Representing Aircraft Control Surface Deflection

1. Representing Aircraft Control Surface Deflection John Ratzenberger Eastern Carolina Plastic Modelers New Bern, NC www.ecpmod.com

2. Purpose • Over a period of years, I have seen models exhibiting outstanding technical workmanship, but basic aeronautical flaws. Likewise, I have talked with outstanding modelers who have some incorrect perceptions of real aircraft and flight. So, I thought I'd try to put something together that might be helpful. • We will discuss how to accurately model the movement/deflection of aircraft controls and control surfaces. While much of this will focus on an aircraft on the ground, it will also cover how to represent simple maneuvers in flight. At the end, attendees should understand the basic aircraft controls, the placement of the corresponding control surfaces, certain "usual" configurations, and where to go look for further information. • While useful to all aircraft modelers, it is oriented toward the "prop" modeler, not jet or helicopter modelers. It will not go into actually hacking the plastic, but it may save someone from having to correct a mistake..

3. Why Bother ? • Kit Option ... • Aftermarket ... • More natural look ... • Jazz it up a bit ... • Fanatic over the subject ... • Show off modeling skill ... Don’t Waste the Effort !!! Larger scales make it more important.

4. Aircraft Nomenclature - Side View Ailerons Rudder Vert. Stab./Fin Wing Trim Tab (Horiz.) Stabilizer Elevator Rudder Bar/Pedals Control Stick/Yoke

5. Aircraft Nomenclature - Top View Rudder Bar/Pedals Control Stick/Yoke Flaps Ailerons Vert. Stab./Fin (Horiz.) Stabilizer Trim Tab Elevator Rudder

6. Aircraft Nomenclature - Back View (Horiz.) Stabilizer Rudder Elevator Vert. Stab./Fin Control Stick/Yoke Ailerons Flaps Rudder Bar/Pedals

7. Stick & Elevator • Stick/Yoke Forward • Elevator goes Down • Tail gains lift • Tail goes Up • so Nose Pitches Down Control Pitch around the Lateral Axis of the airplane. • Stick/Yoke Back • Elevator goes Up • Tail looses lift • Tail goes Down, • so Nose Pitches Up

8. Rudder Pedals/Bar & Rudder • Pedals/Bar push with Left Foot • Rudder goes Left • Tail swings Right • Nose Yaws Left Control Yaw around the Vertical Axis of the airplane. • Pedals/Bar push with Right Foot • Rudder goes Right • Tail swings Left • Nose Yaws Right

9. Stick & Ailerons Control Roll around the Longitudinal Axis of the airplane. • Stick/Yoke Left • Left Aileron Up • Left Wing looses lift. • Right Aileron Down • Right Wing gains lift. • Aircraft will Bank Left • & thus Turn Left • Stick/Yoke Right • Right Aileron Up • Right Wing looses lift. • Left Aileron Down • Left Wing gains lift. • Aircraft will Bank Right • & thus Turn Right

10. A Coordinated Turn • Stick/Yoke Left • Left Aileron Up, Left Wing looses lift. • Right Aileron Down, Right Wing gains lift. • Aircraft will Bank Left & thus Turn Left. • Increased lift on Right Wing causes Increased Drag. • Increased Drag pulls nose to right (Adverse Yaw) ***. • So, a little Left Rudder to compensate. • And a little up elevator to hold the nose level. *** Differential and Frise ailerons will reduce Adverse Yaw.

11. Control Surfaces at Rest & Play • Ailerons: • Being equal & opposite, will tend to a neutral position. • One Up, the other Down, never both up or both down. • Up / Down may not be same amount (Differential, Frise) • Spitfire: Up 26deg, Down 19deg • Wildcat: Up 19deg, Down 15deg • Frise • Neutral • Up • Down

12. Control Surfaces at Rest & Play • Elevator: • Hinge is forward & weight is back, so will tend to down position. • Rudder: • Where left; if wind blown or moved, will tend to original position. • Nose Wheel, Tail Wheel/Skid & Rudder • Fixed • Free • Tied to rudder • Free - Tied - Locked. • Float/Sea Planes -- water rudder !! • Pilots park “square”, especially nose gear ... • General: • Stay in the 10-20deg range, avoid extremes.

13. Flaps • Flaps: • Allow low-speed operation and control. • Shorten take-off distance. • Increase lift, increase drag. • Four Basic Types of Flap: • Plain • Split • Slotted • Fowler

14. Flaps In General • On the Ground: • Usually UP ... • May bleed down from hydraulics. • Plain Flap might be down to prevent walking on. • Take-Off: • Obstacle clearance, short or soft-field takeoff. • If used, then relatively small amount - no more than 1/2. • Landing: • “Always” • “Full” or nearly so, depending on conditions. • Usually one of 1st things done upon landing is Flaps UP. • Prevent damage from prop-blown debris • Eliminate cross/tail wind effects while taxiing.

15. Flap Examples • F4U-1 Corsair • Take-Off: 20deg • Landing: 30deg (Field), 50deg (Carrier) • F6F Hellcat • Take-Off: “As Required” • Landing: Down • P-47 Thunderbolt • Take-Off: Up (but “1/2 may improve take-off”) • Landing: Down • P-51 Mustang • Take-Off: Up • Landing: Full Down • P-40 Warhawk • Take-Off: As Required, “never more than 1/2” • Landing: Down

16. Trim Tabs Trim tabs relieve the need for the pilot to maintain constant pressure on the flight controls. Trim tabs “fly” the trailing edge of the control surface, so they will be opposite direction. On the ground, the above may not hold. Two Types: -- Manually adjusted on ground -- Adjustable in flight May have one of each or have both on a flying surface.

17. Trim Tabs Fixed Adjustablein Flight

18. Trim Tab Examples • F4U-1 Corsair, on Take-Off • Rudder Tab -- set 6deg Nose Right • Aileron Tab -- set 6deg Right Wing Down • Elevator Tab -- set 1deg Nose Up • F6F Hellcat, on Take-Off • Rudder Tab -- two marks, Nose Right • Elevator & Aileron -- Neutral • P-47 • Rudder Tab -- T.O. position is to right. • Elevator & Aileron - Neutral • P-40 • All Tabs -- Neutral

19. Influences on “Natural” • Cable • Jackscrews • Hydraulic • Electric • Friction • Pivot Point • Balance • Locks

20. Cessna 172 - What’s “natural”?

21. Cessna 172 - What’s “natural”? Parked, with control lock in, as per the Checklist. Ailerons neutral, slight down elevator, rudder free.

22. References • Pilot’s Manuals • Photos • Books • www.abebooks.com

23. End Questions ? Discussion ? Suggestions ?