Enroute IFR: Aeronautical Decision Making

The Enroute Instrument Rating (and soon the Basic IR with en-route module) is often dismissed by instructors and instrument rated pilots. But it does serve an important purpose. It is an entry into the world of instrument flight for the ordinary private pilot. In this post, I guide you through a typical flight with this rating, with special emphasis on Aeronautical Decision Making (ADM).

It is correct that you can’t use it in some situations. It has very distinct privileges: You may only fly in clouds during the enroute part of the flight. Your climb and descent has to take place in fair weather. Yet, it helps in flying direct routings through Europe, without fiddling with the airspace mess. You can focus on your main task as a pilot: Aeronautical decision making.

In this post, I would like to show another flight with the Enroute IR. This time with more weather and lots of ADM. I’ll talk you through the entire process of the flight from Northern Germany to Switzerland.

  1. Filing the flight plan and studying the Briefing Pack
  2. Aeronautical decision making on the ground
  3. Aeronautical decision making in the air
Decision time: Proceeding between layers.

Filing the flight plan and studying the Briefing Pack

For my IFR flight plans, I use http://www.autorouter.aero with its Telegram chat bot. Literally a robot that helps me delaying my departure or provides the latest weather, simply by sending it commands like “EOBT 1230” or “GAFOR EDLP LSZG”. It works like magic. I can’t imagine the hassle of past times, when pilots had to use a telex or fax. It all happens now in seconds. On that website, the Autorouter finds the best routing based on my aircraft’s performance and the forecast wind. In the USA, I liked planning the route by hand. Unfortunately, this is very complicated in Europe due to thousands of airway rules and forbidden directs (especially in Switzerland). That’s why this tool is so valuable. It even has an option to limit IFR to the en-route part of the flight.

I like filing my flight plan early, up to five days in advance. The Autorouter provides the Briefing Pack and I usually choose to receive an updated one two hours before EOBT.

Now, let’s look at its key contents.

The prevailing weather was under the influence of heat, convection and a slowly moving cold front over France to the West of our route.

Slowly moving cold front over France.

The significant weather chart indicated occasional embedded thunderstorms throughout the flight. In our Cessna without weather radar, this meant to avoid prolonged flight in clouds. Otherwise we could’ve ended up in a thunderstorm without knowing, so we briefed to remain in visual conditions whenever possible and fly tactically and conservatively with our in-flight weather from our ADL Golze box (iridium weather with up to 15 minute delay).

SIGWX-Chart indicating every pilot’s arch enemy: Embedded thunderstorms

The Autorouter GAFOR (General Aviation FORecast) is an over-simplification of weather, but it gives a great overview besides reading the METARs, TAFs and such. As you may recognize, the flight shouldn’t face any problems to remain in visual conditions until NATOR in the Black Forest and Jura area. Most TAFs warned of a thirty to forty percent chance of thunderstorms. In other words, be vigilant but the storms will most likely be very local.

Autorouter.aero GAFOR

Aeronautical Decision Making (ADM) on the Ground

Aviation is full of acronyms like DECIDE or PAVE. I don’t ever use them word for word. But I think the overarching thinking processes are important and I try applying this thinking on my flights. It helps identifying hazards for judgments based on your risk perception. The biggest hazard is the one you fail to recognize. So, for this matter, I’ll use PAVE:

PAVE: Pilot, Airplane, Environment, External Pressures

The PAVE model

P: I was fit for the flight (IMSAFE) and current enough to feel confident in VMC and IMC. My instrument currency on the day of the flight wasn’t bad, but not top-notch either. During prolonged turbulent IMC, I could fall behind the airplane. (When I flew IFR every second day in the USA, I felt much more confident.) Plus, I had a very experienced copilot to my side.

A: The airplane, a Cessna 175 Skylark, was well equipped for the flight: GTN 650, dual G5, DME, ADL in-flight weather (precipitation, tops, lightnings on the iPad with up to 15 minute delay via Iridium). The Franklin engine, constant speed prop and wing-extension STC provide a stunning climb rate for a Cessna. However, no turbo, no oxygen and no autopilot. Combined with my not-top-notch currency I decided to stay away from solid prolonged IMC. I wanted to know at all times in which direction, vertically or laterally, I would proceed to visual conditions. In case of encountering convection and turbulence, I decided to then consider cancelling IFR and proceed VFR.

V: The weather was difficult to appreciate. The slight chance of thunderstorms in the terminal forecasts caused me to stay pessimistic. During the briefing, I already decided that landing at an en-route alternate would be a possible outcome of the flight.

E: External pressures were very low. The usual get-there-itis, is however never to underestimate as this was the last flight of the fly-out to the home base. The passengers and copilot were informed that we might go home by train and leave our airplane for a week at the alternate. That’s the advantage of being an owner-pilot.

Aeronautical Decision Making in the Air

In retrospect, the flight itself went perfectly as planned and was uneventful. But make no mistake: It was 2h and 39 minutes of constant risk management, or ADM. For that purpose, I added the DECIDE-model to my IFR checklist. Again, not that I would follow it word-by-word, but as a reminder to keep thinking ahead, to always choose a safe way forward.

IFR en-route checklist for staying ahead of the airplane

The DECIDE-model in action:

The planned route.

According to my flight log, we had 6 minutes delay fairly early into the flight. Among other factors, probably because I climbed at cruise climb and not Vy to baby the engine in the hot weather. Due to the tight fuel-reserve, I wanted to reduce this delay. Our route contained a slight detour to avoid the airspace of Frankfurt. So I called up ATC and asked for a more direct route. They were very coöperative and issued the clearance I asked for. I reviewed my flight log and the delay was gone. But the DECIDE-cycle kept going, as a thunderstorm over Strasbourg (probably) influenced the winds-aloft. My ground speed diminished from the planned 118kts to 105kts. The alternates again came to mind.

After a few minor rain cells, we kept pacing South between cloud layers in visual conditions (technically IMC at the cloud base). This helped to always evaluate the options. The bottom layer wasn’t always overcast and we could see that in an emergency we could’ve reached alternates under visual flight rules. It was amazing to see the accurate weather depictions on the ADL in-flight weather.

ADL in-flight weahter (screenshot taken after the flight).

Over Freiburg im Breisgau we made a deliberate decision to proceed to our destination. The latest weather indicated VMC in Switzerland. In these cases the ATIS and METARs are more important than the ADL screen (absence of the grey areas doesn’t mean it’ll be VMC). I cancelled IFR at RINLI and proceeded on an LPV approach (vertical and lateral guidance) into Grenchen. We touched down with eight minutes of delay, compared to my plan. Without the shortcut through Frankfurt, we would’ve come home on a train. Proactive aeronautical decision making is a wonderful tool, isn’t it?


If you are a VFR pilot, I hope I could show you the benefits of flying IFR. At all times, my focus was on decision making: Weather, short-cuts, and is all going according to my plan? If we would’ve been under VFR only, I think the risks would’ve been higher. VFR in such unstable weather requires big detours or dangerous scud-running, or simply not taking off. With the Enroute IR, or the Basic IR, you’ll be trained to stay way ahead of your airplane, assess the weather from high above and decide on the important things. Instead of trying to get a clearance from a tower, while scud-running and worrying. Go get your instrument rating, whichever you may choose, or even just do some instrument time with your instructor. You’ll become a better pilot and up your decision-making-game.

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