Behind the Image: Automatic Landing

 Most of the time, pilots fly the landing manually, except in low-visibility conditions, as seen here aboard this Airbus A220, seconds from the touchdown at Munich Airport. The pilots are fully focused on monitoring the autopilot, and the aircraft systems, as the airplane is about to perform an automatic landing in as little as 200m visibility.


Thankfully flying is an outdoor activity that allows us to witness breathtaking weather phenomenon from a unique vantage point. Luckily, my home base Zurich Airport is located within the moderate latitudes, offering the chance to see all the beauty the four seasons have to offer. But with the beauty come some challenges too: Winter calls for contaminated runways and lengthy de-icing, spring and fall often have far-reaching blankets of thick fog in store for us. Generally, flying within these conditions is safe as long as we follow the supplementary procedures closely. Still, it's fair to say that they create an additional workload for all involved too.


Without diving too deep into technical facts and operational regulations, an airliner can generally be manually landed (flown by the pilot) with a visibility of 550m or more. We can distinguish today's approach types between precision and non-precision approaches. They differentiate mainly by the technology involved. A Non-Precision Approach is based on two-dimensional guidance, while a precision approach is three-dimensional. The recent years have brought a giant leap forward in technology, and navigation tends more and more towards satellite-based navigation. However, all current approach types of operating in low visibility conditions are still ground-based. The most common one is the ILS or instrument landing system. Its lateral and vertical radio signals guide the aircraft from a defined final approach point (FAP) to the runway.

Depending on the installed components and level of certification, an approach gets assigned a particular approach category. The most basic one for an ILS is a CAT1 (requiring 550m visibility or more), and the most advanced one, CAT3c, allows a landing with no visibility at all. As the latter needs significantly constricting back-up systems and comprehensive calibration and certification, no airport has implemented it to my knowledge. And from a practical standpoint, where would you go once you land in zero visibility and stop your aircraft on the runway if you can't see anything? Even if there's a follow-me vehicle to guide you, none of you can see each other to understand which way to take. As a result, you'll be stuck on the runway until and unless the visibility improves. Therefore most bigger airports offer CAT3b approaches that require visibility of at least 75m. It is essential to understand that one needs to distinguish between an automatic landing and low visibility procedures. While the latter is something the concerns operational and procedural aspects on the ground and in the airplane, the first one is purely a matter of installed technology on the aircraft.

Simply put, we could automatically land (let the autopilot do the work) on many runways (of course still with some restrictions) with at least a CAT2 ILS installed as long as all the required airplane systems are functional. But once the visibility reduces below 550m, things start to get complicated. Now the so-called "low visibility procedures" are in force (called-out by the airport/air traffic control), putting a whole set of regulations and requirements in place. They include technical aspects of the ground equipment (a malfunction of individual runway lights or transmitters could cause a downgrade). The aircraft systems require all involved parties (pilots and air traffic controllers) to be trained qualified for the specific level. And above all, the pilot's low-visibility operation is exclusively performed in Command (Of course, with the autopilot engaged).

To put it into a nutshell: Flying in foggy weather is safe but certainly very complex and requires a thorough preparation in the flight deck.


A new day dawns on the horizon as we fly east above the lake of Constance, preparing our approach to runway 26R at Munich Airport. A little over an hour back, we started duty in Geneva and reviewed the briefing package. This pile of information tells us, pilots, what the upcoming day might have in store for us. The information cover weather aspects, just as much as operational information about the assigned aircraft or the airport we will operate from or to and is coded into an aviation-slang that originates back in the day when the communication technology was far from digital. We streak-through the briefing package in a pre-defined order looking for extra-ordinary facts and condensate them into specials and hazards. At first, this might sound "critical," but it is our approach to distinguish between the ordinary and those factors that might call for extra attention. While neither the aircraft nor the airports have any significant deficiencies, the Munich Airport weather forecast predicts thick fog in the morning. We expect that there will be so-called "low visibility procedures" in force calling for a reduced traffic flow rate.

Flying in such reduced visibility is among the primary things we train in every simulator session, while it is rather seldom in real life. It is the moment the autopilot takes over for the landing, and we pilots become spectators in a very complex system.

The thick layer of fog only covers the ground, making it is surreal to slowly descend into this sea of clouds knowing that we are only a few hundred meters above the ground. "Five hundred", the radio altimeter calls out our height above the ground. A few moments ago, we were cleared to land, and we received the final information about the current visibility. It is just over 250m along the whole runway.

Both pilots continuously monitor the systems and navigation indications. Any excessive deviation (could be caused by another airplane taxiing too close to the runway) or a technical deficiency would require a Go-Around. As almost all landings are manually flown, it takes some time to get used to that feeling of "handing over control" to the autopilot. We are diving into the fog, and soon the system will call out "Approaching minimums" as we are coming over the runway. I start to see some faint lights ahead. They gradually become more intense, and I can associate them with the runway light system. To proceed with the landing, I need to acquire specific visual cues. In the case of a CAT3a approach, at least three consecutive lights of the touchdown zone light, the runway edge lights, the runway centerline lights, or the combination thereof. Please take a look at the picture above and try it yourself. "Minimums" - What's your verdict? Are we allowed to land?

About "Behind the Image"

In my photo calendar "Up in the Sky" I get to share my favorite aviation pictures with you. This blog series will complement the product and will tell the story about the moment the picture was taken. It will also share comprehensive information about what happend on the flight deck.