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European and German records with anemoi

European and German records with anemoi

Apr 12, 2024

Stefan Jahnke

1459 km distance in 12 h 27 min flight time at an average speed of 121 km/h.

Not enough superlatives for Benjamin Bachmaier – he added a 1250 km declaration around three waypoints what will end up in probably two European records in the next weeks. Moreover, two German records and the 1250 km-diploma are already accepted by the DAeC. Let’s hear the anemoi-developer’s thoughts to this epic flight.

First, congratulations to your outstanding flight, Benni. What a great achievement!

You commented your flight with “tears in your eyes due to the Sahara sand in the air”. Wouldn’t “tears of joy” after a perfect day of wave flying be more applicable?

One of the great things about soaring is that it often confronts you with the entire spectrum of human emotions. There have been a few instances in my career where I cried tears of joy or relief in the cockpit. Interestingly, most of them were connected to wave soaring. And yes, the final glide of this latest record flight was certainly one of those moments.

Such long-distance flights in the Alps are only possible by using wave- and wind systems. How did you master the difficulties that are coming with high wind speeds in the mountains on your flight?

Many people seem to severely overestimate how much skill I may have inside of the cockpit. In fact, nobody would call me particularly talented if they knew how many hours of long, exhausting ground work is required for me to safely manage such big flights. I study maps of terrain, weather and flight log data almost every single day to sharpen my understanding about what kind of strategies can be applied in what situation under what conditions. Also, flying in any possible conditions - not only on the good days - helps a lot. In total, this one was my 39th flight in Foehn conditions, which is a lot considering there are only 1-4 usable days per year.

I try to understand in detail the theory and practice of how the air interacts with the terrain and what this means for a pilot who wants to fly through it as effectively as possible. The books of Martin Dinges, G Dale and Jean Marie Clement have especially helped me, as well as many long conversations with icons like Klaus Ohlmann. I even developed my own live wind calculation device because I was not satisfied with how the instruments available on the market performed. It has been teaching me what the wind is really doing around the mountains for several years now, and I see the world with different eyes ever since.

Which aspects do you consider for switching between wave flying and ridge soaring?

Choosing the best lift system at the right time was the key to efficient soaring for the recent record. Often times the wave is more effective than the ridge. The outlanding risk in wave compared to ridge soaring is also massively reduced. I always try to connect with the wave whenever I suspect these advantages to outweigh the time initially required to climb up into the system, but particularly on this day I was unable to maintain the wave on three occasions.

In that case the ridges on the north side of the alpine valleys are a convenient fallback option, even tough the turbulence, narrow altitude band, and permanent outlanding risk can soon make you regret it. There are days where the wind in the valleys is too weak to make the ridges work at all, and stable air conditions will make the wind flow horizontally around the mountains instead of over them. On the other hand, especially when the air is thermally active in addition to the wind, the ridges may at least temporarily and locally be the stronger and more reliable option compared to some uncertain wave line. It is always a difficult tradeoff, and getting it wrong can easily end your flight or cost precious time. I am glad that I seem to have got it mostly right this time.

You have been testing a beta version of the new anemoi-firmware. Can you give us a teaser of what we can look forward to?

The 3.0 update for the anemoi sensor unit and display brings some beautiful improvements. The most important change is that not only the live wind vector, but also its reliability is displayed. Some pilots have noticed in the past that after a very long, perfectly straight, unaccelerated glide the live wind sometimes could not be as up-to-date any more, and that during such situations in was hard to tell wether or not to still fully trust the data. The reason for this was that the IMU can not be kept fully aligned and calibrated if there is absolutely no change in motion for several minutes. To help pilots in such edge cases, the live wind arrow now fades away to a lighter color on the display if the uncertainty rises, and fades back in if the data become more reliable again. When the arrow fades out, all it takes is a short rocking of the wings (e.g. 15 degrees left-right-left) or a bit of accelerating and decelerating to bring it back, which makes the live wind completely up to date again. This trick already worked nicely in the past, but with the new update pilots will know when it might be required or not.

Also, a lot has changed "under the hood" of the Extended Kalman Filter, which is the mathematical heart of the algorithm. Over the last years I have learned a lot of details by logging and analysing flight data, and many mathematical weights, time constants and modeling details have been improved to better match a glider's profile of motion.

For anyone who is interested in logging the attitude, wind and motion data of the sensor unit, we added a timestamp to the output data stream to better be able to sync to IGC files. This will make many hobby developers happy I guess.

And finally, a relief to the technicians and mechanics: You can now also mount the sensor unit upside-down. A total of 8 instead of the original 4 mounting orientations is now possible to select in the menu.

How do you use the anemoi for finding ridge lifts and entering thermals?

As I already mentioned above, ridge lift can be very difficult due to low wind speeds below ridge level, or due to stable air masses prefering to flow sideways around the terrain instead of over it. Both cases can be a bad surprise if you find yourself on a non-working ridge on which you have bet the fate of your flight. With live wind indication, it is easy to spot such flow situations before it is too late, for example if you keep finding west wind on the eastern flank of a mountain, and east wind on the west flank. In that case you should better take the time to climb to the maximum altitude right in the middle of the ridge, because if any, this will be the only place with reliable lift.

On ridges, it is also very important to notice early enough when you have a wind component parallel to the main ridge orientation. This can create extreme turbulence around local crests that are perpendicular to the main face, which require large careful detours to avoid the danger zone.

Generally, the live wind arrow in a valley tells you a lot about your options when getting low. Even in unknown terrain, the best option can often be to just fly to the nearest ridge in tailwind direction, which can be a completely different direction than the wind up high. Each time such information helps me solve a difficult situation, it is a real eye-opener.

When it comes to thermals also in the flatlands, live wind indication is amazing to help you see inflow effects: The lower you get, the more you see the live wind pointing towards the center of thermally active zones, and locally towards the strongest lift. I don't know how many outlandings this strategy has prevented especially for me, who is notoriously bad at finding thermals in the absence of mountains.

How do you look for wave entry points and how does the anemoi help you finding them?

In lower altitudes, there really is not much physical difference between the flow field around a thermal or around what many people call a "rotor", which is the turbulent lift structure below a wave system. Except for the sheer level of turbulence, of course. In both thermal and rotor cases, the wind significantly points towards the lowest pressure, meaning the strongest lift, at low altitudes. This also implies something interesting often observed in reality: Inside of the strongest lift core, the local wind speed is minimal. Once you have found lift in a place with 5 km/h wind on a 20 km/h day, or 30 km/h on a 100 km/h storm day, you know that it's time to stop searching further. An extreme example of this was my wave entry at the Arlberg pass near the end of the second leg: The wind along the ridge was extremely turbulent with 50-80 km/h. Suddenly the wind decreased to 15 km/h within two or three seconds, and stayed that way for ten or twenty seconds. I diverted out into the valley and started to fly normal circles like in a thermal. Anemoi showed me that I could safely circle without being blown back against the terrain. In the middle of the valley the average climb rate reached more than 10 m/s, and after three circles I was 1000m higher and could press to the front of the cloud to enter the laminar wave lift. It was by far the strongest climb of my life, and without Anemoi I would likely have missed it.

How/why did you select your turnpoints for the declaration?

The FAI rules allow three declared turnpoints for record and diploma flights. The weather system was broad enough to allow me to fit 1250 kilometers, but the hard decision was: Should I set two turnpoints in the west, and one in the east, or vice versa? I had to get this right, because when flying such long distances it is necessary to be in the right place at the right time for the whole day with no exception. I had prepared both task versions on the evening before the flight, and took the final decision at 5am in the morning, one hour before launch, based on nightly webcam images, the ICON-D2 wave prediction, and wind station measurements. In the end I made a narrow decision for the east-leaning task, and if I look at other flights of the day it appears like the other option would not have been possible due to broken and cloudy conditions in the far west of the alps.

Did the Yo-Yo in the Pinzgau in late afternoon already feel like coming home and you started celebrating?

When I rounded the last declared turnpoint 250 km east of the goal three hours before sunset, I knew that the odds were clearly in my favor. All I had to do was bring it home safely. My plan A was to stay in the wave of the alpine main divide until the end of the flight, all the way to the Gerlos Pass, to establish final glide as soon as possible. Plan B was to fall back north into the ridges, which might have worked as well but eaten up all of my time reserve. So I was very careful to sneak along the primary wave, which in the evening had a strong headwind component of around 225 degrees. Initially I averaged only around 90 km/h ground speed despite flying as high as FL160, but the patience paid off when the spotty wave line got more and more continuous towards the west. I reached the Gerlos Pass more than one hour before sunset, where I met my clubmate Felix, and together we spent the final hour racing the best wave line of the day all the way back to Grossglockner before finally heading home. That last hour, with two 15m gliders in perfectly laminar wave lift, racing at maximum maneuvring speed in dramatic evening light conditions with all the sahara dust in the air, I will never forget.

Everybody who knows you well, knows that you spend hundreds of hours in preparation, analysis and debriefings of flights. Will you pack away your flying hat after such a highlight or is the next challenge waiting for the right weather conditions?

I admit that the 1250 km diploma, which is only the 10th flown in Europe, and 1st one with a 15m glider, was among the highest goals that I had on my list. But I have so many more ideas what to do in wave and thermal conditions, including speed records, long out and return flights, etc... Also, teaching and instructing has become more and more important to me over the years. It happens ever more often that one of my trainees on a good day performs better than I do on a bad day. Eventually the next generation will take over, and I will be happy to hand over my record when the time comes.

Good luck on your next flying adventure, Benni and thanks a lot for your insights.

Thanks for letting me share!