Danish Defence gives up electric aircraft: The batteries are only sufficient for short flight training exercises

14. marts kl. 16:06
Danish Defence gives up electric aircraft: The batteries are only sufficient for short flight training exercises
Although the space is tight, the small electric aircraft Velis Electro has room for two people. All additional equipment has been removed to keep its weight down and extend the battery range. Illustration: Andreas Lindqvist.
When the lease agreement expires in September, this will be the end of electric aircraft in the Danish Defence.
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As the first military in the world, the Royal Danish Air Force received two electric aircraft at Air Base Karup in 2021.

It was a story that was reported around the globe.

Since then, there has been silence about the two single-engine planes, which can accommodate two people. After a year and a half of flying the two electric aircraft, the Danish Defence is now taking stock.

The range is too short and the freedom of manoeuvre too small, so the two electric aircraft will be returned when the lease period expires in September, according to Casper Børge Nielsen, lieutenant colonel and head of aviation at the Danish Ministry of Defence Acquisition and Logistics Organisation (DALO).

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When the idea of using electric aircraft was first brought up in the Danish Defence, both DALO and the Royal Danish Air Force were very sceptical.

“We were actually in doubt as to whether there were any electric aircraft available, because we insist on using only certified aircraft. It turned out that the Velis Electro was, at the time, the only certified electric aircraft on the market,” Casper Børge Nielsen says.

The two electric aircraft are based at the Flying School at Air Base Karup, but have not yet been flown by the Flying School students.

“A large part of the Flying School is about finding and selecting the Royal Danish Air Force’s future pilots. We don’t want to unnecessarily disrupt the intense process that the students have to go through by introducing a new aircraft during a tightly packed programme,” Casper Børge Nielsen says.

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The Danish Defence’s two leased Pipistrel Velis Electro aircraft in formation over Karup:

Remote video URL

The aircraft has therefore only been used for proofs of concept and has not been a part of the actual training of future pilots.

However, this did not come as a surprise to the Royal Danish Air Force.

Velis Electro

  • Top speed: 181 km/h
  • Theoretical range: 100 km
  • Flight duration: 30–50 minutes
  • Charging time to 100%: 45–90 minutes
  • Crew: Two
  • Use: Flight training
  • Manufacturer: Pipistrel

They knew well in advance that the aircraft cannot perform many of the manoeuvres that the student pilots have to go through, such as aerobatics or recovery from a spin.

Theoretical energy density of batteries lags behind

The biggest barrier for the Danish Defence to move forward with electric aircraft such as the Velis Electro is the energy density of the aircraft’s batteries. There is still a long way to go before it becomes comparable to jet fuel.

“The best batteries have a capacity of 500–600 watt-hours per kilogramme. By comparison, that figure is around 12,000 for jet fuel, i.e. 20 times higher. That is the core of the problem,” Casper Børge Nielsen explains.

One of the major differences between electric aircraft and electric cars is the importance of weight, which is significantly greater in aircraft than in cars.

He points out that even with the best available batteries, electric aircraft such as the Velis Electro can only be used for flights with a real range of around 37 nautical miles (68.5 kilometres, ed.).

The remaining battery capacity must be saved as a buffer for unforeseen events.

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The aircraft’s two batteries are located in the nose, where the charging plug is also inserted, and behind the captain’s seat on the left side, where their water cooling system is also located. Each battery consists of 1,152 battery cells in four layers.

The battery design is more reminiscent of that in a drilling machine than in an electric car, because aircraft run at their maximum capacity for longer than a car—for example during take-off.

“We’re learning a lot about how electric aircraft work and what the future of electric aircraft might look like, but if I’m being completely honest, we’ve learned that they can’t be used for much when it comes to training students at the Flying School. The flight time is too short,” Claus Caspersen “CAP”, head of the Royal Danish Air Force’s Flight School in Karup, previously stated to the Danish Defence’s internal magazine Honnør.

The aircraft has a flight duration of 40–45 minutes in the air, which is just below the flight duration of a regular training flight.

“If we add the necessary buffer, we still have time to practice landings.”

If the aircraft is fully charged, eight landings can be completed.

Stripped of extras

Because the range is already limited, all unnecessary equipment has been removed from the aircraft, e.g. The heating system and charging cable.

Landings outside of the school therefore require sending a car in advance with a charger.

The aircraft themselves do not have luggage compartments, transporting the charger would also reduce the usable range, and there are no granny chargers for them.

The 400-kilogram electric aircraft usually rolls out onto the runway from Shelter 81 at Air Base Karup, the hangar closest to the runway:

Remote video URL

The lightness of the aircraft also means that it does not require much wind before it is confined to the hangar.

Advanced aircraft despite limitations

Although the aircraft cannot actually be used operationally and is only very limited to exercises, Casper Børge Nielsen and the Royal Danish Air Force also have words of praise for the small electric aircraft.

“It is an advanced aircraft when it comes to avionics (the aircraft’s electrical systems, ed.) and battery management. Maintenance has been incredibly cheap, almost to the point of being laughable, and it of course is emission- and noise-free,” Casper Børge Nielsen says.

When the aircraft takes off, all of its components and movements are tracked and downloaded onto a small USB key, which is inserted in the side of the dashboard.

Pipistrel can use that data to optimize the aircraft, just as students can use it to evaluate the flight.

When the aircraft taxis on the ground, it has a noise level of 60 dB, which is roughly equivalent to the sound of a spinning washing machine, while the propeller itself still makes noise when it breaks the air.

Although there is still half a year of the leasing period left, Casper Børge Nielsen does not expect it to be extended.

“We have now gained important experience that we can use when the T-17 is to be replaced at some point,” Casper Børge Nielsen says.

Since 1975, the Royal Danish Air Force has purchased 32 T-17s from Sweden’s Saab, which first flew the small monoplane in 1971.

Currently, there are no concrete plans for new purchases of training aircraft in the Royal Danish Air Force.

Therefore, according to the plan, the two electric aircraft will be returned to Green Aerolease, which has purchased a larger number of Velis Electro aircraft to be leased out to flight schools, when the lease agreement expires in September.

“So far, we have no other concrete plans involving electric aircraft. New battery technologies are required before we expect to see a significantly greater flight range. We are under no illusions that we will fly electric fighter jets in the near future, just as I personally do not think I will fly to Mallorca in an electric aircraft in my lifetime,” Casper Børge Nielsen says.

He points to hybrid solutions with two powertrains and a focus on biofuels as more realistic solutions for green transition in the Royal Danish Air Force.

Casper Børge Nielsen points to UK’s Royal Air Force (RAF), which has explored various PtX solutions, and which in 2021 succeeded in producing 15 litters of synthetic aviation fuel, also known as eFuel, which was used to take off and land a small Ikarus C42 aircraft.

The aircraft’s only engine, the Pipistrel E-811, is a liquid-cooled electric motor with a nominal power of 57.6 kW (77 hp). Illustration: Forsvaret.

Last November, RAF fielded the significantly larger RAF Voyager transport aircraft, the military version of an Airbus A330 using only sustainable SAF fuel.

“I think we will see small electric passenger aircraft on the short feeder routes of less than 400 kilometres. Going over that range and load will require hybrid solutions,” Casper Børge Nielsen says.

82 percent of the Danish Defence’s CO2 emissions come from fuel for aircraft, vessels, and vehicles.

If the Danish Defence’s climate footprint is to be seriously reduced, new green fuel sources are necessary.

“The Danish Defence pays a lot of attention to the future use of biofuel in aircraft. Furthermore, there are also other ways to reduce CO2. For example, a lot of training in the new F-35 aircraft will be carried out in simulators, which do not emit CO2 to any significant extent,” Casper Børge Nielsen says.

The green transition in the Danish Defence is not only driven by climate and environmental considerations. It can also be strategically advantageous.

“Getting supplies, including fuel, is a major operational challenge. If, in the long term, we can produce fuel in the field, this will bring great benefits.”

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