Downwash Manipulation

Aerofex has demonstrated its ducted-fan technology can tame the downwash of VTOL aircraft. The technology expands the downdraft and eliminates the recirculating flow typical of open-rotor craft. The enabler is the ducted-fan ejector system.

The exposed blades of helicopters and multi-copters generate tip-vortices and interactions resulting in turbulence and drift. The steady flow characteristics of the Aerofex technology reduces vortices and expands the flow to lessen its energy.

Why does this matter? For spraying crops or laying down fire-retardant the characteristics of the vehicle’s downwash are paramount to reducing drift. In manned applications, open-rotor recirculation can create blinding brownouts that risk injury to personnel and damage to the aircraft and structures.

Robotic Crop Sprayer

With the goal of increasing crop yields, a robotic flyer is coming together at Aerofex. Designed specifically for the precision spraying of crops, its size and lift enables significant capacity for fertilizer, pesticides or seeds.

Rendered here next to the Aero-X testbed, it shares the same control system, lift-train and the ducted fans of its predecessor – allowing safe operations around ground personnel and obstacles.

The platform’s ducted fans eliminate the swirl caused by exposed wing tips and open rotor blades – a major cause of chemical drift. Its flight attitude and favorable downwash will place the input precisely where intended and below the canopy of the crop – increasing efficacy while protecting neighboring properties.

Also like the Aero-X, it is fueled by automotive petrol, enabling continuous use throughout the day – and coverage rates far in excess of battery powered drones.

Developed for field servicing and the rigors of the agriculture environment, it is constructed primarily of high-impact plastics.  It can be lifted  by two men and transported in the back of a small pick-up truck.

Field demonstrations of the robotic prototype will occur by the end of 2017.

Unexploded Ordnance Remediation

According to the International Red Cross, over 2,000 people a month are injured or killed by unexploded ordnance and landmines (UXO).

Sites contaminated with UXO prevent civilian land use for agriculture or development. In the United States alone over 15 million acres may be contaminated by UXO. The US Environmental Protection Agency estimates UXO at 16,000 domestic inactive military ranges pose an “imminent and substantial” public health risk and could require the largest environmental cleanup ever. According to all estimates, remediation costs at suspect sites will exceed $15 billion.

Private sector companies perform the remediation work through contracts from the US government. The US government currently spends $200 million annually on UXO remediation. The work is labor-intensive using current methods. It is estimated that 70-80% is spent on surveying, removing vegetation, transportation, and personnel to manually detect and map UXO with metal detectors.

Other methods of mapping UXO include digital geophysics detection with ATVs or helicopters. The ATVs are limited in their capabilities, particularly in the littorals or overgrown environments typical of the sites. Helicopters are not cost-effective for the task and the very low altitude required by the sensors has been blamed for several accidents.

Development Test-bed

Perhaps not an “application” in the market sense, the use of our prototype as a test-bed does enable us to advance the technology behind the Aero-X and specific applications.

We develop and fly any new sub-system for the Aero-X on the test-bed before incorporating it into the baseline design. Our second-generation prototype, AB-F2 (Air Bike – Flight article 2), includes a re-engineered pilot interface that places all flight control functions in the hand-grips – pitch, roll, yaw and power. The design maintains the same level of intuition for the pilot and allows full control with only one hand – a necessity for useful flight. In addition, a redundant dual-string control system has been integrated, which provides stability augmentation.

Also heading out to the test site for evaluation is a distributed landing gear that will enable us to test the effectiveness of downdraft manipulation devices for agriculture. For hosting industrial sensor payloads, an instrumentation package has been integrated to assess vibration levels and disturbances generated on-board the vehicle in flight.

Optionally Unmanned Crop Dusting

In an important ruling this week, the US Federal Aviation Administration (FAA) issued an exemption allowing the use of an unmanned aircraft (UA) for aerial application. In its ruling the FAA determined “that a grant of exemption is in the public interest. The enhanced safety achieved using a UA with the specifications described by the petitioner and carrying no passengers or crew, rather than a manned aircraft of significantly greater proportions, carrying crew in addition to flammable fuel, gives the FAA good cause to find that the UAS [unmanned aerial system] operation enabled by this exemption is in the public interest.”

Prior to this ruling, unmanned aircraft could not be operated for commercial purposes in US airspace – even over private farmland. The petition for exemption was opposed by several groups concerned about the risks of unmanned aircraft operating in national airspace. The FAA determined the risks could be mitigated, in this case, by limiting altitude and airspeed (400 feet AGL and 45 mph max). The ruling also spells out specific flight operating procedures, as well as fuel reserves and sensors required on-board the craft.

Unlike autonomous drones, the exempted unmanned aircraft is piloted from the ground, with the craft in the operator’s visual line of sight. As a safety precaution the exemption requires the operator to possess a sport pilot rating at the minimum and be accompanied by a spotter in radio contact who must also maintain visual line of sight to the craft in flight.

The ruling is significant in that it recognizes the value of unmanned aircraft to agriculture and establishes a framework for the expansion of aerial application by unmanned craft. The US joins Japan, South Korea and Australia in allowing the commercial use of an unmanned aircraft for aerial application.


In support of two proposals recently submitted to potential partners, Aerofex has finished preliminary design of the Aero-X flotation gear. The floats provide a water-borne capability that will allow the platform to operate safely over water.

The over-water version of the Aero-X would be useful for ship-to-shore or ship-to-ship transport as well as traversing shallow water, rivers, or marshland – where other vehicles have trouble.

Designed to increase lift in ground effect, the water-enabled platform should have the same capacity as the Aero-X, but at reduced altitude – around 6-8 feet. We hope to test the gear early in the development process (the ocean is closer then the desert) – and report performance as we go.

It looks to be a whole lot of fun.

Air Racing

We recently performed a study for a client, in which we explored technology to extend the speed and range of a tandem-duct platform. Several of the technologies assessed in that study would enable specific applications for the Aero-X.

One of those developments involved the addition of two thruster fans located between the tandem-ducts, on each side of the pilot. The thrusters are driven by the same drivetrain powering the Aero-X primary lift fans. They utilize a unique power management system, enabling speeds over 90 mph without sacrificing fail-safe. Their position on the vehicle helps keep the nose down at higher speeds – a constant battle with vehicles of this type.

The addition of the thrusters – and some extra fuel instead of a passenger, would make an exciting platform for fast, low-altitude air racing. The added complexity of the machines could easily be handled by trained flyers. The racecourse could include flight between buildings or trees, under overpasses or through canyons, and even indoors in stadiums. If the vehicles were electric instead of petrol, pit crews could swap battery packs much like they do tires today.

An exciting twist is how these vehicles might react when flying in close formation – particularly against a front-runner aggressively defending his position.

Infrastructure Mapping

Mobile infrastructure mapping is the process of collecting geospatial data of structures and topography from a moving vehicle. Originally it was performed with low-flying aircraft carrying downward looking cameras or radar to map the topography of inaccessible areas. For many applications however, mapping from aircraft proved prohibitively expensive or lacked the accuracy required.

The development of three-dimensional laser scanning systems brought a new capability to infrastructure mapping. The accuracy of the data collected using laser scanners enables detailed comparisons of the position of structures – or the slope of river or road banks, allowing detection of shifts or movement over time.

State-of-the-art laser scanners have become less costly and more accurate. Reductions in size and power have provided a portable capability that allows them to be mounted on automobiles. The combination allows rapid collection of accurate data for assessment of the surface and structures surrounding roads – which is their only limitation.

Where there are no roads – for example in river basins or unimproved worksites, the Aero-X can accommodate two mobile laser scanners and their support electronics. One scanner is oriented for detailed mapping of the surface, while a second scanner mounted atop maps elevated structures such as guardrails, poles, and bridges. The top mounted unit has a video camera and both sensors share the same GPS system.

In a single pass, data gathered after a catastrophe such as a flood or earthquake can be compared to that collected previously to rapidly assess which structures are affected and which can be put back into use.

Agriculture – Unmanned

A 2010 study in Iowa calculated that each $1 spent on aerial application resulted in a $2.68 increase in crop yield. The upside differs by crop, location, and timing but the benefits of aerial application on food production can be dramatic. While routinely employed for distributing fertilizers, fungicides, and pesticides, at its best it can salvage a season’s crop (and resources) by rapidly knocking down a late season infestation.

The cost to aerially treat an acre of land by modern crop-dusting planes is about $9 per acre excluding the applicant. For a helicopter to perform the same task it costs $16 per acre and takes about two-thirds longer. Both costs are dependant on proximity to local airports – if your farm is not near one, your costs are higher. The US has over 5,000 local airports. Among the major growers, Brazil is second with 29% of the airport density of the US. India has only 7%, and Russia and China less then 5%. These countries lack the general aviation infrastructure that is essential for aerial application.

A promising alternative to extend the benefits of aerial application without aircraft is to trailer an unmanned aerial applicator to work the fields instead. Operating just 15’ above the ground and without transitioning through public airspace, the reliance on aviation is broken. An unmanned applicator can treat an acre of land for about $3 per acre regardless of proximity to airports. While not as fast as an ag-plane, total coverage can be comparable as it operates longer hours and without return trips to an airport. Such a system would allow developing countries to increase food production without first having to develop an aviation sector.

The same benefits apply to countries with adequate infrastructure, for different reasons. In Japan and the US urbanization is encroaching agricultural land, limiting ag-aircraft operations in those areas. In Europe as well as the US the incursion of wind turbines and power transmission lines over farmlands creates hazard areas that are putting more land out of the reach of pilots.

Increasing food production is a good reason to encourage unmanned aerial application – it benefits us all.

Agriculture – Manned

A question we are often asked regards the use of the Aero-X in agriculture. The concern is the force of the downdraft – and we think about it all the time.

In aerial application, a certain amount of downwash is a good thing – it disturbs the crop canopy enabling the applicant to penetrate deeper into the crop. This is why helicopters are sometimes more effective than dusting the canopy with an ag-plane. However the coverage rates of purpose-built ag-planes cannot be challenged when time is critical.

The velocity or wind speed is how the energy of a downdraft is characterized. As felt on the ground, downdraft velocity is proportional to the square root of the amount of weight lifted. It is inversely proportional to both the radius of the fans, and the square of the altitude flown above the ground. What this means is that altitude is the most potent term in reducing the downdraft.

Of course, for aerial application we want to get as close as possible to the crop canopy, so let’s look at the other two factors; fan radius and weight. The larger we can make the radius of the fans, the lower the downdraft velocity. The Aero-X fans are as large as is permitted for transport over public roads by trailer. Repositioning on roads is a cost-effective enabler over craft that must be based at airports.

That leaves the last term, which is weight. Through the use of composite materials and limiting equipment to only that required for low-altitude flight, we believe the Aero-X achieves the minimum weight possible for safe manned operations. When used for aerial application the intent is not to replace ag-planes. Instead the Aero-X will allow a grower to inspect crops and apply fertilizers, fungicides, and pesticides locally where they are needed – potentially avoiding or reducing full field spraying. The benefit of this approach reduces the weight of fuel and applicant carried – and the downdraft.

Ducted fans are known to have flow patterns that will be beneficial to aerial application – the flow does not recirculate as from an open rotor or wing tip. We will be characterizing the downdraft of the Aero-X during development, and partnering to test which altitudes are best suited to specific crops.