Authors:  Carl Duley, Brian Luck, John Gaska, Jeff Nelson, Shawn Conley, and Damon Smith

Date:  August 15, 2023

Large Unmanned Aerial Vehicles (UAV, drones) that are capable of low volume liquid applications in production agriculture settings are a very exciting topic this year. These machines provide producers and crop consultants an opportunity to complete late-season applications of inputs with minimal to no disturbance of the growing crop. While these applications, like mid- to late- season fungicide or rescue herbicide, are not new to the industry the use of agricultural sprayers with sufficient clearance to successfully apply these treatments  can cause damage to the crop and contribute to soil compaction if conditions are right. While the Sprayer UAV is not an ideal solution in all cases, they can be a viable option in situations where a large sprayer, crop duster, or helicopter are not ideal, like small/irregularly-shaped fields or fields surrounded by trees or power lines.

We have used a Sprayer UAV for the first time in 2023 and have been discussing their use with folks around Wisconsin. From what we’ve heard, the field capacity of these machines ranges from 20 – 40 ac/hour depending on the size of the UAV, number of batteries, and refill setup. One thing to note is that there is a temptation to increase the concentration of the spray mixture in order to meet application rates, but increase the area covered by one tank of spray with the UAV. Doing this is considered applying off-label for these particular products and is not best practices for chemical applications. We recommend avoiding this situation as making off-label applications can add the risk of compromising the sale of the crop at harvest.

Below we’ve compiled some recommendations and considerations when planning to contract or use Sprayer UAV’s in your operation.

Rules and Regulations:

• Make sure your farm is in an area that allows these drones to operate (i.e. not within a restricted airport zone or military flight path). You will need permission of the airport operator to fly within restricted zones. Many of the new drones will simply not even operate within these zones and will require remote permission from the drone manufacturer to be uploaded into the controller. This can be done once the manufacturer receives written permission from the airport operator.
• FAA Part 107 Remote Pilot License is required.
• Exemption from FAA to operate above 55 lbs is required
• Dealerships have the exemptions and can add additional units/pilots
• Pesticide applicator training required. 1.1 Field & Veg. subcategory aerial application is required to spray by drone. A base category is required to get the subcategory.
• Subcategory aerial applicator training required. WDATCP also requires proof that you have achieved all the requirement that you have to get from the FAA to operate the drone itself.
• Permissions and/or notification of surrounding farms and businesses when flying
• Be sure to contact your insurance company to see both about insuring for drone damage and liability.

Purchasing and Support:

• Price: $30,000 – $50,000 (as of August, 2023)
• Consider buying extra batteries to maximize operation time in the field. Up to $2,500 per battery
• Do business with a reputable dealership ideally in your area
• Ask what opportunities there are for training on machine use and operation
• Ask what the dealership provides for support of the product as the machine ages
• Firmware updates will be required and you should understand the process fully before attempting
• Is there any warranty associated with the machine?
• What options are there for machine service and what intervals should these be performed at?

Operation:

• Operation under high voltage transmission lines can be tricky or impossible – may lose complete control under some conditions.
• Develop a check list of items needed before heading to the field to spray
  • This includes an up-to-date flight log
• Ensure all components of the machine are operational and in good working condition
• Confirming the batteries on the UAV, the controller, and the interface device (phone, tablet, etc.) are fully charged
• Keep a spare battery, or multiple spares, charged and on hand in case you have one fail to take a charge or otherwise not be operational
  • Large spray drones will need a portable generator as well to charge batteries.
• Keep at least one spare set of propellers on hand and replace any propellers if there is any question about their structural integrity
  • Propellers can be damaged by any number of things, including insects and other debris. A small chip in a brittle carbon fiber propeller can lead to failure and an unintended emergency or uncontrolled landing of your UAV.
• Wildlife can be a problem and interact with the UAV during flight, especially birds. Maintain line of sight and visual contact with the UAV and avoid interaction with birds when possible.

Maintenance:

• Dust and debris is the number one enemy of the electric motors that allow your UAV to fly
  • Avoid take-off and landing in dusty environments whenever possible – choose staging
    area carefully
  • Blow out motors with compressed air after every use
• Battery use log
  • Lithium-ion batteries have a finite life and should be replaced before they fail
  • Keep a log of the number of charge/discharge cycles for each of your batteries
  • 200 charge/discharge cycles is the maximum for most batteries under regular
    use – more cycles for the larger batteries used in these drones
  • Allowing batteries to sit unused for extended periods of time can reduce their lifespan
    as well
  • Replace batteries about every three years
  • Monitor discharge rate during flights to get an understanding of normal/safe operation time
  • Any discrepancies in this discharge time should be noted and the battery should
    likely be replaced.
• Propellers
  • Replace propellers annually – $500 – $1,000
  • Do a thorough inspection of used propellers for any sign of damage and discard
    damaged propellers immediately
  • Props take more of a beating than you might think – bugs, etc.
  • Keep undamaged used propellers for emergency replacement when needed.
• Air frame and Landing Gear
  • Inspect for damage after every flight
  • Keep spare components on hand to replace broken or damaged structural members
    when needed
  • Landing gear is highly likely to be damaged during normal operation and should be
    replaced

Other Useful Links

University of Georgia Links:

Spray Drones – Regulations and Operational Considerations

Pesticide Application Considerations with Spray Drones

Federal Aviation Administration Drone Links:

https://www.faa.gov/uas/advanced_operations/dispensing_chemicals

https://www.faa.gov/uas

Wisconsin DATCP Commercial Applicator License Info.:

https://datcp.wi.gov/Pages/Licenses_Permits/CommercialApplicator.aspx

This article was posted in Precision Agriculture, Uncategorized, Unmanned Aerial Vehicles and tagged Sprayer Drone, UAV.