Tag Archives: Icing

Showdown at the Lake of Constance

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This trip went way too smooth. Neither technical nor any other problems lead to the desasters that our scandal loving readership expected. After an additional day of spa wellness in Dubrovnik, the stars promised luck for today's leg home. Few clouds enroute, mostly blue skies north of the Alps and a broken layer of clouds at our destination. The icing on the cake was a strong tailwind so we were convinced our last leg was going to be a home run.

The first two hours were just like we expected, maybe a few clouds more than forecast but 30 knots of free thrust from behind. North of the Alps no clouds, just a bit of mist. Starting at the Danube Valley the situation changed completely: an overcast cloud layer at about 8000 feet and a bit later another layer of clouds on top. We continued to our destination Heubach (50km east of Stuttgart) at 10 000 feet, hoping to find a hole in the clouds allowing us to change from IFR to VFR (visual flight rules). Our backup strategy was to continue north to Schwäbisch Hall, slide down the ILS (instrument landing system) through the clouds and continue visually to Heubach.

Overhead Heubach we had a short discussion with Jörg Lohmann on the tower and it was clear that we would not land there today. So we continued to Schwäbisch Hall. The colleague there just told us "forget it, 400 feet cloud cover, no way to make it to Heubach". Not great either.

So on we go to Stuttgart, still reporting a broken cloud layer 1200 feet above the runway. Stuttgart Airport is not cheap but from there we can take the metro. Air traffic control was very supportive and allowed us to continue at 8000 feet (outside clouds) to the instrument landing system of runway 25 in Stuttgart. When it was time to descend, we saw once again an overcast cloud layer which appeared to be rather thick. We could descend through the cloud layer but would pick up some ice and might have a problem if we have to go around. We were allowed to hover around the airport looking for the reported holes and the controller asked airplanes in the vicinity for holes but nothing. The controller on the tower of Stuttgart also reported an overcast layer. The weather report for Stuttgart was definitely wrong which is quite scandalous as pilots have to rely on it.

Now we were out of preplanned options and had to look for something else. We had good weather coming from the south and it was getting worse the more north we got so we had to return south. The DFS controller was extremely professional and first asked for our endurance to judge the options and urgency. 3.5h so no problem at all. We discussed possible aerodromes, contacted Mengen but were told there is the same overcast cloud layer. While discussing other options, the controller contacted us and told us he spent some time phoning airports and recommends Friedrichshafen (EDNY, Lake of Contance) with blue skies. This was the perfect solution: only 20 minutes away, fully equipped with an instrument landing system, excellent infrastructure, customs and reasonable prices. So we continued to the beautiful Lake of Constance, were put on the ILS runway 24 by Swiss Air Traffic Control and landed with excellent weather. The aircraft was tied down, we passed immigration, had a little snack and reevaluated our options.

We did not expect conditions in Heubach to improve today and the short jump to Stuttgart would help much (other than increasing the cost). So we got a rental car and took off to Heubach where Markus's car is waiting in the hangar.

The real final of this journey will be in a few days when Achim takes the train to Friedrichshafen and brings the Cessna home to its hangar in Heubach. By this time, Markus will be sitting in his cube farm working on support tickets.

The worst case has happened

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The worst case that everybody feared has happened: we are stuck in Croatia. Markus determined that the weather is a no go and is looking forward to the excellent weather forecast for Monday. In reality, the weather is definitely doable without taking risk.

An important role in this decision played the fantastic spa of the hotel and the view from our hotel room. Achim is now forced to look at Markus’s wobbly body for a whole day and find a way to get the work schedule for Monday done on a Sunday in a hotel room.

Stuck in Croatia?

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A little background in flight planning for our non pilot friends. The weather is the main factor her and wind (mostly determining our speed over ground) and the the different types of clouds are most important. For planning our route, we have gotten to like a chart called “GRAMET” which is a prognosis based on a computer weather model (GFS) and giving an aeronautical weather forecast for a specific route.

The above example shows the GRAMET for our planned trip from Dubrovnik (LDDU) to Heubach (EDTH). As Heubach isn’t really of international relevance and does not have a weather station of its own, we selected Stuttgart (EDDS) as our destination — just around the corner.

On the picture you see the profile of the surface, showing that our journey starts at sea elevation (0 feet), leads us over the Alpa and later the Swabian Jura. The highest elevation is somewhere in the Alps at roughly 10,000 feet (3,300 meters).

The red dotted line represents the 0°C border. You can see how it moves lower as we get further north. Also you can see the different layers of clouds and their types. On the left you see a few towering cumuli, those are clouds of large vertical extent one tries to avoid due to strong up and down drafts — meaning turbulence. Also there is precipitation forecast in Dubrovnik. The green areas with the strange read symbol mean that there is danger of icing meaning there are water droplets with less than 0°C waiting for a Cessna to come so they can instantly freeze and stick to the leading edges. Not the best thing for us as we don’t have deicing equipment like airliners, meaning we cannot get rid of the ice and therefore get heavier and less aerodynamic and at some point would no longer be able to hold our altitude.

You can also see that for some areas we would expect clouds from the surface up to flight level 200. In principle, clouds are no problem but flying inside clouds for hours isn’t very entertaining and with one engine there is always the theoretical danger of a failure and being able to see the surface and finding an emergency landing spot is a great advantage.

All in all not the optimal weather. We should be able to take off avoiding the towering cumuli but with the Alps inside clouds a technical problem would turn into a huge problem. In addition to that icing on the north side of the Alps where at some point we’d have to descend for landing.

So we have to look at different route alternatives (for example going further west via Italy where the weather should be better), hope for a positive surprise or stay grounded tomorrow. The latter option isn’t the worst one considering the fantastic spa of our hotel (besides the fact that I’d have to visit it together with Achim).