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1
Design of a Light Sport Aircraft
Marc LeRoy
Dominic Contenza
Nathan Butt
Submitted to: Dr. Marquart
5/2/2014
2
Table of Contents
1. Introduction pg. 3
2. Design Description pg. 4
3. Conclusion pg. 8
4. NACA 8-H-12 Airfoil Polars pg. 9
5. Engine Selection Chart pg. 12
6. EES Programs pg.13
7. References pg. 15
8. Parameter Calculations
Lift Analysis pg. 16
Thrust Analysis pg. 18
Turning Analysis pg. 19
Rate of Climb/Ceiling Analysis pg. 20
Landing/Takeoff Distance Analysis pg. 21
Fuel Weight/Range Analysis pg. 23
9. Preliminary Aircraft Drawings pg. 24
10. Project Description Handout pg. 27
3
Introduction
The purpose of this report is to communicate an idea for a design of an LSA (light
sport aircraft). An LSA is a category of aircraft described by the FFA as a simple to
operate, easy to fly aircraft that follows certain specifications. For example, a few
constraints include a maximum weight of 1,320 lbs, a maximum speed of 138 mph, a
maximum stall speed of 51 mph, and maximum service ceiling of 10,000 feet. Other
constraints exist as well like fixed landing gear, a single reciprocating engine, a fixed
or ground adjustable propeller, and an unpressurized cabin. An LSA must be
designed so the average person can own an aircraft and enjoy flying. This means the
price of the aircraft cannot be astronomical, and the aircraft itself must have very
easy controls and be very stable in the air. In an ideal situation, an LSA should have
the capacity for a pilot and a passenger. The plane can be sold to a much larger
market if it can carry two people. This is an important design point for this project.
In the following sections, design parameters are summarized, assumptions are
stated, and justification for these assumptions and design decisions are explained.
4
Design Description
This section contains the details of the preliminary design. The configurations and
parameters of the aircraft design are laid out in the following table:
Table 1: Aircraft parameters (all performance values @ sealevel)
Engine Direction tractor, propeller in noseWing low placement, dihedral of 3 degrees, straight with a
slight taper, chord at fuselage = 6 ft, chord at wing tip = 4 ft, NACA 8-H-12 airfoil, s = 125 ft2, wingspan = 25 ft. (tip
to tip is 30 ft. including the 5 ft. width of the fuselage
Fuselage Single boom with a width of 5 ft. at its widest part, needs to be this wide to accommodate 2 people sitting side by
side, 18.5 ft. in length, a bubble canopy for good visibility
Tail T-tail configuration, top of tail is 8.5 ft. off the ground
Landing Gear tricycle arrangement
Powerplant Information Engine model – Rotax 503 UL, rated at 50 hp, propeller efficiency = 85%, thrust = 266 lbs, max range of 1,580
miles on 30 gallons of fuel
Weight Max takeoff weight = 1215 lbs, 360 lbs, for 2 people, 182 lbs for fuel, 673 lbs. max weight for empty aircraft
Wing Loading 1215/125 = 9.72 lbs/ft2
Thrust to Weight Ratio 266/1215 = 0.219
Max Rate of Climb 13.7 ft/sec
Stall Speed 39 mph
Max Speed 300 mph
Takeoff/Landing distance
577 ft./1,140 ft.
Service/Absolute Ceiling
60,000 ft./63,200 ft.
Min Turn Radius 126 ft.
Max Turn Rate 36.9 degrees/sec.
The calculations for these values are shown in the Parameter Calculations Section.
5
Aircraft Configuration
An LSA needs to be a very stable aircraft. A low placed wing with a slight dihedral of
3 degrees will help provide this stability. A straight wing will provide the maximum
lift, and slight taper will help to decrease the wing drag. The NACA 8-H-12 is a high
lift airfoil, normally used for helicopter rotary blades. The polar graphs for this
airfoil are shown in the Airfoil Polar Graph section. However, it can be used for an
aircraft wing as well. The high lift capabilities make it ideal for an LSA as the higher
lift can help reduce the stall speed of the aircraft. A planform area of 125 ft2 will
help with lift as well. The fuel will be held in two 15-gallon tanks, one in each of the
wings. Single Slot flaps on the wing will help to give the CLmax of 2 required for
takeoff and landing. These flaps also help to achieve the 39 mph stall speed. A T-tail
was chosen strictly for aesthetics purposes. It is just as effective as a normal tail
configuration. A single boom fuselage is the simplest type of fuselage, and simplicity
is important for an LSA. The tricycle landing gear will provide easy maneuvering on
the ground. Also, tricycle landing gears are safer and easier overall for novice pilots
to work with. It should be noted that in this analysis of this aircraft design, the drag
polar used (aka the CD,0 and k values) was that of just the wing of the aircraft, not the
entire aircraft.
Powerplant Information
The engine chosen for this plane is a Rotax 503 UL, with a rated maximum
horsepower output of 50 hp. An estimated propeller efficiency of 85% is used to
find the thrust available for the engine. This thrust available was used in all
subsequent calculations.
6
Weight
In these initial design stages, the goal for maximum weight fully loaded is 1,215 lbs.
The two passengers are 360 lbs, and the fuel weight is 182 lbs. This leaves the
aircraft to weigh up to 673 lbs. This is reasonable when compared to other
successful LSA designs. The design should not be up to the limit of 1,320 lbs.
because then the passengers could bring some baggage (extra weight) with them
(another selling point of this design).
Rate of Climb
The rate of climb value of 13.7 ft/sec is reasonable for a preliminary design. Again,
the assumptions made with the drag polar effect the accuracy of this value. The
actual rate of climb for a given velocity can also be found in the rate of climb
analysis in the Parameter Calculation Section.
Max Speed/ Stall Speed
According to the max velocity analysis, the max speed for the design is 440 ft/sec
(300 mph). This is high for an LSA as the max speed allowed for an LSA is 138 mph.
Even thought the value is rather high, it is not unreasonable. Using the drag polar for
the entire aircraft would give a more accurate approximation of this max speed
value. For a first shot at design, this is an acceptable value, which will surely
decrease as the design progresses and become more accurate to the real thing. A
stall speed of 39 mph is well below the maximum stall speed of 51 mph. This is
excellent for the beginner pilots who want to learn to fly.
Takeoff/Landing Distance
The calculated takeoff and landing distance are found using a CLmax of 2. The
distances given in Table 1 are similar to that of other successful LSA designs. The
extensive calculations, again, are shown in the Parameter Calculations Section.
7
Service/Absolute Ceiling
These calculated values are very high, too high in fact for an LSA. One explanation
for this error is the drag polar. Since it was only of the wing, technically it doesn’t
truly represent the aircraft. An LSA has a maximum altitude of 10,000 ft. This design
must be trimmed so the aircraft has a maximum altitude of around 10,000 ft.
Developing a drag polar for the entire aircraft would give more accurate CD,0 and k
values, which would allow for a more accurate calculation of the real service and
absolute ceilings for this design.
Min Turn Radius/Max Turn Rate
The value for minimum turn radius is a relatively small, but within reason. In reality,
the real turning radius might be 1.5 – 2 times larger than the calculated. The value
for Max Turn rate, 36.9 degrees/sec. seems to be very large. Normally, aircraft do
“rate” turns. For example, a Standard Rate turn is turning at a rate of 3 degree/sec.
Some low speed aircraft (an LSA is considered a low speed aircraft) can perform a 2
Rate Turn, or 6 degrees/sec. Again, using a drag polar of the entire aircraft would
give a more accurate Max Turn Rate value.
8
Conclusion
The proposed design meets most the requirements for an LSA. For example, the
weight estimate is well within the required specifications and the engine is of the
correct type. There is no limit on the power output of the engine, just that it must be
single reciprocating. The 50 horsepower engine chosen for this design is small,
lightweight, and costs around $5,000. This is great when it comes to selling the
plane because it can be sold at a lower price. The stall speed requirement is fulfilled,
and landing and takeoff distances are normal compared to other successful LSA. The
rate of climb at sea level for this design, 13.7 ft/sec, is reasonable for an LSA.
It is very important to note that the drag polar used in all the calculations was for
the wing of the aircraft alone, not the entire aircraft. This is going to cause some
discrepancies in the parameters as they will differ from what they would actually be
if the aircraft drag polar was found and used. The service and absolute ceilings are
very high for an LSA. Since an LSA can only go to 10,000 ft. max, the performance
will have to be restricted in some manner. The drag polar for the aircraft would help
with this, but it would probably need to be trimmed back in other design ways as
well. The max speed of 300 mph is excessive as the max speed for an LSA is 138
mph. However, this could be trimmed back to make the max speed of the design
within range of LSA specifications.
With some refining, this design could easily produce a successful LSA. The
inexpensive engine in the design helps greatly to save on cost, and the two-
passenger capability is a great selling point for the design. The design could easily
be made so all parameters are within the LSA specifications. The low wing will give
better stability, and the bubble canopy will allow a better all-around view for the
pilot and passenger.
9
Airfoil Polars for NACA 8-H-12 Airfoil
-The curves are from a Reynolds number of 1,000,000.
10
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12
Engine Selection Sheet
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EES Code and Plots
Rate of Climb vs. Elevation - plot and code
0 10000 20000 30000 40000 50000 60000 700000
2
4
6
8
10
12
14
16
h (ft)
RC
max
(ft/s
)
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Maximum Velocity – Plot and Code
15
References
1. J. Marquart, Final Aircraft Design Project Handout, Ohio Northern University,
2014.
2. Anderson, John D. Aircraft Performance and Design. 1st ed. McGraw-Hill
Companies, 1999. Print.
3. Airfoil Tools, “NACA 8-H-12 airfoil,” http://airfoiltools.com/airfoil/details?
airfoil=n8h12-il, April 2014.
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