https://pdfs.semanticscholar.org/54ec/8bdc1bf0d2d59d4555ca9f02b0bf6d67e9c9.pdf
https://www.fzt.haw-hamburg.de/pers/Scholz/HOOU/AircraftDesign_9_EmpennageGeneralDesign.pdf

Basics of RC Model Aircraft Design by Andy Lennon

Aircraft Design Conceptual Approach by Raymer

Initial Design Guidelines

Aileron

• 35 - 40% of semi-wing span

• Width typically 15-25% of the wing chord

Elevator & Rudder

• Generally begin at the side of the fuselage and extend to the tip or 90% of the tail span

• Width is typically 25 - 50% of the tail chord

• Control surfaces are usually tapered by same ratio as the wing or tail surface

• For the elevator

  • hinge line perpendicular to fuselage centerline for manually-controlled aircraft

  • allows connecting left and right elevators

Mass Balancing

• mass balancing required to greatly reduce fluttering tendencies of control surfaces about their hinge

• balance weight should be located as far forward as possible to minimize weight

  • may be mounted to the boom attached to control surface

Aerodynamic balance

• portion of the control surface in-front of the hinge line as shown below

  • lessens the force required to deflect the surface & reduces flutter tendencies

• Notched balance not recommended for high-speed flight

• Hinge axis SHOULD NOT be farther than ~20% of the avg chord of the control surface

Aileron Design

Sources: Chapter 12. Desig of Control Surfaces (Aileron).pdf (us.es)

Key design parameters for an aileron:

• Aileron planform area (S_a)

• Aileron chord/span ratio (C_a/C_b)

• Maximum up and down deflection (delta_A)

• Location of inner edge of aileron along the wing span (b_ai)

Typical values:

Sa/S = 0.05 - 0.1, ba/b = 0.2-0.3, C_a/C = 0.15 - 0.25, b_ai/b = 0.6-0.8, delta_Amax = +/- 30 deg

Important aspects of aileron design:

• Aerodynamic moments about the aileron hinge that must be overcome, same as hinge moments

• Aileron effectiveness depends on how well the aileron deflection can produce the desired rolling moment

• Easier to use the rear wing spar as the hinge

Summary of steps:

1. Layout design requirements:

   1. Roll control requirements, critical flight phase for roll control, research standards i.e. time required for aircraft to roll from initial bank angle to a specific angle

   2. Select inboard and outboard positions of the aileron. Determine b_ai/b, b_ao/b, and C_a/C.

   3. Determine aileron effectiveness parameter tau_a.

   4. Determine I_xx (moment of inertia about the roll axis, estimate since not everything is finalized)

2. Performing calculations:

   1. Calculate aileron rolling moment coefficient derivative (C_l-delta-A). Use the following equation:

      

      1. C_r = root chord. yo = outboard distance from fuselage, yi = inboard distance from fuselage, S = wing planform area, b = wing span

      2. C_L_alpha_w = wing sectional lift curve slope - assumed to be in the constant region, therefore, the aileron sectional lift curve slope is also the same…

   2. Select maximum aileron deflection (delta_Amax). Typ +/- 25 degrees.

   3. Calculate rolling moment coefficient (C_l) when aileron is deflected with max. deflection using

      

   4. Calculate aircraft rolling moment (L_A) for maximum aileron deflection using

      

   5. Determine steady-state roll rate (P_ss) using

      

   6. Calculate the bank angle at which aircraft achieves steady state roll rate.

      

   7. Calculate the rate of change of roll rate (before steady state is reached)

      

   8. If phi_1 > phi_req (aka the total desired bank angle) determine time to reach phi_req using the formula

      

      1. If phi_1 < phi_req (most likely not the case for general aviation and transport), use

         

   9. Compare t_2 with t_req. Minimum difference must not exceed 10%. If this isn’t the case, choose different aileron params and repeat the calculations.

Working on a matlab calculator for this because excel will be a pain.