Recently, the surge in the interests in unmanned aerial vehicles has soared dra-matically worldwide due to many potential benefits foreseen by this technology. The most widespread use of the commercial drones is a multi-copter form of unmanned aerial vehicle, because of its vertical takeoff and landing (VTOL) capability. However, due to the structural characteristics, it has a disadvantage that the flight time is quite short, which is typically ranging between 15 to 30 minutes. The fixed wing type of unmanned aerial vehicles has a longer flight time and duration, but it is not easy to secure a safe landing space, especially in the city areas. For this reason, demand for vertical fixed take-off and landing aircraft is rapidly increasing throughout the world. This study analyzes the trends and recent development of global VTOL technology and provides a direction into which the current state of the technology should be heading. By comparing the advantage and disadvantage of various VTOP propulsion types, we can clearly identify the most effective form of VTOL propulsion types. Such analysis will be highly beneficial to the drone researchers and scientists in terms of future development.
One can clearly see the recent surge and wide applications of unmanned aerial vehicles in many areas, such as agriculture, forestry, surveillance, rescue operations, security, aerial photographing, and so on. The most widespread use of the commercial drones is a multi-copter type of unmanned aerial vehicle. For example, most aerial photography drones are this type. It is because this type of drones doesn’t require a length runway and it can hover in the air while filming. This kind of convenience is necessary, especially in the congested areas like city centers. However, it has a disadvantage that the flight time is too short (typically ranging between 15 to 30 minutes). The fixed wing type drones can stay afloat for a much longer time, typically over 1 or 2 hours. However, it is not always easy to find a safe landing space, and it is not easy to manually control this type of drones [1] [2] . Due to these reasons, the most commercial drones are multi-copter types.
The third type of unmanned aerial vehicle is often referred to as a VTOL drone, which can vertically takeoff and land, while flies like a fixed-wing aircraft once airborne. It doesn’t require a runway, and land like a helicopter. The VTOL drone can hover in the air, yet capable of flying a much longer time. Due to these advantages, the VTOL drone is taking a great interest among researchers and commercial applications. In order for VTOL drones to hover and make a transit flight like airplane, its propulsion system should be very different than those of multi-copter type drone or fixed-wing type drones. Our initial analysis shows that there are so many varieties already developed, while a thorough study of analyzing VTOL types is not present until this time. In this regard, our goal is to collect the different types of VTOL propulsion technologies and analyze the advantages and disadvantages of each type. Such study will provide valuable insights for the drone community.
2. Analysis of VTOL Propulsion Systems
The analysis classifies each type of VTOL into 3 categories. This include: 1) TYPE1, which has a wing and a TILT-ROTOR, 2) TYPE 2, with no wings and similar to helicopters, and 3) TYPE 3 with wings and no tilting mechanism functions. The details are defined in Table 1 [3] - [10] .
Tables 2-5 show the specifications of VTOL drones in major countries. In fact, there are over 35 VTOL drones we have identified. Due to similarities, in this paper, we only show the representative types of VTOL drones. Those are illustrated in the tables below.
3. Analysis Contents
First, the percentage of VTOL types has been investigated, as shown in Figure 1. It shows that the Type 2 and Types 3 take the majority of the VTOL drones. VTOL with a tilt mechanism only takes about 18%. The reason can be conjectured that Type 1 drone can be unstable during the transit flight (i.e., from hover to forward flight), and the tilting mechanism can add substantial weights as well as increase the complexity in the system. Due to these reasons, the Type 1 VTOL drones are comparatively limited. Type 2 and Type 3 VTOL drones are quite
Classification of VTOL types
TYPE1
TYPE2
TYPE3
Wing
O
X
O
Tilt Rotor
O
X
X
VTOL
O
O
O
There presentative VTOL drones in Korea and USA
Contents
Picture
Picture
TYPE1
Name
TR-100
Sky Prowler
Manufacturer
KARI
Krossblade Aerospace
Country
South Korea
USA
Length
5.0 m
0.5 m
Payload
100 kg
0.5 kg
Flying time
5 hrs
1 hrs
propellant
Gasoline
Motor
Max speed
500 km/h
100 km/h
TYPE1
Name
JOBY S2
JOBY LOTUS
Manufacturer
JOBY AVIATION
JOBY AVIATION
Country
USA
USA
Length
N/A
N/A
Payload
176 kg
27 kg
Flying time
15 hrs
1 hrs
propellant
Gasoline electric hybrid
Gasoline electric hybrid
Max speed
200 km/h
185 km/h
There presentative VTOL drones in Taiwan and Canada
Contents
Picture
Picture
TYPE2
Name
DTI RTN KSM 150
APID 60
Manufacturer
N/A
TOP Engineering
Location
Taiwan
Taiwan
Length
2.1 m
4.0 m
Payload
15 kg
55 kg
Flying time
2.5 hrs
5 hrs
propellant
Gasoline
Gasoline
Max speed
100 km/h
110 km/h
TYPE2
Name
Navig 8 Gas
Navig 8 Electric
Manufacturer
4FRONT ROBOTICS
4FRONT ROBOTICS
Country
Canada
Canada
Length
3.1 m
1.64 m
Width
2.9 m
1.0 m
Payload
31 kg
4 kg
Flying time
2.5 hrs
1 hrs
propellant
Gasoline
MOTOR
Max speed
200 km/h
83 km/h
There presentative VTOL drones in Japan and USA
Contents
Picture
Picture
TYPE3
Name
SR-1
ARCTURUS JUMP-20
Manufacturer
CQV
ARCTURUS
Country
Japan
USA
Length
1.7 m
2.9 m
Payload
0.7 kg
27 kg
Flying time
0.5 hrs
9 hrs
propellant
MOTOR
Gasoline
Max speed
55 km/h
133 km/h
TYPE3
Name
V-Bat
Current MK1
Manufacturer
MARTIN UAV
Current MK1 (MK2)
Country
USA
USA
Length
2.4 m
2.0 m
Payload
2 kg
18.5 kg
Flying time
8 hrs
15 hrs
propellant
Gasoline
Gasoline
Max speed
350 km/h
148 km/h
similar in terms of numbers among the drone that we have investigated. Each type bears specific merits and also disadvantages, so each type takes about the same percentages. Second, we have analyzed each type according to the number of criteria investigated. The results are organized in Table 5 and Table 6. The table mainly shows the engine types (electric motors, gasoline powered, diesel, or hybrid engines), and flight durations (less than 2 hours of flying time, less than 4 hours, and over 4 hours).
By analyzing the content of the payload specification, the larger the size of the airframe, the more likely it was to see the airframe size increase. It appears to affect the flight time with drag on airframe, depending on whether or not the airframe is aerodynamically well balanced. Third, we have classified the VTOL drone in accordance with their size and payload. It appears that the size and payload will continue to increase in the future.
4. Conclusion
The analysis shows that the higher the payload, the bigger the size of the aircraft.
Analysis of VTOL propellant technology
VTOL TYPE
Model
Engine Type
Flying Time
Motor
Gasoline
Diesel
Hybrid
2 Hr↓
4 Hr↓
4Hr↑
TYPE 1
FE-Panther
O
-
-
-
KUS-TR (TR-60)
O
O
TR-100
O
O
Sky Prowler
O
O
JOBY S2
O
O
JOBY LOTUS
O
-
-
-
TYPE 2
Air Mule
O
-
-
-
Airbus DS Tanan 300
O
-
-
-
HEF32
O
O
VSR700
O
O
DTI RTN KSM 150
O
O
APID 60
O
O
Navig 8 Gas
O
O
Navig 8 Electric
O
O
DP-6XT WHISPER
O
O
UAV IT180-120
O
O
DP-12 RHINO
O
O
DP-14 HAWK
O
O
TYPE 3
Aerosense
O
O
Wingtra
-
-
-
-
-
-
-
VD 200
-
-
-
-
O
X-Plane
O
-
-
-
SR-1
O
O
ARCTURUS JUMP-20
O
O
V-Bat
O
O
Current MK1 (MK2)
O
O
FALCON-V
O
O
PIGEON-V
O
O
JOUAV CW-20
O
O
FOXY pro
O
O
The percentage of VTOL types
Analysis of payload and wing span of VTOL drones
VTOL TYPE
Model
Payload
Wing Span
10 Kg↓
20 Kg↓
20 Kg↑
2 m↓
5 m↓
5 m↑
TYPE1
FE-Panther
O
O
KUS-TR (TR-60)
O
O
TR-100
O
O
Sky Prowler
O
O
JOBY S2
O
O
JOBY LOTUS
O
O
TYPE2
Air Mule
O
O
Airbus DS Tanan 300
O
O
HEF 32
O
O
VSR 700
O
O
DTI RTN KSM 150
O
O
APID 60
O
O
Navig 8 Gas
O
O
Navig8 Electric
O
O
DP-6XT WHISPER
O
O
DP-5X WASP
O
-
-
-
UAV IT180-120
O
O
DP-12 RHINO
O
O
DP-14 HAWK
O
O
TYPE3
Aerosense
O
O
Wingtra
O
-
-
-
VD 200
O
O
X-Plane
O
O
SR-1
O
O
ARCTURUS JUMP-20
O
O
V-Bat
O
O
Current MK1 (MK2)
O
O
FALCON-V
O
O
PIGEON-V
O
O
JOUAV CW-20
O
O
FOXY pro
O
O
JOUAV CW-10
O
O
It is more likely that a bigger air frame affects the flight time. For drones that use electric motors, the battery capacity is directly related to the flight time. However, a bigger battery size inversely affects the payload capacity. According to the analysis of three types, it appears that the fixed wing type VTOL drones with no tilting mechanism are getting more and more popular. It is due to the facts that this type of VTOL drone can provide a stable transit flight while reducing the complexity associated with tilting mechanism. So the drones can be built at a lower cost and a lot lighter. It is judged that the surge in global demand for a wide range of VTOL drone is expected, and a growing competition is expected around the world.
Acknowledgements
This work was supported by the Ajou University research fund.
Cite this paper
Jo, D. and Kwon, Y.J. (2017) Analysis of VTOL UAV Propellant Technology. Journal of Computer and Communications, 5, 76-82. https://doi.org/10.4236/jcc.2017.57008
ReferencesPanther-FE Fixed Wing VTOL Drone Demonstrated in Flight.
http://dx.doi.org/10.1080/028418501127346846Yu, S., Heo, J., Jeong, S. and Kwon, Y.J. (2016) Technical Analysis of VTOL UAV. Journal of Computer and Communications, 4, 92-97.
https://doi.org/10.4236/jcc.2016.415008The 16-Rotor Convertible Aircraft for Long-Range, High-Speed, Electric VTOL Commuting. http://newatlas.com/joby-s2-tilt-rotor-vtol-multirotor-aircraft-concept/40662/Kang, Y.S. (2015) Tilt-Rotor UAV System to Monitor Illegal Fishing. KIRI.High Eye VTOL Manufacture. http://www.higheye.nl/hef-32/Airbus to Fly VSR700 VTOL UAV before End of the Year.
http://www.janes.com/article/67281/airbus-to-fly-vsr700-vtol-uav-before-end-of-the-yearAPID-55 VTOL Minature UAV.
http://www.airforce-technology.com/projects/cybaero-apid55-uav/Watch Sony’s First Aerosense Drone Take Flight.
https://techcrunch.com/2015/08/24/watch-sonys-first-aerosense-drone-take-flight/JUMP 20 VTOL Unmanned Aerial Vehicle.
http://www.naval-technology.com/projects/jump-20-vtol-unmanned-aerial-vehicle/Fisher Jr, R.D. (2016) China Reveals Data on VD200 Flying-Wing VTUAV. Washington DC, IHS Jane’s Defence Weekly, 30 March.