sport aviation of the future. possible concepts for future sport aircraft using different...

Sport Aviation of the Future.Possible Concepts for Future Sport Aircraft Using

Different Environmental Friendly Propulsion Concepts

Patrick Berry

Fluid and Mechatronic Systems

Introduction

A new generation of sport aircraft will require radical changes to the propulsion system

Why?

In the future fossile fuel will be scarce or at least limited and too expensive

Fossile fuel is bad for the environment and might also be prohibited to use in the future because of its environmental impact

So what are the options?!

1) Use bio fuels

2) Go electric

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Introduction

This study will focus on electric propulsion and what this means for the design and use of such aircraft

Different power sources like the sun, batteries and fuel cells will be covered

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Solar powered aircraft

Sources of inspiration:

Human powered aircraft

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Gossamer Albatross

Daedalus (MIT)


Sources of inspiration:


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Powered configuration

Configured as a glider

Solair 2

Questions

Is it possible to design something like this which is commercially viable?

…. and to which category do we certify it?

Is there a market?

Will the market accept it?

ICAS 2010


The Sun peaks at 1000 W/m2 (in summertime, at noon on a clear day)

An average of 800 W/m2 can be expected (in southern Europe)

This indicates flight times around 7 hrs on pure solar power

But the aircraft won´t be able to take-off and climb on solar power, so it needs to be a hybrid using batteries to assist

Batteries are an additional dead weight which needs to be minimised, so we are looking for a battery with high energy density (Wh/kg)

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Battery trends in energy density

Quinetic Zephyr using Li-S (350 Wh/kg)Endurance: 2 weeks

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Affordable solar cells are in the range of 15-20% in efficiency. We need to work with the most efficient ones in order to reduce size, weight and stay reasonable in cost

Essential to minimise losses in the overall power chain

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How would you use such a plane?

Due to its low power-to-weight ratio it´s more suitable as a powered glider, i.e. a glider with self launch capability

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Specification for a solar powered aircraft

Average solar radiation = 800 W/m2

Max. sink rate in glider configuration: less than 0.7 m/s

Cruise speed in solar powered mode: 20% higher than stall speed

The aircraft shall be a hybrid, i.e. battery power for take-off and climb, solar power for cruise

Min. climb speed: 2m/s

Single seater or two seater

Pilot or passenger weight: 90 kg (+7 kg for parachute)

Certification: CS 22, motorgliders

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Typical sizing diagram for solar powered flight

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Solar constraints

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0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000

Altitude (ft)

(W

/S)o

(k

g/m

2)

Stall margin

Minimum sinkrate

Solar powered cruise

Initial cruise altitude

Design point solar powered a/c


Two configurations are presented:

1. Conventional layout

2. Canard configuration

ICAS 2010

ICAS 2010

23-04-19 Linköpings universitetSid 17

Conventional Single-seater Two seater

Overall length (m) 7.1 7.5

Span (m) 21.2 18.7 26.8 26.5

A 23 23

S (m2) 19.6 15.3 31.2 30.4

Empty weight (kg) 135 122 270 251

Battery weight (kg) 36 (Li-ion) 25 (Li-S) 66 (Li-ion) 42 (Li-S)

Pilot+parachute (kg) 90+7 194

MTOW (kg) 268 244 530 487

Max shaft power (kW)(T-off, climb)

8 16

Solar shaft power (kW)(cruise)

2.2 2 4.1 4

Propeller dia. (m) 2 2

Cruise speed (km/h) 77 76 77

(L/D)max 33 33

Endurance (h) 6.9 6.9

Climb rate (m/s) 1.8 2.1 1.7 1.9

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Canard Single-seater Two seater

Overall length (m) 7.4 8

Span (m) 16.7 15.8 21.8 20.5

A 18 18

S (m2) 15.4 13.9 26.5 23.4

Empty weight (kg) 114 101 218 189



MTOW (kg) 247 222 478 422

Max shaft power (kW)(T-off, climb)

8 16

Solar shaft power (kW)(Cruise)

2.2 2 3.7 3.3


Cruise speed (km/h) 80 76

(L/D)max 33 35

Endurance (h) 6.9 6.9

Climb rate (m/s) 2 2.2 1.8 2.1

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Typical V-n diagram for a solar powered aircraft

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Problem areas

Requires skilled pilot due to lack of excess power

Solar cell integration on wing and stabilizer

Solar cell integration requires stiff surfaces (brittle cells)

Solar cells need to be embedded for low drag (without too much energy losses)

Aircraft limited in use as to where and when you can operate it

Big question= Maintenance of solar cells!!

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Problem areas

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Battery powered aircraft

Source of inspiration:

PC Aero Electra One

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Battery powered aircraft

Battery powered aircraft are based on the sun powered configurations shown previously

Main difference: Wing loading can be increased since sun power is eliminated (saves weight)

Since battery weight will be even more dominant in this case, we need to decrease structure weight as much as possible (wing essentially)

No sun power means no need for non-tapered wings any more, i.e. weight potential

Aspect ratio can be reduced (weight saver), which means somewhat reduced soaring performance,

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Specification for a battery powered aircraft

Maximize range/endurance

Min. cruise speed : 20% higher than stall speed

Min. climb speed: 2m/s

Single seater or two seater

Pilot or passenger weight: 90 kg (+7 kg for parachute)

Certification: CS 22, motorgliders

23-04-19 Linköpings universitetSid 26 ICAS 2010

ICAS 2010



Span (m) 11.7 16.4

A 15 15

S (m2) 9.1 17.9

Empty weight (kg) 101 189



MTOW (kg) 274 538

Max shaft power (kW) 12 25


Min. cruise speed (km/h) 84 84

(L/D)max 26 27

Endurance (h) 2.7 4.5 2.7 4.4

Climb rate (m/s) 2 1.8

Max cruise speed (km/h) 160 160




Span (m) 10.8 15.2

A 13 13

S (m2) 9 17.7


Battery weight (kg) 76 (Li-ion) 76(Li-S) 155 (Li-ion) 155 (Li-S)


MTOW (kg) 270 532




(L/D)max 28 30

Endurance (h) 2.9 4.5 2.9 4.4

Climb rate (m/s) 2.7 2.6

Max cruise speed (km/h) 160 160


Pros and cons

Battery powered aircraft are probably the easiest way to replace current combustion engine types (except for bio fuels)

Battery powered aircraft have power to spare, thus easier to fly, require ”normal skilled pilots”

Might be more interesting for the market since range of speed is greater

Big pro = existing infrastructure!

Limited use in terms of over the year useage

Batteries don´t work that good in a cold environment

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Fuel cell powered aircraft

Source of inspiration:

23-04-19 Linköpings universitetSid 32

DLR Antares

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Fuel cell powered aircraft compared to battery powered

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The DLR Antares is a derivative of an existing aircraft. It carries two external wing pods. One is the hydrogen tank the other is the fuel cell

In a blank paper design you would probably try to integrate the tank and fuel cell more

One big problem is to house the large pressurised tank (45 MPa), needs to be placed close to the C of G

Suggestion: place it in the main spar!

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The fuel cell powered aircraft concepts are based on the battery powered concepts previously shown

Same specification

Battery weight exchanged for fuel cell + tank weight

Only differrence is in endurance

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Span (m) 11.7 16.4

A 15 15

S (m2) 9.1 17.9


Battery weight (kg) 76 (Li-ion) (Fuel cell) 155 (Li-ion) (Fuel cell)


MTOW (kg) 274 538




(L/D)max 26 27

Endurance (h) 2.7 3.5 2.7 3.2

Climb rate (m/s) 2 1.8

Max. cruise speed (km/h) 160 160




Span (m) 10.8 15.2

A 13 13

S (m2) 9 17.7


Battery weight (kg) 76 (Li-ion) (Fuel cell) 155 (Li-ion) (Fuel cell)


MTOW (kg) 270 532




(L/D)max 28 30

Endurance (h) 2.9 3.5 2.9 3.2

Climb rate (m/s) 2.7 2.6

Max. cruise speed (km/h) 160 160


Pros and cons

Technology seems promising

Still in early development stage, not mature

Lack of infrastructure!!

Use is limited by the same reason as battery powered aircraft:

Gas performance degrade with lower temperature

ICAS 2010

How we prepared the study

We used an in-house design program, which we rearranged

The rearrangement included:

Adding solar power model

Adding electric motor model

Adding battery model

Adding fuel cell model

Rearranged weight equations in weight module

The electric motor model and weight equations were trimmed against published Solair 2 data

We benchmarked against existing aircraft in the category and found good relevence


Conclusions

This study has shown that it´s quite possible to design electric aircraft with different power sources, even using today´s technology

The ability to design light and with low drag is emphazised more than ever

”Green aircraft” won´t be any high speed machines

Live ”green”= eat ”slow food”

Fly ”green”= fly slowly

Will the market accept slow flight?

Personal view: the market might digest battery powered aircraft in the very near future, but the other variants will probably have to wait for a while

ICAS 2010

Questions?

ICAS 2010

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