© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Aerodynamics Chapter 1 Forces Acting on an Airplane

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-1. Drag counteracted by thrust.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-2. The airplane is supported by the ground, and in the air by lift.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-3. The four main forces are in equilibrium during unaccelerated flight.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-4. Weight acts downward through the center of gravity (CG).

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-5. Airfoil shape.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-6. Left aileron.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-7. Vertical stabilizer and rudder.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-8. Wing flaps.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure 1-9. Laminar flow.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Turbulent flow.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Total reaction.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Pressure around an airfoil.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Dynamic pressure increases with airspeed.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Dynamic pressure is greater in dense air.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Airflow can lift a flat plate (but not efficiently).

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Examples of various airfoil shapes.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure A cambered airfoil with internal structure.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure More camber, more lift, less drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Mean camber line.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Camber.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Chord line.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The production of lift and drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The aerodynamic force acts through a point on the wing called the center of pressure.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Relative airflow (measured relative to the “free-stream” airflow).

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Same angle of attack, but different pitch attitudes.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Same pitch attitude, but different angles of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The angle-of-incidence is fixed during design and construction.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Coefficient of lift versus angle of attack; each angle of attack produces a particular C L value.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure A cambered and a symmetrical airfoil.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Lift curve for a symmetrical airfoil.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The size of the aerodynamic force and the CP position change at various angles of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The elevator keeps the attitude constant.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Contamination on the wings can seriously affect the lifting characteristics.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Low drag requires only low thrust to counteract it.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Skin friction and form drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure A stalled wing increases form drag substantially.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Streamlining, especially behind the shape, greatly reduces form drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Streamlining reduces form drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Ice accretion on the airframe will increase drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Parasite drag increases with airspeed.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Induced drag increases as angle of attack increases.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The production of lift creates wingtip vortices and induced drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Induced drag is greatest at low speeds and high angles of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure High aspect ratio.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Total drag versus airspeed.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Aspect ratio.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Minimum drag speed.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Coefficient of drag versus angle of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Design features that minimize induced drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure C L versus angle of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure C D versus angle of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Lift/drag ratio versus angle of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Same lift at a different cost in total drag.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Lift/drag ratio versus angle of attack.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Typical flap installation—a Cessna wing-flap system.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Same airspeed: increased camber and/or wing flaps give higher lift.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Flaps lower the stall speed (and nose attitude).

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Effect of flaps on lift/drag ratio.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Lowering the flaps can cause the airplane to balloon unless you simultaneously adjust the pitch attitude.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Extending the flaps may cause the nose to pitch.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure A Fowler flap.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Slats and slots delay the stall.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Propeller terminology.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The speed of the blade section depends on the radius and RPM.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Each propeller blade-section follows its own path.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The propeller blade angle is made progressively larger from tip to hub to provide efficient angles of attack along its full length.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Forces on a propeller blade.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Fixed-pitch propeller—the angle of attack varies with forward speed and RPM.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure A constant-speed propeller maintains an efficient angle of attack over a wide speed/RPM range.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Constant-speed propeller controls.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure An offset fin helps counteract propeller-slipstream effect.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure The down-going propeller blade produces more thrust when the airplane is in a nose-high attitude, causing P-factor.

© 2009 Aviation Supplies & Academics, Inc. All Rights Reserved. The Pilot’s Manual – Ground School Figure Questions 68 to 70.