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An actual instrument approach to minimums

February 21, 2023/in Personal stories, Tips and technique/by Eric Radtke

During your instrument training, you routinely fly instrument approach procedures to “minimums” under simulated conditions. The more likely scenario when flying under instrument flight rules (IFR) is the option to complete the flight under visual flight rules (VFR), flying a visual approach procedure, or flying an instrument procedure in which you acquire the runway visually well above the charted “minimums.”

How to choose an alternate airport when planning an IFR flight

February 20, 2023/in IFR flying/by Bret Koebbe

There are a lot of factors that go into choosing an alternate airport when filing an IFR flight plan. Here we’ll take a deep dive at the approach and alternate minimums charts and look at the legal and practical considerations to help you make the best decision.

An actual instrument approach to minimums

February 21, 2023/in Personal stories, Tips and technique/by Eric Radtke

How to choose an alternate airport when planning an IFR flight

February 20, 2023/in IFR flying/by Bret Koebbe

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An actual instrument approach to minimums

February 21, 2023/in Personal stories, Tips and technique/by Eric Radtke

During your instrument training, and likely as part of ongoing currency or an instrument proficiency check (IPC), you routinely fly instrument approach procedures to “minimums” under simulated conditions. In the case of a precision approach, this would be to the decision altitude (DA). On a non-precision approach, this would be at the minimum descent altitude (MDA) and the designated missed approach point.

As part of the training routine, at the missed approach point the instructor or safety pilot would typically either call the runway in sight at which point you would transition to landing or call for a missed approach to be flown. This is good practice because a) it is rarely done during your everyday flying b) it is the ultimate test of your basic attitude instrument flying and procedures and c) it demonstrates your capability in handling a stressful, task-heavy scenario in close proximity to the ground.

The more likely scenario when flying under instrument flight rules (IFR) is the option to complete the flight under visual flight rules (VFR), flying a visual approach procedure, or flying an instrument procedure in which you acquire the runway visually well above the charted “minimums.”

Needless to say, I was surprised to be faced with a scenario in which the weather was forecast to be at or below approach minimums on a recent leg from Florida to Cincinnati (KLUK – Cincinnati Lunken Airport). A stationary front with a lot of moisture resulted in a temperature and dew point at an identical 11°C and low IFR conditions. In plain language, it was a soupy mess throughout the Ohio valley in which the morning fog was replaced by mist and low-level clouds.

The fact that low IFR conditions existed throughout the region also made identifying a legal and practical alternate airport a challenge. As a refresher, § 91.169 (IFR flight plan: Information required) requires an alternate airport be filed if, from one after before to one hour after the estimated time of arrival, the ceiling (lowest broken or overcast layer) will be below 2,000’ or the visibility less than 3 statute miles. To be eligible as an alternate airport, if the airport has a precision approach, the ceiling must be at least 600’ and visibility at least 2 statute miles at the estimated time of arrival to the alternate.

In our case, the Lexington Blue Grass Airport (KLEX) met the alternate approach criteria. But to comply with § 91.167 (Fuel requirements for flight in IFR conditions), we had to plan for enough fuel to fly to our intended destination and then fly to the planned alternate airport plus an additional 45 minutes. And we also planned for enough fuel to execute an approach procedure at each airport and considered additional time for vectors and even a potential delay as low IFR conditions can create congestion in busy terminal airspace such as Cincinnati. As you can imagine, this resulted in a substantial increase in fuel required for the flight which we were thankfully able to accommodate.

With our planning complete and passengers aboard, we departed the clear skies and warmth of Florida for the cool cloudiness of the Midwest. Monitoring the destination enroute courtesy of ADS-B, the ceiling and visibility was maintaining just above minimums as forecast. However, after briefing the RNAV (GPS) Rwy 21L approach and beginning our initial descent for Cincinnati, the latest METAR indicated a ceiling and visibility just at landing minimums.

KLUK 062002Z 00000KT 3/4SM R21L/5500VP6000FT BR OVC003 11/11 A2998 RMK AO2 T01110111

While the procedure for the RNAV (GPS) RWY 21L indicates a DA of 756’ (281’ above the airport), a FDC NOTAM raises the DA to 797’ (322’ above the airport) – always check NOTAMS!

FDC 1/3864 LUK IAP CINCINNATI MUNI/LUNKEN FLD, CINCINNATI, OH.

RNAV (GPS) RWY 21L, AMDT 1D…

LPV DA 797/HAT 322 ALL CATS.

We were able to learn through ATC that aircraft were still landing at Lunken airport in spite of the most recent METAR with multiple pilot reports that the weather conditions were “right at minimums.” Given this information, and plenty of reserve fuel, we opted to continue to our planned destination as opposed to diverting to our alternate.

After a magnificent vector from the controller (thank you CVG TRACON), and a stable autopilot-coupled approach, we were approaching our DA. Given a two-pilot crew, the pilot monitoring was able to focus attention on monitoring DA as well as acquiring the required visual contact for landing. Given the conditions, I anticipated being able to see the approach lighting system before the runway and included that information in the approach briefing. In the case of the Rwy 21L, the chart indicates a medium intensity lighting system (MALSR) with sequenced flashing lights – a big help in these low visibility conditions.

At the DA, I was able to see the approach lighting system. Are we allowed to continue?

Yes, 91.175(c) (Takeoff and landing under IFR) allows for flight below the published DA if the approach light system is visible, but only down to 100’ above the touchdown zone elevation unless the red terminating bars or red side row bars are “distinctly visible and identifiable” or the runway environment is in sight which includes:

The threshold.
The threshold markings.
The threshold lights.
The runway end identifier lights.
The visual glideslope indicator.
The touchdown zone or touchdown zone markings.
The touchdown zone lights.
The runway or runway markings.
The runway lights.

Within seconds of identifying the approach lights, the runway threshold came into view and we landed in calm winds; however, the advanced planning included having our missed approach altitude set and procedure committed to memory along with rehearsing the action items upon executing the missed which is universal:

Go-Around Power
Go-Around Pitch
Flaps (appropriate setting)
Positive rate/gear up
Navigate
Communicate

And we leave the hangar with the satisfaction of having completed a safe, disciplined flight with the entire system working together from meteorologists, to air traffic controllers to the other pilots in the system willing to share up-to-date vital information via pilot reports. It was a good day on the flight deck!

How to choose an alternate airport when planning an IFR flight

February 20, 2023/in IFR flying/by Bret Koebbe

One of the most important skills pilots learn during flight training is sound decision-making. Every flight, regardless of the complexity of the airplane or the distance of the trip, is comprised of a continuous series of decisions involving a host of variables that the pilot must make in order to safely get from point A to point B.

When flying a VFR cross-country, one of the early lessons is to always be evaluating alternate airports in case you’re not able to land at the intended destination. This is not only common sense, but it’s a legal requirement too:

Preflight Action (FAR 91.103) – Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight. For a flight under IFR or a flight not in the vicinity of an airport, weather reports and forecasts, fuel requirements, alternatives available if the planned flight cannot be completed, and any known traffic delays of which the pilot in command has been advised by ATC.

Though it’s rare, your destination airport could become unusable due to a thunderstorm moving in, or a disabled airplane on the runway. To be clear, you are not required to declare an alternate airport in any official capacity flying VFR, but rather you should have a few airports in mind along the way and near your destination.

IFR Alternate Airport Planning

Contingency planning is even more important for IFR pilots on cross-country flights where a cloud ceiling shift of 100’ or visibility change of a ½ mile can mean the difference between seeing the runway at the end of an instrument approach or having to go around and find another place to land.

While every IFR flight requires you to file an IFR flight plan and receive an ATC clearance, not every flight is flown in IFR conditions. After 3,000 hours of flying on IFR flight plans, I’d say most of that time was actually spent in VFR conditions and with only a handful of the flights in any given year requiring an instrument approach to be flown at the destination.

Regardless of the weather, my preference is to always file an IFR flight plan on cross-country trips, primarily for the benefit of the ATC services provided along the way. The IFR flight plan form requires much of the same information as when flying VFR, except you have to treat the Alternate Airport field more seriously. FAR 91.169 describes two scenarios as it relates to IFR alternate airport requirements:

If the weather at the destination, for at least 1 hour before and 1 hour after the estimated time of arrival, is forecast to have at least a 2,000 foot ceiling (above the airport elevation) and visibility of at least 3 statute miles, you are not required to list an alternate airport in the IFR flight plan.
If either the ceiling or visibility is forecast to be less than 2,000 feet or 3 statute miles during that arrival window, you are required to file an alternate. Also, the destination airport must have at least one instrument approach procedure or an alternate airport will always be required.

Many pilots refer to this as the 1-2-3 rule: Plus or minus 1 hour from arrival, ceilings at least 2,000 feet and visibility at least 3 statute miles.

The first scenario above only states that you don’t have to legally file an alternate on the IFR flight plan if the weather is forecast to be good at the destination, but as discussed earlier during the VFR flight scenario, FAR 91.103 still requires you to have an alternate in mind in the event that the runway at the destination airport becomes unusable for any other reason.

Now, let’s assume that the weather forecast at the destination is for low IFR conditions and an alternate airport is required. There are legal requirements that the filed alternate airport needs to meet, but similar to the weather briefing, start with a big-picture view of what’s causing the IFR conditions at the destination and a few practical aspects about potential alternate airports:

Is there a cold front moving through at the arrival time forecast to cause localized areas of low visibility? Look for a nearby airport to the east of the destination ahead of the front.

Is there widespread fog? You’ll need to search further away from the weather system over the destination and carry plenty of extra fuel.

Is there another cloud layer above the fog and no wind? The fog may not clear out as fast as forecast due to inadequate solar heating.

What time of day is the flight? Low visibility conditions tend to improve several hours after sunrise into late morning, but then deteriorate at night as temperatures cool.

Is there rising terrain nearby or large variations in airport elevations within 50 NM of the destination? A nearby airport at a lower altitude may provide additional clearance under a cloud layer (with the caveat that it could be prone to fog if near a body of water).

What services are available at the alternate airport? As we’ll discuss later in this article, the alternate airport needs to have reliable weather reporting, and you’ll likely need fuel and/or FBO services when you get there. Think about choosing a towered airport with an ATIS broadcast and a 24-hour FBO.

If you are planning with ForeFlight or Garmin Pilot, you’ll find some helpful Alternate Airport planning tools to help you decide. In ForeFlight, enter your basic flight plan information, and then tap the Alternate field. This will display a list of suggested alternate airports and key information: airport name, forecast weather for the arrival time, longest runway length and the time/fuel to divert there after executing a missed approach at the planned destination.

Legal requirements for selecting an alternate airport

After selecting the best option based on the criteria above, you’ll next need to verify that it meets the legal requirements to use the selected airport as an alternate. Once again, this is based on the weather reports or forecasts. The ability to include “reports and forecasts” in this decision is important. On a relatively short flight, reports may be more meaningful than a forecast. You can also determine trends by examining a series of reports versus relying solely on a forecast.

The same regulation that outlines whether or not an alternate is required, FAR 91.169, also specifies the weather conditions that a filed alternate airport must meet. These rules are designed to build some extra ceiling and visibility margins above the approach minimums to make it as much of a sure thing as possible if you actually have to divert. The weather reports or weather forecasts, or a combination of them, indicate that, at the estimated time of arrival at the alternate airport, the ceiling and visibility at that airport will be at or above the following weather minima:

A ceiling of at least 600 feet and a visibility of two statute miles if the airport has a precision approach (ILS Approach)
A ceiling of at least 800 feet and a visibility of two statute miles if the airport has a non-precision approach (RNAV/GPS or VOR)

The key point here is that those are the standard alternate minimums, but there are exceptions and many airports have nonstandard alternate minimums that may require a forecast of higher ceilings and/or higher visibility. To determine if an airport has nonstandard alternate minimums or another exception, reference the chart for the planned instrument approach and look for a black triangle with the letter A:

This symbol indicates that nonstandard alternate minimums apply and you need to refer to the IFR Alternate Airport Minimums reference. If you are using paper charts, these can be found in the front of the approach chart book. If you are a ForeFlight user, navigate to the Airports screen, select the Procedures tab, select Arrival and then Alternate Minimums.

The first thing you’ll notice is that the majority of the airports include the line “NA when local weather not available”, which simply means you can’t plan to fly that approach at the alternate airport if the AWOS or ASOS is out of service (or in very rare cases the ATIS).

Next, you’ll see instrument approaches with notes indicating that higher alternate minimums are needed if you are planning to fly that approach. For example, at Pellston, MI (PLN), if your only option is to fly the RNAV Rwy 5 approach based on strong winds out of the northeast, the forecast would need to be for 900 foot ceilings and 2 miles visibility for Category A and B speeds for you to be able to file PLN as a legal alternate airport.

The last thing to pay attention to is that just because one instrument approach has nonstandard alternate minimums listed, it doesn’t mean that it applies to all the approaches at the airport. Take a look at Jackon, MI (JXN), and you’ll see that the ILS Rwy 25 approach chart shows the black A symbol with the notes that you cannot plan to use Jackson as an alternate airport and fly the ILS when the local weather is not available and/or the tower is closed:

There are actually five instrument approaches at JXN and if the RNAV 32 looks like a viable option, you can use the standard alternate minimums (forecast of 800 foot ceilings and 2 SM visibility) since there is no black A symbol on the chart. This means you can legally file JXN as an alternate even if your planned arrival time is after hours when the control tower is closed.

Additional GPS Approach Considerations

There is one last legal consideration when planning for the alternate and it relates to the avionics in your panel. The first generation of IFR-approach GPS receivers were approved to fly LNAV-only approaches and require the pilot to verify receiver autonomous integrity monitory (RAIM) will be available during the approach (e.g. Bendix/King KLN94, the original Garmin 430/530/G1000).

If you are flying today with one of these systems, you can only plan to fly an RNAV approach based on LNAV minimums at either the destination OR alternate airport, but not at both. From a practical standpoint, this means that if your original destination only has RNAV approaches, your alternate airport must have an approved instrument approach procedure, other than GPS, that is anticipated to be operational and available at the estimated time of arrival, and which the aircraft is equipped to fly.

The current generation of GPS navigators which include WAAS capability (e.g. Garmin 430W/GTN650/G1000 NXi) provide additional flexibility when it comes to alternate planning with one exception. You can plan to fly RNAV approaches at both the destination and the alternate, but for flight planning purposes, you have to make the assumption that you will be flying to the LNAV minimums. The reasoning here is to build extra safety margins as the LNAV minima will be higher than LPV minimums and helps to provide additional assurance that you will be able to complete the approach when arriving at the alternate.

Keep in mind, this is just for planning purposes; if you actually divert to the planned alternate, the rules say it’s perfectly ok to still fly the LPV approach when you get there. And it is also perfectly fine to select a diversion airport other than what was filed if the circumstances warrant.

Which weather forecast should you use?

We just spent a lot of time reviewing alternate airport selection criteria that is 100% dependent on the weather reports and forecast for the time of arrival. If you’re flying to a larger airport that publishes a TAF, that forecast type is your main product for determining the ceiling height and visibility for your destination and alternate airport. Pay close attention to TEMPO or PROB30 periods that apply to your arrival time as you’ll need to use the ceiling or visibility listed here for legal planning, even if it’s just speculation on the part of the forecaster.

If your destination or alternate doesn’t offer a TAF, you’ll need to use the Graphical Forecast for Aviation resource, available here. This provides a model-based forecast for the entire U.S., showing expected cloud bases and tops 18 hours into the future. You can enter your flight plan at the top right of the map, select the Clouds overlay, and then Bases from the top left of the map. Drag the time slider to your planned arrival time and zoom in on your destination to see the forecast ceilings. You can check the forecast visibility the same way, by selecting the CIG/VIS layer. The resolution of the color-shading isn’t great, but it is helpful to locate areas where the visibility or ceiling is forecast to be better (or worse) than the location of your destination airport.

Flight Planning vs. Reality

Everything we’ve discussed so far relates to flight planning only and the process to choose an alternate airport for the IFR flight plan form. While it may seem arduous, it is designed to make you do your homework and ensure that is always a viable alternate airport available for every flight.

For a three hour cross-country flight, this is probably done at least an hour before takeoff, meaning at least four hours before you actually arrive at your destination. The reality is that the weather doesn’t know or care what was forecast in the TAF, and is often much different when established on the approach.

Keep an eye on the weather as you approach the destination, using both ADS-B datalink weather, and by tuning in the local ATIS/AWOS on the radio. If it looks like the weather will be near the minimums for the approach, it is time to start thinking about what the best alternate airport will be based on the current weather. If it still looks like the planned alternate is the best option, go for it. And remember that the 600-2 or 800-2 ceiling/visibility was just for planning; you’re just looking for the weather to be above the approach minimums for the airport at this point.

However, if the weather reports are showing that the planned alternate is no longer a viable option, it’s time to throw all that planning out the window and start looking for a new option. Again this is where flying with ADS-B datalink weather and an iPad is worth every penny as you can scan the visibility and ceiling reports on the map to help determine the best option.

Keep ATC informed of your plans too, even if you do decide it’s best to go to the filed alternate. They do not have access to all of the information you filed and cannot see the airport you listed as an alternate (and don’t care for that matter), so choose the best option based on all the information you have at that moment in time.

Half Sized Blog Element (Single Author Style)

Half Sized Blog Element (Multi Author Style)

An actual instrument approach to minimums

How to choose an alternate airport when planning an IFR flight

An actual instrument approach to minimums

How to choose an alternate airport when planning an IFR flight

Full Sized Blog Element (Big Preview Pic)

An actual instrument approach to minimums

How to choose an alternate airport when planning an IFR flight

IFR Alternate Airport Planning

Legal requirements for selecting an alternate airport

Additional GPS Approach Considerations

Which weather forecast should you use?

Flight Planning vs. Reality

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