# Remote Control Airplane Design

and Construction

June 16, 2015 Alfred A. Gates, Ph.D., P.E. Department of Engineering Central Connecticut State University

Alfred A. Gates, Ph.D.,P.E., © 1

## Remote Control Airplane Terminology

Conventional Remote Control Airplane

Alfred A. Gates, Ph.D.,P.E., © 2Alfred A. Gates, Ph.D.,P.E., © 3

# Remote Control Airplane Electronics

Radio Control Receiver RC Aircraft Servos

Motor Electronic Speed Controller (ESC)

Alfred A. Gates, Ph.D.,P.E., © 4 LoPo Battery

# Brushless Motors Basics

• Motor max current capability must be less than ESC 

# max current capability

• Motor max current capability must be less than max Lipo battery current discharge

• High KV rating = Low Torque and High RPM

– High speed flight, slow acceleration

– ( Use smaller diameter and pitch props)



## • Low KV rating = High Torque and Low RPM

– Low speed flight heavy lifting ( Muticopters )

– Higher acceleration

– (Use larger diameter and pitch props)

Alfred A. Gates, Ph.D.,P.E., © 5

# Brushless Motors Basics

• Motor efficiency: The percent efficiency goes 

# into power to the propeller. The remainder goes into generating heat.

• Example 85% efficiency, 85% power goes to 

# the propeller thrust, 15% power goes into generating heat. If the motor is large and the power demand is high the soldered wires could be melted.



# • Always go with high efficiency.

Alfred A. Gates, Ph.D.,P.E., © 6Max Current Draw From Motor < ESC and < Battery

Max current draw from motor is 20A

Max continuous current is 25A

Max continuous current 1.8A X 30C = 54A 950KV X 11.1V = 10545 RMP

Alfred A. Gates, Ph.D.,P.E., © 7

Acceptable/no firesNo load max RPM capability

11500KV X 3.7V /Cell (3S cells) = 127,650 RPM

Alfred A. Gates, Ph.D.,P.E., © 8 RPM Estimation From KV, Max RPM, Low Torque

Max no load RPM = motor KV rating X Voltage/cell X Number of cellsRPM Estimation from KV, High Torque

Alfred A. Gates, Ph.D.,P.E., © 9 360KV * 3.7V/Cell * 6S/Cell = 7,992 RPM Put a big propeller on this (15 inch)

Max thrust 2080 grams (4.6 Lb ) 14.7Amps, 6S Lipo Propeller size 15 inchesAlfred A. Gates, Ph.D.,P.E., © 10 • Max power 14.7 A X 3.7V/Cell * 6S/ Cell = 14.7A * 22.2V = 326.4W

• 326.4W X 6 motors in a Hexcopter = 1951 W ( 2.6 Hp )

• Flight time = (Battery amps pr hr )5000mah /(14.7A *6)* 60min/hr = 3.4 min

• Lifting capability = 2080g X 6 motors /454 g/Lb = 27Lb for 3.4 min

• 27 pounds for 3.4 min

# Lipo Batteries

• Must be charged with a Lipo charger.

• Min voltage must not go below 3.2V/ cell.

• ESC are programed to cut power to the motor at 3.2V/ cell.

• Must be disconnected from circuit when not used.



# • Must be stored in a cool place.

• The can be damaged due to freezing.

• They can explode if shorted out. They will definitely catch on fire

.

Alfred A. Gates, Ph.D.,P.E., © 11Alfred A. Gates, Ph.D.,P.E., © 12 

# Lipo BatteriesAlfred A. Gates, Ph.D.,P.E., © 13 1800 Mah X 1A/1000Ma X 11.1V = 20 Watt hr This battery can produce 20 Watts for 1 hr

C rating the battery can produce 30 times the amperage or power 30C X 1800Mah X 1A/1000Ma = 54 Amps

How long will this battery last at discharge rate of 54 Amps

(1800 Mah X1A/1000Ma) /54Amps = .033hr X 60min/hr = 2 min

3S battery pack (3 cells at 3.7Volts/ cell) = 11.1 volts

Power output for 2 min = 54Amps X 11.1 Volts = 599. Watts (.8hp)Alfred A. Gates, Ph.D.,P.E., © 14

ESC regulates the amperage/power being applied to the electric motor Controlled by the receiver.

This one can send 25Amps to motor at 4S X 3.7V = 370 Watts It says it can only send 250 Watts = .33 hp

746Watts = 1hp 

# Electronic Speed Controller

# Flying Wing

Pusher



# Canard

Elevons 

# RC Airplane Types

Alfred A. Gates, Ph.D.,P.E., © 15

# Starship Enterprise

Free Remote Control Airplane Plans http://www.rcfoam.com/stpg.php?page_id=free_rc_airplane_plans

Alfred A. Gates, Ph.D.,P.E., © 16Remote Control Airplanes with Elevons

Elevons replace elevator and aileron by electronic mixing

Alfred A. Gates, Ph.D.,P.E., © 17Location of motor

Elevator Rudder

Aileron

Cg CL Horizontal Stabilizer CL Wing 

# Canard

Alfred A. Gates, Ph.D.,P.E., © 18Additional Types of Planes

Alfred A. Gates, Ph.D.,P.E., © 19

# Rules of Thumb

• Center of lift (Center of Pressure, Aerodynamic Center): Point at which all of the lift force can be applied on an aircraft. Function of airfoil and geometry. [Fixed does not change]

• Center of gravity (Center of Mass): Point at which all of the weight 

### can be applied on an aircraft and it will balance. [Can be changed by moving battery]

• Center of gravity, Cg, behind center of lift, Cl, airplane can stall/ Spin and not recover. (Spin into the ground)

• Center of gravity, Cg, in front of center of lift, Cl, airplane will be controllable and can recover from stalls/spins.

• Center of gravity, Cg, too far in front of center of lift, Cl, airplane will nose dive. Elevator will not be able to cause a balancing moment.

• If the fin is too small for an airplane it will barrel roll in a turn and spin out of control with a Cg in front of the CL.

Alfred A. Gates, Ph.D.,P.E., © 20

# Cg Range For Controllability

Alfred A. Gates, Ph.D.,P.E., © 21 Center of lift does not change (function of geometry) Elevator
Max FWD position If further forward the elevator will not be able to lift the nose of the aircraft
up Max AFT position if further back, at slow speeds the aircraft will become uncontrollable and unable to regain control

# Terminology

Alfred A. Gates, Ph.D.,P.E., © 22Center of gravity, Cg, behind center of lift, Cl, airplane can stall/ spin and not recover.

Adjust Cg with battery position

Alfred A. Gates, Ph.D.,P.E., © 23 1⁄4 to 1/3 chord length back from leading edge

# Lift

• Increase in airspeed over top of wing creates a vacuum

• Decease in airspeed on bottom of wing creates 

# increase in pressure.

Alfred A. Gates, Ph.D.,P.E., © 24 Typically the body and wing creates lift. The front of the aircraft creates lift. The air will accelerate over the canopy reducing the pressure Top of wing must be smooth to prevent flow separation/ stall

# Wing Angle of Attack

Desired quality is a wing that can fly at a high angle of attack. Smoother wings can handle a higher angle of attack.

Alfred A. Gates, Ph.D.,P.E., © 25 • Increase angle of attack causes deflection of air and increase in vacuum.Sharpe edge will cause stall at a low angle of attack Rounded leading edge will cause stall at a higher angle of attack

Alfred A. Gates, Ph.D.,P.E., © 26

# Flat Plate

Round corners to increase stall angel of attack

Alfred A. Gates, Ph.D.,P.E., © 27 This type of wing is used for this week

# Rules of Thumb, Preflight Testing

First Test Flight

• Cg is in proper location. Check by balancing on fingers

• Motor thrust line is neutral. Check by holding airplane vertical and running 

### motor. Only should feel torque.

• Control surfaces move correct direction with motor off. Check by moving them.

• Control surfaces move aircraft is correct direction with motor on and holding aircraft. Check by holding airplane vertical and running motor and cycling control surfaces.



### • Servos motor, receiver, ESC and battery are secure and will not move.

• Aircraft glides nose down and does not settle

• Aircraft settling means it will stall

• Glide test 

# Demonstration

Alfred A. Gates, Ph.D.,P.E., © 28

# Rules of Thumb, Flight Testing

• Glide with no power (provided the aircraft is light 

# and the landing area is soft, tall grass is ideal)

– The aircraft should glide nose low



# • Glide at a low power setting straight and land

– Slight climb slight turns

– Check



# • Fly at altitude, 75ft, to check slow and normal 

# flight, stall, stall turns.

– Land and check electronics

Alfred A. Gates, Ph.D.,P.E., © 29

# Computing Cg of Design

Flying Wing CG calculator https://danielhubert.wordpress.com/rc

- project

- help/dollar

- wing /
Aircraft CG calculator http ://www.instructables.com/id/Introduction

- 65/step5/Find

- the

- Center

- of

- Gravity

CG

- with

- the

- Static

- Marg /

RC Foam Aircraft Plans http:// www.pic2fly.com/RC+Foam+Plans.html http:// betterfly.ca/RC_plan_F_pusher.html

Alfred A. Gates, Ph.D.,P.E., © 30

# Remote Control Airplanes VTOL

• Use foam building insulation, 1⁄4 to 3/8 inch TK



# • Flat plate design

• Types

– Flying wing

– Pusher

– Conventional

– Different

Alfred A. Gates, Ph.D.,P.E., © 31 Cg range was unknown so the gild test was used to determine the Cg

# Remote Control Airplane Building

• Monday design only, Tuesday design and cut 

# out on foam board.

• Cutting foam board with box cutter

• Control surfaces



# • Gluing on spars

• Music wires

• Servos



# • Cut foam board and glue on spars and body.

Alfred A. Gates, Ph.D.,P.E., © 32Draw Plans on 3/8 thick building insulation foam

Alfred A. Gates, Ph.D.,P.E., © 33

### Note: Balsa leading edge is 

### not required. Sand the foam leading edge. Sand Leading Edge

Alfred A. Gates, Ph.D.,P.E., © 34Cut out Rudder, servo holes, assembly slots, and make elevons out of balsawood

or foam balsawood is better. If you use the foam you can use strong duct tape as a hinge. Once side of the elevons and rudder must be sanded to a 45 degree angle so the surface can move in two directions.

Epoxy hinge tape Onto wing and elevon

Alfred A. Gates, Ph.D.,P.E., © 35Cut out wings and body

Better to glue balsa sheet as spar onto wing Sand Leading Edge

Alfred A. Gates, Ph.D.,P.E., © 36 Make the front and the rear of the balsawood smooth. Sharp edges will disrupt the air flow and decrease the critical angle of attack.Lipo Battery Servo Receiver (RX) Electronic Speed Controller (ESC) Motor

Alfred A. Gates, Ph.D.,P.E., © 37 Can use Velcro to secure ESC, Receiver and Battery to Aircraft Verify CG first with battery placementInstall control rods and foam supports

Bend music wire as control rods

Alfred A. Gates, Ph.D.,P.E., © 38

# Anything can Fly

• Need to have correct control surfaces and


# movement

• Need to have enough power

• Need to have acceptable Cg, Cl locations

Alfred A. Gates, Ph.D.,P.E., © 39

# Will It Fly

• Foam Missile



# • FWD Swept Wing

Alfred A. Gates, Ph.D.,P.E., © 40

All that is needed is:

• Cg is in the proper location

• Thrust line is on axis of aircraft

• Control surfaces move enough to direct pitch, roll and yaw

# Stall Speed Estimation

• Lift Force = Aircraft Weight



# • Lift = (1/2) Lift Coefficient X Air density Velocity 2 

# X Wing Area

Alfred A. Gates, Ph.D.,P.E., © 41http://en.wikipedia.org/wiki/Airfoil

Alfred A. Gates, Ph.D.,P.E., © 42 We are using a flat plate Cl approx. .6 to 1

# Stall Speed Estimation

• Air density at sea level = 1.29 Kg/m 3



# • Coefficient of lift, CL = .6 for a flat plate at 6

- 8 

# degrees angle of attach.

• V = Velocity airplane

• A = Perpendicular wing area

Alfred A. Gates, Ph.D.,P.E., © 43

# Stall Speed Estimation Example Solving for minimum airspeed to keep the aircraft in flight

WA: Wing area 36inch X 8inch = 288 in 2 = .1858 m 2 AD: Air density = 1.29 Kg/m 3 CL = .6 , flat plate at 6 to 8 degrees V: Stall speed, unknown

Wt: Aircraft weight = 300grams = .3 kg, .66Lb 1Lb = 454g

Lift = Weight = 1⁄2 CL (AD) (WA) V 2

Solve for minimum velocity

V =[ Wt *2/(CL (AD) WA) ] 1/2

V = [.3Kg * 9.81 m/s 2 *2/(.6*1.29 Kg/m^3*.1858m 2 )] 1/2 = 6.39 m/s = 21 ft/s = 14.53 MPH Vmin

Alfred A. Gates, Ph.D.,P.E., © 44

## Stall Speed Estimation Applied to a micro UAV

V min

Alfred A. Gates, Ph.D.,P.E., © 45 L Chttp://wright.nasa.gov/airplane/drageq.html Alfred A. Gates, Ph.D.,P.E., © 46 Parasitic Frontal area Angel of attackAlfred A. Gates, Ph.D.,P.E., © 47 Power is required to over come the total drag.

Example Dependent on airflow type Laminar or turbulent Form Drag coefficients for shapesAlfred A. Gates, Ph.D.,P.E., © 48 V = 14.5Mph

This example does not include calculating the propeller thrust force and efficiency

Best possible

t = 8.88W/ hr /34.1W * 60min Blockage Area Aircraft Body Aircraft Wing Surface area Due to wing angle of attackAlfred A. Gates, Ph.D.,P.E., © 49 V = 20Mph

This example does not include calculating the propeller thrust force and efficiency

Best possible

# Stall Speed Estimation Example Adding 100 grams of More B atteries

WA: Wing area 36inch X 8inch = 288 in 2 = .1858 m 2 AD: Air density = 1.29 Kg/m 3 CL = .6 , flat plate at 6 degrees V: Stall speed, unknown

Wt: Aircraft weight = 300grams + 100grams of more batteries = 100grams = .400 kg, .88Lb 1Lb = 454g

Lift = Weight = 1⁄2 CL (AD) (WA) V 2

Solve for minimum velocity (Stall)

V =[ Wt *2/(CL (AD) WA) ] 1/2 AD : Air density, WA: Wing Area

V = [.36Kg * 9.81 m/s 2 *2/(.6*1.29 Kg/m 3 *.1858m^2)] 1/2 = 6.39 m/s = 21 ft/s = 16.7 MPH Vmin

Alfred A. Gates, Ph.D.,P.E., © 50Alfred A. Gates, Ph.D.,P.E., © 51 V = 16.8 Mph Time = 30.5min for 3 batteries There will be a point at which the number of batteries will decrees the time of flight. Due to the drag At a higher velocity required to keep the aircraft aloft and motor required This example does not include calculating the propeller thrust force and efficiency

Best possible