Multi-Disciplinary Senior Design Conference
Kate Gleason College of Engineering
Rochester Institute of Technology
Rochester, New York 14623
Project Number: 10232
UAV AIRFRAME C
PLATFORM FOR AERIAL IMAGING
Daniel Graves (ME) – Project Lead
Alex Funiciello (ME)
James Reepmeyer (ME) – Lead Engineer
Michael Hardbarger (ME)
Brian Smaszcz (ME)
ABSTRACT
Cd – coefficient of drag
Airframe C is a second generation large scale remotecontrol aircraft aimed at carrying a multi-spectral
imaging package. Airframe C’s goal is to carry a 15
pound package for a 20 minute flight. Building on
progress made by the Airframe B design team,
Airframe C proceeded with special focus on the wing
structure. After selecting a stronger wing structure
along with other design improvements Airframe C was
successfully completed and flown on April 29th, 2010.
Airframe C successfully took aerial pictures on May
7th, 2010 at North Hampton airfield. Due to weather
and time constraints neither the maximum flight time
nor the maximum payload could be tested directly;
however non-flight testing and simulations
demonstrate the ability for greater than 20 minute
flight duration and a maximum payload in excess of
15 minutes.
Chord – Length between the leading edge and the
trailing edge of the airfoil
Cl – coefficient of lift
Curb weight – the weight of the finished vehicle in its
fully assembled form including fuel, oil, etc, but not
including any cargo.
ESC – Electronic Speed Controller
FoilSim – Airfoil analysis software
ID – Internal Diameter
LiPo – Lithium Polymer Battery
NOMENCLATURE
MSD – Multiple Disciplinary Senior Design
AoA – angle of attack
NACA – National
Aeronautics
Aspect Ratio – The length of the wing in relation to
the chord
Advisory
Committee
for
OD – Outer Diameter
Prop-strike – When the propeller of an airplane strikes
the ground on takeoff or landing
CA – Cyanoacrylate (adhesive)
Camber – The asymmetry between the top curve and
bottom curve of the airfoil
RC – Radio Controlled
Copyright © 2010 Rochester Institute of Technology
RIT – Rochester Institute of Technology
Selig – A common airfoil standard
UBEC – Battery Elimination Circuit
attachment. It is believed that large wing deflections
inhibited control authority of the control surfaces,
limiting the pilot’s ability to fly the aircraft.
Xfoil - Airfoil analysis software
Analysis of the design and construction of Airframe C
confirmed these concerns regarding the wing. The
fiberglass antenna mast used as the main wing spar
was found to be insufficient for use as a structural
element. The wing box and mating surfaces between
the wing sections, constructed from balsa wood, were
found to be insufficient to handle flight loading.
Furthermore the body structure of Airframe B was
excessive, leading to increased aircraft weight and
additional strain on the wing.
INTRODUCTION
CUSTOMER SPECIFICATIONS
Airframe C is a second generation airframe developed
as part of the Open Architecture, Open Source
Unmanned Aerial Imaging Platform project; a 5 year
research program working towards the ultimate goal of
delivering an unmanned aerial imaging platform. The
end goal of this family of projects is to create an
airplane capable of fully autonomous flight. This
airplane will have the ability to carry a variety of
imaging packages as well as navigation, control, and
telemetry data. Potential applications of such aircraft
include thermal (infrared) imaging of forest fires to aid
in identifying hot spots, infrared imaging of nuclear
power plants to detect leaks or areas with insufficient
shielding, multi-spectral aerial surveying of both urban
and wild land environments, and aiding in search and
rescue operations. Infrared cameras, as well as multispectral imaging equipment are substantially heavier
and larger than standard imaging equipment. A
standard model airplane does not possess the payload
capabilities to support such imaging systems.
The primary goal of building this plane was to carry a
15 pound payload in stable flight. In order to provide
time to take pictures of a given target in multiple
passes as well as travel time to and from the target and
runway a target flight time of 20 minutes was set. In
order to trigger the camera it was necessary to have a
radio controlled interface with the payload of the
plane. Finally, Airframe C is meant to be an open
source, open architecture platform capable of carrying
and interfacing with current and future payloads
including a variety of cameras and telemetry packages.
Wing Root – The section of the wing which is joined
to the fuselage of the aircraft
Wingspan – Tip to tip distance off the wing
XFLR5 – Airfoil analysis software
The P10232 UAV Airframe C project continues the
efforts of P09232 UAV Airframe B MSD design team.
Airframe B was the first attempt at constructing and
testing a large scale airframe. Airframe C, like
Airframe B, focuses on the development of the
Aircraft itself, not the telemetry, control, or camera
packages associated with the aircraft.
PREVIOUS RESULTS
The P09232 team completed construction of UAV
Airframe B in the spring of the 2008-2009 academic
year. Airframe B had a 13 foot 3-piece wing and had
a curb weight of approximately 42 pounds. Airframe B
did not successfully complete its first flight; crashing
moments after it suffered from wing separation 18
seconds into the maiden voyage. There were many
factors attributing to the crash. The most significant
factors were related to concerns about the bending
moment of the wing, wing deflection, and wing
DESIGN
Wing Design
Airframe C’s wing design focused on overcoming the
issues associated with Airframe B’s design flaws. In
order to reduce the bending moment at the wing root
generated by lift, the design focused on reducing the
wingspan. In order to accomplish the reduction in
wingspan while maintaining the same amount of lift at
similar speeds a new airfoil shape was needed.
From research on model planes from sources such as
airfield models[1] and discussion with members of the
model airplane community including the Radio
Control Club of Rochester and the RIT Aero Club, it
was determined that an aspect ratio less than 8 is
preferred as enables sufficient space within the wing
for structural materials. An aspect ratio of 7.5 was
selected as a base point for further wing analysis.
Using FoilSim it was discovered that a highly
cambered airfoil was capable of meeting all the
desired design constraints. Several airfoils were
analyzed in XFLR5 and finally a NACA 9412 airfoil
was selected.
Proceedings of the Multi-Disciplinary Senior Design Conference
Page 3
Figure 1: NACA 9412 Profile
In comparison to the Selig 7055 airfoil used on
Airframe B, the new airfoil has more camber at 9%
with an under camber design instead of a flat bottom
airfoil. The camber on the NACA 9412 airfoil
generates more lift at a given angle of attack and speed
than the non-cambered Selig 7055 at the cost of
increased drag and pitching moment. Although the
new airfoil selection increases drag, it allows for a
decreased wing size. Airframe B’s wing measured 13
feet by 18 inches while the new airfoil selection
allowed the wing dimensions were reduced to 10feet
by 16 inches. This leads to a decreased aspect ratio
from 8.67 to 7.5. More importantly it was determined
that the bending moment at the wing root was reduced
from an average of 57 ft-lbf to 44 ft-lbf when
generating 40 lbs of lift.
While the wing root loading has been reduced there is
still a significant bending moment to account for. A
variety of materials were considered for use as wing
spars. Carbon Fiber Tubing was selected as the
material of choice for its strength per cross sectional
area as well as its strength per weight. For the main
spar, a Carbon Fiber tube with an 0.75” OD and
0.625” ID was chosen, with a supporting backspar of
0.575” OD and 0.5” ID. To assist in resisting the
deflection cause by flight loading, the wing was
sheeted with 1/32” balsa, then epoxied over with a
single fiberglass sheet.
Although the NACA 9412 airfoil creates more drag
than the Selig 7055 airfoil, the reduction in wing size
lead to an average drag increase of just 1 lbf at 40lbf of
lift.
The optimal cl/cd ratio is achieved at
approximately 41 mph. In order to cruise at this speed
it is necessary for the wing to be at approximately a 2
degree angle of attack. In order to provide the best
possible imaging platform the wing is placed on the
body of the plane at a 2 degree inclination to allow the
plane to cruise level.
Figure 2: Cl vs. AoA Comparison of Airfoils
Tail Design
The pitching moment generated by the cambered
airfoil is countered by using a negative lifting tail.
Although the tail’s airfoil is symmetrical (NACA
0408) and does not provide lift on its own the entire
tail has been placed at a negative 4 degree angle of
attack. Analysis of the wing and tail combination in
XFLR5 has determined that this angle yields a zero
pitching moment in flight.
Using the following equations found in Raymer’s
Aircraft Design: A Conceptual Approach
𝑐𝑉𝑇 ∗ 𝑏𝑊 ∗ 𝑆𝑊
𝑆𝑉𝑇 =
𝐿𝑉𝑇
𝑐𝐻𝑇 ∗ 𝐶𝑊 ∗ 𝑆𝑊
𝑆𝐻𝑇 =
𝐿𝐻𝑇
where Cvt is the vertical tail chord, bw is the wing span,
Svt is vertical tail area, Lvt is the length form ¼ chord
to the vertical tail, Cht is the chord of the horizontal
tail, Sw is the wing area, Lht is the length from the ¼
chord to the horizontal tail; it was determined that the
horizontal tail surface of 2.222 feet2 and a vertical tail
surface of 1.333 feet2 were desired. A horizontal tail
length of 4 feet was selected semi-arbitrarily (partially
due to aesthetic concerns) which meant the chord
would be 7.5 inches to achieve the desired area.
Similarly the vertical tail was chosen to be a 16 by 16
inch triangle with a 4 by 16 inch rudder.
Figure 3: XFLR 5 Analysis of Plane Body/Wing
Copyright © 2010 Rochester Institute of Technology
Control Surfaces
Utilizing industry standards from Raymer the aileron,
elevator, and rudder surface areas were calculated.
The rudder was chosen to be 40% of the vertical tail
chord, or 3.2 inches, and spans the entire height of the
vertical tail. Ailerons were designed to be 50% the
length of the wingspan, and thus were designed to be
2.5 inches long. On the horizontal tail it was
determined that the elevator would have a chord of
3.375 inches and span 3.6 feet (90% of the tail span).
Analysis of the control surfaces in XFLR5 verified the
elevators maintained control authority of the aircraft in
the presence of the pitching moment created by the
wing. At lower speeds the elevators are capable of
overcoming the pitching moment at ½ their maximum
travel, ensuring that there remains more travel for
increased lift. Finally it was confirmed through a
static analysis that standard servos would have
sufficient torque to maintain control authority over
control surfaces.
Propulsion and Electronics
The UAV Airframe B team completed a propulsion
assessment while designing Airframe B and concluded
that for their flight time of 1 hour an electric
propulsion system was infeasible. For airframe C the
target flight time was reduced to 20 minutes which is
achievable utilizing an electric propulsion system.
Electric propulsion systems offer many benefits over
fuel based propulsion systems including significantly
reduced vibrations, and increased reliability. In order
to verify the validity of the electronic propulsion
system it was first necessary to assess the size of the
motor required. Using a model aircraft rule of thumb
it was determined that an airplane requires 50 watts
per pound minimum in order to take off. It is further
recommended that 75 watts per pound be available to
provide the plane with ‘trainer like performance’. For
a target aircraft gross weight of 40 pounds it was
determined that the a minimum of 2000 watts were
necessary for take-off and 3000 watts would be
preferred for ‘trainer-like’ performance.
A simplified take off model was created in Simulink.
The model accounts for increases in drag due to air
resistance and rolling resistance. Air drag was
approximated from data obtained from XFLR5.
Rolling resistance was obtained experimentally by
mounting the landing gear to a board, attaching
weights, and recording the force required to pull the
assembly through a grass field. The thrust developed
by the motor was calculated using the equation
𝑚𝑜𝑡𝑜𝑟 𝑝𝑜𝑤𝑒𝑟 ∗ 𝑝𝑟𝑜𝑝𝑒𝑙𝑙𝑒𝑟 𝑒𝑓𝑓𝑖𝑐𝑒𝑛𝑐𝑦
𝑇ℎ𝑟𝑢𝑠𝑡 =
𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
It is important to note that this equation does not hold
for near zero velocities. Therefore a saturation limit
was used on the motor torque output. This saturation
limit was estimated for initial testing.
It was
determined using the model that a static thrust limit of
20 pounds would be sufficient to ensure takeoff.
Testing has since proven our propulsion system
capable of producing 26 pounds of static thrust.
After takeoff the model assumed an 8 degree climb
angle from the ground to a cruising altitude of 1000
feet. In the simplified version of the model it assumed
the motor would be pulling its maximum current for
the entire takeoff and climb procedure.
Power draw at cruise was estimated using the
equations
𝑤𝑒𝑖𝑔ℎ𝑡
𝑑𝑟𝑎𝑔 =
𝑐𝑙/𝑐𝑑
𝑑𝑟𝑎𝑔 ∗ 𝑠𝑝𝑒𝑒𝑑 ∗ 1/𝑒𝑓𝑓𝑖𝑐𝑒𝑛𝑐𝑦
𝑖=
𝑠𝑦𝑠𝑡𝑒𝑚 𝑣𝑜𝑙𝑡𝑎𝑔𝑒
By then multiplying the current draw by time the total
power requirement can be computed.
Through
experimentation with the model it was determined that
10000 mAh of battery power would be necessary to
meet the flight time requirement.
With this power requirement in mind batteries were
selected. Lithium Polymer (or LiPo) batteries were
chosen for their capacity to rate ratio and affordability.
It was decided that the plane would fly using a
combination of 4 batteries (2 in series, 2 pairs in
parallel). The batteries used are Zippy Flightmax 5s
15c 5000mAh batteries. Each battery would provide
18.5 volts at a continuous discharge rate of 75 amps.
After selecting the batteries a motor in the given
power range was identified. A Turnigy Aerodrive XP
Sk seris 63-74 Brushless motor was paired with a
Turnigy Sentilion 100A HV 5-12s BESC speed
controller. A Turnigy 5-7A HV UBEC for LiPo was
purchased in place of a receiver battery to save weight.
The servos controlling the ailerons, elevators, and
rudder are Futaba s3004 servos. These were selected
for their price and availability. The receiver and
transmitter were re-used from Airframe B. The radio
is a 6 channel digital proportional system. Since 5
channels are necessary for the ailerons, flaps, elevator,
throttle, and rudder there is a remaining channel that
can be used to interface with on board payload.
Proceedings of the Multi-Disciplinary Senior Design Conference
Page 5
to aiding manufacturing this modular design offers
break away points in case of a crash. Rather than
having the plane suffer from catastrophic damage
upon impact the aircraft body will separate, containing
the damage into more easily repairable sections. The
cost of this modularity is a decrease in overall plane
structural rigidity, which was deemed to be an
acceptable design consideration.
Figure 4: Propulsion System on Test Stand
Airframe Design
The goal of designing Airframe C’s main structure
was to reduce the weight of the main airframe
configuration without sacrificing the structure’s
rigidity and resistance to impact. The majority of the
research completed for this aspect of the project was
done while auditing a test run class for model plane
building, taught by an RIT Aero Club member and
Mechanical Engineering graduate student, Shawn
O’Neil. Through the analysis of construction
procedures, review of different model plane structures,
and taking the advice of club members we began the
process of modeling what would be our open
architecture airframe. The entire structure was
designed to be able to fit together like a large 3D jig
saw puzzle, as well as be modular to allow for
multiple stage construction. The airframe modules
consist of: the front battery bay module, the landing
gear box module, the camera bay/wing box attachment
module, and the tail section.
The main structure of the airframe was created from
.25” (.233” actual) Baltic Birch plywood which was
laser cut by Foxlite Inc. The Baltic Birch ply created
the main skeleton of the airframe which was then
connected together by Balsa wood stringers. The tail
of the airframe, which consists of nothing but
consecutive Baltic Birch bulkheads connected by
stringers, was constructed per the CAD model
dimensions using a precision fixture. The fixture held
the bulk head to bulk head distance while the center
line of each bulk head was aligned by sight. Once
positioned correctly in the mold, the stringers were
added and glued in place using CA adhesive. The
battery bay, landing gear box, camera bay, and tail
were all constructed separately and then joined
together once the entire structure was ready to be
assembled.
RESULTS AND DISCUSSION
While Airframe C was under construction the
electronic and propulsion sub-systems were analyzed
on a test stand. The propulsion system was found to
deliver a peak static thrust of roughly 26 pounds. The
selected batteries were proven capable of delivering
full throttle power to the motor for approximately 10
minutes when under static loading. This test data was
then used to update the model parameters and it was
concluded that the propulsion system would provide
sufficient power for takeoff and the batteries would
provide sufficient power for the flight duration.
Assembly of Airframe C was completed on Saturday,
April 24th 2010 with initial aircraft testing that
afternoon. Several successful attempts at taxing the
aircraft around a grass airfield were performed to
gather data on ground testing. After several common
ground maneuvers such as S-Bends and 180° turns as
well as straight line taxi attempts, it was determined
that the airframe had sufficient ground control and was
ready for skip testing.
Figure 5: CAD Model Assembly
The design started with the main focus of the camera
holding bay and wing mount system and was modeled
outward from there. Each module was connected to
one the adjacent module by mating the stringers into
the bulkhead of the adjoining bulkheads. In addition
Three skip tests (low power, low altitude flight) were
performed that afternoon into a slight headwind of 5
MPH. On the first attempt, the plane was throttled up
until both wheels left the ground, but significant roll
was observed. A second skip test was executed where
the plane taxied straight and level until it briefly lifted
Copyright © 2010 Rochester Institute of Technology
from the ground. On the attempt, the plane flew
straight and level until the engine throttle was cut and
the aircraft descended back onto the field. A third and
final skip test was attempted; however a strong gust of
wind occurred immediately prior to takeoff, resulting
in the plane gaining approximately 10 feet in altitude.
Initially the engine throttle was cut in an attempt to
force the plane into a glide back to the ground. On
approach, the wing tip stalled out creating a right roll
moment on the aircraft which was corrected by
throttling the motor and introducing aileron. Control
was restored to the aircraft once the motor was
reengaged and the aircraft landed on the field. Upon
review, it was determined that during normal fullthrottle take-off, wing stall would be avoided and the
gain in attitude would provide sufficient time to
correct and control the aircraft during gusting winds.
creating excess lift. On the third landing attempt, the
aircraft was brought down at a more aggressive angle
to reduce the lift and put the plane onto the landing
strip. While descending at a negative angle-of-attack, a
strong gust of wind struck the top surface of the wing,
forcing the plane into the ground rapidly. The nose of
the aircraft and landing gear impacted the ground and
caused the fuselage to separate into three pieces. The
propeller, motor mount, and battery bay of the
fuselage were damaged beyond repair. The landing
gear mounting bay, wing, wing box, and tail section
incurred only minor damage from the incident. A
detailed incident report is also available on the P10232
EDGE website.
Figure 7: Moment of Impact During First Landing
Figure 6: Initial Flight During Skip Test
On Thursday, April 29th 2010, Airframe C was taken
out to the Hasman Airfield in Spencerport, NY for full
flight testing. The aircraft was assembled on-site and
ready to fly in approximately fifteen minutes. At 9:30
am, the controls were turned over to Trevor Ewell and
the decision was made to begin flight trials in a 10
MPH head wind. After taxi testing on the airfield, the
tail servo malfunctioned resulting in loss of ground
maneuverability. The cause for this was later
determined to be gear jamming in the servo, most
likely cause from the stress fracture of an internal gear.
The tail wheel was fixed into position, and flight
testing continued. After two attempted skip flights
which were hampered by prevailing crosswinds, it was
determined that the best course of action was to
throttle the airplane to full and attempt a full take-off.
On take-off, the airplane was throttled to full and left
the runway after approximately 15 feet of foreward
travel. Ewell brought the plane to flight altitude and
proceeded to make several circuits around the airfield
while trimming the aircraft. After about five minutes
of flight, the aircraft was brought down to make
landing passes. The first two passes were aborted by
the pilot due to the gusty conditions which were
The aircraft was returned to full flight capability as of
May 6th, 2010. The battery box was re-ordered from
Foxlite and over-nighted. A new propeller, balsa
wood stringers, and landing gear servo were purchased
locally and installed. As per the test pilot’s request the
control surfaces were re-trimmed to suit his
preferences.
Figure 8: Airframe C in Flight
On May 7th 2010 Airframe C was once again turned
over to Trevor Ewell, this time at North Hampton
Airfield in Spencerport, NY. After the plane was
assembled and a camera system mounted, a successful
flight of approximately 4 minutes and 30 seconds was
completed at approximately 10am that morning. This
Proceedings of the Multi-Disciplinary Senior Design Conference
time the landing was smooth and no damage was done
to the plane. Unfortunately the on-board camera
malfunctioned and failed to capture any images during
the flight. After addressing the issues with the camera
payload the plane was sent out for a second flight.
This flight had a smooth takeoff and successfully
captured several images while in flight. While landing
the aircraft was running out of runway and the pilot
was forced to make a more aggressive landing,
resulting in a prop strike. Upon inspection there was
no disruption to the payload and the majority of the
aircraft was untouched. There was minimal damage to
the front of the battery box where the motor mount
connected to the airframe, however this damage was
minimal and the bulkhead can be repaired instead of
being replaced.
Page 7
Acknowledgments
P10232 would like to thank; Michael Koelemay along
with Impact Technologies LLC for their support and
sponsorship of the project. Dr. Jason Kolodziej and
Philip Bryan for their guidance throughout the span of
the project. Shawn O’Neil and the RIT Aero Club for
advice and assistance on the aircraft design. Joe
Pinzone and P10236 team for their DAQ device and
help with motor testing. Our test pilot Trevor Ewell
for flying our airframe and design suggestions. The
Radio Control Club of Rochester for allowing us use
of their private airfield, as well as their
encouragement, and advice. Jim Capuano for
recording the flight videos, as well as posting them for
viewing. Fox Lite, inc. for laser cutting our parts. Eric
Irish, Elyssa Raspaut, and Tristram Coffin for taking
some excellent pictures.
Figure 9: Aerial Image of P10232 Team
REFERENCES
[1] Johnson, P. K., 2002, Airfield Models, April 30,
http://airfieldmodels.com/
[2] Raymer, D. P., 2006, Aircraft Design: A
Conceptual Approach, American Institute of
Aeronautics and Astronautics.
[3] Reyes, C., 2009, Rcadvisor's Model Aircraft
Design Made Easy, RCadvisor.com.
[4] Schleicher, R., 2005, "How to Build and Fly
Electric Model Aircraft," MBI Publishing Company,
St. Paul, Minnesota.
[5] Theunissen, D., 2010, Fly Electric, April 30,
http://www.flyelectric.ukgateway.net/
[6] Weiss, M., Flutter,
http://www.giantscaleplanes.com/flutter.htm
Copyright © 2010 Rochester Institute of Technology