This document outlines a project to design a radio controlled model airplane to set a new FAI world endurance record for electric powered airplanes. The key objectives are to exceed the current record of 12 hours and 36 minutes while meeting FAI requirements. The document discusses the physics challenges, potential design approaches for the airplane and propulsion systems, and the importance of design trade studies and testing to optimize endurance. It provides initial estimates for wing area, aspect ratio, weight distribution and performance predictions to guide the design process.

1. Aero Project 2010
Design a FAI World Record Setting Electric Powered Radio
Controlled Model Airplane
•Project design requirements, objectives and criteria
•FAI Requirements and criteria
•Physics of challenge
•Design approaches ~ airplane
•Design approaches ~ propulsion
•Design trade studies
•Program Schedule
Current Record; 12 h 36 min 46 sec
Date of flight: 30/07/2008

2. Project design requirements, objectives and criteria
• Set World Endurance Record
– Recognized by FAI
– Just/vastly exceeding current record
• Other Objectives and Criteria
– Use commercial parts;
• Motors
• Batteries
• Propellers
• Flight controls etc.
– Transportable in?
– Weather conditions
– Location of attempt
– Level of autonomy / telemetry
– Ease of construction / skill / tools / materials
– Durability;
• Number of flights anticipated
• Number of attempts (set up and tear down)
– Cost
– Schedule
– ?

3. Physics of Problem
Speed Lift
Thrust Drag
Weight

4. Physics of Flight
Induced Drag Di
Lift L
• Other Vorticity
Profile Drag = ½ ρ . V2 Sw. CDO
Lift, L = ½ ρ. V2 S. CL. e Drag D = Profile Drag + Induced Drag
Ideal Power Required L/D
HP = T x V / 550 Flight Speed V plus induced speed vi
Flight Speed V plus induced speed 2vi
Flight Fuel
Speed V
Horse
Weight
Thrust Power
of fuel
.
Mass Flow Rate m
Propeller Weight of
Disk area A engine and
Efficiency ηp propeller
Weight = Structure, controls + L/G
Propulsion .
Thrust T = m . 2 vi
Fixed Useful Load
Fuel Power Required = T . (V+ vi)
Payload 550 . ηp

5. Flight Conditions for Maximum Endurance and Maximum Range
at Fixed Weight
ED
UIR
R EQ
ER
MINIMUM
POW
POWER,
MAXIMUM
Power ENDURANCE
Required
Drag
0
0

6. Gliding Flight Lift
Speed
Rate
Of Descent Drag
is D/L
Glide Slope
Weight

7. Aerodynamic Trades

8. Reynolds Number Issues
with Aspect Ratio

9. The Endurance Potential for Electric Airplane
Lift, L = ½ ρ. V2 S. CL. e = W
V= √ {W /(½ ρ. S. CL. e)} = K. √ {W/S}
For a given airplane size and aerodynamics;
V = K1 . √W
For fixed airplane aerodynamics
V = K1 . √{We + Wb} the L/D at Vbe is aproximately constant
with variation in gross weight*
Power = V . Drag/550 = V . (W/L/D)/550
Drag = W/(L/D) = K. W = K2 . {We + Wb}
So Power = K3 . {We + Wb}1.5
Endurance = K4. {Wb . Kb}/Power Endurance Potential with Battery Fraction
1.000
Endurance = K5. Wb / {We + Wb}1.5
0.800
Endurance
Max endurance occurs with Wb = 2 x We 0.600
0.400
But What should the size 0.200
and weight be? 0.000
0 0.5 1 1.5 2 2.5
Battery Weight/Weight Empty

10. Model Design Parameters
FAI REQUIREMENTS
•Wing Area
•Wing Aspect Ratio •Max weight 5Kg
•Wing airfoil (flaps?) •Max wing + tail surface
•Tail volume area 1.5 sq M
•Control surfaces
•Empty Weight (All Up Weight less Batteries)
•Motor/gearbox/propeller
•Maximum speed
•Maneuver envelope
•Drag enhancement / rate of descent
•Maneuver capability
•Maximum rate of climb
•Minimum rate of climb
•Visible altitude
•Transport dimensions
•Wing construction
•Tail construction
•Fuselage construction

11. Size and Weight Factors
Aerodynamics (Reynolds Number) Size Weight (speed)
Wing Loading (power required)
Structural weight ~ Size
Wing aspect ratio ~ aerodynamics ~ Structural weight
Weather ~ wind capability ? aspect ratio (structure)
Transportability ?
Visibility in thermals ~ size aspect ratio
Possible answer;
Max size max weight A/R 10;
Wing span 145 in mean chord 14.5 in, w/s 12 oz/sq ft.
Empty weight 58 oz Battery weight 117 oz
L/D max ~ 17

12. Approximate Performance for Guessed Design Solution
Power Required at 70% overall propulsive efficiency
Possible answer;
•Max size max weight A/R 10; 160
•Wing span 145 in 140
•Mean chord 14.5 in,
120
•w/s 12 oz/sq ft.
Power ~ watts
•Empty weight 58 oz 100
•Battery weight 117 oz 80
•L/D max ~ 17 60
40
20
Cruise power required ~ 35 watts 0
0 10 20 30 40 50 60
Speed ~ fps
Battery energy using current LiPo
technology at ~ 4.5 watt hours / oz and 116
ounces weight; 520 W hrs.
Approximate endurance ~ 15 hours vice
current record of 12 h 36 min
Design Space for optimization
•Improved L/D
•Improved propulsive efficiency
•Reduced wing loading
•Increased battery specific energy

13. Design Space Possible Solutions ~ L/D and W/S
30
Baseline Guessed Answer
Minimu Power Required @ 100%
25
L/D
20
15
efficiency
20
15
25
30
10
5
0
6 7 8 9 10 11 12
Wing Loading ~ oz/sq ft.
Airspeed at CL and Wing Loading at CL = 1.0
35
30
25
Airspeed ~ fps
20
15
10
5
0
4 5 6 7 8 9 10 11 12
Wing Loading ~ oz / sq ft

14. Comprehensive Performance Math Model

15. Math Model Validation ~ Motocalc
Big Stardust / Aveox
450.0
400.0
Initial Climb to 400 meters (1320 ft or 1/4 mile) in 64 seconds
350.0
300.0
Descent from 400 meters 600 seconds (ten minutes)
Altitude Meters
250.0
Second Climb to ensure sufficient battery energy
for the SAM 90 seconds climb
200.0
150.0
100.0
50.0
Dive down to end flight
0.0
0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0
Time seconds

16. Weight and Balance
Model 108 inch Stardust Special Texaco
CG inches 7.31
Chord 11.3 * from LE CG % 0.65
Target CG Location 7.375 Weight 63.2
Wing Loading 7.9
Weight at 8 oz 63.9
Weight Location* Moment Comments
Airframe From LMR
Fuselage (aveox) pushrods servos 22 5.5 121.00
less motor @ 13.5 -13.5 0
Fairings 4 7
Wing 15 4 60.00
Empenage 3 41 123.00
L/G 3 2.25 6.75
Structure 0.00
W heels 0.00
Airframe Sub total. 33.5
Propulsion Texaco 0.00
Motor/ Gearboxes 4 -2 -8.00 Hacker B20-36 with 4.4:1 and 2:1 in series
Nose Weight 3.5 7 24.50
Prop 2 -3 -6.00 Aeronaut 20 x 11
Spinner 1 -5.00
Motor mount 0.00
Allowable 14 cells 1500 AUL cells in 2 x 7
Power Battery 15 7 105.00 Batt W t. 15.80 parallel.
Propulsion wiring 1 -1 -1.00
ESC 0 0 0.00
0 -2 0.00
Propulsion Sub total. 25.5
Systems 0.00 From LMR
Radio Rx 4.2 10 42.00 FMA M5
0.00 2 cell LiPoly
0.00
0.00
0.00
0.00 2 x HS 85?
0.00
Servo Mounting 0.00
0.00
Systems Sub total. 4.2
Ballast 0 0 0.00
Total Weight 63.2 63.2 462.25
CG inches 7.31
CG % 0.65

17. Weight Trends
1000
Wing Weight ~ grams
Two-Piece Wing Trend
y = 0.013x1.5011
100
``````````````````````````````````````````````````````````````
One-Piece Wing Trend
y = 0.0076x1.5482
10
100 1000 10000
Wing Area ~ sq inches

18. Wing Design and Optimization
Design Space
•Aspect Ratio
•Airfoil
•Maneuver envelope
•Strength
•Flutter
•Control authority
•Flutter
•Flight modes
•Climb
•Cruise
•Dive out of thermals
•Construction and materials
•Experience
•Tooling
•Transportation

19. Advanced Wing Design
The Swiss solar powered aircraft
'Solar Impulse' (HB-SIA prototype)
flies for the first time with test pilot
Markus Scherdel on board at the
military airport in Payerne,
Switzerland, Wednesday, April 7,
2010. The prototype with the
wingspan of a Boeing 747 and the
weight of a small car started to a
two-hour test flight to examine if
the plane can keep a straight
trajectory.
Minimize wing bending moments by distributing propulsion and batteries span-wise

20. Build and Fly
See how it is done; www.dhaerotech.com/giantblog.htm