A Pilots Primer on Aerodynamics Maj William J

A Pilot’s Primer on Aerodynamics Maj William J. Doyle, Jr. Pennsylvania Wing / Group 3 G 1000 Project Officer Check Pilot / Instructor-Pilot CFI A&I, AGI, IGI, FAAST Rep

Aerodynamics Lesson Plan • What is an Airplane and What Makes It Fly • The Airplane • Flight Controls • Axes of Rotation • Forces Acting on the Airplane in Flight • Dynamics of the Airplane in Flight • Ground Effect • How Airplanes Turn • Torque (Left-Turning Tendency) • Airplane Stability • Stalls and Spins

How Do the Flight Controls Work? • Push the stick (or yoke) forward and the houses get bigger. • Pull the stick (or yoke) back and the houses get smaller. • Hold the stick (or yoke) back too long and the houses get really small then they get bigger again. (You just did a loop. )

How Do the Flight Controls Work? • Push the stick (or yoke) forward and the houses get bigger. • Pull the stick (or yoke) back and the houses get smaller. • Hold the stick (or yoke) back too long and the houses get really small then they get bigger again. (You just did a loop. )

Parts of An Airplane

Airplane Components

Airplane Components - Fuselage · Open truss - · clearly visible struts and wire braces Stressed skins - monocoque · - skin supports all loads semi-monocoque · sub-structure riveted to skin to maintain shape and increase strength

Airplane Stressed-Skin Types

Airplane Truss-Type Fuselage Structure

Airplane Components - Wings · Monoplane - · Biplane - · single set of wings two sets of wings Ailerons - move in opposite directions for turns controls roll (or bank) controlled by yoke or stick · · · right pressure turns right left pressure turns left Flaps - extend downward to increase lifting force for landings and sometimes takeoffs controlled by flap handle or switch · pre-selected positions or variable positions

Airplane Wings: Monoplane vs. Biplane

Airplane Wing Components

Airplane Components - Empennage · Vertical Stabilizer and Horizontal Stabilizer · help steady airplane for straight flight Rudder controls yaw - controlled by floor pedals · · · Elevator (stabilator on Cherokee) controls pitch - controlled by yoke or stick · · · right pressure moves nose to right left pressure moves nose to left forward pressure lowers nose back pressure raises nose Trim Tab helps hold pitch attitude - controlled by trim wheel · · move wheel forward for nose down trim move wheel back for nose up trim

Airplane Empennage

Airplane Components - Landing Gear · Gear Types - · Landing Gear Struts - · Fixed Gear Retractable Gear Tricycle Gear Conventional Gear (tail dragger) Spring steel struts bungee cord struts oleo struts shock disks Brakes - Disc brakes Differential braking

Airplane Landing Gear

Airplane Components - Powerplant · Engine - · Firewall - · provides power to turn propeller distinguishes airplane from glider separates cockpit from engine mounting point for engine Propeller - translates engine rotational force into forward-acting force called thrust

Airplane Powerplant

Wing Planforms Aspect Ratio = Wing Span ÷ Average Chord

What Makes an Airplane Fly? • For an airplane to takeoff, thrust must overcome drag and lift must overcome gravity (sometimes called weight) • So is there relevancy here to what you study in school? – Applicable Subject in School = Science – High School Course = Physics (study the chapter on Bernoulli’s Law)

What Makes an Airplane Fly? • The laws of physics apply to everything. • They apply to F-16 fighters and to the USAF Thunderbirds.

What Makes an Airplane Fly? • The laws of physics apply to everything. • They apply to ultra lights.

What Makes an Airplane Fly? • The laws of physics apply to everything. • They even applied to the Wright Brothers in the Wright Flyer at Kitty Hawk, NC.

Four Forces of Flight Vector

Four Forces of Flight · Lift - · Weight - · downward force of gravity Thrust - · upward force from airflow over and under wing forward force propelling airplane through air Drag - rearward force retarding force limiting speed

Four Forces of Flight

Newton’s Laws of Force and Motion · Newton’s First Law - · Newton’s Second Law - · A body at rest tends to remain at rest, and a body in motion tends to remain moving at the same speed and in the same direction. When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force. Newton’s Third Law - For every action there is an equal and opposite reaction.

Bernoulli’s Principle • Explains how the pressure of a moving fluid (liquid or gas) varies with its speed of motion. • States that as the velocity of a moving fluid (liquid or gas) increases, the pressure within the fluid decreases. • Explains what happens to air passing over the curved top of the airplane wing.

Bernoulli’s Principle - 1 of 3

Bernoulli’s Principle - 2 of 3

Bernoulli’s Principle - 3 of 3

In-Flight Application of Bernoulli

Illustration of Vectors and Resultant Vectors

Types of Air Foils

Components of an Airfoil • • • Airfoil: a structure designed to obtain reaction upon its surface from the air through which it mo Camber: curvatures of the upper and lower surfaces of the airfoil. The camber of the u Chord Line: a straight line drawn through the profile connecting the extremities of the leading Mean Camber Line: reference line drawn from the leading edge to the trailing edge, eq Leading Edge faces forward in flight and is rounded. Trailing Edge faces aft in flight and is narrow and tapered.

Relationship of Flight Path to Relative Wind

Angle of Attack Examples

Angle of Attack Examples

Angle of Attack and Wing Stalls Air circulation around an airfoil occurs when the front stagnation point is below the leading edge and the aft stagnation point is beyond the trailing edge.

Effect of Wingtip Twist Wingtip Wing Root

Effect of Stall Strip Wingtip Wing Root

Flaps Increase Both Lift and Drag

Types of Flaps and Leading Edge Devices

Types of Drag · Parasite Drag - Caused by any aircraft surface which deflects or interferes with smooth airflow around airplane Form drag · - Interference drag · - occurs when varied currents of air over an airplane meet and interact Skin friction drag · · results from turbulent wake caused by the separation of airflow from the surface of the structure caused by roughness of the airplane’s surfaces Induced Drag - Generated by the airflow circulation around the wing as it creates lift

Examples of Drag

Examples of Reducing Drag

Total Drag and L/Dmax Ratio

Ground Effect · · · Result of earth’s surface altering the airflow patterns around the airplane. Occurs within one wingspan above the ground. When in ground effect - Induced drag decreases and excess speed in the flare may cause floating. Airplane may become airborne before it reaches its recommended takeoff speed.

Three Axes of Flight

Longitudinal Stability and Balance · Longitudinal Stability - · Center of Pressure - · Pitching motion or tendency of airplane to move about its lateral axis. Determined by the location of the center of gravity in relation to the center of pressure Point along wing chord where lift is considered to be concentrated. Sometimes called the center of lift Center of Gravity - Determined by the distribution of weight, either by design or by the pilot. Can affect longitudinal stability.

Center of Pressure

Three Axes of Flight Center of Gravity (CG)

CG Range - Forward CG & Aft CG

CG Range - Forward CG & Aft CG

Longitudinal Stability • Quality that makes an aircraft stable about its lateral axis. • Involves the pitching motion as the aircraft’s nose moves up and down in flight. – A longitudinally unstable aircraft has a tendency to dive or climb progressively into a very steep dive or climb, or even a stall. – An aircraft with longitudinal instability becomes difficult and sometimes dangerous to fly. • Static longitudinal stability or instability in an aircraft, is dependent upon three factors: – Location of the wing with respect to the CG – Location of the horizontal tail surfaces with respect to the CG – Area or size of the tail surfaces

Longitudinal Stability

Horizontal Stabilizer and Tail Down Force

Static Stability • Initial tendency, or direction of movement, back to equilibrium. – Refers to the aircraft’s initial response when disturbed from a given angle of attack (AOA), slip, or bank. • Positive static stability – the initial tendency of the aircraft to return to the original state of equilibrium after being disturbed • Neutral static stability – initial tendency of the aircraft to remain in a new condition after its equilibrium has been disturbed • Negative static stability – initial tendency of the aircraft to continue away from the original state of equilibrium after being disturbed

Static Stability

Dynamic Stability • Dynamic stability refers to the aircraft response over time when disturbed from a given angle of attack (AOA), slip, or bank. It has three subtypes: • Positive dynamic stability – over time, the motion of the displaced object decreases in amplitude and, because it is positive, the object displaced returns toward the equilibrium state. • Neutral dynamic stability – once displaced, the displaced object neither decreases nor increases in amplitude. A worn automobile shock absorber exhibits this tendency. • Negative dynamic stability – over time, the motion of the displaced object increases and becomes more divergent.

Dynamic Stability

Horizontal Stabilizer and Tail Down Force Center of Lift Center of Gravity

Directional Stability · Directional Stability - Stability about the airplane’s vertical axis. Steadying influence of the vertical stabilizer. · · Acts like a weather vane. Interaction of Directional Stability with Lateral Stability - Dutch Roll · · - Combination of rolling / yawing oscillations caused by control inputs or wind gusts. Dihedral (lateral stability) more powerful than directional stability. Spiral Instability · Directional stability more powerful than lateral stability.

Lateral Stability · Lateral Stability - · Stability about the airplane’s longitudinal axis (nose to tail). Tendency to resist lateral roll. Dihedral - Common design approach to build in lateral stability. Upward angle of the wings with respect to the horizontal. Less dihedral in high wing airplanes than in low wing aircraft. · · Cessna 172 versus Mooney M 20 J Keel Effect - Steadying influence of side area of the fuselage and the vertical stabilizer.

Illustration of Dihedral

Illustration of Dihedral

Airspeed Indicator (ASI) and V-speeds · V-speeds - Vx = best angle * Vy = best rate * Va = maneuvering * Vfe = flap extend Vs = stall clean configuration Vso = stall landing configuration - Vno = max structural cruising speed - Vne = never exceed speed * not on ASI - • Arcs - white · · - green · · - bottom = Vs top = Vno yellow · · - bottom = Vso top = Vfe bottom = Vno top = Vne red line = Vne

Airspeed Indicator (ASI)

Types of Airspeed · Indicated Airspeed (IAS) - · Calibrated Airspeed (CAS) - · Corrected for instrument and installation errors True Airspeed (TAS) - · Speed indicated on ASI Uncorrected for instrument and installation errors No variations in air density CAS corrected for · altitude · nonstandard temperature Groundspeed (GS) - Speed over the ground - TAS adjusted for wind

Types of Stalls · Proficiency Stalls (Student Mastery) - · Demonstration Stalls (CFI Demonstration) - · Power-off stalls: landing conditions & configuration Power-on stalls: take-off conditions & configuration Secondary stalls Cross-control stalls Accelerated stalls Stall Recovery - Decrease angle of attack Smoothly apply maximum power Adjust power & configure for normal, coordinated flight.

V-g Diagram

V-g Diagram

Spins · Definition of a Spin - · Types of Spins - · Aggravated stall accompanied by autorotation. One wing stalled more than the other wing. Erect Inverted Flat Stages or Phases - Incipient spin Fully developed spin (steady-state) Spin recovery

Spin Recovery · · · · Throttle to idle Neutralize ailerons Determine direction of spin via turn coordinator Full opposite rudder Briskly apply forward elevator pressure Neutralize rudder Gradually apply back elevator pressure

Left-Turning Tendencies • The left turning tendency of the airplane is made up of four elements which cause or produce a twisting or rotating motion around at least one of the airplane’s three axes. – – Torque reaction from engine and propeller, Corkscrewing effect of the slipstream, Gyroscopic action of the propeller, and Asymmetric loading of the propeller (P-factor).

Left-Turning Tendencies

Left-Turning Tendencies

Airplanes in Glide · Best Glide Speed - · See POH C-172 = 70 knots Glide Ratio - See POH E. G. glide ratio of 10: 1 means airplane will travel 10, 000 feet (1. 6 nm) horizontally for each 1, 000 feet of altitude lost · · · Typical Cessna 172 Typical Piper Cherokee (Warrior) Factors Affecting Glide - Weight Configuration Wind 9. 1 : 1 11. 5 : 1

Types of Turns · Shallow turns - · Medium turns - · Less than 15° Tendency to return to straight-and-level flight (positive static stability) 15° or more but not more than 30° Tendency to return to remain in the turn (neutral static stability) Steep turns - More than 30°, usually 45° Tendency to steepen the turn (overbanking tendency) (negative static stability)

Rate and Radius of Turns · Rate of Turn - · Amount of time it takes an airplane to turn a specified number of degrees If airspeed increases with angle of bank constant, then rate of turn decreases. If angle of bank increases with airspeed constant, then rate of turn increases. Radius of Turn - Amount of horizontal distance an airplane uses to complete a turn If airspeed increases with angle of bank constant, then radius of turn increases. If angle of bank increases with airspeed constant, then radius of turn decreases.

Forces Acting on Airplane in A Turn

Normal, Slipping and Skidding Turns

Bank Angle Effect on Load Factor

Bank Angle Impact on Load Factor

Bank Angle Impact on Load Factor and Stall Speed

Components of Lift • Division of Lift - Vertical Component of Lift - Horizontal Component of Lift • Offsetting Forces - Vertical Component of Lift Weight - Horizontal Component of Lift Centrifugal Force - Total Lift Load Factor • Horizontal Component of Lift = sideward force that causes airplane to turn (centripetal force)

Effects of Division of Lift • Division of lift reduces lift supporting airplane, produces altitude loss unless: - Increase angle of attack - Increase airspeed - Increase angle of attack and airspeed - Trim up when passing 30º bank into 45º bank - Roll-out to 30º as necessary to regain altitude

Load Factor, Stall Speed, & Bank Angle · Stall speed increases by – 30° bank = load factor of 1. 1 1. 05 * VS – 45° bank = load factor of 1. 4 1. 20 * VS – 60° bank = load factor of 2. 0 1. 40 * VS · Maximum bank angle = 50º -- 60º · Load Factor versus Bank Angle – 60° bank = 2 g – 70° bank = 3 g – General Aviation airplanes stressed for max 3. 8 g

Limit Load Factor · Definition of Limit Load Factor · · Normal Category · · · 3. 8 positive G’s 1. 52 negative G’s Utility Category · · · Amount of stress or load factor that an airplane can withstand before structural damage or failure occurs. 4. 4 positive G’s 1. 76 negative G’s Acrobatic Category · · 6 positive G’s 3 negative G’s

References and Information • • Downloading This Presentation – http: //williamjdoylejr. net/pvt/Aerodynamics. ppt – http: //williamjdoylejr. net/pvt/Doyle. WJ_CFII/ FAA Airplane Flying Handbook – FAA-H-8083 -3 A – Airplane Structure, Chapter 2 http: //www. faa. gov/library/manuals/aviation/pilot_handbook/media/PHAK%20%20 Chapter%2002. pdf – Principles of Flight, Chapter 3 http: //www. faa. gov/library/manuals/aviation/pilot_handbook/media/PHAK%20%20 Chapter%2003. pdf – Aerodynamics of Flight, Chapter 4 http: //www. faa. gov/library/manuals/aviation/pilot_handbook/media/PHAK%20%20 Chapter%2004. pdf – Flight Controls, Chapter 5 http: //www. faa. gov/library/manuals/aviation/pilot_handbook/media/PHAK%20%20 Chapter%2005. pdf Pilot Handbook: A Comprehensive Text/Reference for All Pilots (Eighth Edition), Irvin N. Gleim, Ph. D. , CFII and Garrett W. Gleim, CFII, MEI – Airplanes and Aerodynamics, Chapter 1, pp 15 – 66 Other Resources – Maj Bill Doyle – http: //home. netcom. com/~doylewj/Aviation/student_pilot_flight_training/default. htm – http: //home. netcom. com/~doylewj/default. htm – http: //williamjdoylejr. net/Careers/Career_Awareness_Aviation_St_Marks_2010 -06 -02. ppt

About the Presenter • Aviator – Commercial, Instrument, ASEL & AMEL – 2, 900 hours total time; 770 hours TAA; 500 hours KFC 150; 665 hours Garmin 430, 140 hours Garmin G 1000 • Instructor – – CFI A&I, AGI, IGI, ASC 1, 400 hours as CFI Cessna FITS Course and CFAI Course FAA PHL FSDO CFI of the Year 2009 -2010 • Civil Air Patrol – Instructor-Pilot, Check Pilot, and Check-Pilot Examiner – G 1000 Project Officer • Technologist & Teacher – Director of Technical Services, Hatboro-Horsham School District – Nursing Informatics Instructor, La Salle University Graduate School of Nursing • Author – Two books on electronic spreadsheets, with a Russian translation – Self-study manuscript on computer concepts for nurses – Articles on gear up landings and fuel management published by FAA

Aim High! But Not On Final!