Markus Uhlig flew in the E-Glide Concept Contest in September. Here are his impressions of this new type of glider contest where engine use is allowed.
Major advances have been made in the technology of electro mobility recently, not just for the automotive industry but also in gliding. FES (Front Electric Sustainer) engined gliders now rival the turbo engines.
E-mobility is not just a new way of creating thrust but is bringing new approaches to using power to augment gliding flight. The fact that the 'gliding feel' remains largely unchanged during engine use is the big difference between the FES and noisy, vibrating turbo engines. This provides the opportunity for further experimentation in combined engine / glider flight.
A committee within the IGC, together with some FES enthusiasts, created a competition concept that allowed the use of the engine during competition which they named E-Glide Contest. However, there was a lack of practical experience in terms of scoring rules, so a test under competitive conditions was the next logical step. The first E-Glide competition was held in parallel with the 13.5m World Cup in Pavullo Italy, September 2019.
In February, Tilo Holighaus talked up this event during the C-Kadertreffen on the Wasserkuppe and urged pilots to take part. It sounded like an exciting idea to me and I started to search for an airplane with FES. I asked around and learned that HPH could provide me with a FES Shark. After a few phone calls, I had a glider to fly. Excited about the competition, I picked up the glider at the home of HPH in Kutna Hora, Czech Republic and drove to Italy to start the seven day competition.
The competition space
The Pavullo Airfield is located in the northern Apennine foothills in the Emilia region at an altitude of 684m above sea level. The Alpine arc and the intervening Po plain shields this region from the classic Central European weather formations. Northeast of the airfield, the terrain is almost at sea level and the air mass in this area is influenced by the Po Valley.
Northern Italy with the competition area of the Apennine Mountains and the wide Po Riiver valley.
The adjoining hill country around Pavullo lies in the range between 400m to 1500m above sea level. The slopes are partly steep, but are still used for agriculture with many small fields. This hill country is almost completely developed with infrastructure, and the villages, houses and roads lead up to the summit of these hills. If you take a closer look, you can see isolated fields from the air, which could make potential landing sites. Most likely, however, the significant slope means they are emergency options only.
The landscape is carved by larger river valleys, which lead from the hills in the northeast to the plane. In the upper river courses, the valleys are narrow and the terrain is strongly sloped down to the riverbed. The closer you get to the plain, the wider the valleys and the bigger the flat fields and occasional airfield or ultralight landing spot.
Cavola is in this hill country 30km northwest of Pavullo and often produces excellent soaring conditions. Especially in marginal weather, many routes were flown as a yo-yo around this newly created airfield. The next landable areas were found only after long glides along the river valleys towards the plain, but they are almost at sea level.
The airfield itself is located in a bowl with hills between 600m and 900m, which made aerotowing and final approaches exciting.
Relaxing at Pavullo Airfield
About 30km southwest of the airfield, the middle hills turn into the main ridge, which is high at around 2,000m. One of the highest peaks in the region is Monte Cimone (2,165m). The south side of the main ridge drops steeply and flows relatively quickly into the Mediterranean Sea. This means that pressure gradients usually create a breeze system in which the air flow causes a convergence on the main ridge. During the day, the wind typically freshened up to around 20kph towards the main ridge.
The humid air mass from the lowlands, however, usually provided a low cloud base and often made the upper 500m of the main ridge disappear into clouds. The heat at the beginning of the competition caused thunderstorms along the convergence lines, which caused a little precipitation in the afternoon, but before the clouds overdeveloped, large thermals flowed up the hills. Flying over the main ridge in the direction of the sunny side was not at all possible due to the low cloud base.
As the airfield is so high, the target circle was often set to around 1km. The base was rarely over 1,600m and the afternoon thunderstorms often moved towards the airfield and final approach. For this reason, the target circle was set in the lowlands at about 700m and 15km distant from the airfield.
The position of the sun and the wind direction in our flying area were offset by 180 degrees at the usual flying time. The hills are arranged in a relatively unstructured manner and are not suitable for slope soaring. Even just trying to stay on course was difficult, as it was necessary to keep shifting from thermal to thermal, at only 100m to 500m above the summit of the cultivated hills. Later on, stable, dry cold air flowed in. The base rose slightly, but the climbs did not improve much. The perfect weather for this region seems to be dry warm air, if the convergence lines are not overdeveloped and the base is sufficiently above the main ridge. Unfortunately, we did not get to enjoy conditions like these.
Competition aircraft - HPH Shark 304eS
On arrival in Kutná Hora, the first sight of the HPH workshop overwhelmed me. The company building had been completely rebuilt several years ago and creates perfect working conditions for the employees. High ceilings, air conditioners and a final assembly with parquet flooring - you feel almost as if you are in the living room. The range of manufacture in this building is enormous. With the exception of painting, everything from metal work for control drives, to spar and wing production, to final assembly is carried out within this one hall. Huge CNC portal milling machines are even available in one compartment for the production of the moulds.
A HpH Shark 304es with ist engine running.
I had expected I would be given a well-used factory aircraft. I did not quite trust my translation skills when test pilot Martin dropped the word ‘new’ from his lips, but the perfectly shining Cobra, with its hull in bright white, proved it was true. The glider’s logbook listed two starts total. Wow!
With due respect for the responsibility to avoid scratching the plane over the next two weeks, I reached the Pavullo airfield. On the aircraft many Glasflügeltypische solutions were combined with HPH’s love of detail. The automatic rudder connections and the generally solid construction of the wings led to fast assembly and disassembly every day. During the tour around the plane, the high-quality workmanship with first-class paint surface was quickly established, and the controls in the cockpit are also designed for ergonomics, haptics and resistance to wear. After a one-time setup of the spacious cockpit, the seating position was extremely comfortable.
Checking it over in more detail after my first flights, I now understood the words of Jaroslav, who tried to explain the target group of his plane. His wish was not to construct a plane that had been designed for aerodynamic competition down to the very last detail but compromise on handling. It should rather be aimed at pilots who want simple handling on the ground and in the air, combined with high-quality workmanship.
Large surface wheels and a large tail wheel are rarely seen at world championships, but they prevent paint scratches on outlandings and simplify pushing on the ground. The wing is relatively thick and measure 11.8sqm, which is large for an 18m glider and means that HPH swims against the tide of ever thinner and smaller wings with extremely high wing loads. In the high speed range, this brings certain disadvantages, but the Shark climbs even in weak lift and handles well in the air. In the range up to 150kph, with the same wing loading, it is possible to fly with other aircraft for long distances, and when flying at high speed, the pilot's influence is probably much greater than the aerodynamic difference between the aircraft.
The cockpit was designed according to the latest crash regulations and, due to the use of thicker materials, results in a somewhat heavier plane. Together with the drive system and battery, the Shark’s empty weight is 400kg and thus slightly above the curb weight of the other participants. During the competition the wing load was limited to 45kg/sqm and since I had the largest wing area of 11.8qm, I was always the heaviest glider in the field, weighing 530kg. On the other hand, we were all equipped with the same propulsion system, which in turn means that my climb power during engine flight was slightly reduced, since with the same power more mass had to be lifted.
The drive system
In principle, all gliders with electric drive were eligible for this competition. However, it quickly became clear that only the FES can be used effectively for this type of competition. The biggest differences between the drive types are the position of the motor. The FES sits like a model airplane directly on the nose with permanently attached propeller blades. To put the engine into operation, all you have to do is turn on the main switch and set the speed with a rotary knob; the centrifugal force turns the propellers into the wind. When switched off, they are pushed by the airflow back to the hull.
The 16 kg batteries on charge for the night
The other frequently used design - used by Schleicher, GP and the Antares – is similar to a turbo, with the electric motor mounted on a tower. After using the engine, the tower, including the electric motor and the propeller, are returned to the hull.
The FES principle was developed by Luka Znidarsic, who competed with the new Ventus, which was powered by two batteries, each 16kg, which in total store about 4kWh of energy. The maximum power of the engine is about 23 kW at an operating voltage of 100 V and a maximum speed of 4,500rpm. Chargers charge overnight with 600 watts. The batteries are installed in the turbocharger at the beginning of each day of flight, and the system must then be connected to the plane via two finger-thickness power cables and a data cable for temperature sensors.
The actual arming of the system takes place in the grid, for which the last connecting bridge between the batteries is introduced and the circuit is finally closed. The two batteries are then connected in series and only the main switch in the cockpit separates the engine from the battery pack. After a functional check of the fire alarm and a short test run on the ground, the system is ready for flight.
A self-start is not possible with the current engines in 18m gliders. In the 13.5m Class, aircraft including the MiniLAK and the Silent 2 Elektro are already approved for self-launching due to their low mass with the same system. There was talk of the development of stronger engines and larger batteries, in order to make FES solutions for two-seaters or self-start for larger single seaters possible.
The scoring rules
The aim of the competition was to allow a defined amount of engine energy for use in the flight. Typically, the usable amount of energy between the start and finish lines was limited to 2kWh, which is about half the energy stored in the batteries. It was possible to use additional energy before departure and after entering the target circle. In the LX9000, a software update shows the used energy in an information box. Anyone who has used up more than the allowed energy, receives a time penalty of 15 minutes per kWh.
The start was the same as a Grand Prix start, that is, there was no departure window with individual departure times. Everyone had the same start time and during the competition pilots are able to see who is ahead and who is behind. The tasks were racing tasks with turn-of 1 km radius.
After entering the target circle, the actual average speed was calculated on the task and then the corrected average speed could be determined with an aircraft specific index. From this, the index-corrected task time could be determined. Penalties for engine use over 2 kWh or too deep a finish were applied as necessary.
As an example, Stefan Langer flying a LS8 eNEO 15m, was able to finish at the same time as me, but was 3 minutes faster than me in the corrected time because I had a higher index with 18m wingspan. From the corrected task time, the winner of the day and then the next places could be determined not as scored points, but as the corrected difference time in minutes, indicating the winner of the day. This difference time was then added up over the competition, similar to the Tour de France.
In order not to fall completely out of the standings in the case of an outlanding or a task cancellation, the corrected task time was set to a maximum of 1.2 times the previous pilot.
With this scoring system, flying a Grand Prix style finish was not always best. Finishing just behind another glider did not necessarily mean that you got fewer points. On the other hand, on long days with worsening conditions, one could negotiate along part of the competition course and not lose penalty minutes, since they count only from the slowest finisher. This time-based scoring system still had some weak points and might need to be modified a little bit, possibly taking the Grand Prix scoring system or revising the factor of 1.2 to a distance-length and speed-dependent factor. However, this would complicate the scoring and, for reasons of audience engagement, the goal should be an easy to follow scoring system.
As a further adjustment, the available 2kWh on good days could be lowered to only 1kWh. Turning points and a maximum height limit could be other options. There are many conceivable variantions.
Flight style and flight tactics
Since we did not necessarily have to find lift straight off tow, launches were often only to 400m over the airfield, sometimes even in conditions in which a normal competition could never have started. Because of the possibility of using the engine before opening the starting line, you could relax 20km next to the airfield in better weather and wait until the line opend and then switch on the engine and motor to the starting line. The 2kWh was only counted after crossing the starting line. Nevertheless, you could not waste energy because the batteries have a total of just under 4 kWh and you want to keep a buffer.
One of the river beds with a possible landing place marked
The extraordinary advantage of FES over retractable engines soon become apparent. For a start you can use the engine without being in the circuit of a landable field. For example, if you are 20km from a field with a marginal final glide, you can just use the engine to get to a more comfortable altitude. If the engine does not work, the propellers stay flat against the fuselage and you can still glide to the field.
Flying a glider with a folding tower can be a very exciting affair. If you deploy the tower but the engine fails to start, you have increased drag until the motor is put away. If it does not retract correctly you have a deteriorated glide angle and can easily loose glide slope to the airfield.
If the engine does start, the goal is to fold away the additional drag created by the tower as quickly as possible. From this point of view using a 100% power setting is the most efficient, on the other hand using the propeller and battery at such high speeds uses more battery power. No matter what tactic is used, the energy loss from the available 2kWh is considerably larger with a tower-mounted engine.
The 2 kWh is enough to cover a distance of about 50 km. With a task length of 140km you should therefore start in good time to use the energy piece by piece, because a dose used in the right place is much more efficient than just using the engine to obtain final glide. The biggest tactical task for the pilot was to estimate the weather over the whole task and use his available energy at the optimum time.
For example, if you anticipate difficult weather at the beginning of the task, improving along track, it would be better to use the energy to get through the difficult weather quickly and then finish the task as normal in regular thermals. But if you misjudge and the weather does not improve, you have already used your 2 kW, which means you have gambled and lost.
The big secret during the flight is the energy consumption that the other competitors have used and their current true rate of climb. In the cockpit you have no way to read the previous energy consumption of the other gliders and adapt your own flying style accordingly. If one pilot flies ambitiously in the direction of final approach, he can either fly a good path, or use his residual energy as needed. But if you have no energy in reserve and are not sure of finding good air, you need to fly more conservatively. If you see two other planes in the middle of the valley climbing well from the cockpit or via Flarm display, you can’t tell, unless you are very close up, if they have a good thermal or are using their engines - FES propellors are small and difficult to see. The tactical variability in the cockpit thus increases by a gigantic proportion compared to pure gliding competitions.
Despite these many new possibilities, certain guideline for the use of the engine quickly emerged:
-The engine has a higher efficiency at lower speeds, the optimum is probably between 4 to 10kW of power, which is approximately horizontal flight up to a climb of half a meter per second.
-The best speed for engine use was around 100 kph. If you use the engine in straight-ahead flight and fly through a sinking air mass, you will be in it for longer at low speed.
-When to fly 100 kph? Normal cruising speed in a modern glider is usually 120 kph or faster. The best use is thus during cruising. Engine use at higher speeds is possible but inefficient.
- If water is still in the glider, it uses more energy to climb and shortens the available engine runtime. Engine energy was more useful in horizontal flight at 5-6 kW or over a long glide at about 4 kW, since the engine ran in a reasonable speed range here. If the weather was weak, you had to pull the water in time, so you would not have to climb with unnecessary mass.
- Without thermal support, you had only a very limited range of action. If you needed 300m of altitude in the lee of a slope without thermals, you could use your entire 2 kWh to get over the ridge. The view and understanding of the air currents and updrafts in the hills is critical. Just because the engine was running, you could not stop thinking and calculating.
-With weak unsafe weather the energy was only used in the most necessary case and saved as long as possible. It was used to maintain the final approach altitude to landing fields or to arrive in straight horizontal flight over the next ridge. Alternatively, one could get a very weak lift at tactically important locations, for instance, before a valley crossing, which would make you arrive on the other side below ridge height. Using motor power to increase the climb rate could enable you to arrive without detour on the ridge.
- If you arrive in the thermal 200m lower than the others, but consider it useful to be up with them, you can quickly switch on the motor, climb up to the same tactical position as the others.
- In the case of bad weather, when you have used your 2 kWh, it is possible to exceed the limit. For example you could switch on the engine and use an extra 0.67 kWh to get home. Although this would result in a 10-minute penalty, it may be faster than climbing the last 300m at 0.1m/sec.
- A good indicator of how much total energy you have already thermally collected on the task was the final approach calculator for the whole task. If you are 2,000m above the starting line, then you could approximately estimate at the time of 1,000m to have made the energetic half of the scoring flight. As an orientation then about half of the quota could have been used here.
- In better weather, the engine was seen as redundant. A classic 2m/sec thermal is always much more energy efficient than a charged battery. Using the engine in the middle of a fast flight would be inadequate compared to the power of a good thermal. In order to consume the 2 kWh nevertheless, the sporting risk could now be set a little higher. Weak thermals could be left, even if you get a bit lower on the next ridge.
If the thermal is strong, you have saved energy and can be quickly on your way. Alternatively you can use the motor to climb in a weak thermal and maintain your speed. As a backup, if the entire 2 kWh were used, you could simply put the sporting risk back on the classic glider flight and complete the task thermally.
On the podium winner Luka Znidarsic with Markus Uhlig in second place and Tilo Holighaus in third.
I would like to say that this form of competition allows the pilot to factor in much greater variation than normal competitions. Only those who recognize a tricky situation at the right moment and use the engine at the right time in the right place will reach their destination quickly. For this competition the concept was perfect, because you could always stay within reach of landing options and could bridge difficult sections by using the engine.
The system offers a lot of potential for competitions in atypical and difficult gliding areas, or for competitions early or late in the season. To what extent this form of competition in the lowlands makes sense in homogeneous good weather must be tested in the future. In any case, it offers the chance to get more flying days and to make flying in the mountains safer.
It was two educational weeks for me, in which I met many new interesting personalities and broadened my flying horizons. Finally, it should be noted that all participants were fired up by the new form of competition and are looking forward to future events!
I would like to take this opportunity to say thank you to
- HPH for the glider
- The Aeroclub Pavullo and the competition management team of Brian and Aldo for the warm welcome and well run event
- The German team, the Holighaus family, the couple Schwenk and Stefan / Julia) for the social company.
Fliegerclub Grossrückerswalde e.V.
Translated from German by computer software... with some help from Sean Young