground, you wil call them through a dedicated frequency or the Ground Communications Outlet (GCO) - aka a phone number - and cancel manually.

It's not uncommon for pilots wanting to cancel in the air. If you decide to cancel on the ground you will need to remember to do so (see here what happens if you don't). Moreover, at untowered fields, there can only be one IFR movement at a time. That means that if you are landing, no one can move under IFR until you canceled your flight plan. Because this can cause delays and annoy ATC who needs to keep airplanes holding in the wait, many pilots prefer to cancel early and help out.

Canceling in-air is very simply regulated; if you cancel IFR in-air, you must be able to continue your flight under VFR. Most pilots believe that means VMC, which is incorrect. You must be able to continue under VFR, which means that VFR conditions must exist at the field (which depends on the airspace class). This is dictated by 14 CFR 91.155, which states that if VFR conditions are not met (visibility > 3SM and ceilings >1,000 ft) "no person may take off or land an aircraft, or enter the traffic pattern of an airport, under VFR, within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace".

And there's more! The VFR conditions must also be reported at the field (AWOS must report VFR). Per this FAA letter to Baginski (2012), the pilot's observations do not supersede the AWOS. So if only a small part of the airport has bad weather, or the AWOS hasn't updated yet for some reason, the pilot cannot cancel IFR.

Baginski 2012.pdf

Download PDF • 400KB

So let's say the airport you're going to is class E. You break out of the clouds at 900 ft. You cannot cancel because a 900 ft ceiling is IFR, not VFR. Would you be able to maintain VFR separation from clouds? Of course not! Not being able to cancel is also sensible in case you have to go missed (say an airplane enters the active or something). If you have to go missed and you canceled IFR, you don't have the option. Of course, the VFR requirements are different fror class G, but let's trust in pilots' sanity....

So, in essence, be careful before you cancel IFR!