Manned Helicopter Research Articles

Hierarchical Framework for Optimizing Wildfire Surveillance and Suppression Using Human-Autonomous Teaming

The integration of manned and unmanned aircraft can help improve wildfire response. Wildfire containment failures occur when the resources available to first responders, who execute the initial stages of wildfire management referred to as the initial attack, are ineffective or insufficient. Initial attack surveillance and suppression models have linked action spaces and objectives, making their optimization computationally challenging. The initial attack may be formulated as a multi-agent partially observable Markov decision process (MPOMDP). We divide the initial attack MPOMDP into surveillance and suppression processes with their respective planners operating on different, but constant, time scales. A hierarchical framework iterates between surveillance and suppression planners while also providing collision avoidance. This framework is exemplified by a set of multirotor unmanned aircraft surveying an initial attack fire while a manned helicopter suppresses the fire with a water bucket. Wildfire-specific solver extensions are formulated to reduce the otherwise vast action spaces. The hierarchical framework outperforms firefighting techniques and a myopic baseline by up to 242% for moderate wildfires and 60% for rapid wildfires when simulated in abstracted and actual case studies. We also validate the early dispatching of additional suppression assets using regression models to ensure wildfire containment within thresholds established by wildfire agencies.

USING UNMANNED AERIAL VEHICLES IN RECOGNIZING TERRAIN ANOMALIES ENCOUNTERED IN THE GAS PIPELINE RIGHT-OF-WAY (ROW)

The objective of the undertaken research was to characterize and evaluate the impact of weather and lighting conditions on recording terrain anomalies in the photographs obtained during a UAV photogrammetric flight. The present work describes the use and capabilities of the UAV in the mapping of photo acquisition conditions similar to those performed during inspection flights with the use of a manned helicopter equipped with a hyperspectral camera, in the target range of visible light. The research was conducted in the southern part of Poland (between Gliwice and Katowice), where 7 routes were selected, differing from one another in terms of terrain anomalies (buildings, types of land areas, vehicles, vegetation). In the studies, which involved photogrammetric flights performed using a UAV, different seasons and times of day as well as changes in light intensity were taken into account. The flight specification was based on the main parameters with the following assumptions: taking only perpendicular (nadir) RGB photographs, flight altitude 120 m AGL, strip width 160 m, GSD ≤0.04 m and overlap ≥83%. The analysis of the photographic material obtained made it possible to correct the catalog of anomalies defined previously, since the recognition of some objects is very difficult, being usually below the orthophotomap resolution. When making and evaluating orthophotomaps, problems with mapping the shape of objects near the edges of the frame were found. When a 12 mm lens is used, these distortions are significant. It was decided that for the purpose of generating training data from orthophotomaps, only the fragments containing objects which shape would be mapped in accordance with the real one would be used. Thus, the effective width of orthophotomaps obtained from simulated flights will be approximately 100 m.

Experimental study of the influence factors of the droplet size of rotary nozzles during manned helicopter spraying operations

The droplet size significantly affects the performance of aerial spraying operations. Thus, it is crucial to develop rotary nozzles for helicopter spraying operations and analyze the influence of droplet size. We conducted a calibration test of the nozzle rotation speed to analyze the effects of air velocity, blade installation angle, hub diameter, and blade length on the rotation speed. The results showed that the rotation speed increased with an increase in air velocity and nozzle diameter and decreased with an increase in the blade angle. The rotation speed of three types of rotary nozzles was measured in the range of 576–15 358 r/min. A high-speed wind tunnel test was conducted to determine the droplet size of the rotary nozzles at different rotation speeds, spray flow rates, and hub mesh numbers. The influence degree of the three factors on the droplet size was rotation speed > spray flow rate > mesh number. The multiple linear regression equation of the volume median diameter (VMD) of the droplet size was obtained. The droplet size obtained from wind tunnel and flight tests at 5000 and 7000 r/min was compared. The droplet size was in the range of 148.56–259.39 μm and was slightly larger under wind tunnel conditions than during the flight test. The relative width of the droplet spectrum was small for both test methods, indicating that the droplet size distribution of the three rotary nozzles was uniform. Finally, the spray nozzles were used for insect control in forest areas and achieved a control efficiency of 94.6. This study provides a reference for optimizing the operating parameters of spraying nozzles and improving the performance of helicopter-based low-volume spraying operations.

Comparison of sampling precision for nearshore marine wildlife using unmanned and manned aerial surveys

Aerial surveys of large marine wildlife in nearshore areas can support management actions to ensure conservation of this megafauna. While most aerial surveys of marine wildlife have been carried out using manned aircraft, unmanned aerial systems (commonly known as drones) are being increasingly used. Here, we compare the relative accuracy and precision of marine wildlife surveys from a multirotor drone and a manned helicopter for the first time. At two locations on the east coast of Australia, we simultaneously surveyed sharks (including white sharks, Carcharodon carcharias), dolphins, rays, and sea turtles in nearshore coastal areas using a multirotor drone (DJI Inspire I) and a helicopter (Robinson 44 Clipper II) over 26 separate flights. Sampling included the real-time quantification of marine wildlife by an observer in the helicopter and the pilot of the drone. The video feed from the drone was then later re-sampled in the laboratory. Of the three methods, post-hoc analysis of drone video footage is likely to provide the most accurate and precise estimates of marine wildlife in nearshore areas. When real-time data are required (e.g., for shark-risk mitigation), manned helicopters (over larger stretches of coast) and drones (across localised beaches) will both be useful.

Comparing the Performance of Multispectral and Hyperspectral Images for Estimating Vegetation Properties

Multispectral and hyperspectral data have been used to investigate various land cover characteristics. Hyperspectral data have more potential to retrieve information of ground features than multispectral data; however, their limited availability leads to fewer studies in the literature. This research aims to acquire both multispectral and hyperspectral images and compare their performance for estimating vegetation properties (i.e., chlorophyll content). A hyperspectral image (with 325 bands in the visible near infrared (NIR) range) was obtained using a compact hyperspectral sensor mounted on a manned helicopter. A modified camera-based three-band image (with blue, green, and NIR) and a RedEdge sensor-based five-band image (with blue, green, red, red edge, and NIR) were simulated using the hyperspectral image. These three images were compared for the estimation of vegetation chlorophyll content. Partial least square (PLS) regression and random forest regression (RFR) were both applied to estimate chlorophyll using image-derived variables, including vegetation indices and imagery textures. Results show that the RedEdge image achieved good accuracy (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ~ 0.80, RMSE ~ 14 μg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), close to the accuracy of using the hyperspectral image (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ~ 0.81, RMSE ~ 13 μg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). The extra bands in the hyperspectral image did not substantially improve chlorophyll estimation. The three-band multispectral image yielded the lowest accuracy (e.g., R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ~ 0.42, RMSE ~ 24 μg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). The RFR performed consistently better than the PLS, owing to its use of randomly-selected training data and predictor variables to build regression trees. These results are expected to provide insights into future studies on the selection of remote sensing images for different monitoring needs.

Effect of the Simultaneous Variation in Blade Root Chord Length and Blade Taper on Maneuvering Manned Helicopter Control Effort

In this article, the influence of simultaneous variation in blade root chord length and blade taper on the flight control effort of maneuvering helicopter is researched. For this intention, helicopter models which are complex, control-oriented, physics-based models and capturing the main-physics and essential-dynamics are benefited. The influence of simultaneous variation in the blade root chord length and blade taper (i.e., in both chordwise and lengthwise directions dependently) on the control effort of a maneuvering manned helicopter and also on the closed-loop responses are worked. Comparisons in terms of the control effort and peak-values with and without variations in the blade root chord and blade taper changes are followed. For helicopter control variance-constrained controllers (i.e. output variance-constrained controllers) are useful.

Evaluation of droplet deposition and effect of variable-rate application by a manned helicopter with AG-NAV Gu韆 system

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.

Atomization characteristics of multi-type aerial nozzles in wind tunnel and low airflow velocity condition in manned agricultural helicopter

In order to explore the atomization characteristics of the LICHENG series nozzle for manned agricultural helicopter under medium and low airflow velocity conditions, droplet size tests on five sizes of nozzles 11002, 11003, 11004, 11006 and 11010 were carried out by laser diffraction device (LDD), based on the high-low speed composite wind tunnel for agricultural aviation designed by the National Center for International Collaboration Research on Precision Agricultural Aviation Pesticides Spraying Technology (NPAAC) of South China Agricultural University (SCAU). The results showed that under the three spray pressures of 30, 40 and 50 psi, the droplet sizes of the five types of nozzles expressed similar trends with the increase of airflow velocity. Among them, the droplet size variation of nozzles 11006 and 11010 with larger orifice size was the most significant, the largest range of D V0.1 was nozzle 11010, and the largest range of D V0.5 and D V0.9 was nozzle 11006. In addition, the changes of spray pressure would directly affect the quality of spray, especially the nozzles 11002, 11003 and 11004 with small orifice sizes were significantly affected. Under the condition of medium and low airflow velocity of 0-27.8 m/s, 89% of spread value (SV) by the five nozzles were in the range of less than 15%, but there were some test nozzles with poor spray stability during the test, which made the measurements of droplet size value larger, resulting in a maximum test deviation of up to 210.9 I¼m. The result also exposed the limitations exist in wind tunnel droplet size testing by using LDD, and an increase in airflow velocity resulted in a larger measurement droplet size. This phenomenon was particularly significant in the D V0.5 test results of various types of nozzles. This study can provide experimental data guidance for the optimization design and parameter selection of aerial nozzle for manned agricultural helicopter. Keywords: manned helicopter, aerial nozzle, wind tunnel, droplet size, agricultural application, spray classification DOI:  10.33440/j.ijpaa.20190201.0031  Citation: Yao W X, Lan Y B, Hoffmann W C,  Guo S, Chen S D, Wen S, et al.  Atomization characteristics of multi-type aerial nozzles in wind tunnel and low airflow velocity condition in manned agricultural helicopter.  Int J Precis Agric Aviat, 2019; 2(1): 9–17.

Evaluation of ecological half-life of dose rate based on airborne radiation monitoring following the Fukushima Dai-ichi nuclear power plant accident

Airborne radiation monitoring was conducted in order to evaluate the influence of radionuclides emitted by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident throughout Japan. Carrying out airborne radiation monitoring using manned and unmanned helicopters, the we have developed and established an analysis method concurrently with the development of this monitoring method. In particular, because the background radiation level differs greatly between East and West regions of Japan, we have developed a discrimination method for natural radionuclide and cosmic rays using the gamma energy spectra. The reliability of the airborne radiation monitoring data was validated through comparison with large amounts of ground measurement data. The ecological half-lives of short and long components for decline of the ambient dose equivalent (air dose rate) were 0.61 years and 57 years, respectively, based on the results of air dose rate of airborne radiation monitoring using manned helicopter. These results indicate the importance of airborne monitoring to evaluate and predict the radiation exposure of residents.

Performance analysis of GNSS units in manned helicopter operations

Global Navigation Satellite System (GNSS) receivers make use of the United States' Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), Europe's Galileo, China's Beidou, and Japan's Quasi-Zenith Satellite System constellations to determine the geolocation of the receiver based on the location of satellites and measurements of the distance and travel time of the GNSS signals. GNSS signals are dependent on line of sight to satellites with reflections or obstructions resulting in errors in the estimated position [1]. GNSS systems, while having their origin in military applications [2], have been adopted for many civilian uses from recreational navigation [3] to automated vehicle location systems [4]. While the GPS Standard Positioning Service without any correction sources establishes a 30 m range error limit for civilian use, GPS receivers typically perform better than this standard with errors primarily from atmospheric interference [5]. This is further improved in mobile devices by assisted GPS, WiFi, and cellular positioning when available [6].

Evaluation of ecological half-life of dose rate based on airborne radiation monitoring following the Fukushima Dai-ichi nuclear power plant accident

Airborne radiation monitoring was conducted in order to evaluate the influence of radionuclides emitted by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident throughout Japan. Carrying out airborne radiation monitoring using manned and unmanned helicopters, the we have developed and established an analysis method concurrently with the development of this monitoring method. In particular, because the background radiation level differs greatly between East and West regions of Japan, we have developed a discrimination method for natural radionuclide and cosmic rays using the gamma energy spectra. The reliability of the airborne radiation monitoring data was validated through comparison with large amounts of ground measurement data. The ecological half-lives of short and long components for decline of the ambient dose equivalent (air dose rate) were 0.61 years and 57 years, respectively, based on the results of air dose rate of airborne radiation monitoring using manned helicopter. These results indicate the importance of airborne monitoring to evaluate and predict the radiation exposure of residents.

The Power Line Inspection Software (PoLIS): A versatile system for automating power line inspection

A large amount of data, provided in the form of video data, is acquired during manned inspections flights of electric power lines. This data is analyzed by expert human inspectors to detect faults in the power lines infrastructure and prepare the inspection reports. This process is extremely time consuming, very expensive and prone to human error. In this paper, we present PoLIS: the Power Line Inspection Software, which has been developed with the objective of assisting the analysis of the data acquired during inspection flights. PoLIS is based on the cooperation between computer vision and machine learning techniques to automatically process video sequences acquired during inspection flights, resulting in a set of representative images per electric tower which we call Key Frames. These representative images can then be used for inspection purposes, leading to a drastic reduction of the human operators’ workload. At the core of the strategy lies an electric tower detector, which is in charge of estimating the location of the towers within the images based on the combination of a sliding window search technique and a supervised classifier. The location of the tower is then tracked using a tracking-by-registration algorithm based on direct methods, estimating the position of the tower in different images. Finally, different criteria are applied for defining whether the image corresponds to a Key Frame image or not. Extensive evaluation of the proposed strategy is conducted using videos acquired during manned helicopter inspections. The videos constituting this database contain several thousand frames representing both medium and high voltage power transmission lines in the infra-red (IR) and visible spectra. The obtained results show that the proposed strategy can reduce the large amount of data present in the inspection videos to a few Key Frames for each tower. It is also demonstrated that the learning-based approach proposed in PoLIS is appropriate for detecting electric towers, a process which is made faster and more robust by coupling it with a tower tracking algorithm. A Graphical User Interface allowing the application of PoLIS to user-provided videos is also presented in this paper, illustrating the whole process and the automated generation of an inspection report.

Application of topographical source model for air dose rates conversions in aerial radiation monitoring

After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in 2011, aerial radiation monitoring (ARM) using a manned helicopter was conducted to rapidly measure air dose rates and the deposition of radioactive nuclides over a large area. Typically, the air dose rate is obtained by conversion from the count rate using conventional flat source model (FSM). The converted dose rate obtained via aerial monitoring poorly matches the results of ground measurement in the mountain and forest areas because FSM does not consider topographical effects. To improve the conversion accuracy, we developed new methods to analyze aerial monitoring data using topographical source model (TSM) based on the analytical calculation of the gamma-ray flux. The ARM results converted using both FSM as well as TSM were compared with ground measurement data obtained after the FDNPS accident. By using TSM, the conversion accuracy was improved. In addition, to determine a parameter sensitive to topographical effects, we examined five parameters and it was clear that the difference between the elevation just below the helicopter and the mean elevation within the measurement area was the most influential.

Controlling Multiple Unmanned Aircraft from a Manned Helicopter: The Need for Advanced Autonomy and Refined Pilot-Vehicle Interface

Manned-Unmanned Teaming (MUM-T) is a military concept that employs unmanned aerial systems (UASs) in support of traditional manned aircraft. The current ratio of manned to unmanned aircraft in MUM-T operations is one to one with a goal to expand to multiple UASs to further enhance the capability, but this imposes significant challenges on the operator. To address these challenges, this research implemented automated UAS behaviors combined with a pilot-vehicle interface tailored to provide supervisory control over multiple UASs. Results demonstrated that this combination of technologies allows a single crewmember to effectively manage up to three UASs while executing complex MUM-T tactical missions with manageable workload, improved situational awareness, and improved mission performance. Experimental results also identified areas where the current implementations can be further refined.

Testing unmanned aircraft systems for salmon spawning surveys

Unmanned aircraft systems (UASs) were tested for counting Chinook salmon ( Oncorhynchus tshawytscha) redds as a more accurate, safer alternative to manned helicopter flights. Counting redds from the helicopter was less expensive and time consuming, but of the total redds counted at selected sites with a UAS, an average (± SD) of only 77% ± 14% was counted from the helicopter. A river-wide census of redds was not possible with a UAS because the study area was too large for the single field crew to survey. Simulation analyses were used to compare stratified random sampling (STRS) and sampling proportional to size (PPS) for estimating annual total redd counts from data collected with a UAS. The STRS estimates were more accurate and precise, whereas the PPS estimates, though biased, had 95% CIs that included the observed redd count more frequently. We strongly recommend that researchers conduct simulation analyses to evaluate alternative survey sampling methods if they are considering replacing census counts made from manned aircraft with counts estimated from data collected with a UAS. We conclude that UAS application reduces the risk inherent to manned aircraft flights, but the reduction in risk can come at the cost of estimates of population parameters that can sometimes be inaccurate and lack 95% CI coverage.

UAV-Borne Profiling Radar for Forest Research

Microwave Radar is an attractive solution for forest mapping and inventories because microwave signals penetrates into the forest canopy and the backscattering signal can provide information regarding the whole forest structure. Satellite-borne and airborne imaging radars have been used in forest resources mapping for many decades. However, their accuracy with respect to the main forest inventory attributes substantially varies depending on the wavelength and techniques used in the estimation. Systems providing canopy backscatter as a function of canopy height are, practically speaking, missing. Therefore, there is a need for a radar system that would enable the scientific community to better understand the radar backscatter response from the forest canopy. Consequently, we undertook a research study to develop an unmanned aerial vehicle (UAV)-borne profiling (i.e., waveform) radar that could be used to improve the understanding of the radar backscatter response for forestry mapping and inventories. A frequency modulation continuous waveform (FMCW) profiling radar, termed FGI-Tomoradar, was introduced, designed and tested. One goal is the total weight of the whole system is less than 7 kg, including the radar system and georeferencing system, with centimetre-level positioning accuracy. Achieving this weight goal would enable the FGI-Tomoradar system to be installed on the Mini-UAV platform. The prototype system had all four linear polarization measuring capabilities, with bistatic configuration in Ku-band. In system performance tests in this study, FGI-Tomoradar was mounted on a manned helicopter together with a Riegl VQ-480-U laser scanner and tested in several flight campaigns performed at the Evo site, Finland. Airborne laser scanning data was simultaneously collected to investigate the differences and similarities of the outputs for the same target area for better understanding the penetration of the microwave signal into the forest canopy. Preliminary analysis confirmed that the profiling radar measures a clear signal from the canopy structure and has substantial potential to improve our understanding of radar forest mapping using the UAV platform.

有人ヘリコプタを用いた放射線モニタリング

有人ヘリコプタを用いた放射線モニタリング

ANALYSIS OF THE OPERATING LOAD OF THE TURBINE ENGINE DURING DECELERATION TO DASH MANEUVER

The article presents the analysis of the loads on the gas generator of turbine engine power of unmanned helicopter. The analysis was performed for deceleration to dash maneuver. Particular attention was paid to loads of bearing assembly in gas generator of turbine engine. The analysis was based on the timelines of changes in velocity of manned helicopter PZL W3-Falcon. The dependence of velocity changes during the flight was made as approximation by the least squares method and then determined for its change in acceleration. On this basis, the forces acting on the bearing gas generator assembly in static and dynamic conditions were determined. These values were compared with values obtained during maneuvers such as "jump up and jump down" and "acceleration and deceleration maneuver".

Methodology for High-Throughput Field Phenotyping of Canopy Temperature Using Airborne Thermography.

Lower canopy temperature (CT), resulting from increased stomatal conductance, has been associated with increased yield in wheat. Historically, CT has been measured with hand-held infrared thermometers. Using the hand-held CT method on large field trials is problematic, mostly because measurements are confounded by temporal weather changes during the time required to measure all plots. The hand-held CT method is laborious and yet the resulting heritability low, thereby reducing confidence in selection in large scale breeding endeavors. We have developed a reliable and scalable crop phenotyping method for assessing CT in large field experiments. The method involves airborne thermography from a manned helicopter using a radiometrically-calibrated thermal camera. Thermal image data is acquired from large experiments in the order of seconds, thereby enabling simultaneous measurement of CT on potentially 1000s of plots. Effects of temporal weather variation when phenotyping large experiments using hand-held infrared thermometers are therefore reduced. The method is designed for cost-effective and large-scale use by the non-technical user and includes custom-developed software for data processing to obtain CT data on a single-plot basis for analysis. Broad-sense heritability was routinely >0.50, and as high as 0.79, for airborne thermography CT measured near anthesis on a wheat experiment comprising 768 plots of size 2 × 6 m. Image analysis based on the frequency distribution of temperature pixels to remove the possible influence of background soil did not improve broad-sense heritability. Total image acquisition and processing time was ca. 25 min and required only one person (excluding the helicopter pilot). The results indicate the potential to phenotype CT on large populations in genetics studies or for selection within a plant breeding program.

Volcanic plume measurements using a UAV for the 2014 Mt. Ontake eruption

A phreatic eruption of Mt. Ontake, Japan, started abruptly on September 27, 2014, and caused the worst volcanic calamity in recent 70 years in Japan. We conducted volcanic plume surveys using an electric multirotor unmanned aerial vehicle to elucidate the conditions of Mt. Ontake’s plume, which is flowing over 3000 m altitude. A plume gas composition, sulfur dioxide flux and thermal image measurements and a particle sampling were carried out using the unmanned aerial vehicle for three field campaigns on November 20 and 21, 2014, and June 2, 2015. Together with the results of manned helicopter and aircraft observations, we revealed that the plume of Mt. Ontake was not directly emitted from the magma but was influenced by hydrothermal system, and observed SO2/H2S molar ratios were decreasing after the eruption. High SO2 flux of >2000 t/d observed at least until 20 h after the onset of the eruption implies significant input of magmatic gas and the flux quickly decreased to about 130 t/d in 2 months. In contrast, H2S fluxes retrieved using SO2/H2S ratio and SO2 flux showed significantly high level of 700–800 t/d, which continued at least between 2 weeks and 2 months after the eruption. This is a peculiar feature of the 2014 Mt. Ontake eruption. Considering the trends of the flux changes of SO2 and H2S, we presume that majority of SO2 and H2S are supplied, respectively, from high-temperature magmatic fluid of a deep origin and from hydrothermal system. From the point of view of SO2/H2S ratios and fumarolic temperatures, the plume degassing trend after the 2014 eruption is following the similar course as that after the 1979 eruptions, and we speculate the 2014 eruptive activity will cease slowly similar to the 1979 eruption.