RC Aircraft Design

Our team designed a small-scale remote-controlled aircraft to fly at least one, single-lap empty flight and to complete at least one, single-lap flight while carrying a payload of twelve golf balls. Due to the importance of ease of manufacturing and the expectation of a rough dirt field, the aircraft was a conventional, high-winged, single nose motor, taildragger design. The fuselage was primarily constructed from wood and the wing and stabilizers were cut out from high-density foam. A removable cargo pod was implemented to enable an empty flight by shifting the center of gravity using the battery.

Key Design and Performance Parameters

Mission Requirements and Profile

  • Take off, fly a lap, land safely

  • Perform 3 flights:

    • Empty flight without golf ball payload

    • Half of max payload flight (6 golf balls)

    • Max payload flight (12 golf balls)

  • High crashworthiness/repairability

Configuration

  • Propeller: APC 9 x 7.5-E

    • Selected APC 9 x 7.5-E due to greater pitch which generates more thrust at higher speeds

    • J ≃ .4

  • Fuselage: Built-up wooden Frame

  • Wing: Foam

    • High wing attached to fuselage using bolted on, 3D-printed wing mount

  • Tail Stabilizer: Foam

    • Directly attached to fuselage frame

  • Payload: Removable container

    • Removable container holding golf balls placed into fuselage cavity beneath the main wing

  • Landing Gear: Tail dragger design

    • Easier to link steering via rudder

    • Greater prop clearance

APC 9 x 7.5-E at 9000 RPM

Airfoil Selection

  • Selected NACA 6412

    • High efficiency at realistic speeds

    • Thickness at trailing edge will not be a problem

NACA 6412

Wing and tail configuration

Wing:

  • MAC = 15 cm

  • b = 79 cm

  • S = 1200cm2

  • AR = 5.20

  • λ = 1.0

  • Λ = 0°

Horizontal Tail:

  • MAC = 9 cm

  • b = 30 cm

  • S = 280 cm2

  • AR = 3.33

  • λ = 1.0

  • Λ = 0°

Vertical Tail:

  • MAC = 9 cm

  • b = 30 cm

  • S = 140 cm2

  • AR = 6.67

  • λ = 1.0

  • Λ = 0°

Drag Buildup

The resulting parasitic drag coefficient was calculated to be 0.0305

Detail Design

Final CAD Model

Final Assembly - front

Final Assembly - back

Wiring Diagram

Assembly Weight Components

Flight Test Results

  • Successful takeoff

    • Rough runway did not present issues with prop clearance or small ailwheel

  • Max speed of 28 m/s reached

    • On par with predicted 29 m/s

  • Altitude of 63 m reached

  • Nose-first crash landing

    • Broken propeller

    • Snapped wing at root

  • Successes

    • Nylon breakaway bolts in main landing gear sheared, protecting fuselage from critical loads due to crash

    • Built-up, wooden fuselage remained intact

    • Breakaway motor mount protected motor from damage

    • Pilot had throttle to spare during empty flight

      • 70% power reached 28 m/s

  • Failures

    • Undersized elevator was susceptible to overspeed effects resulting in a loss of pitch authority

    • Too much flaperon authority

Post Test Flight Redesigns

  • Horizontal stabilizer

    • increase span by 4 inches

    • Increase chord length by 2.25 inches

    • Increase elevator chord length by 0.5 inches

    • Use separate foam pieces instead of one continuous stabilizer

      • One servo per side instead of continuous, underside linkage

  • Vertical stabilizer

    • Increase span by 2 inches to match horizontal stabilizer resizing

  • Main wing

    • Increase main wing chord length by 1.25 inches

    • Same flaperon chord length as previous wing design