Nestled in the corner of an anonymous industrial estate just metres outside the perimeter of the UK’s Farnborough airport, high-flying innovator AALTO’s production facility is gearing up for output of its unmanned Zephyr to take off.
Inside its Kelleher building, the result of the company’s work is an extraordinary sight. With a 25m (82ft) wingspan – roughly the same as an ATR 72 twin-turboprop – its ultra-endurance Zephyr 8 has a maximum take-off weight of just 75kg (165lb), and the aircraft can fly as high as 75,000ft, in the stratosphere.
Stripped of the two small electric motors, wing- mounted solar arrays and batteries that enable it to sustain round-the-clock operations, its bare airframe weighs in at only 30kg.
In 2022, a flight-test example flew nonstop for 64 days after being launched in the USA, covering a total distance of 140,000nm (259,000km). The aircraft narrowly failed to exceed an endurance record due to experiencing a subsystem failure as it laboured to remain above unusually high-altitude, storm-related turbulence recorded at around 57,000ft.
Equipped with a lightweight payload, the Zephyr is intended for use during tasks such as providing mobile phone signal coverage, online connectivity services, or Earth observation. Military applications could also include establishing secure communication networks.
Serving as a mast in the sky, a single Zephyr could enable the same mobile phone coverage as up to 250 ground-based towers in the most difficult terrain, AALTO claims. Crucially, this can be done more efficiently and at a much lower cost than using low-Earth orbit satellites, it adds.
OPERATIONAL PLANS
AALTO is now working in pursuit of certification, while honing its industrial and operational plans for the programme, which traces its development roots back through Airbus Defence & Space and Qinetiq ownership and over 20 years.
The niche company now operates as a subsidiary of Airbus, which span it out in May 2022 but still retains full ownership.
“The idea is to grow the company, to bring in external partners as shareholders that will be strategic in nature, not just financial,” explains AALTO chief executive Samer Halawi.
“We have been engaged with a number of potential strategic partners, but we just want to make sure that we get it right,” he says. “Those conversations are ongoing, but the objective is not time-based – it is quality-based.”
Type certification via the UK Civil Aviation Authority (CAA) is currently targeted before the end of 2025, at which point the company wants to be ready to start delivering managed services to customers using fleets of the aircraft.
PORT POSITIONING
Central to this will be the establishment of potentially half-a-dozen so-called AALTOports around the globe. Each will serve not only as a launch and recovery point for the aircraft, but also host production and maintenance facilities.
“We need places around the world where the weather is favourable to us, and for the longest duration of the year as possible,” Halawi says. This multi-site plan means that “if we cannot take-off from one particular location, we go from another”, he says.
AALTO plans to establish its first such facility in Kenya, which came out on top following meteorological assessments, and also spans the equator, maximising potential for charging solar panels while airborne. Talks continue with Kenyan authorities.
“We are still looking as to where to put the other three, four or five hubs around the world,” Halawi says. Brazil is viewed as another possible location, while a suitable global spread also suggests that sites could be established in the Middle East and Asia-Pacific regions.
“It puts the country at the forefront of innovation, and brings high-level jobs,” Halawi says of the benefits available for potential hosts.
Meanwhile, AALTO’s lead engineers are working to perfect its manufacturing and assembly process. This will include appointing subcontractors to take on manufacturing at scale. Its industrialisation plan is bold, ultimately looking to complete one aircraft per week on the Farnborough assembly line alone.
“We need to bring in the best people from across the industry to make it a success, which is why Airbus carved AALTO out from the core and attracted the C-suite that we have,” says chief engineer Philip Briggs. “We have very different skills that will enable us to get to market in the most efficient way.”
Chief technology officer Pierre-Antoine Aubourg, for example, brings considerable such knowledge, having formerly worked as a production expert overseeing industrial transformation at Airbus Helicopters.
“We will outsource, so we can have a simpler final assembly line,” Briggs says. This also will be standardised at overseas locations – a practice which Halawi refers to as an “Ikea-type” assembly model.
The vehicle’s construction involves the use of lightweight carbonfibre components which are assembled to form the wing structure, which is then wired and covered in Mylar. The number of solar arrays and batteries installed can vary according to mission and endurance requirements.
Current payload options include the Airbus Defence & Space-developed Opaz Earth observation sensor, which weighs just 5kg. From 65,000ft, its coverage is roughly 22 x 11nm (40 x 20km), with a ground imaging resolution of 18cm. An alternative communications payload weighs up to 8kg.
The stratosphere poses unique operational challenges, with low atmospheric pressure, high temperatures during the day and extreme cold at night.
After hours spent in darkness, the aircraft’s batteries gradually regain the charge needed to enable the Zephyr to return to its maximum altitude of 75,000ft by around noon, and then begin to store excess capacity.
“Two hours before sunset, we stop charging, and then as it descends we convert the potential energy into kinetic energy, and throttle back the motors,” explains vice-president flight operations Rich Tyler. It then cruises through the night at around 60,000ft, “using less power than a standard microwave”.
“We have demonstrated in the stratosphere that we can use the payload overnight – that is the really difficult bit,” Briggs says.
AALTO has already tested battery life of up to 180 days, but aims to eventually be able to sustain nonstop flight for up to one year.
David Hansell, the company’s head of aviation, explains the complexity of seeking regulatory approval. “You are certificating an entirely new form of aviation,” he notes, pointing out that “the operator may be two continents away”.
While this means that regulators may be “a couple of steps behind industry”, he says: “it has been very positive so far, from the regulators, countries and up to ICAO”.
“There is an opportunity for the CAA and others to be at the forefront of technology, by certifying a very high level of innovation that at the same time is something that is really good for humanity – that is, offering a service that is connecting people,” Halawi says.
A key requirement will be for AALTO to secure parallel validation approvals from multiple authorities.
As an example of its progress, Tyler notes that “Over four days [in 2022], we exited the US National Airspace System and flew all the way down to Belize, operating in multiple flight information regions.
“We did live capture with multiple payloads, and took 14,500 images over 24 hours. We mapped an extensive geographic range during this mission, beyond the capabilities of a satellite.”
While commercial traffic will fly far below Zephyr vehicles, AALTO’s aircraft must be able to make their slow way to operating altitude after launch without causing inconvenience or risk to others.
UNIQUE PERSPECTIVE
Hansell has a unique perspective on the high-altitude sector, having also previously run aviation policy on the Google Loon project and worked on Facebook’s Aquila effort – both of which sought to broaden internet connectivity around the globe.
Facebook axed the solar-powered Aquila aircraft project in 2018, while Google called time on its Loon venture – which used high-altitude balloons – in 2021.
“For many good reasons, and for some outdated reasons, the model of certifying aircraft relies on a highly skilled crew sitting in a flightdeck having immediate control over that aircraft, and so regulators live in that world,” Hansell says.
“It is incumbent on us to go and prove every time that not only are we safe, but we are good partners in the airspace. We are not inconveniencing travellers or cargo, and people should never even know [that we are there] aside from the benefit that we give.”
“We are not flying over high-population areas or congested airspace,” Halawi adds. “We don’t carry passengers – we are way down the risk scale.”
Discussions with regulators include seeking the flexibility to move a vehicle off station and into a pre-defined temporary sanctuary area in the event of adverse weather, degraded performance or the interruption or loss of a communication link.
“The aircraft can fly autonomously for up to seven days,” Tyler notes. During this time, its operator can attempt to re-establish communication, or if required opt to terminate the platform. This would be achieved by placing the aircraft into a stall over a safe area, after which it is designed to descend in a controlled manner, which Tyler likens to a sycamore seed falling.
However, were it to encounter a structural failure, its batteries are tethered directly to the aircraft’s spine, and its wing will separate at its outer dihedral point, and “flutter down”.
AALTO has an in-house pilot training team and simulator which can mimic different weather phenomena and system failures. It has trained 100 operators to date – from experienced unmanned air vehicle pilots to others with no prior experience – with each completing a course lasting up to six weeks.
TRAINING ACADEMY
The company also has its own mission planner academy for the Zephyr’s other supporting personnel, who are trained to prepare for up to the next seven days of a flight’s activity. This is supported by the aircraft sending text messages about its status every 30s, with a system latency of roughly 5-6s.
But with the aircraft requiring little in the way of manual intervention, the company plans to eventually have one operator and mission planner taking responsibility for multiple vehicles simultaneously.
AALTO has entered its next round of activity, using a sub-scale low-level test vehicle. A first flight was conducted in mid-February, using a military range off the west coast of Wales.
“It uses exactly the same avionics as the larger aircraft,” Tyler says. “We are looking at changes in the flight-control system, and also the motor controller.”
But why does AALTO believe it can succeed when the financial and innovative might of two of the world’s leading technology players previously failed?
“Google Loon had the technology and they had a good market penetration, but when you use balloons, you cannot control exactly where they go,” Hansell notes. Facebook, meanwhile, incurred high costs by developing an aircraft with a 43m wingspan.
“They are mega companies with huge resources,” he says. “But at their core, Facebook and Google are not aviation companies. They do not think and operate the way aviation companies have for decades. We appreciate the economies of building aircraft, the timelines of return on investment, and the regulatory view of what is required to build and operate aircraft safely. We have the right balance of capability and performance.”
Notably, that capability also has matured over time: an earlier iteration of the Zephyr first reached the stratosphere in 2008, but it took another decade for the technology to fully catch up with design requirements.
Halawi views AALTO’s ability to offer customers a fully managed service as a clear differentiator in the market. Potential users should find the experience more akin to using a chauffeur than simply hiring a car, he suggests.
“What we are looking at is providing the service so that our customers are not concerned about aviation elements related to flying something, taking off from somewhere, doing the maintenance. It’s the application that is important, not the ownership of the vehicle.”
And with environmental considerations also of growing importance globally, he points to the solar- and battery-powered Zephyr’s green credentials. “We are offering a service that is completely sustainable, from beginning to end. We don’t need fuel to launch rockets or operate satellites.
“We think we are going to have more demand than we can supply at least initially, until we ramp up our production,” he says of the strength of market interest.
“We have already been engaged with a number of potential customers that are either working with us on demonstrating a certain capability or for whom we are running some actual missions,” he says. “They are big believers in what we are doing.”
PENT-UP DEMAND
The company has previously announced the sale of two Zephyr aircraft to the UK Ministry of Defence.
“Customer demand is very pent up,” says Briggs, who notes that AALTO also is contacted “whenever there is a natural disaster”, to see if the company could provide support for humanitarian response efforts.
“We are just on the cusp of exponential demand – certainly with the interest that we see and the work that we have planned for the next two years,” he says.
And for the longer-term, AALTO is studying the development of additional aircraft, potentially including a larger model which would offer increased endurance or a multi-payload capability.
