In this post we will take a look at the particular challenges we face with aerial spraying in Australia and why bigger isn’t always better in some situations…


In the early 1990’s, Yamaha Motorsports in Japan developed the RMAX unmanned helicopter as a successor to the prototype R-50.

Flown line-of-sight by a single operator on a Mode 1 (36 megahertz) radio system, the 100KG RMAX had only basic stability control, no autonomous failsafe functions and no telemetry feedback to the operator. The tuned 2-stroke 250cc boxer engine was noisy and the airframe was bulky and cumbersome to transport.

The RMAX was developed because the small size of Japanese rice farms made spraying with traditional manned aircraft both hazardous and impractical. It has since found additional uses in scientific research and military roles but it was primarily designed as an agricultural tool.

With a hefty lease-only ownership arrangement and limited 16 liter capacity for its size, few companies outside of Japan operated the RMAX. However, for the handful of skilled RMAX pilots in Australia (of which I was one), it was a capable and exhilarating machine to fly.


Fast-forward to today and the world of unmanned precision agriculture is a very different place. The rapid development of multirotor technology has given rise to a swathe of manufacturers, all producing large autonomous aerial spraying platforms.

Of course, top of the pile is Shenzen Da-Jiang Innovations Technology Co Ltd – or DJI to most of us.

From a foundation in small aerial camera drones, DJI soon sought to capitalize on the agricultural market with its “AGRAS” range of aircraft. The T20 is the latest in the range boasting a 20 liter payload capacity, full autonomy, object avoidance and terrain sensing along with a whole host of other technological innovations which make the poor old RMAX look like a bloated rotary winged dinosaur.

So why is this technological masterpiece not suitable for operations in Australia?


Don’t get me wrong. I’m sure plenty of operators will buy the AGRAS T20, just as they did the T16, the Phantom 4 or the Mavic 2. Machines such as the AGRAS are readily available, require little skill to fly and minimal technical knowledge to maintain. It isn’t the aircraft itself I have a problem with, rather the environment in which it is used…

Remember earlier when I said:

“The RMAX was developed because the small size of Japanese rice farms made spraying with traditional manned aircraft both hazardous and impractical”

Drone manufacturers are still trying to design aircraft that compete with the RMAX. They are constantly trying to come up with bigger airframes that carry bigger payloads. The problem is that they haven’t looked at where these drones are being sent.

Australia is a big place. When we put in a field of crops it covers the size of an average town in Japan. Spraying crops with a manned aircraft is not impeded by residential buildings or sharp inclines. However, spraying 20,000 hectares with a drone that can cover 1.5ha per flight would take forever and is prohibitively expensive. I can only speak for myself, but I’ve never been engaged to spray a large flat field of crops with a drone.

Where drones do offer an advantage in Australia is for difficult and remote access spraying. Take Burdekin Falls Dam in Queensland. The largest dam structure in Queensland (maybe Australia) it is 876m wide, 55m high, and holds back 1.8 million megaliters of water.

In recent years trees and shrubs have taken hold at the edges of the dam, their roots digging in to the concrete and threatening to damage the structure. Access to these groins is nearly impossible for the onsite staff without significant risk, so the decision was made to try applying pesticide using drones instead.

For this we used the TXA UAV R16 platform. This 16 liter drone has a maximum operating weight of 36kg and efficiency of 1.4ha per flight. It uses the same control system and software as the AGRAS; TXA UAV being partly owned by DJI.

To cut a long story short; we got the job done and the client was very pleased with the result (so much so that we head off again in the next few weeks).

The ideal agricultural drone for Australia is?

For my money, the ideal agricultural drone for the Australian environment is something smaller. A quadcopter (4 motors) with a 6 – 10 liter capacity and narrow spray width. I’ll list some reasons why I think this:

  1. Smaller drones have a lower inertia. This makes them more responsive to the controls and easier to get into tight spots whilst minimizing the risk to airframe or infrastructure.
  2. Smaller drones are more likely to use readily available battery packs. This gives us the option to vary the packs used meaning we can use higher C rated packs for steeper inclines and harsh environments. (The R-16 cannot handle a steep climb with a full tank on it’s OEM battery packs).
  3. Features such as terrain following and autonomous field planning are redundant. Not only is the environment not conducive to autonomous operations but autonomous control of agricultural drones is prohibited by law in Australia!
  4. Smaller drones are easier to transport. Being able to carry everything in the back of a Ute or 4WD is a bonus when operating in remote areas where a trailer would be difficult to tow.
  5. Drones such as the one pictured tend to be simpler in construction. This makes them easier to deploy, maintain and repair. Again, this is a bonus when operating in remote locations.

For the coming season Skyline UAV will continue to operate the TXA UAV R16 as well as a smaller 10L platform designed and built by RemotePilot UAS. We are already heading to locations in NSW and Queensland with capacity to add a lot more work.

Agricultural pesticide application in remote and difficult access areas needs precision. Make sure you talk to an operator who is not only experienced in this type of work, but is also licensed, certified and insured to work in your state. Using unlicensed operators can leave you in a precariously dangerous spot should something go wrong…

Contact us directly using the link at the top of this page or at to discuss remote and difficult access pesticide application or to request a quote.