Wind of no change: Exploring the promise of turbulence cancelling technology

As the Earth warms, turbulence is becoming a greater risk to aircraft. There were over 65,000 recorded cases of turbulence last year, with incidents increasing by more than 50% in past four decades.

Earlier this year a Singapore Airlines Boeing 777-300ER experienced severe turbulence that resulted in the death of one passenger and injuries to 31 others on a flight from London to Singapore. The compensation payout from these events alongside fuel inefficiencies, rerouting, delays and maintenance amounts to almost $2.6bn per annum across commercial aviation.

Turbulence events are also a concern for the AAM community, particularly when thinking about flights in urban areas, where the effects of buildings can make operational environments hard to predict at best and dangerous to life at worst.

Tall buildings provide frictional drag on the movement of air, this friction creates turbulence which can result in a rapid drop in aerodynamic lift. Complex air flow features can include downdrafts, updrafts, funnelling between neighbouring buildings, wakes behind buildings, shear layers close to the building corners and horseshoe vortices.

The risks associated with urban air mobility operations have prompted numerous academic studies, including Politecnico di Milano’s paper entitled Review of Wind Flow Modelling in Urban Environments to Support the Development of Urban Air Mobility published earlier this year.

Due to a rise in safety challenges due to the inevitable micro-wind conditions in an urban environment, flight testing complexity is increased – in turn extending the duration of an aircraft certification process, Politecnico’s paper stated. It also detailed several micro-scale wind models which can be used to generate synthetic wind data for a range of UAM applications, streamlining the testing process in certain areas.

Turbulence cancelling

But what about if turbulence could be mitigated almost completely? This is the mission of Vienna-based company Turbulence Solutions – born out of a research project at the Vienna University of Technology – which has spent the past six years developing active turbulence cancelling technology its founders say can reduce effects by more than 80%.

The patented system makes use of counteracting control surface deflections that dynamically adjusting the wing shape instead of rotating the whole aircraft – like a bird does. Proven in a series of manned tests using light fixed-wing aircraft, the system has been developed for use in light aircraft (Part 23, UL, LSA), airliners (Part 25) and powered-lift AAM aircraft (CS23).

“We employ a sensor on the front of the aircraft [about 50cm in front of the leading edge of the wing]. Which gives us enough anticipation time to calculate how the specific aircraft type moves based on the incoming turbulence. Then our system calculates how much counter turbulence has to be created to mitigate it using flaplets integrated into the wing,” Oliver Breiteneder, head of Market and Business Development at Turbulence Solutions tells us.

Those flaps, which look similar to the rudder on the aircraft tail, move between three and five times per second to reduce the effects of turbulence. Breiteneder likens the principle to noise cancelling technology which overlays an opposite base to neutralise the original sound.

Although testing and certification for Part 25 and AAM aircraft remains in the pipeline, the system is now available for purchase with Slovakia-based Shark.Aero’s single engine, low wing ultralight aircraft, Shark 600.

Path to market

The company first targeted the ultralight market because aircraft of this type only require certification on a national level, lowering the barrier of entry. It also means Turbulence Solutions has a product on the market less than three years after its first manned demonstration flight.

Following its minimum viable product, the next iteration will see Turbulence Solutions certify its technology for use on Part 23 aircraft before moving up again to Part 25s. “These aircraft are impacted turbulence in the lower atmosphere and also by clear air turbulence in the jet stream, which is increasing. Here, like AAM, I think the decision is based largely on the cabin experience, comfort plays a significant role. But there are also cost savings benefits too for operators.

“Then we will be ready to move into solutions for advanced or urban air mobility.”

The techonlogy can be installed on new aircraft as part of a type certificate or retrofitted under supplemental type certificate, says Breiteneder. “If the aircraft has flaps, we can build the mechanics required for the turbulence flap inside the existing wing. It looks something like a twin rudder once complete, just very fast moving.”

Advanced air mobility research 

Urban canyon turbulence is of particular significance to aircraft designed for urban air mobility operations. Flying at lower speeds in close proximity to multiple buildings will be much more dependent on the rotors in the case of winged eVTOLs. Solving this challenge requires an adaptation of Turbulence Solutions’ technology. Currently in the development phase, the technology would likely use a sensor probe to enable predictive calculations that correctly alter independent rotor speeds across the array.

“You have to be a fan of rollercoasters if you are willing to get into an eVTOL and fly in an urban area without turbulence cancelling technology on the aircraft,” says Breiteneder. “Even if you can guarantee safety whilst still experiencing turbulence at its fullest, passengers will be scared to get on the aircraft.”

Breiteneder also recommends eVTOL developers integrate a turbulence cancelling technology into the wing of the aircraft to assist during the cruise phase of flight. “Turbulence cancelling is a key enabling technology which increases confidence and trust and thus supports the air taxi operating models. Passengers associate a smoother flight with a greater sense of safety. And that is the key to the regular use of this new air transport solution and thus to the success of the business model.”

Funding

Turbulence Solutions has been funded in large part by various Austrian government innovation funds including Austria Wirtschaftsservice Gesellschaft – the promotional bank of the Austrian federal government. To date it has raised just over €2m ($2.2m) through government grants and contributions from private shareholders. The company is also in the application process for the European Innovation Council’s accelerator programme.

With enough funding in the bank from the ultralight sales to date and projected sales in the near-term, Breiteneder says the company will be able to deliver its product for the light aircraft market next year.

“If we go into the AAM market, we forecast reaching breakeven in 2028 because we need time to certify against regulations that are yet be fully defined. For that we will need roughly €10m. Then, if we go into large aircraft, we think there is even more time required for certification. To achieve breakeven in that segment we think it will cost us €60m and will take us into the 2030s,” Breiteneder explains.

If turbulence incidents continue to increase at the same rate there will be a 12.5% increase by the mid-2030s. Add in to the mix projected increases in aircraft production and continued acceleration of adverse weather patterns that figure is likely to grow, and with it the need for mitigating technology.

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