Electric UAV Using Regenerative Soaring
and Solar Power
(project proposal)
Abstract: Autonomous Electric Aircraft using no Fuel (Unmanned Aerial Vehicle – UAV)
Propeller powered electric UAV takes off on batteries and actively searches for updrafts. After
encountering an updraft the UAV switches of the propulsion electric motor and soars. Air passing
through the propeller during soaring revolves it and the movement is transmitted to the electric motor.
Electro motor works as a generator in this mode. The produced energy recharges batteries and powers
the electric equipment of the UAV. Energy gain is improved using solar power. The proposed UAV
can stay aloft for long (indefinite) periods of time and can be used in reconnaissance and other
applications. The control system of the UAV is responsible for autonomous behavior (searching for
updrafts, optimization of flight trajectory with regard to the mission objective and power management,
solving critical situations, etc.) and for implementation of the human issued commands.
Table of Contents
1 Introduction............................................................................................................................................2
1.1 Outline of the Idea..........................................................................................................................2
1.2 Regenerative Soaring.....................................................................................................................3
1.3 Electric Aircrafts............................................................................................................................4
1.4 Features, Equipment and Instruments of the Proposed UAV........................................................5
1.5 Functions of the Control System....................................................................................................6
2 Feasibility Analysis................................................................................................................................7
2.1 The Aircraft....................................................................................................................................7
2.2 Energy Balance...............................................................................................................................9
2.2.1 Self Launch and Climb to 300m...........................................................................................11
2.2.2 Cruise for 20 minutes in search for updrafts........................................................................11
2.2.3 Recharge batteries to full capacity .......................................................................................12
2.2.4 Cruise till 50% of the battery capacity remains....................................................................12
2.2.5 Recharge batteries to full capacity and land.........................................................................13
2.2.6 Conclusion, energy balance..................................................................................................14
2.3 AI and Control System.................................................................................................................15
3 Estimated Project Impact.....................................................................................................................16
1 Introduction
1.1 Outline of the Idea
We propose an electric unmanned aerial vehicle (UAV) capable to take-off and fly using electric motor
and to land with fully charged batteries. Batteries of the UAV are recharged by regenerative soaring
and solar power. The UAV is expected to stay aloft for a long time (hours and possibly days). During
the time aloft the UAV searches autonomously for updrafts, optimizes flight trajectory with regard to
the mission objectives and power management, solves critical situations and responds to human issued
instructions. The instructions are expected to be defined as partial and general objectives instead of
detailed commands. The advantages of the UAV are the following:
• quiet and clean
• fossil fuel independent
• very low operational cost
• can potentially remain aloft indefinitely
• "parked" in air when not in use
• has interesting application potential
• study for manned regenerative soaring aircraft
The possible applications include:
• Long time surveillance of road traffic, traffic jams avoidance
• Bird eye view during rescue operations or catastrophic events
• Search for missing persons at sea (flock of UAV's to cover large areas)
• Transponding radio signals in mountainous areas
• Following migrant birds, marine mammals etc.
• Weather forecast and study
Many of the ongoing projects of electric aircrafts are aimed on high altitude solar powered UAV's.
These try to avoid weather in order to get maximum exposure to sun and to protect their fragile
lightweight construction. The UAV proposed here should operate in low altitudes in visual contact with
the surface of Earth and take advantage of the vertical atmospheric motions.
1.2 Regenerative Soaring
Illustration 1: Regenerative soaring, aircraft design (Credit [4]).
Traditional sailplanes utilize updrafts to stay aloft and travel. In the typical scenario the sailplane
searches for an updraft after initial climb (tow, self launch …), gains altitude by circling in an updraft
and then glides in direction of the intended destination. Two important parameters the sailplane's
performance are minimum sink rate and glide ratio. Minimum sink rate determines how fast will the
sailplane gain altitude and the glide ratio (usually expressed as X :1, meaning the sailplane will glide to
the distance of X kilometers if starting 1km above ground) determines how good will the sailplane
utilize the gained altitude. Most of the updrafts used by sailplanes are either thermal columns or
upwind slope lifts.
Illustration 2: Soaring in thermals
Thermal columns (thermals) are basically bubbles of rising
warm air which was warmed over sun irradiated surfaces.
Upwind slope lift arises when air is forced to flow over an
obstacle. It is also possible to apply dynamic soaring –
technique used by many migrant birds and remote control
pilots. This technique uses the change of wind speed in the
wind profile close to surface to gain energy. Albatrosses
travel almost effortlessly thousands of kilometers in any
direction using dynamic soaring. However, this technique
requires to make sharp, high speed maneuvers close to the
ground.
Regenerative soaring feature is easily added to most of the Illustration 3: Upwind slope lift
self launching sailplanes. In this case the propeller (or
propellers) serves as a wind turbine while flying in the updraft. Because of the increased drag during
regen the aircraft can not climb as fast as a clean sailplane but the energy generated by the turbine can
be stored for future use. The most common means to store the energy are batteries, pinwheels, springs
or twisted rubber bands. This energy can be used for free or emergency cruising, for new start and
climb or to power devices on board of the aircraft. In the optimal case the aircraft will fly entirely
without fuel or recharging on the ground.
1.3 Electric Aircrafts
Electric motors are widely used in remote
controlled (RC) airplanes and in several manned
airplanes. The limiting factor in application of
electric motors in aviation is the energy storage.
Batteries or ultracapacitors provide low energy to
weight ratio which means that electric airplanes
have small range. Solar and atmospheric energy can
be used to increase the range and the time in air.
Helios prototype was a UAV of NASA, ultralightweight flying wing aircraft with a wingspan of
75.3m, powered by solar cells, batteries and
Illustration 5: Sunseeker II
Illustration 4: Helios prototype
hydrogen-air fuel cell. Sunseeker II was as of Dec,
2008 the only manned solar powered airplane in
flying condition. In 2009 it became the first solarpowered aircraft to cross the Alps. Its solar array
charges Li-Polymer battery powering a 6kW electro
motor. Max speed on solar power is 64kph.
Sunseeker II takes advantage of thermals if possible.
Several self launching electric sailplanes are
available on the market, e.g. Antares 20E of Lange
Aviation. Antares 20E is equipped with 42kW
electric motor. It climbs to 3000 meters in app. 13
minutes when the batteries are depleted. Electric
aircrafts slowly start to appear also as commercial
products. Electric Aircraft Corporation [1] produces
two types of electric aircrafts: rigid wing Electraflyer-C and Electraflyer trike (motor hang glider with
Stratus wing [3]). Their lithium-polymer battery pack with capacity 5.6kWh lasts for 1-1.5 hours
flying. The electric motor used is 13.5kW brushless motor with 90% efficiency. Further examples of
electric aircrafts are described in Chapter 2 Feasibility Analysis.
Illustration 6: Electraflyer trike, Electric Aircraft Corporation
1.4 Features, Equipment and Instruments of the Proposed UAV
Propulsion system components:
•
propeller – large (more efficient) with symmetrical blades cross section possibly mounted as a
ducted fan
•
brushless electric motor (dual role as turbine)
•
battery pack – (Li-polymer, Li-Ion ... )
•
battery heating system – to ensure optimal performance of the batteries
•
solar cell array
•
motor-generator controller
•
charger
Flight controls (fly-by-wire):
•
primary controls: 3 (roll, pitch, yaw)
•
secondary controls: elevator trim, wing flaps, airbrakes etc. (optional)
Other equipment:
•
retractable landing gear (optional)
•
rocket parachute – deployed in critical situations
Avionics and Instruments (digital):
•
GPS
•
altimeter
•
airspeed indicator
•
rate-of-climb indicator (variometer)
•
attitude indicator (gyro horizon)
•
turn coordinator
•
indicators (battery, g-force, fire, stall, landing aids etc.)
Special devices:
•
Force feedback (aerodynamic load on the steering surfaces)
•
Diagnostic system
•
Radio receiver: for data and commands
•
Cameras and optional sensing devices
•
Video and data transmission system
•
Control computer
1.5 Functions of the Control System
The proposed control system intends to use ground based and on-board AI. The ground based system
will analyze available meteorological data and 3D model of the surface of Earth. This system will
provide hints to the UAV regarding areas with high likelihood to produce updrafts. The ground based
AI system would be vital for night operation when thermal updrafts and solar array do not provide
energy and UAV depends mostly on upwind slopes lift. The onboard AI will be responsible for the
following:
•
Automated take-off and landing
•
Reaction in critical situations:
stall and spin recovery, parachute deployment etc.
•
Optimization of flight trajectory with respect to the mission objective and to the atmospheric
conditions (power management)
•
Localization and utilization of updrafts
(variometer, vision and ground AI data)
•
"Parking" in air – when not in use aircraft is commanded to stay within certain space and fly
autonomously until new mission objective is uploaded.
2 Feasibility Analysis
2.1 The Aircraft
We have chosen SWIFT rigid wing hang glider produced by Belgium based firm Aériane as an
candidate aircraft [2]. It was designed by Bright Star Gliders in collaboration with engineers at Stanford
University The SWIFT is a high performance sailplane, designed to combine some of the convenience
of hang gliders with the
soaring
performance
of
sailplanes. It takes off and
lands like a hang glider, yet
maintains
exceptional
performance at high speeds,
achieving a lift-to-drag ratio
of about 25:1. Although it is
a fully-cantilevered rigid
wing with aerodynamic
controls and flaps, it weighs
only 48 kg and is easily
transported on the top of a
car. It is sold in many
countries including Japan.
Aériane produces also engine Illustration 7: SWIFT rigid wing hang glider
kit (with combustion engine)
which is easy to adapt to a standard SWIFT frame (with steerable front wheel, disk brake, wheeled
tiplets for taxing). The optional equipment of SWIFT includes rocket parachute and car roof
transportation container. Instead of human pilot the payload of the aircraft will consist of lithiumpolymer battery pack (5.6kWh [1]), brushless electric motor (13.5kW [1]), solar array, electric
equipment (control computer,
servos, radio transmission system
etc.) and other equipment used for
adaptation of the aircraft. Table 1
summarizes the specifications of
the SWIFT with the proposed
adaptations. The estimated payload
weights approximately as much as
an average pilot. The propulsion
system is taken from Electraflyer
trike [1] which weights 112kg
empty and approximately 200kg
with a pilot. This ensures that the
UAV will be sufficiently powered.
In fact, human pilot can be on
board of the aircraft during initial
Illustration 8: SWIFT with engine kit
experiments,
observing
the
behavior of the control system, making measurements and ensuring safe operation. The motor and the
propeller will enable to climb at estimated rate of 1ms -1. The propulsion system of Electraflyer trike is
sold also adapted for regenerative soaring [2]. It will be necessary to develop a new propeller optimized
for regenerative soaring. The commercially available propellers are optimized to provide maximum
trust. The propeller for our purpose should be optimized to work also as a turbine with high efficiency
which among other requires symmetrical blades sections [4]. Optional features of the propeller include
adjustable pitch and collapsibility.
Glide ratio (best, at 75km/h) [2]
24:1
Minimum sink rate (at 45km/h) [2]
0.65ms-1
Never exceed speed (VNE) [2]
120 km/h
Climb rate (estimated)
1ms-1
Wing area [2]
12.5m2
Maximum load [2]
+5.3g/-2.65g
tested +7.95g/-3.98g
Weight empty [2]
48kg
Payload total:
74kg
battery pack (5.6kWh [1])
el. motor (13.5kW [1])
solar array 1
electric equipment
other
Gross weight
35kg
12kg
10kg
7kg
10kg
122kg
2
Estimated costs :
7.2Mil Yen (80 000USD)
SWIFT LIGHT with pod + closed fairing [2]
Air brakes [2]
Rocket parachute [2]
lithium-polymer pack 5.6kwh [1]
Electraflyer propulsion kit 3 [1]
Solar array (10m2, with installation costs)
Carbon fiber propeller 4
Other (modifications of SWIFT) 5
Transportation container [2]
21820EURO
2000EURO
1850EURO
8500USD
4200USD
8000USD
10000USD
5000USD
3550EURO
Table 1: Proposed UAV specifications.
1 With installation aids and accessories
2 Does not include electric equipment developed during the project
3 Includes: motor, electronic controller, power dial and switch, fuse, connectors, ammeter and shunt, voltmeter, custom
machined propeller hub, and digital motor temperature display with probe
4 Development, design, manufacture costs - estimated
5 Development, design, manufacture costs - estimated
2.2 Energy Balance
The purpose of this section is to show that it is possible to build an electric aircraft capable of self
launch, long daytime flight and landing with a full battery. The proposed aircraft is described in the
previous section. The scenario investigated consists of 5 phases:
1. Self launch and climb to 300m,
2. 20 minutes cruise in search for updrafts,
3. Recharge batteries to full capacity
4. Cruise till 50% of the battery capacity remains.
5. Recharge batteries to full capacity and land
The following calculation requires to estimate certain values. The estimated values were carefully
calculated, consulted (see Acknowledgments) and adjusted to slightly under or over estimate the actual
values against the benefit of the UAV. Also, only the energy balance considering the electric energy is
shown here. It is ignored that the plane can use the potential energy gained by climbing in the updrafts
during regeneration for travel by gliding. But please note that traditional sailplanes utilize only this
form of energy to fly over large distances (Free out-and-return distance record: 2 247.6 km, [6]) and to
stay aloft for long periods (~15 hours).
The proposed battery pack lasts for 1-1.5 hours of Electraflyer trike's powered flight. By takeoff the
proposed UAV weights 78kg less than Electraflyer trike. Therefore is is assumed that the battery pack
will last for at least 1.5 hours in the UAV. The proposed propeller works with 85% estimated efficiency
([4], efficiency of airborne turbine is defined differently than efficiency of a ground based turbine and
Betz limit does not apply here). The brushless electro motor used in this example is 90% efficient as a
generator [2].When the propeller works in a turbine mode it creates drag which leads to increased sink
rate. If we assume the sailplane to be in level flight in steady air it is loosing potential energy at certain
rate corresponding to the sink rate at given speed. If additionally electric energy is to be generated the
sailplane has to loose potential energy at higher rate. Assuming the potential energy is converted into
kinetic energy and then to electric energy with the overall efficiency corresponding to the efficiency of
the propeller-turbine times the efficiency of the generator the increase of the sink rate of the aircraft can
be calculated if the gross weight of the aircraft is known. We assume that increasing the sink rate by
0.75ms-1 will not seriously impair the flight performance of the UAV. Therefore we estimate to obtain
687W on the output of the generator during regenerative soaring. The battery charger works with 80%
estimated efficiency (charging efficiency of the batteries is 99.9%). The charger works only when the
power balance is positive. We estimate that 80% of the wing area can be used to install solar cells. The
efficiency of solar cells suitable for airplanes varies between ~6% to ~20% [5]. Let us assume installing
solar cells with 15% efficiency providing maximum output 150W per m 2. The solar cells are estimated
to provide on average 70% of their maximum output during cruising (the UAV flies sometimes under
the shadows of clouds and the wing is not always in the optimal position relative to the sun). During
regeneration are the solar cells estimated to provide on average 40% of their maximum output (the
UAV is moving in banked turns and the wing is only part of the time exposed to the sun). The electric
equipment of the UAV (controll computer, servos, radio transmission system etc.) is estimated to
consume on average 150W. Table 2. summarizes the values and estimates used in this example.
Battery pack [1]
5.6kWh (20.2MJ)
Average powered flight time [1]
1.5 hour
Electric motor [1]
13.5kW, 90% efficient
Average energy consumption rate – motor
3.7kW
Equipment input
150W
Propeller efficiency (turbine mode)
85%
Electric motor efficiency (generator mode)
90%
Charger efficiency
80%
Generator output in regen [4]
687W
Solar power per m2 max [5]
150W
Solar cells surface
10m2
Solar array output - max
1500W
Solar array output - cruising
1050W
Solar array output - regen
600W
Sink rate total in regen [2]
1.4ms-1
Table 2: Values and estimates used for calculation.
2.2.1 Self Launch and Climb to 300m
300m is an altitude suitable for search for thermal updrafts [4]. The electro motor is running at full
power during the start only [2]. The climb is done at reduced power (high discharge rate more rapidly
depletes the battery capacity). During climbing electric energy is used to sustain flight (compensate the
drag) and also converted to potential energy of the aircraft The only source of energy now is the solar
array . Table 3 summarizes the energy balance for this phase. The values are rounded.
Altitude gained = 300m
Balance:
Time spent = 5 minutes
Power (Watt)
Solar array
Energy (Joule)
1050
315000
0
0
-150
-45000
Motor (sustain flight)
-3733
-1120000
Motor (to potential energy)
-1197
-359046
Total
-4030
-1209046
Turbine (Regen)
Equipment
Battery capacity spent:
6%
Battery capacity spent total:
6%
Table 3: Self launch and climb to 300m, energy balance.
2.2.2 Cruise for 20 minutes in search for updrafts
It is likely that the aircraft will encounter updraft in 20 minutes after start. As it maintains the same
altitude the motor spends energy only to sustain flight level flight. Table 4 summarizes the energy
balance for this phase. The values are rounded.
Altitude gained = 0m
Balance:
Time spent = 20 minutes
Power (Watt)
Solar array
Turbine (Regen)
Equipment
Motor (sustain flight)
Motor (to potential energy)
Total
Energy (Joule)
1050
1260000
0
0
-150
-180000
-3733
-4480000
0
0
-2833
-3400000
Battery capacity spent:
17%
Battery capacity spent total:
23%
Table 4: Cruise for 20 minutes in search for updrafts, energy balance.
2.2.3 Recharge batteries to full capacity
The aircraft has found an updraft (thermal, upwind slope lift) and it is regenerating. The propeller
works as a turbine. The aircraft will continue to recharge until the batteries are full. The efficiency of
the charger has to be taken into account in this phase. If the updraft is strong enough (1.4ms-1 is the
minimum sink rate in this phase) the aircraft gains altitude. It can then glide in the direction of the
mission objective and continue recharging.
Altitude gained = Ignored
Balance:
Time spent = 85 minutes
Power (Watt)
Energy (Joule)
Solar array
600
3041135
Turbine (Regen)
687
3480455
-150
-760283
0
0
NA
NA
Total
Recharge (80% eff.)
1137
909
5761307
4609046
Battery capacity spent:
-23%
Equipment
Motor (sustain flight)
Motor (to potential energy)
Battery capacity spent total:
0%
Table 5: Recharge batteries to full capacity, energy balance.
2.2.4 Cruise till 50% of the battery capacity remains
The aircraft is cruising freely and accomplishing the mission objectives.
Altitude gained = 0m
Balance:
Time spent = 59 minutes
Power (Watt)
Solar array
Turbine (Regen)
Equipment
Motor (sustain flight)
Motor (to potential energy)
Total
Energy (Joule)
1050
3735529
0
0
-150
-533647
-3733
-13281882
0
0
-2833
-10080000
Battery capacity spent:
50%
Battery capacity spent total:
50%
Table 6: Cruise till 50% of the battery capacity remains, energy balance.
2.2.5 Recharge batteries to full capacity and land
The aircraft is recharging and continues to accomplish the mission objectives. The turbine generated
power is higher during the final descent what can shorten the recharge time before landing but the
turbine power is considered to be constant during the entire final phase of the investigated scenario for
simplicity.
Altitude gained = NA
Balance:
Time spent = 185 minutes
Power (Watt)
Energy (Joule)
Solar array
600
6650974
Turbine (Regen)
687
7611767
-150
-1662744
0
0
NA
NA
Total
Recharge (80% eff.)
1137
909
12600000
10080000
Battery capacity spent:
-50%
Equipment
Motor (sustain flight)
Motor (to potential energy)
Battery capacity spent total:
100%
2.2.6 Conclusion, energy balance
Following this analysis it has been shown that it is possible to build an unmanned aircraft powered
with solar power and regenerative soaring from an existing aircraft so that it would be capable to self
launch, fly and land with full battery. The total flight time in the investigated scenario was 5 hours and
53 minutes. In this configuration the ratio between free cruising and regen is 1:3.1 which means that
the aircraft would need to regenerate for 3.1 minutes for every minute of powered cruising to have the
batteries fully charged by landing. It should be considered that the regeneration time may be used to
accomplish mission objectives (e.g. the UAV can perform surveillance and regen at the same time).
The analysis shows that using regenerative soaring shortens the recharge time significantly during the
day. Regenerative soaring is the only source of energy for the aircraft during the night.
To maximize the efficiency of the UAV the following should be considered:
•
solar cells should cover maximum of the suitable surfaces and have the highest possible
efficiency
•
power input of the equipment should be minimized
•
drag of the aircraft should be minimized
•
large and slow (more efficient) propellers should be used (possibly installed as ducted fans)
•
the control system should efficiently search for strong updrafts enabling higher recharge rates.
A grand challenge for the aircraft would be to stay aloft during the nighttime when two important
sources of energy vanish: sun and thermal updrafts. UAV could still use upwind slopes and dynamic
soaring. Using upwind slopes for lift would require reliable ground analysis of atmospheric conditions
(information on wind speed and direction used to model air motion in a 3D map of the operation area).
Dynamic soaring requires precise flight control in sharp low altitude maneuvers (20-150m over
ground) and a reasonably small and sturdy aircraft (dynamic soaring is often used by RC pilots).
2.3 AI and Control System
Autonomous soaring for UAV's was first
proposed in 1998 [7]. Recursive learning
was used to center updrafts and neural
networks were used to identify updraft
positions. Algorithms were too intensive for
real-time use at that time. Since then several
other works were focused on soaring UAV's
(e.g. [8,9]). The SoLong unmanned aerial
vehicle from AC Propulsion flew on June 13, 2005 over 48 hr nonstop fueled only by
solar energy. The plane sports a wingspan
of 4.75 m and weighs 12.6 kg. NASA
Dryden Flight Research Center supported a
project of an autonomous soaring UAV [8]
(CloudSwift, Span: 4.26m, Weight: 6.58kg,
Stall speed: 33kt, Mission speed: 46kph).
Illustration 9: SoLong UAV, AC Propulsion.
The experiments were first performed in simulation. Simulation results showed that a small UAV can
benefit significantly by exploiting updrafts and simulation study assumed that a small UAV could
autonomously detect and center updrafts. CloudSwift UAV was used for real world experiments.
Updraft detection sensors were not used.
Updrafts were only detected after the
UAV had physically encountered them.
Archimedes spiral pattern was chosen for
the UAV to fly while searching for
updrafts. During 17 test flights
CloudSwift found 23 updrafts, climbed
maximum 844m in a single updraft and
gained 172 meters in an updraft in
average.
These results indicate that it is possible
for an UAV to autonomously search and
utilize updrafts. We propose to improve
the performance of the UAV by using a
vision system for recognition of typical
signs of updrafts (cumulus clouds) and
ground wind and weather analysis for Illustration 10: CloudSwift, NASA Dryden
identification of areas producing updrafts (upwind slopes and thermals). We also propose application of
artificial neural network learning to fly by observing actions of a human pilot. This can be done either
off-line using recorded flight data or on-line because the proposed aircraft enables presence of human
pilot on board during experiments. The trained artificial neural network can be used as a subsystem of
the control system. The core of the control system is proposed to be rule based.
3 Estimated Project Impact
Results of this project would contribute to several scientific fields: aeronautical engineering, electric
engineering, robotics and artificial intelligence. The proposed UAV is intended to fly with or without a
human pilot. The possibilities of this design are important because it enables straightforward step to
manned flight without fuel. In this setup artificial neural network can be used to learn how to fly from a
human pilot. Comparison of performance of manned and unmanned aircraft would be possible.
Regenerative soaring has not been practically tested on an aircraft yet. The measurements taken could
be helpful for future applied research. Important are also the results obtained in the field of artificial
intelligence and robotics. These results could be important for development of completely autonomous
UAV's for extra-terrestrial research e.g. for Mars exploration.
Acknowledgments
I would like to thank to the following people who contributed to the project proposal by providing
advice and consultation:
Phil Barnes is Principal Engineer at Northrop Grumman Corporation. He has
a Master’s Degree in Aerospace Engineering from Cal Poly Pomona and a
Bachelor’s Degree in Mechanical Engineering from the University of Arizona.
He has 25-years of experience in the performance analysis and computer
modeling of aerospace vehicles and subsystems at Northrop Grumman. Phil
has authored technical papers on aerodynamics, gears, and flight mechanics.
Phil Barnes is the author of the paper “Flight Without Fuel - Regenerative
Soaring Feasibility Study” [4]
Randall Fishman is the president of Electric Aircraft Corporation. He has
won numerous awards and accolades for his work on electric flight and already
has built an electric-powered ultralight and a single-seat motorglider. In April
2007 the Electric Aircraft Corporation began offering complete electric
ultralights and engine kits under the ElectraFlyer brand name, to convert
existing ultralight aircraft to electric power, in what is the first commercial
offering of an electric aircraft.
Jukka Tervamaki graduated from the Helsinki University of Technology in
1963 specialized in Aeronautical Engineering. Experimenting, creating,
designing and building has been everyday work as well as a hobby for him for
four decades. He designed and build several rotary wing aircrafts (autogyros),
a motor glider and cooperated on development of a fixed wing tow plane. He
has logged total 2200 flight hours of which 150 hours in autogyros. He is
aviation writer for several Finnish and foreign aviation magazines.
Sources:
[1] Electric Aircraft Corporation, http://www.electraflyer.com/, email correspondence with Randall
Fishman, president of Electric Aircraft Corporation
[2] Aériane SWIFT rigid wing hang glider http://www.aeriane.com
[3] Northwing, Stratus, http://www.northwing.com/
[4] Philip Barnes - Pelican Aero Group, Flight Without Fuel - Regenerative Soaring Feasibility Study,
presented at General Aviation Technology Conference & Exhibition, August 2006, Wichita, KS, USA,
Session: Propulsion Dynamics and Advanced Engine Concepts,
http://www.sae.org/technical/papers/2006-01-2422, email correspondence with Philip Barnes.
[5] NASA Dryden Fact Sheet - Pathfinder Solar-Powered Aircraft http://www.nasa.gov/centers/dryden/
news/FactSheets/FS-034-DFRC.html;
[6] The Worlds Air Sports Federation http://records.fai.org/, as of Oct. 26 2009.
[7] J. Wharington, I. Herszberg (1998), 'Control of High Endurance unmanned air vehicle', Proc. 21st
Congress of the International Council of the Aeronautical Sciences, Rodney S. Thomson & Murray L.
Scott, eds., AIAA Electronic Publication - CD ROM, ISBN:1-56347-287-2 98-1141, (ICAS '98, 1318 Sept. '98 - RMIT Fishermen's Bend, Melb. Vic.)
[8] Allen, Michael J. (2005) Autonomous Soaring for Improved Endurance of a Small Uninhabited Air
Vehicle. Meeting Presentation AIAA-2005-1025, Research Engineering, NASA Dryden Flight
Research Center. http://dtrs.dfrc.nasa.gov/archive/00001168/
[9] Guidance and control for an autonomous soaring UAV, United States Patent 7431243