Showdown at the Lake of Constance

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.

Weather — go or no go?

We've already talked a bit about it — the weather is what pilots fear more than anything else. We are allowed to fly through clouds (IFR, instrument flying) but there are limits to this, as below 0°C ice forms on our aircraft which can quickly become a major problem. We can fly below, above, beside and through the clouds, provided they don't cause icing. Before taking off, we would like to know the odds of reaching our destination as planned. It would be unfortunate if we came to realize en route that we have to turn around due to icing or make a major detour. In general, we will only take off if we know that we can land safely, i.e. there are a few inches of clear air between the cloud base and the landing strip. Our certification only requires us to have 400 meters of visibility and 200 feet (60m) between the clouds and and the runway but we don't want to get even close to such conditions — this is only for pilots that fly frequently and are well trained in such conditions.

There are regular weather reports for pilots, those report actual conditions at the weather stations and therefore are very reliable. Larger aerodrome have a system which every 30 minutes determines visibility, cloud coverage, temperature, dew point, pressure, etc. The weather of the future is an entirely different animal. Meteorologists (similar to fortune tellers) specialize in asking their crystal balls (read: expensive computer models) for aviation weather which not only covers the surface weather but also conditions at higher altitudes. Everybody knows that predictions are hard, especially about the future. Some weather conditions are easy and reliable to predict, others almost impossible. Fog formation is an example of a weather phenomenon that until today, meteorologists don't grasp as it depends a lot on local conditions which are not accurately represented in the computer models. Our start aerodrome is ideally situated and only very rarely a victim of fog. Another aerodrome just a few miles away is basically covered in fog throughout the winter.

A private pilot knows a few basic things about weather. There are lows and highs. In low pressure areas, air ascends, condensates and forms clouds with rain or snow. In high pressure areas, air descends, stabilizes and we get clear skies. High is good, low is bad (incidentally, that's also Markus's attitude towards life). Even worse are fronts, those are the boundaries of air masses with different characteristics. There are cold and warm fronts. Especially cold fronts are evil as they produce thunderstorms, strong rain and reach up very high with severe icing. We definitely don't want to fly through a cold front, that's for cowboys. In the above map from the French Met Office (yes, smart pilots collect data from all over the world because instead of having one decent European Met Office, we have a zillion of mediocre national weather services doing exactly the same thing) we see the weather from today 16:00 UTC (Greenwich Mean Time or Universal Coordinate Time, used by pilots all around the world). Over Croatia, there is a cold front (blue line with teeth), moving east with 15 knots and northwest of it a small warm front (red with semi circles), moving to Italy. In the area of the cold front we expect thunderstorms, let's check this with the current lightning chart (sferics) shown above.

Indeed, there are thunderstorms (the yellow and red dots) and this is a no-go zone for us. However, the front is moving and by tomorrow it will be a Greek problem (don't they have enough already?). Let's have a look at the forecast for our destination aerodrome Dubrovnik, the Terminal Aerea Forecast (TAF):

LDDU 131125Z 1312/1412 12017KT 9999 BKN040 TX10/1412Z TN04/1405Z TEMPO 1312/1321 RA BECMG 1322/1324 04015KT BECMG 1409/1411 18007KT

A bit cryptic but in order to be able to read that, pilots attend ground school. We can see that today (Feb 13) between 12:00 UTC and 21:00 UTC there is supposed to be rain (RA). Yes, that fits to what we've seen earlier. The rain is going to stop at 22:00 and only a feeble wind (7 knots) coming from south (180°) will remain. Everything that could be bad for us like thunderstorms, rain, snow, storms would be listed here.

Now let's look at the TAF of our start aerodrome Heubach (EDTH). Unfortunately Heubach does not provide its own weather but we have the large airport of Stuttgart (EDDS) just around the corner and can use its forecast:

EDDS 131100Z 1312/1412 VRB03KT 9999 SCT040 PROB40 TEMPO 1312/1321 4000 -SN BR BKN014

Also looking good. Very little wind (3 knots) from variable directions (VRB), good visibility, scattered clouds 4000 feet above the airfield, a little bit of snow with 40% probability and some fog between 12:00 UTC and 22:00 UTC combined with low clouds. After that until the end of the forecast period on Feb 14 at 13:00 UTC only good weather. Fantastic.

So it's looking good in A (Stuttgart) and in B (Dubrovnik), but what about the weather between A and B, that's a full 1000km? Here, we resort to a larger scale forecast model based on the Global Forecasting System (GFS), the weather model of the USA which, in contrast to the semi-capable European systems, is freely accessible (in the USA, all data produced with tax money is generally freely available, something the Europeans should take a closer look at). Here a very nice rendering of our flight profile from GFS for the planned time of flight.

This is really good. The yellow line is us at flight level 150 (15 000 feet, ca. 5km). Below you see the topography with the Alps and Dubrovnik at sea level. The dashed red line is the zero degree line which is currently at the surface in Germany and 5000 feet in Dubrovnik. In the middle you can see areas with a green shading meaning moderate icing (which in reality is quite serious with our little plane), however well below our planned altitude. There you also find clouds but they are broken, i.e. we will find our way around them. The temperature at the planned altitude is forecast between -19°C and -22°C so we hope our heater will work and we won't regret boarding the aircraft in our Egyptian beach wear.

Another interesting image is the infrared satellite photo. Using a color scale it shows the temperature of the cloud tops. Given that we have temperature data for many places on the surface and a rough idea about how air cools with altitude (the standard model assumes 2°C per 1000 feet), we can roughly estimate the top of the clouds and know which clouds we will be able fly over, fly through or (as we prefer) circumnavigate. This is a current picture, by tomorrow the nasty stuff will be gone because it's directly related to the high reaching cold front.

In summary: gorgeous weather. Markus can return his $19 Easyjet ticket that he purchased earlier. Oh, there are no refunds with Easyjet!


Flying is dangerous says the mother. In Egypt, saber-rattling islamists have taken over, says the grandmother. Leaving in winter at sub zero without deicing equipment isn't just stupid but deadly, says Markus. So it's about time to look at the safety aspects of this trip.

We are going to fly with a single engine aircraft according to instrument flight rules (IFR), i.e. we will go right through the clouds when they're in the way. In Europe, we are expecting winter weather and the Alps need to be crossed. The trip will include several hours over the open sea. This adds up to a few potential dangers that we have keep in mind.

Engine failure

In real life, engine failures are very rare and pretty much at the bottom of the most frequent accident causes. Most failures are due to fuel exhaustion and incorrect operation but still, it is a theoretical possibility. In case of an engine failure, a single engine piston airplane will go down but not as most people think in an uncontrolled crash but a controlled "soaring". The Cessna has a glide ratio of about 1:10 (modern gliders offer 1:40 or even better). For each foot of altitude we can advance 10 feet in distance. When flying at about 15 000 feet, we can gap a distance of about 25 nautical miles and have about 15 minutes to prepare our emergency landing. In most cases, it should be possible to find an aerodrome (no matter what kind, even a military base) or another suitable landing field. The odds are much worse when flying over low level clouds because one cannot look for a suitable landing field early on. In this case, only good maps provide some relief.

Water ditching

Directly linked to the engine failure but still worth a separate look is the emergency water landing. Even when flying at very high altitudes, we would be unable to soar to the cost if we lose the engine half way between Crete and Egypt. A water ditching would be the unevitable consequence. Several aspects play a role in water ditchings. First of all the actual ditching which one can survive or not. Our aircraft has a retractable gear which is ideal for water ditching as the biggest danger during a water landing is a loop on impact. Thanks to the retractable gear, we'd be like a very fast boat hitting the water at 50 knots. Once past the ditching one has to quickly leave the aircraft as it is most likely going to sink. It can sink within a minute but it can also stay afloat forever, this is very hard to predict.

Aircraft regulations require all passengers to wear life jackets at all times while flying over the sea. Maritime stores offer comfortable life jackets at reasonable cost, using a small CO2 bottle and – most importantly – manual activation so that one doesn't block the exit should the jacket get wet before having left the aircraft. Right before the impact, it is important to open the cabin doors to make sure they don't get blocked by the water pressure (there is also the option to smash the rear window with the feet and we always carry an axe on board). The sea is colder than the human organism and therefore there is limited time until one freezes to death. In the Med in winter, this is about one hour. Getting out of the water is therefore important and this is what inflatable life rafts are designed for. For this trip, a life raft was purchased, hoping that we will never have to find out whether it actually works.

In any case, one has a lot of time to prepare the water ditching, at least 15 minutes at the planned altitude. There is a lot of ship traffic on the sea and one can choose which ship is supposed to be the savior. Better not too large so it will spot you and actually be able to maneuver. A fishing boat is probably the best choice. The landing is then planned in a fashion where the coroner will not have to note "run over by a ship" as the cause of death.

If not successfully spotted and rescued by a ship, it is important to have additional options to make others find you. There are flight plans with the goal of allowing the search and rescue services (SAR) to determine if somebody disappears and where that most likely happened but we're flying between Greece and Egypt — the former probably currently on strike and the latter occupied with street riots while we're afloat on the ocean. During descent, the radio is used to report the position and plans. Depending on the position and altitude, it is possible that radio contact cannot be established as there are no radio stations over the sea. Airliners high up are usually available to serve as message relays. In addition, the aircraft carries an ELT (emergency locator transmitter) as part of its safety equipment. The ELT can be activated manually or automatically on impact (similar to airbags in cars), sending the current GPS position and a unique identifier to a special satellite network, alarming the search and rescue service. The transmitter will continue to send its signal until either the battery is drained or the airplane sinks below the water line. In theory this could not be enough time to alarm the rescue crews so there are also PLBs (portable locator beacon). Once on the life raft, the PLB antenna is extended and activated until the Greek rescue service shows up. A PLB was purchased for this trip.

Signal flares are the icing on the cake, letting you start a firework, hoping that other ships will like the spectacle and steer to the source of it. The real flares with little parachutes are beyond our reach as we don't have the mandatory license to buy them so we have to stick to the toy variant.

Just like professional sailing crews, we have a grab bag, a water tight bag containing some emergency equipment. Before taking off for the sea leg, all things important to survival on the sea are packed into the grab bag which we would take with us on the life raft. The grab bag will contain:

  • PLB (emergency transmitter)
  • Bottled water
  • Documents (so the coast guard won't sink our raft because they think we're illegal immigrants)
  • Mobile phone (there is a chance they'd work, some large vessels have mini GSM cells)
  • Signal flares
  • Markus' collection of Victoria's Secret prospectus


Even though we're going to fly under instrument rules (IFR) and therefore are allowed to fly in bad weather and through clouds without visual references, there is a serious limitation for most small sports aircraft: icing. Clouds (or better "visible moisture") may consist of small liquid water droplets with less than 0°C. These are called "supercooled water droplets". In order to freeze, water needs a nudge, a so called condensation nucleus. Up in the skies, the air is typically rather clean and free from condensation nuclei and so the supercooled water droplets sit there and wait … until a Cessna arrives! On impact with the aircraft's structure they immediately freeze and stick to the leading edge of the wings, the windscreen, the propellor, the elevator. This causes the aircraft to lose power (propellor icing), create less lift due to the new shape of the leading edges, cause more drag while also becoming heavier. As a result, at some point the airplane will no longer be able to keep its altitude and has to go down. If it eventually gets to positive ambient temperature,t he ice quickly dissolves from the aircraft. However, in winter the freezing level often is at ground level making the thing considerably more dangerous.

Icing only occurs under certain circumstances. Ambient temperature has to be below 0°C but not colder than -25°C as then cloud mostly consist of ice crytals. The type of cloud also plays an important role in what kind of icing you get and how severe it is. Cumulus clouds generally cause more icing than stratus clouds. The worst of all are cumulus nimbus (thunderstorm clouds) — they are the feared most by pilots for other reasons, too. Luckily they are mostly found in summer.

Our Cessna does not have any deicing equipment, apart from the heated pitot tube (to determine the airspeed). We are able to enter clouds with icing but we better make sure that we get out on top of them quickly and only collect small amounts of ice. Best is having the option to decend below the cloud into positive ambient temperature. Normally, one tries to quickly climb above the weather and then only have blue sky for the whole trip. At the destination one might have to descend through clouds but this happens rather quickly (descends are faster than climbs). We will definitely have to put a strong focus on icing scenarios and this will ultimatively determine when we take off and it will be our biggest threat for this trip.


The higher you go, the "thinner" the air gets. From a technical point of view, air pressure decreases with altitude and so does the oxygen partial pressure. Even high up, the air still contains 20% oxygen but at such a low pressure that osmosis in the human cells no longer works. You don't get enough oxygen which is nasty because at the time you notice, it might be too late. Strange things happen to you, you get euphoric, you consciousness gets clouded (like with Markus at sea level), you get blurry vision. Larger aircraft have a pressurized cabin, simulating an altitude of 8000 feet. Starting at around 10 000 feet, one can feel the first negative effects and starting at around 12 500 feet it starts to get critical. Our Cessna does not have a pressurized cabin, so without additional equipment we'd have to stay below 12 500 feet which would negatively impact our airspeed and fuel consumption but most importantly make it a lot harder to get above the clouds, which often go up much higher. The Cessna has an integrated oxygen supply system, meaning a bottle with medical oxygen that we breathe through nose cannulas. Normal air at sea level and 100% oxygen at 40 000 feet have the same oxygen partical pressure, thus roughly the same effect on the body. We are going to fly at 20 000 ft (possibly up to 24 000 feet if required) so we're fine. An additional device helps us to use the oxygen more efficiently (you can't refill your bottle in Southern Europe or Africa). It's got a pressure sensor to determine when the person breathes and also what the ambient pressure (i.e. altitude) is and serves the right amount of oxygen at the right time.

It is very important to constantly monitory blood oxygen saturation. 90% or more is a good value and passengers should regularly monitor each other. Should the oxygen system fail, there is an emergency bottle serving the pilot a few breathings and helping him with the emergency descent.

Technical problems in Africa

Just like with a car, airplanes can break down when you expect it least. Compared to cars, aircraft are ancient low tech, built in very small quantities. Avionics (for navigation etc.) come from 3rd party suppliers and are usually a mix from several decades. Only authorized mechanics are allowed to perform repairs and no two aircraft are the same. Spare parts are not available at Home Depot. Our strategy to deal with this has three elements:

  1. Common spare parts and tools are carried on board
  2. In Cairo there's a US licensed aircraft mechanic (who in theory would not be allowed to work on an aircraft on the European registry)
  3. If everything fails, we can fly in a mechanic from Europe

Of course it's not easy to decide which spare parts and tools to carry. You'd need two ship containers to ship the contents of Achim's hangar. This is what we determined to be worth carrying:

  • Screw drivers, monkey wrench
  • Cable ties
  • Duct tape
  • 2 spark plugs
  • 8 quarts engine oil
  • 1 oil filter
  • air filter (in case we experience a sand storm)
  • safety wire
  • safety wire pliers
  • ground power connector (in case the battery fails)

With cable ties and duct tape, one can already solve 90% of all technical problems on this planet and in addition we'll be able to perform an oil change should this be required for any reason.

Fuel supply

From a pilot's point of view, Dubrovnik is the last stop in the civlized world. In Greece, fuel supply is already a major challenge and in Africa it is pretty much non existant. Even when being promised fuel, one should consider the consequences should this fuel not be available or look and smell different from what one expects. We are confident that the 6th of October airfield actually has AVGAS but at a bargain price of $5.20 per liter ($20 per US gallon) its attractiveness is somewhat limited. Thanks to the awesome load capacity of the Cessna and due to the fact that there is just two of us in the airplane, we've packed 4 jerry cans at 30l each (8 US gallons) so that we can carry another 120 liters (32 US gallons) in addition to the 333l (88 US gallons) found in the aircraft's wings. That's not enough for Sitia – Egypt – Sitia so that we will either have to buy some of the precious $20 fuel or do something really naughty and mix the fuel with car gas. We'd only do this in one wing tank so that for takeoff, climb and landing we can use the pure stuff and for the enroute segment the adulterated fuel. This will work just fine but it's not according to the aircraft's certification. In any case we will be dealing with jerry cans in Egypt so we are going to carry: 

  • 4 30l jerry cans (8 US gallons) with UN certification for the transport of dangerous goods
  • funnel with integrated filter (you never know what animals live in Egyptian fuel)
  • syphon hose (to transfer fuel from the jerry cans to the aircraft)
  • blankets for the wings so the jerry cans won't scratch the paint

Pilot errors

Human errors are the most important reason for accidents in aviation. The complexity of the aircraft, the movement in 3 dimensional space and the many influencing factors such as wind, weather, airspaces, radio communication etc. demand a lot from the human pilot — often too much. The basic ingredient for a safe flight is thorough preparation, taking into account what can go wrong and how to react in such situations. There is one thing that you never have in an emergency situation: sufficient time.