Earth’s Horizontal Plane CG Root Wing Chord Relative Wind Flightpath Lift Drag Weight Thrust Resultant force Resultant force Thrust Angle of A $_{t}$tack Total thrust to climb Root Wing Chord Relative Wind Flightpath Component of weight  to oppose lift Lift Resultant force  required to lift weight Thrust required  to overcome component  of weight Excess Thrust (Total thrust  minus Drag) used to climb Angle of Attack CG Weight Figure 2-21. Typical forces in climbing flight. Figure 2-20.  Typical forces in level fl ight.  AOA is the primary control of increasing and decreasing  speeds, and increasing thrust generally does not produce  higher speeds, but additional thrust is required to maintain  level flight at higher speeds.  Ground effect is when the wing is flying close to the ground  and there is interference of the ground with the airfl ow  patterns created by the wing. At the same angle of attack,  lift increases slightly and the drag decreases signifi cantly.  The most apparent indication from ground effect is the  unexpected lift given to an aircraft as it flies close to the  ground—normally during takeoffs and landings. More details  for ground effect aerodynamics are found in the Pilot’s  Handbook of Aeronautical Knowledge. Flight characteristics  for ground effect are covered in the takeoff and landing  chapters. The CG is the theoretical point of concentrated weight of  the aircraft. It is the point within the WSC aircraft about  which all the moments trying to rotate it during fl ight are  balanced. The most obvious difference in the CG for a WSC  aircraft is the vertical position compared to an airplane, as  it is always lower than the wing. The Pilot’s Handbook of  Aeronautical Knowledge accurately states the CG is generally  in the vertical center of the fuselage. The same is true for the  WSC aircraft. However, the WSC wing is higher above the  fuselage/carriage and, since most of the weight is centered  in the carriage, the CG is well below the wing. In a two-seat WSC aircraft, the second seat is typically behind  the pilot’s seat and the CG is usually located close to the rear  passenger seat. Therefore, the CG location does not change  significantly with a passenger. Fuel tanks are typically located  near the vertical CG so any difference in fuel quantity does  not significantly change the CG fore and aft with different  fuel quantities. For level fl ight, the CG is directly below the wing/carriage  attachment point known as the hang point, and the propeller  thrust line is typically designed to be near the vertical position  of the CG.  [Figure 2-22]  Above the lowest total drag airspeed  [Figure 2-18],  faster  speeds (lower angles of attack) for level and climbing fl ight  requires greater thrust because of the increased drag created  from the faster speeds.  Thrust Required for Increases in Speed  Ground Effect  Center of Gravity (CG) 2-11