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Electric Jet V1.1 Lochie Ferrier

Figure 1 - Rendering of electric jet

ABSTRACT This document outlines the initial design and performance of a personal electric aircraft as an

improvement upon currently available light aircraft. The design performs well in the three elusive

transport criteria of cost, speed and environmental effects. The document has non-technical elements,

especially in the beginning, but mainly it is intended for technical review and is written as such. The design

was developed by a single engineer, with minimal simulation and verification, so it is expected that there

are mistakes and potential for improvement in areas. Note that although this design is quite specific in

terms of components and sizing, it is the general concept that is of interest. The reason for specificity here

is to ensure that the idea is valid, as little direct comparison exists and nobody wants to read a paper that

just goes through the mathematics. Negative feedback is encouraged at lochieferrier@gmail.com .

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TABLE OF CONTENTS Abstract ......................................................................................................................................................................... 1

Background .................................................................................................................................................................... 3

Electric Jet ...................................................................................................................................................................... 4

Propulsion ................................................................................................................................................................. 6

Batteries ................................................................................................................................................................ 6

Motor Controller ................................................................................................................................................... 7

Motor .................................................................................................................................................................... 7

Ducted Fan ............................................................................................................................................................ 7

Charging ................................................................................................................................................................ 7

Aerodynamics ............................................................................................................................................................ 9

Configuration Choice ............................................................................................................................................ 9

CFD Testing ........................................................................................................................................................... 9

Possible Improvements ....................................................................................................................................... 11

Control ..................................................................................................................................................................... 11

Elevons ................................................................................................................................................................ 12

Thrust Vectoring ................................................................................................................................................. 12

Fly by Wire Coordination .................................................................................................................................... 13

Force Feedback ................................................................................................................................................... 13

Performance ............................................................................................................................................................ 14

The Yosemite Scenario ........................................................................................................................................ 14

Speed .................................................................................................................................................................. 15

Energy Cost ......................................................................................................................................................... 15

Environmental Sustainability .............................................................................................................................. 16

Combined Factors ............................................................................................................................................... 17

Safety .................................................................................................................................................................. 17

Range .................................................................................................................................................................. 18

Maintenance ....................................................................................................................................................... 19

Manufacturing .................................................................................................................................................... 19

Altitude ............................................................................................................................................................... 20

Conclusions .................................................................................................................................................................. 20

Future work ................................................................................................................................................................. 20

improvements ............................................................................................................................................................. 20

Acknowledgements ..................................................................................................................................................... 20

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BACKGROUND Despite improvements in road transportation, little is being done to solve the problem of aircraft

emissions and efficiency. In the past few decades, airlines have poured money into research, but have

only been able to achieve incremental gains through small innovations such as winglets. It’s clear that a

fundamentally new approach is needed for air transportation, as the modern jet airliner has been nearly

fully optimized.

Two factors affect the sustainability of an aircraft design. The first is aerodynamic efficiency, which can be

seen in the difference between a cruising albatross and a frantic hummingbird. The albatross can fly for

long periods with little food, as a result of its good lift to drag ratio, whereas the hummingbird quickly

burns through high energy nectar with its short wingspan. The second is the propulsion system, which has

traditionally been air-breathing and polluting. Electric aircraft offer improvements in both, as an electric

propulsion system can be more aerodynamic and efficient than an air breathing system.

Due to these improvements, electric motors overtook IC engines as the preferred propulsion method for

model aircraft in the 1970s. However, the technology was not been scaled up, due to the low specific

energy of available batteries. Today, there is no reason why a reasonable full scale aircraft cannot be built,

as battery specific energy has greatly improved, and is now being pushed by electric car development.

Gliders fitted with electric propulsion have achieved good results as a result of their high aerodynamic

efficiency. Though gliders are often only capable of operating from specialized airfields and their wingspan

requires large storage space and assistance in launch. Light sport aircraft similar to the Cessna 152 have

also been modified to run electric, however the utility of this configuration has been counteracted by the

aerodynamic inefficiency of such a design, resulting in short flight times and terrible range.

In March 2014, Airbus flew their prototype E-Fan aircraft, which attempted to solve both the utility and

the aerodynamic efficiency problems. Despite the expertise of the Airbus/EADS group, the aircraft

achieved mediocre performance with a maximum 160 km range. This doesn’t make sense, given the

current level of battery and motor technology.

To understand why the Airbus E-fan didn’t work well, I came up with a simple electric conversion for the

BD-5J, a small, high efficiency homebuilt aircraft design. The performance was fantastic, with a range of

over 300 km even with generous reserves. Though I quickly realized that simply replacing the powertrain

does not deliver all of the benefits that electric propulsion has to offer, so I set out to create a small electric

jet design from scratch. The idea was that electric aircraft could be scaled up as battery technology

improves, using capital from each size iteration to fund progressively larger aircraft. This document is the

result of that work.

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ELECTRIC JET

Figure 2 – Three part rendering of aircraft geometry model

Figure 3 – Fuselage components layout

Figure 4 – Wing components layout

Transfer

pipe

Electric

ducted

fan

Motor

controller Thrust

vectoring

unit

Single pilot

cockpit Battery

Battery Battery

Elevon Elevon

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The jet carries one passenger and is propelled by an electric ducted fan with energy stored in a lithium-

ion battery pack. It is controlled by elevons and a thrust vectoring system, coordinated with fly by wire

electronics.

The BD-5J was used as a loose beginning for the design, and has been used for some sizing factors, such

as empty structural weight. The main differences between the BD-5 are the propulsion system and wing

loading.

General Specifications

Lift to Drag Ratio 27

Wing Loading 62 kg/m^2

Wingspan 6.6 m

Capacity 100 kg / 1 passenger

Cruise Velocity 300 – 350 km/h

Empty Mass 162 kg

Battery Mass Fraction 50 %

Battery Specific Energy 300 Wh/kg

Battery capacity 78.6 kWh

Theoretical range (electric Breguet equation) 1190 km

Range with 45 min reserve 965 km

Range with 15 min reserve 1115 km

Efficiency 66 Wh/km

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Propulsion The heart of the aircraft is an electric propulsion system, which is efficient, high performance, cheap to

run and environmentally sustainable. This system consists of lithium-ion batteries for energy storage, a

power distribution system and an AC electric motor driving a ducted fan.

Batteries Lithium-ion batteries with a total weight of 262 kg at a specific energy of 300 Wh/kg and energy density

of 620 Wh/L are used to power the aircraft. These batteries are the majority component of the take-off

weight of the aircraft and take up much of the volume. Alongside specific energy issues, a problem with

using batteries for energy storage is that they do not decrease in mass during flight, unlike a tank holding

jet fuel. It would be fantastic if there was a way to somehow drop depleted batteries in flight but even

with parachutes this would be extraordinarily expensive for the pilot and dangerous to people on the

ground.

100 kW

93-98%

efficiency

Electric

ducted fan

15 kWh

Wing battery

Backup

controller

50 kWh

Fuselage

battery

Controller

15 kWh

Wing battery

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Accompanying such a large and heavy battery whilst maintaining balance and aerodynamics requires

some redesign. The solution I have found to this is to store most of the battery in an extended rear

fuselage, with small units in the wings providing balance and redundancy. The battery is split into three

parts, with two small units in the wings and one large fuselage component (see figures 4 and 5).

Cooling for the battery has not yet been covered, though it is anticipated that even at cruise velocity, air

driven cooling may not be sufficient, given the high rate of energy consumption. Liquid cooling is probably

preferable, as it would allow for long taxi runs without overheating, which has been a significant problem

for light sport aircraft electric conversions.

Motor Controller An AC motor requires a complex electronic motor controller to ensure that the motor runs at maximum

efficiency in a safe manner. Until recently, motor controllers were not available at low cost and weight

that could handle the power requirements of an electric aircraft. Now, several controllers (such as the

Zilla 1K by Manzanita Micro) are available off the shelf at the right power level with good efficiencies and

densities of well under 10 kW/kg. These controllers have been developed for high performance electric

cars. A pair of controllers in the 150 kW range should be sufficient, providing redundancy at a total

combined weight of around 15 kg.

Motor To ensure a high cruise velocity, a 100 kW AC electric motor is used. The EMRAX 228 motor, developed

for glider launching, is used as a model. This motor has a continuous power of 45-55 kW, dependent on

the cooling method that is used. The motor also has a fantastic power to weight ratio of 8.4 kW/kg,

resulting in a motor weight of 12.3 kg.

Ducted Fan A ducted fan system is used to convert the kinetic energy from the motor to airspeed. A ducted fan offers

better propulsive efficiency than a propeller as blade tip vortex losses are minimized and aerodynamic

advantages as its small diameter can be integrated into the fuselage. Jet turbines also offer the same

advantages over propellers, which explains their popularity. A ducted fan can also be used to partially cool

the motor driving it, as the point where the airflow is travelling at the highest velocity is just as it flows

over the motor casing. Thrust vectoring can also be accomplished with a nozzle, minimizing servo weight

and air inlets can be placed at the boundary layer of the wing, increasing aerodynamic efficiency.

Charging If the batteries cannot be recharged quickly, then the appeal of the aircraft is lost. At the moment, it is

impossible to reach the refueling times of a conventional aircraft without battery swapping, but

reasonable recharge times are still possible. Three different chargers are used as examples, a standard

110 volt outlet (1.3 kW), a NEMA 14-50 high power outlet (9.6 kW) and a Tesla Supercharger (120 kW).

These three chargers roughly represent three different orders of magnitude in terms of power and

availability. The NEMA 14-50 option represents the realistic scenario, which would be available at over

90% of airfield hangars.

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Figure 5 - Time needed to fully recharge the 185 kWh batteries.

Figure 6 - Effective charging speed, using the 15 min reserve range of 375 km.

With a Tesla Supercharger, the effective charging speed is close to the actual cruise speed of the aircraft,

and would make multiple flights per day in a cross country style quite feasible. If Tesla Superchargers (or

comparable installations) were available at every airport, the aircraft could cross the United States

(approx. 4500 km LA to NY) with 12 charges totaling less than 18 hours at an electricity cost of $266.

However, the more realistic scenario with a NEMA 14-50 outlet is not so encouraging, enabling only one

full length flight per day. To use the aircraft in a cross country capacity, a network of high power chargers

would be required, however for simple weekend or roundtrip use current outlets could work.

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Standard 110 V Outlet NEMA 14-50 Outlet Tesla Supercharger

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Aerodynamics

Configuration Choice A tailless, short delta wing configuration was chosen for the basic aerodynamic configuration. A tailless

design minimizes drag and weight from tail surfaces. However, it does not blend the fuselage with the

wing, as in a flying wing, which means that fuselage can provide some inherent stability in yaw and roll.

Such a design should deliver a good lift to drag ratio, whilst maintaining structural simplicity,

maneuverability and stability. The NASA X-31 experimental tailless aircraft verified that tailless aircraft

can be stable and highly maneuverable, whilst the BD-5 has shown that short wingspan designs can

perform with high lift to drag ratios. A pure flying wing design is being looked into, though there are issues

with internal volume and cockpit visibility.

CFD Testing

Figure 7 - Aerodynamic model of aircraft in XFLR5 software.

To verify the assumptions made about aerodynamic performance, the aircraft geometry model was

exported to XFLR5 CFD analysis software. The aircraft was analyzed using an aquilasm-il airfoil at a cruise

velocity of 100 m/s. The Reynolds number at tip was calculated to be 7.933 million, with root Reynolds

number at 7.935 million. A Horseshoe vortex analysis produced an achievable lift to drag ratio of 27 (with

pitch inaccuracy of 5 degrees) and the results depicted below. The airflow through the electric ducted fan

was not simulated.

This computer simulation will soon be verified using flying model aircraft tests and a small wind tunnel.

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Figure 8 - Surface pressure coefficient result.

Figure 9 - Surface velocity result.

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Figure 10 - Air stream path after leaving trailing edge and fuselage rear, showing turbulence developing at jet outlet and

vortices forming at wingtips.

Figure 11 - Lift distribution result.

Possible Improvements There are several areas of the aerodynamic design where it is suspected that an adjustment could produce

significant benefits. The first is in the delta wings, where a larger root chord with similar tip chord could

provide greater lift with a minimal drag increase, boosting ceiling and landing performance. Through

optimization of the powertrain geometry, a shorter fuselage should also be possible, however there is

probably a point where having a shorter fuselage would decrease performance. A smaller thrust nozzle

may make encountering this point less likely, as it would result in less turbulence off the back of the

aircraft. The injection of airflow from the EDF should reduce this effect nonetheless. Winglets are another

option, although their minimal gains may not be worth the extra cost and complexity.

Control As a result of the low specific energy power source, the range of an electric aircraft is particularly reliant

on the maintenance of a stable flight condition. A high lift to drag ratio can only be achieved when the

angle of attack of the aircraft is within a small range of around 5 degrees. This requires precise control,

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beyond what an experienced pilot can be expected to provide over a long time period. To provide this

precise control, a fly by wire system with elevons and thrust vectoring is used.

The reasons for this come down to performance. In a traditional aileron, elevator and rudder

configuration, the pitch and yaw controls must be mounted on a tail boom, creating dag. If a combination

of thrust vectoring and elevons is used, a tail boom is not necessary, and less control surfaces are exposed

to the airflow when deflected, reducing drag. Also, there is an improvement in redundancy in the pitch

axis, as either the thrust vectoring system or the elevons can control this axis. Safety, landing performance

and aerobatic envelope can also be improved, as a thrust vectoring system can maintain flight at a higher

angle of attack than a traditional system. The elevon and thrust vectoring approach has been used by

many birds of prey and the B-2 bomber to great effect.

Elevons To provide roll and pitch control, two elevon control surfaces are mounted at the tips of the wings. These

surfaces are solely controlled by a servo embedded within the wing. Reliable servos are manufactured by

Garmin at this scale.

Thrust Vectoring Thrust vectoring is somewhat more difficult to accomplish at this scale, however it is made easier by the

air temperature exhaust. The first choice to make is how many thrust vectoring paddles are used. The

minimum is two, with one deflecting airflow up and down whilst the other moves left and right. These

paddles would be mounted in the center of the jet outlet. This would provide yaw and pitch control. Two

could be used fine, but it is probably wiser to go for three. With three paddles arranged in a symmetrical

fashion around the edge of the outlet (as in the X-31), advantages in redundancy and performance can be

had over two without the cost and complexity of a many paddle system such as that seen in the

Eurofighter. In a three paddle system, if one of the paddles fails and becomes stuck, the other paddles

Elevon Elevon

Elevon

servo

Elevon

servo

Flight

computer

Force

feedback pilot

controls

Thrust

vectoring

system

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can adjust to the same deflection, simply adjusting the nozzle diameter and not changing the control

force. When all three paddles are functioning, this ability to adjust the nozzle diameter could be used to

optimize the turbulence produced at the end of the fuselage traded off with thrust depending on flight

condition Reynolds number. If the vectoring system is mounted outside of the fuselage, then the paddles

can deflect outward to provide airbrakes and minimal pitch and roll control if power is lost. It is not yet

decided whether the thrust vectoring paddles should be housed within the aircraft fuselage or attached

to the end, as extra functions have to be balanced with the increased drag that comes with a rough aft

fuselage.

Figure 12 – Diagram showing thrust vectoring system housed within fuselage and externally attached.

Fly by Wire Coordination Coordinating aileron, rudder and elevator interference with a mechanical system is difficult. Coordinating

thrust vectoring and elevon mixing, whilst accounting for failures is near impossible with a mechanical

system. A fly-by-wire system for this aircraft is not only advantageous, but necessary for safe flight.

Aside from tuning the aircraft control response and coordinating failure response, a fly-by-wire system

offers several advantages over a mechanical system at this scale. Lower weight and less maintenance

result from the mechanically static nature of the signals, as opposed to a system with pulleys, levers and

cables. A fly-by-wire system can also increase safety by preventing the pilot from overstressing the aircraft

or even taking complete control if the pilot loses falls unconscious or becomes disabled due to medical

issues. Use of a fly-by-wire system also means that the full advantages of thrust vectoring, such as lower

landing speeds, can be reliably used. A fly-by-wire system may also allow for unmanned test flights early

in a development program to maximize safety.

Force Feedback The one thing a fly-by-wire control system lacks that a mechanical system has is flight condition feedback

through the controls. This requires a force feedback system, similar to that used on the Space Shuttle or

modern fighter aircraft, so that the pilot can sense airspeed and be alerted to stalls and other conditions

through the joystick controls. This can be achieved using low-powered servos and springs attached to a

control joystick. Such a system would require careful tuning to mimic aerodynamic response, perhaps

using a simulator.

servo

servo

paddle

paddle

paddle

paddle

servo

servo

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Performance

The Yosemite Scenario We should judge transport on its speed, cost and its environmental sustainability. To illustrate the

performance of the electric jet in comparison to other modes of transport, a trip from San Francisco to

Yosemite National Park is analyzed. For the road-based transport, this is done using the route

recommended by Google Earth software, and for aircraft it was standardized as the “as the crow flies”

route from SFO to Pine Mountain Lake airport. This means that the comparison between the aircraft and

the ground transport isn’t exactly clean, but comparisons between air modes and ground modes are

accurate.

Figure 13 - Routes for Yosemite scenario. Blue path is ground route, red line is air route.

The ground route was measured as 275 km, whereas the air route was only 180 km. This should be taken

into account when reading these comparisons, along with the differences in convenience, weather

dependence and pleasure between road and air travel.

Five different modes of transport were analyzed, each representing high performance in their class. The

Model S was used to represent electric cars, contrasted by the Subaru Forester for IC powered ground

travel. To show the airline option, the cost and airspeed of a United Airlines EMB-120 was used. The EMB-

120 is a typical twin turboprop configuration short range airliner. The popular single engine Cessna 152

was used to represent a personal aircraft. The electric jet design presented here was used to represent

the possibilities of electric aircraft.

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Speed

Figure 14 - Graph showing the time taken to travel from San Francisco to Yosemite. Ground times are estimated using Google

Earth software. Air times are calculated based on 180 km route and published cruise speeds.

As mentioned above, this speed comparison isn’t exactly fair due to a distance in difference, however it

does provide some idea of magnitude. What also isn’t factored in is differences in preparation time,

ranging from extremely long for the airline, to rather short for the personal aircraft and then almost non-

existent for the ground based vehicles. Despite preparation time, air travel will usually be faster over 200

km + distances because of the higher speeds as a result of lower friction and lack of speed limits.

Energy Cost

Figure 15 - Cost of energy or cost of ticket in the case of the airline flight.

What’s important to remember here, with the exception of the airline, is that only the cost for that

particular trip has been included. All maintenance, storage and purchase costs are ignored. For the airline

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flight, these costs along with all sorts of other things like staffing and insurance costs are included. For an

electric jet, as with an electric car, the maintenance costs would likely be less than an air breathing aircraft

due to minimal vibrations and moving components. This is discussed further below.

Environmental Sustainability

Figure 16 - CO2 emissions based on 0.000689 kg/kWh for electrics (EPA), 8.3 kg/gallon for Cessna 152, 0.2 kg/km for Forester

and 0.25 kg/km for airline.

Even using a fairly high emission rate for the electric vehicles, they still produce less emissions than the

air breathing transportation methods. These emissions represent the maximum, as electric emissions can

be reduced to zero with solar power. It is also worth noting that any emissions from the electric jet are

produced at a ground power plant, eliminating the magnifying factor of releasing pollutants at altitude

that is present with the airline and Cessna 152 (but not accounted for in this analysis).

36.2

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Tesla Model S Subaru Forester Cessna 152 Electric Jet United AirlinesEMB-120

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Combined Factors

Figure 17 - Graph showing the products of the three factors of merit discussed above.

To see how well each mode of transport as a whole, the three factors of merit were multiplied together

for each mode and then compared. This isn’t exactly fair, but the magnitude of each factor is about the

same, so it is close. Different people value each merit differently, which also makes a direct comparison

subjective.

Not surprisingly, the electric car has far more merit than the petrol powered vehicle. Another predictable

result is that the Cessna 152 outperforms the airline by a similar margin, which is why many people own

small aircraft purely for transportation purposes. The electric jet shows a 50x improvement over the Tesla

Model S, primarily because it has a lower energy expenditure per kilometer, and can fly, avoiding traffic

and speed limits. It is also better than the similar sized Cessna 152, because of good efficiency, higher

speed and lower energy cost.

Safety Aircraft are inherently dangerous, as they involve travel at high speeds and altitudes suspended by only

the flow of a shape through air. It would take several hundred pages to go over all of the potential safety

issues with aircraft, so I will just look at the benefits that an electric jet has to offer. As the electric motor

has fewer moving components and less temperature gradients, it is inherently (and has been proven to

be) more reliable than air breathing engines. This minimizes the risk of loss of power whilst flying over

hostile environments such as mountains or oceans. Use of a fly-by-wire system also ensures that the

aircraft remains within the flight envelope at all times, and a thrust vectoring system can be used to slow

landing speeds by controlling the aircraft at higher angles of attack. A redundancy in pitch control through

the elevons and thrust vectoring is another unique safety feature. Use of a ducted fan minimizes the risk

of ground incidents involving people being struck by propellers, or ingested, as the ducted fan is housed

within the fuselage and does not need to be idled for long periods before flight. In the event of a complete

structural failure, there is enough provision in the payload for the pilot to wear a parachute, and the pilot

would be at no risk of tail or propeller strike if they egressed.

52909

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Tesla Model S SubaruForester

Cessna 152 Electric Jet United AirlinesEMB-120

Pro

du

ct

Product of Three Factors of Merit

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Range Range for traditional aircraft is dependent on the well-known Breguet equation where V is velocity, (L/D)

is lift to drag ratio, Isp is specific impulse and Wi/Wf is empty mass fraction. Credit to MIT Unified

Engineering course notes.

We can adapt this equation for electric aircraft, where E* is battery specific energy, ntotal is total

propulsion system efficiency (cell to airflow), 1/g is 1/9.8 or inverse gravity, L/D is lift to drag ratio and

mbattery/m is battery mass fraction. For this aircraft design, each of these parameters has been optimized

as much as is possible with current technology. Derivation.

This equation nicely gives us an ideal range of 1190 km, which is the upper limit on possible range. Of

course, an aircraft cannot fly an ideal range distance due to the need for safety reserves in case of weather,

equipment or other situations. With a 15 min safety reserve (reasonable given the glide slope, gliders of

a comparable performance carry zero reserve), the range becomes 1115 km. This is quite large when

compared with a Cessna 152 (768 km), and is capable of linking most city pairs in one flight.

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Figure 18 - Range circles for Cessna 152 (red) and electric jet (green). Map data from Google Maps.

Maintenance Aircraft need to be kept in a reliable state, otherwise they become incredibly dangerous. This is difficult

with air-breathing aircraft, as they have thousands of moving parts, optimized for low weight, operating

at different temperatures within a confined volume for long time periods. This difficulty translates into

high maintenance costs, meaning that many light aircraft owners must account for maintenance at a rate

more than twice the hourly energy cost of flying.

With the electric jet, these costs should be dramatically reduced, as there is only one moving part, the

electric ducted fan. The only downside that can be thought of in terms of maintenance is higher landing

weight than is typically seen (due to the batteries), so tire wear may be more aggressive.

With a fly-by-wire system, some research has also shown that an aircraft can be capable of self-evaluating

its performance using flight sensors, minimizing the need for inspections.

Manufacturing The distinguishing part in manufacturing cost is the electric powertrain. A decent quality 60 kW piston

aircraft engine such as the Jabiru 2200 can be purchased for approximately $20,000. Whereas even at less

than a $200/kWh manufacturing rate for the lithium-ion batteries, the 100 kW electric jet powertrain

would cost around $30,000. This is a significant difference, to be balanced with the lower operating costs

of an electric aircraft.

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Altitude As an electric jet does not breathe air, it does not lose propulsion performance as it gains altitude. This

means that extremely high altitudes can be reached, as shown by the NASA Helios solar powered plane,

which reached 29,524 m, well above an air breathing U2 at approximately 21,000 m. For the electric jet

studied here, the ceiling is lower at around 8-9,000 m, due to a smaller wing area, however this is still

above the 4,480 m limit for a Cessna 152.

CONCLUSIONS To make the arguments clear, let’s go over the fundamental advantages and disadvantages of this concept

again.

Advantages:

Lower energy and maintenance costs than comparable fuel powered aircraft.

Higher performance in altitude and speed than comparable fuel powered aircraft.

More environmentally sustainable than comparable fuel powered aircraft.

Safer than comparable fuel powered aircraft.

Higher ceiling than comparable fuel powered aircraft.

Approximately the same range as comparable fossil fuel powered aircraft.

Disadvantages:

Realistic recharging times are almost two orders of magnitude greater than typical gas refuel.

Electric powertrain is roughly twice more expensive to produce.

Once again, negative feedback is encouraged at lochieferrier@gmail.com

FUTURE WORK The design and verification of a suitable airframe is the immediate task, so that empty weight can be more

accurately determined and used for sizing. Powertrain cooling methods also need to be investigated, as

well as landing gear design (there is space for the front wheel, however adjustments may need to be made

to accommodate rear tricycle wheels). There is the possibility of massless in-air charging with airships as

well, especially at the general aviation scale. Full costing is also required.

IMPROVEMENTS At the moment the design has a very high wing loading, which limits service ceiling, gives high landing

speeds and restricts aerobatic performance. This could be fixed with a longer root chord delta wing, or

larger wingspan. Given the available motor power, it may also be possible to create some sort of ducting

system to enable VTOL, which would give the aircraft increased range and utility.

ACKNOWLEDGEMENTS Thanks go to Jim Bede for sending me a copy of his design notes for the BD-5, and to Joshua Fridgant, for

helping with initial criticism.