172 January, 2019 Int J Agric & Biol Eng Open Access at https://www.ijabe.org Vol. 12 No.1
Evaluation of droplet deposition and effect of variable-rate application by
a manned helicopter with AG-NAV Guía system
Weixiang Yao
1,2
, Yubin Lan
1,2*
, Sheng Wen
2
, Huihui Zhang
3
, Yali Zhang
1,2
,
Juan Wang
1,2,4
, Chunchun Xie
5
(1. College of Engineering, South China Agricultural University, Guangzhou 510642, China; 2. National Center for International
Collaboration Research on Precision Agricultural Aviation Pesticides Spraying Technology (NPAAC), Guangzhou 510642, China;
3. USDA-Agricultural Research Service, Fort Collins, CO 80526, USA; 4. Mechanical and Electrical Engineering College, Hainan
University, Haikou 570228, China; 5. Shandong Ruida Pest Prerention & Control Co., Ltd, Jinan 250101, China)
Abstract: The variable-rate application is an important aspect of precision agriculture. In order to determine the regular
patterns of droplet deposition and compare the actual variable-rate spraying effect of the AS350B3e helicopter with the
AG-NAV Guía system, spray tests were conducted with different operating parameters and operating methods. In this study,
the deposition distribution of droplets in the effective swath area was evaluated for six single-pass applications at four different
flight velocities. The effects of adding adjuvant on droplet deposition, drift and droplet size were compared, and the actual
variable effect of the forth-back application was verified. The analysis results showed that the position of the effective swath
area was affected by natural wind velocity and wind direction, and would shift to the downwind direction area from the
helicopter route of a different degree. The effective swath width increased slowly and then decreased sharply with the
increase of flight velocity. It was found that flight velocity of 100 km/h was the peak inflection point of effective spray width
variation. Moreover, the effect of flight velocity on the distribution uniformity of droplet deposition in the effective swath
area was not significant. In the single-pass application of 90 km/h, adding adjuvant could increase droplet size in the effective
swath area. The deposition increased by 8.98%, and the total drift decreased by 28.65%, of which the upwind drift decreased
by 28.31% and the downwind drift decreased by 29.06%. In the forth-back application of 90 km/h, the error between actual
application volume and system setting dose was 12%. The results of this study can provide valuable references for future
research and practices on variable-rate aerial applications by manned helicopters.
Keywords: manned helicopter, precision agriculture, variable-rate aerial application, spray test, adjuvant, droplet deposition
DOI: 10.25165/j.ijabe.20191201.4039
Citation: Yao W X, Lan Y B, Wen S, Zhang H H, Zhang Y L, Wang J, et al. Evaluation of droplet deposition and effect of
variable-rate application by a manned helicopter with AG-NAV Guía system. Int J Agric & Biol Eng, 2019; 12(1): 172–178.
1 Introduction
In the 1990s, an aerial variable-rate application system was first
used in the United States and then gradually developed
[1]
. An aerial
variable-rate application system includes navigation system and
variable flow control system that allows variable spray of pesticides,
herbicides, soil amendments and fertilizers for specific areas. The
research on aerial variable-rate application system started earlier in
developed countries and there have been some commercial aerial
variable-rate application control systems for manned agricultural
Received date: 2018-03-05 Accepted date: 2018-12-18
Biographies: Weixiang Yao, PhD candidate, research interests: precision
agriculture technology and equipment, Email: 1913835329@qq.com; Sheng
Wen, PhD, Associate Professor, research interests: precision agricultural
aviation application, Email: 58675023@qq.com; Huihui Zhang, PhD, Research
Agricultural Engineer, research interests: airborne and ground-based remote
sensing, Email: huihui.zhang@ars.usda.gov; Yali Zhang, PhD, Associate
Professor, research interests: precision agricultural aviation application, Email:
ylzhang@scau.edu.cn; Juan Wang, PhD candidate, research interests: precision
agriculture technology and equipment, Email: 49792740@qq.com; Chunchun
Xie, Senior engineer, research interests: application of pesticides in agriculture
aerial, Email: rdff@foxmail.com.
*Corresponding author: Yubin Lan, PhD, Distinguished Professor, research
interests: precision agricultural aviation application. College of Engineering,
South China Agricultural University, Guangzhou 510642, China. Tel:
+86-20-85281421, Email: ylan@scau.edu.cn.
aircraft. The common feature of these systems is to provide
precision navigation guidance for pilots, and automatically adjust
spray flow rate according to the flight parameters during flight
[2,3]
.
In view of the accuracy and practicability of aerial
variable-rate application systems, researchers have carried out some
exploratory research. Kirk and Tom
[4]
installed SATLOC Flow
Control/ Monitor (AgJunction, Inc., Hiawatha, USA) system on a
Cessna AgHusky aircraft (Cessna, Inc., Wichita, USA), and
compared the spray uniformity of variable spraying and
conventional constant spraying under different meteorological
conditions. The test results showed that spray control errors of the
flow control system was less than the conventional constant spray
errors. Smith
[5]
evaluated AutoCal I and AutoCal II (Houma
Avionics, Inc., Houma, USA) systems with an Air Tractor 402
aircraft (Air Tractor, Inc., Olney, USA). The performance of the
two systems was evaluated by experimental and theoretical errors.
He found that experimental error was not significantly affected by
the application rate in either system, but increased with the number
of spray passes. The theoretical error of AutoCal I system
gradually increased from 0.79% to 3.20%. Thomson et al.
[6]
conducted a comparative test on the flow control reaction speed
and accuracy of SATLOC M3 (AgJunction, Inc., Hiawatha, USA)
system and improved the control system accordingly. Smith and
Thomson
[7]
also calibrated the GPS positioning accuracy and
response time of SATLOC M3 system. It was proved that the
