Turbulence Cancelling Technology for Turbulence-Free Flights of the Future
Atmospheric turbulence is an unsolved problem for aviation, affecting economics, safety and, above all, comfort and passenger trust. To date there has been no solution to this, apart from long detours or gritting your teeth and flying through. Turbulence Cancelling was developed and successfully demonstrated 2021 in manned flight tests based on research at the TU Vienna. This system is available for purchase on a European high-performance ultralight aircraft from 2024. Further development projects to implement Turbulence Cancelling also in AAM and CS25 aircraft are carried out from 2023.
Turbulence Impact on Aviation rising
Recent accidents show the heavy impact turbulence can have even on big airliner. The Boeing B777 of Singapore Airlines flight SQ321 experienced extreme turbulence resulting in -1.5 g negative g-force leading to the death of one passenger and dozens of injuries. Only five days later a Boeing B787 of Qatar Airways flight QR017 hits turbulence resulting in twelve injured persons. While airlines do their best to avoid such events, rising turbulence levels will require more and more rerouting and more optimized forecasting to be able to deliver flight experience and passenger trust. Unfortunately, every additional flight minute and every additional kg of flight mass increases fuel burn and thus CO2 emissions. In total, turbulence leads to about 10% of additional fuel requirement for air mobility, due to increased flight distance and flight time, inefficient flight logistics, and heavy and inefficient. As Climate and Aviation take place in the same environment, there is a bidirectional influence of climate change leading to more frequent and stronger turbulence, and aviation responding with even higher flight emissions.
A different solution to overcome the negative impact of turbulence other than rerouting is to actively counter the arising g-force by means of active flight control, also known as Turbulence Cancelling technology. As most of the turbulence scenarios are rather comfort limiting than safety limiting – the last airliner that disintegrated in flight due to turbulence was the BOAC 911, light counter-turbulence up to 0.5 g is already sufficient to cover most of the turbulence scenarios. Even in moderate to severe turbulence limited counter-turbulence of 0.5 g drastically improves the situation in the cabin, with the potential to alleviate negative g-forces – which levitate unfastened passengers towards the ceiling – back to positive g-forces. In principle, even severe to extreme turbulence can be actively countered by advanced flight control, however, this requires large flight control authority and a guaranteed function, which significantly raises complexity and criticality compared to a limited authority assistance system, which is limited to 0.5g and can be always turned off.
Modern aircraft also fly through bad visibility conditions, such as clouds and fog, as they are equipped with systems to handle IMC conditions, without avoiding every cloud. Similarly, rising turbulence levels will lead to even more need for systems which enable to also cross turbulence fields without negative impact on aircraft, crew and passengers. Thunderstorms adding risks of lightning and hail – recently Austrian Airlines flight OS434 was heavily impacted by hail – will still need to be avoided. For the rest of turbulence scenarios Turbulence Cancelling systems can create a completely new quality of flight experience, especially in light aircraft, including Turboprops, Business Jets and eVTOLs (Advanced Air Mobility). Performance, safety, economy, planning security are just a few arguments in favor of implementing Turbulence Cancelling systems. The most important aspect given the rising turbulence levels is passenger comfort and trust.
How does Turbulence Cancelling work?
The patented system works similarly to the already established “Noise Cancelling”. Based on targeted counter-deflections of control surfaces, the disruptive effects of turbulence, particularly the unpleasant vertical acceleration, can be reduced by more than 80%. Initial tests with a manned prototype in 2021 also confirmed these effects in practice (damping by approx. 60%). Through further research and refinement into a product ready for series production, which will be available for purchase on a European high-performance ultralight aircraft from April 2024, the dampening effect could be increased to approximately 80%. Instead of damping, we can already speak of cancelling.
For the upgrade a urbulence Sensor is installed either on the aircraft nose or in front of the wings to measure the turbulence even before it hits the wing. Existing flap systems are extended by small and fast Turbulence Flaplets, which are capable of generating the required counter-turbulence. Depending on the available avionics system, a separate processing unit or an existing flight control unit can be used for the processing of the actual Turbulence Cancelling control logics.
#Inventor and managing director of Turbulence Solutions GmbH, András Gálffy, explains that “aircraft that fly at low altitudes and are therefore exposed to thermal and orographic turbulence, such as gliders, sports aircraft and business aircraft with turboprop engines, can particularly benefit from Turbulence Cancelling”. “In the future, it should be possible to fly directly and reliably through turbulence while further increasing comfort.”
“So-called eVTOL aircraft with wings (note: Electric Vertical Take-off and Landing), which will be used in the future as a cost-effective and fast air transport solution within cities or as air taxis on short-haul routes, are also extremely affected,” adds András Gálffy. “Especially in urban areas, extreme turbulence and turbulence arise. However, the sustainable use of the new flight services will largely depend on acceptance. And this is supported above all by the feeling of safety, to which a turbulence-free flight contributes significantly”.
But the use and capacity utilization of conventional aircraft also depends on the weather. “I often see that our aircraft remain on the ground when the weather indicates turbulence,” explains Oliver Breiteneder, who, as president of flylinz – Flugschule Linz, has deep insight into the usage behavior of sport pilots. “However, it is rarely the pilots themselves who are afraid of turbulence, but rather the passengers, often family members.” Oliver Breiteneder expects that the utilization of those aircraft that are equipped with Turbulence Cancelling will increase significantly. “In our aircraft replacement and new investments, we will closely examine which models have Turbulence Cancelling available. That would be a decisive competitive advantage for us.”
The technology works particularly effectively on fast aircraft with a broad airspeed envelope and on aircraft with low wing loading. “We therefore initially looked for contacts with manufacturers of high-performance ultralight aircraft,” explains András Gálffy. “In the meantime, contacts have also been established with manufacturers of light aircraft and eVTOLs at international trade fairs, all of whom are impressed by the possibilities of our technology.”
As one of the next steps, manufacturers of business jets and airlines who want to offer their passengers a special comfort experience and save the costs of turbulence-related detours will also be addressed. “We estimate that simply by avoiding detours around known turbulence zones, fuel savings of around 3-5% are possible,” explains András Gálffy. “Studies show that the total costs for turbulence-related detours and extra maintenance due to so-called high g-loads in global aviation are estimated at up to $ 3 billion.” “By the way: our calculations show that gliders perform better in turbulent updrafts with our system. “But that also means that in engine-powered aircraft the drag and thus the consumption decreases or the speed increases.”
Similar to the already established Noise Cancelling, targeted deflections of control surfaces – so-called “Turbulence Flaplets” – generate counter-oscillations that overlap with the turbulence-related movements and thus cancel them out. In aircraft with fly-by-wire controls, the control logic can be upgraded to include Turbulence Cancelling without having to install additional control surfaces. Furthermore, Turbulence Cancelling does not alleviate the pilot’s maneuvering loads or interact with primary flight controls, such as aileron, elevator, and rudder. In contrast to the “Gust-Load-Alleviation” systems already in use, Turbulence Cancelling focuses on passenger comfort and not just on reducing the weight of wing structures. In this context, the limited control authority of small flaplets is already sufficient to cover most turbulence scenarios for passenger comfort and trust, while Gust-Load-Alleviation needs to generate significantly higher g-forces when aiming for guaranteed alleviation of structure limiting gust loads. Future Turbulence Cancelling systems might be step-by-step expanded to raise complexity from limited-authority assistance systems focusing mainly on passenger comfort, up to full-authority fail-operational systems including alleviation of limiting gust loads in some decades. This can be compared to the development from first low-complex flight instruments giving assistance to pilots in reduced visibility conditions, up to high-complex fail-operational navigation systems for intentionally entering instrumental flight conditions.
When will Turbulence Cancelling be available?
Discussions are currently underway with several aircraft manufacturers. It is intended to start the series production process with 2 – 3. Inventor and managing director András Gálffy: “Ultralight aircraft have simple and therefore quickly implementable approval regulations combined with a high level of willingness to innovate. We therefore have focused on this area. We are looking forward to presenting the first model available on the market at AERO Friedrichshafen 2024.” Turbulence Cancelling is offered as an option for new aircraft, and on the other hand, retrofit kits (as part of STCs) are also planned for existing aircraft.
At the same time, discussions are underway with several manufacturers of electrically powered air taxis (eVTOL). “These manufacturers are currently in very intense competition for certification. The first purely electric air taxi available on the market will certainly have advantages,” explains Oliver Breiteneder. “However, paying passengers who regularly use this service will be crucial to the lasting success of this innovative and environmentally friendly transport solution. And that depends largely on trust in this new technology. In fact, we have a critical enabler technology for this new market.
“Surveys show that even in heavier and therefore more stable, large aircraft, around ¼ of all passenger struggle with discomfort due to turbulence. In the case of eVTOL, more than half of those surveyed are afraid of flying with these significantly lighter, partially autonomous aircraft in the future, even in light winds”.
