University of California, Irvine – UCI Team Caddyshack

The UCI AIAA student chapter participates in the annual AIAA

Design Build Fly (DBF) competition.

This competition gives the engineering students a chance to apply

classroom knowledge, gain hands on skills, and experience an

industry level project-development from conceptual design to

building and testing an optimized final product.

Over the past 6 years this project has grown substantially in size

and skill with the help of previous DBF students, currently

working in the aerospace industry, who meeting with the current

team weekly.

Introduction

Team Organization

2011 Competition

Conceptual Design

Preliminary Design

Detailed Design

Manufacturing

Testing

Expected Final Performance

Aerodynamics: Computes flight characteristics and necessary wing

dimensions.

Propulsion: Analyzes propulsion system to find best motor, propeller and

battery combination.

Structures: Optimizes load-bearing components and maintains a weights

build-up of the aircraft.

Payload: Designs and manufactures steel payload and restraints for the

payload and aircraft.

Stability & Control: Ensures aircraft meets S&C standards and

works closely with aerodynamics to predict flight performance.

Competition consists of 3 missions:

◦ Mission 1: Complete as many laps as possible in a 4-minutes. time

frame (M1 = Nlaps/Nmax)

◦ Mission 2: 3 laps with a steel bar payload.

(M2 = 3x(Payload weight/Flight weight))

◦ Mission 3: 3 laps with

a team-selected

quantity of golf balls.

(M3 = 2x(Nballs/Nmax))

Constraints for 2011:

◦ Battery weight: ¾ lb

◦ 20 amp slow-blow fuse

◦ Aircraft must fit in a commercially-available carry-on suitcase.

◦ L + W + H = 45 inches (no dimension can exceed 22 in.)

◦ Suitcase must include entire flight system, including aircraft, battery and

all required parts and tools.

◦ Golf balls are regulation sized and the steel bar payload dimensions are

constrained: 3 in. width x 4 in. length minimum.

◦ Aircraft must be hand-launched.

Sensitivity Analysis

Configuration Figures of Merit

◦ Aircraft Configuration

Subsystems Selection

◦ Motor Position

◦ Landing Methods

◦ Yaw Control

◦ Wing Attachment Methods

◦ Payload Configuration

Final Configuration

The objective of this analysis is to identify the mission parameters

that have the largest impact on the score.

A maximum of 64 golf balls and 9 laps were the benchmark values,

determined using the data from past DBF competitions.

Thrust and drag models were used in a simulation program to

design hundreds of planes and perform this analysis.

Mission 1 favors a small plane and

payload with a large propulsion

system.

Missions 2 and 3 favor a large

plane with a high wing loading.

In order to select an aircraft configuration, a scoring system

based on figures of merit was produced. Each was weighted

based on results of the scoring analysis:

◦ System weight (35%)

◦ L/D (20%)

◦ Cargo space (15%)

◦ Maneuverability (10%)

◦ Manufacturing (10%)

◦ Hand launch (10%)

Mono Plane- (Conventional)

•Relatively easiest to design and build. Known

comparative values for performance.

•Relatively heavy configuration not optimized for

specific competition.

Flying Wing

•Efficient use of space. Lack of unnecessary

elements decreases weight. High L/D

•Significantly less stable and more difficult to

manufacture.

Delta Wing

•Fly at high angle of attack. Allow additional cargo

placed in wing.

•More unstable than a conventional and somewhat

more complex to design and manufacture.

Biplane

•Slightly more stable and higher structural strength.

•Much heavier and unnecessary additional elements.

FOMWeight

Conventional

AircraftFlying Wing Delta Wing Biplane

System Weight 35 0 2 1  -1

L/D 20 0 1 0 -1

Cargo Space 15 0 0   1 0

Stability 10 0 -2 -1 1 

Manufacturability 10 0 -1 -1 -1

Hand Launch 10 0 -1 0  -1

Total 100 0 50 30 -65

Final Decision: Flying Wing

Would be able to hold a maximum amount of cargo

using the lifting surface as the payload bay without a

significant drag penalty.

Tractor- Lightweight, higher efficiency and

less dangerous hand launch.

Pusher- greater lift due to lack of prop-

wash, limits the maximum amount of

sweep and a dangerous hand launch.

Double Tractor- Smaller propellers,

increased cargo space in center, less

dangerous hand launch, increased weight

and difficulty in locating the CG.

Push-Pull- Increased weight, limits

maximum sweep and provides a more

dangerous hand launch.

FOMWeight

Single

Tractor

Single

Pusher

Double

TractorPush-Pull

System Weight 45 0 0 -1 -1

Drag 20 0 1 -1 0

Hand Launch 15 0 -2 1 -2

Stability 10 0 -1 0 -1

Cargo Space 10 0 1 2 -1

Total 100 0 -10 -30 -95 

Belly Landing- Low weight, low drag,

would be difficult to hand launch and

vulnerable to fatigue.

Skid/ Handle- Improved hand launch,

increased structural support, potential

additional storage space and slight

increase in weight and drag.

Skid & Wire- Decreased stopping

distance, minor increase in weight and

increase in drag.

Tricycle- Reliable and high strength,

however significant increase in weight,

drag and difficulty of hand launch.

FOMWt

Belly

LandingHandle/ Skid

Skid and

Piano wireTricycle

System Weight 45 0 -1 -1 -2

Drag 20 0 0 -1  -2

Hand Launch 15 0 2 -1 -2 

Stability 10 0 0 1 2

Cargo Space 10 0 2 0 0

Total 100 0 5 -70 -140

Winglets- Reduced drag, light

weight and provides yaw stability.

Wingtip rudders- Increased pilot

control and increased weight.

Aft Vertical tail-Greater moment

to correct yaw and significant

increase in weight.

Split Flaps- Provides only a minor

increase in weight, complex and

difficult to implement correctly and

cause and increase in drag.

FOMWeight Winglets

Wingtip

Rudders

Aft Vertical

Tail

Split

Flaps

System

Weight45 0 -1 -2 -1

Drag 25 0 0 -1 0

Hand Launch 15 0 0 -1  0

Stability 15 0 1  2 0

Total 100 0 -30 -100 -45

Fully enclosed internal payload compartment- Less drag and a

lower weight. Requires a larger t/c airfoil or a larger aircraft.

Fuselage (BWB) style compartment- More efficient method of

cargo placement near the Center of Gravity, increased drag and

difficulty to manufacture.

SolidWorks: used to model aircraft prototypes and to help determine airfoil selection

XFOIL: Used to analyze possible airfoil choices for aerodynamic characteristics

Microsoft Excel: Used extensively for data analysis, storage and graphing

AVL: Used for flight-dynamic analysis and to ensure overall stability of the aircraft

MATLAB: Used to create an optimization program

The Aerodynamics team planned and organized the design process

into several design steps outlined in the flowing diagram.

A conceptual design is produced using the sensitivity analysis results.

A preliminary design is developed using the conceptual design results

and initial estimates.

An optimization program is developed in Matlab to model the

performance of a design for all of the missions.

Several iterations of optimizing, building and testing are done to produce

a high performance aircraft.

The mission profile was modeled using for loops and while loops in

MATLAB.

The aerodynamic and propulsion forces were computed for every

loop-iteration to determine the change in position and velocity of the

aircraft during that period of time.

The program assumed some initial conditions for takeoff such as hand

launch velocity and wind conditions.

The mission model program computes:

◦ the energy used

◦ the number of laps completed in 4 minutes

◦ The maximum payload capacity a design could carry.

The total flight score is computed for several designs which resulted in

an optimized design.

The majority of airfoils that were considered were the reflex type for our flying wing.

Studies were done using XFOIL and SolidWorks to determine which airfoil best

suited our needs.

Coefficient of moment vs. angle of attack NACA 4-digit symmetric series study

Wing loading was optimized

based on the total flight score

using our mission profile MATLAB

program.

The figure to the right shows a

plot of the total drag as a function

of the aspect ratio for mission

three during takeoff.

Battery Selection

Considered several different

battery types and the

capacity-to-weight ratios.

A mission profile was used

to determine an estimate of

the amount of energy

needed to complete each of

the missions. Motor Selection

Based on the battery and

the current limitation of

20A, the maximum power

the battery could supply to

the motor is 300 W.

Propeller Selection

Pitch-High pitch

performs better at high

speeds while low pitch

performs better at low

speeds.

Diameter- Larger

diameter= more thrust

and more power

required from motor.

o Mission 1: High pitch

small diameter.

o Missions 2 & 3: Lower

pitch and larger

diameter.

Battery Capacity mAh Ah / oz

Redicom500 1.56

Nimh700 1.75

Elite 15001500 1.92

Elite 17001700 1.7

Elite 20002000 1.72

Elite 22002200 1.44

Elite 33003300 1.71

Name Weight oz

Kv RPM/V

Max Current

Amp

Power W

Resistance

Ω

Hacker A30-14L

4.6 800 35 490 0.038Hacker A30-12L

4.6100

0 32 400 0.041Hacker A30-10L

4.8118

5 35 450 0.023Hacker

A30-8XL5.5

1100 35 600 0.015

The drag was computed using the equivalent flat plate area method.

The wing was optimized

for the cruise of mission

two and three.

Washout helped focus

the peak of the CL

distribution.

We calculated our MAC and

simulated our aircraft’s geometry

through AVL

The figure to the right shows the

resulting pole-zero map of the

eigenvalues calculated by the

program.

WINGLETS

An eignemode analysis made in AVL

showed that the flying wing was susceptible

to low Dutch roll damping.

Dutch roll was clearly visible during test

flights, but Pilot still maintained good control.

Sized for Dutch roll damping above 0.02.

Optimized Winglet Dimensions

Height c/4: 9.5 in

Sweep: 37 degrees

Distance behind LE: 6.0 in

Taper ratio: 0.7

We modeled the wing spar

as an I-beam.

Carbon strips were laid on

the top and bottom of the

wing with a 5/8” diameter

carbon rod running between

the strips to create our spar.

Testing later on showed that

the wing with two spars was

favored over the single spar.

In an effort to reduce weight, the motor mount, landing skids and launch

handle were combined into one carbon fiber structure that was integrated into

the center wing section.

This design proved to be very efficient in cargo space utilization.

The forward end is used as an electronics compartment to house the speed

controller and the fuse.

The skid and handle section was designed as a channel that was sized to fit

the propulsion battery pack.

We used molding methods investigated over summer to create our

center section.

A male and female mold were created using SolidWorks template

printouts and hotwire cut foam.

Foam wings were

created and hollowed

out using wooden

templates and a hotwire

as investigated over

summer.

Wings were then coated

with fiber glass and a

strip of carbon fiber for

strength.

Wingtip Testing

Propulsion Testing

Handle Design Tests

Flight Tests

Wing tip testing was used to confirm and validate wing-spar

calculations and our hollow core foam design.

Testing was performed

by securing the tips

of a wing and loading

it mid-span until

failure occurred.

Static thrust testing was conducted to measure the performance of various

propulsion systems.

Dynamic thrust testing was conducted using a load cell that was mounted to a

custom-designed sliding motor mount and was used to collect dynamic thrust

data during flight.

This data was used to accurately model the dynamic thrust in the mission

profile optimization program.

Fuse and battery testing were also conducted in the lab to determine the limits

and range of operation.

Different handle designs were

created and tested initially to

find which best suited the hand

launcher to give him control

and stability at take off.

The following are a combination of both

prototypes, and were used to calibrate the

preliminary design.

Takeoff speed: 30 ft/s

Max wing loading: 28 oz

Locating CG for stable flight: 15% static

margin

Dutch roll damping: Controllable

Lap time: 37 s

Prototype I

Prototype II

Prototype I

◦ Provided insight into launch and landing techniques.

◦ Provided data for the calibration of the wing loading.

Prototype II

◦ Improved stability.

◦ Increased payload space.

Maximum of 4 flight attempts allowed Mission One:

◦ 1st flight attempt: 6 laps in 4 minutes Late in the day

Mission Two:◦ 2nd flight attempt: fuse blew within seconds after hand

launch Noon, +90°F, No wind

◦ 3rd flight attempt: ran out of battery with one more turn left in the course Late in the day Very spectacular flight

◦ 4th flight attempt: Propulsion strategy gone amiss Noon, Even with a reduced payload, our plan to increase thrust on

the downwind blew the fuse.

The conditions surrounding the fuse in Tucson are very different than those in Irvine. The fuse will blow at a lower current in Tucson.

Flying later in the day helped with the above handicap, when it was cooler. In fact, heavy planes like those from Israel and MIT skipped their noon rotation and waited till the late afternoon to fly their airplanes (9 lbs!!).

Conduct propulsion tests and test flights with competition weather conditions in mind.