Concerns with UAS Efficiency Statements
One statistic frequently cited by the UAS industry regarding the potential for UAS in the National Airspace System (NAS) is that 90 percent of crop protection in Japan is done utilizing one UAS, the Yamaha RMAX. What many UAS proponents fail to mention is the fact that the average farm size is 3.7 acres in Japan compared to 441 acres in the United States. Further, the RMAX has a chemical capacity of 4.25 gallons of liquid compared to 300+ gallons in a manned agricultural aircraft and operates at 15 miles per hour compared to a 160 mph for a manned ag aircraft. Another point to consider when making an effective aerial application to protect a crop is that the amount of air pushed down to the crop canopy—either from a rotor or from a fixed wing—is exactly proportional to the weight of the aircraft that the air is holding up. A small aircraft—manned or unmanned—does not displace much air. While there are UASs that could likely be retrofitted to perform aerial application operations now and in the future, they are the larger, military grade, and more expensive aircraft that can cost millions to build and maintain compared to a manned ag aircraft costing between hundreds of thousands of dollars to $1.5 million for the largest fully equipped models. Given these limitations, it is unlikely UAS will be utilized for mass aerial application in the US in the near future; however NAAA does acknowledge that UAS may be cost-effective in certain niche circumstances, such as small-scale vineyards and specialty crop situations, along with sensory applications, also of which are conducted by manned agricultural aircraft.
NAAA has also had meeting with the EPA, crop protection product manufacturers, agricultural trade press and conducted presentations at the Pesticide Policy Dialogue Committee and Association of American Pesticide Control Officials to explain that continued study of UAV pesticide application efficacy and drift potential is needed. EPA conducts a sophisticated spray drift risk assessment when registering a product for aerial use. The AgDRIFT model used for this predicts spray drift for fixed wing and single rotor applications. Other inputs into the model include weather conditions and boom length. These models do not necessarily apply to UAVs with two, four, six or more rotors. Reabe told the PPDC that without a similar model for unmanned aircraft, a proper spray drift risk assessment cannot be performed. Therefore, aerial pesticide labels should not apply to these unmanned aircraft until a proper drift assessment can be performed.
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