Aerodynamics - EngBrasil · ♣National Advisory Committee for Aeronautics ♣Chartered in 1915,...
Transcript of Aerodynamics - EngBrasil · ♣National Advisory Committee for Aeronautics ♣Chartered in 1915,...
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“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”
AerodynamicsAerodynamicsAerodynamics
Written for the Notre Dame Pilot Initiative
By the Pilots of the University of Notre Dame
Written for the Notre Dame Pilot Initiative
By the Pilots of the University of Notre Dame
Getting to the PointGetting to the PointGetting to the Point
Orville Wright Wilbur Wright
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Four Forces of FlightFour Forces of FlightFour Forces of Flight� Lift opposes Weight
� Thrust opposes Drag
� In straight, unacceleratedflight, L = W & T = D
� Lift opposes Weight
� Thrust opposes Drag
� In straight, unacceleratedflight, L = W & T = D
� Lift created by pressure differential around wing. High pressure on lower surface and low pressure on the upper surface – low pressure caused by increased airflow velocity over top of airfoil.
� Weight – downward force of gravity
� Drag – rearward retarding force
� Thrust – forward force propelling airplane through air
� Lift created by pressure differential around wing. High pressure on lower surface and low pressure on the upper surface – low pressure caused by increased airflow velocity over top of airfoil.
� Weight – downward force of gravity
� Drag – rearward retarding force
� Thrust – forward force propelling airplane through air
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AirfoilsAirfoilsAirfoils
�What is NACA?
♣ National Advisory
Committee for Aeronautics
♣ Chartered in 1915, operational
from 1917-1958
♣ The National
Aeronautics and Space Act of 1958
created NASA
from NACA
�What is NACA?
♣ National Advisory
Committee for Aeronautics
♣ Chartered in 1915, operational
from 1917-1958
♣ The National
Aeronautics and Space Act of 1958
created NASA
from NACA
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Aerodynamic SurfacesAerodynamic SurfacesAerodynamic Surfaces
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Aerodynamic SurfacesAerodynamic SurfacesAerodynamic Surfaces
Jet
Prop
B727 Spoilers
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Airfoils - NomenclatureAirfoils Airfoils -- NomenclatureNomenclature
� Chord line - straight line connecting the leading and trailing edges of an airfoil
� Camber line – locus of all points equidistant from top and bottom of airfoil� Camber – distance between chord line and camber line � Thickness – maximum distance between top and bottom surfaces of wing� Leading Edge� Trailing Edge� Wingspan (b)� Aspect Ratio (AR = b2/S)
� Chord line - straight line connecting the leading and trailing edges of an airfoil
� Camber line – locus of all points equidistant from top and bottom of airfoil� Camber – distance between chord line and camber line � Thickness – maximum distance between top and bottom surfaces of wing� Leading Edge� Trailing Edge� Wingspan (b)� Aspect Ratio (AR = b2/S)
Low p
High p
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FrostFrostFrost
�If wing is below
dewpoint which is
below freezing, frost
will form
�Sublimation of air to
solid ice crystals
�Disrupts smooth
airflow over the wing
�If wing is below
dewpoint which is
below freezing, frost
will form
�Sublimation of air to
solid ice crystals
�Disrupts smooth
airflow over the wing
�Why is this bad?
♣ Decreases lift
♣ Increases drag
�Frost removed
before take-off
�Rime Ice
�Clear Ice
�Why is this bad?
♣ Decreases lift
♣ Increases drag
�Frost removed
before take-off
�Rime Ice
�Clear Ice
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Angle of AttackAngle of AttackAngle of Attack
�Angle between wing chord line and relative
wind
�The angle of attack at which airplane stalls
does not change
�Angle between wing chord line and relative
wind
�The angle of attack at which airplane stalls
does not change
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Published NACA Data – NACA 2415Published NACA Data Published NACA Data –– NACA 2415NACA 2415
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Airfoils - NomenclatureAirfoils Airfoils -- NomenclatureNomenclature
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FlapsFlapsFlaps
� Flaps increase lift and decrease stall speed� Flaps allow steep rate of descent for approaches
without increasing airspeed
� Flaps increase lift and decrease stall speed� Flaps allow steep rate of descent for approaches
without increasing airspeed
Fowler Flap
Split Flap
Slotted Flap
Plain Flap
-Slotted Flap allows high pressure air underneath wing to join airflow above wing. This effectively increases velocity of top airflow and thus increases lift.
-Fowler Flap effectively increases the wing area by rolling backwards on a roller system.
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Laminar v. TurbulentLaminar v. TurbulentLaminar v. Turbulent
Laminar flow about a sphere
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Laminar v. TurbulentLaminar v. TurbulentLaminar v. Turbulent
Turbulent flow about a sphere
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Bernoulli’s Principle - LiftBernoulliBernoulli’’s Principle s Principle -- LiftLift
� “As the velocity of a fluid increases, its internal pressure decreases.”
♣ From Newton’s 2nd (F=ma)
♣ Shown by Venturi tube
� “As the velocity of a fluid increases, its internal pressure decreases.”
♣ From Newton’s 2nd (F=ma)
♣ Shown by Venturi tube
Low Pressure
High Pressure
A1V1=A2V2
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Bernoulli’s Principle AgainBernoulliBernoulli’’s Principle Agains Principle Again
Courtesy of FAA: Pilot’s Handbook of Aeronautical Knowledge, AC 61-23B
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Bernoulli’s Principle AgainBernoulliBernoulli’’s Principle Agains Principle Again
Courtesy of FAA: Pilot’s Handbook of Aeronautical Knowledge, AC 61-23B
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Bernoulli’s Principle AgainBernoulliBernoulli’’s Principle Agains Principle Again
Courtesy of FAA: Pilot’s Handbook of Aeronautical Knowledge, AC 61-23B
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Lift VectorLift VectorLift Vector
Courtesy of FAA: Pilot’s Handbook of Aeronautical Knowledge, AC 61-23B
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Drag TypesDrag TypesDrag Types
�Induced drag is the unavoidable by-product of lift
and increases as the angle of attack increases
�Parasite drag is caused by any aircraft surface
that deflects or interferes with smooth airflow
around airplane
♣Skin-friction drag - between the outer surfaces
of the aircraft and the air through which it
moves. Reduced by using glossy, flat finishes on
surfaces
♣Form drag - resistance of air to the shape of the
aircraft. Form drag can be reduced by
streamlining the aircraft shape.
�Induced drag is the unavoidable by-product of lift
and increases as the angle of attack increases
�Parasite drag is caused by any aircraft surface
that deflects or interferes with smooth airflow
around airplane
♣Skin-friction drag - between the outer surfaces
of the aircraft and the air through which it
moves. Reduced by using glossy, flat finishes on
surfaces
♣Form drag - resistance of air to the shape of the
aircraft. Form drag can be reduced by
streamlining the aircraft shape.
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Drag – Body ComparisonDrag Drag –– Body ComparisonBody Comparison
cylinder
airfoil
sphere
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Wingtip Vortices – “Twin Tornadoes”Wingtip Vortices Wingtip Vortices –– ““Twin TornadoesTwin Tornadoes””
‘High pressure on the lower surface creates a natural airflow that makes its way to the wingtip and curls upward around it to the area of low pressure. When flow around the wingtips streams out behind the airplane, a vortex is formed. These twisters represent an energy loss and are strong enough to flip airplanes that blunder into them.’
A few words on wingtip vortices:
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Wingtip VorticesWingtip VorticesWingtip Vortices
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Why Winglets?Why Winglets?Why Winglets?
�Equivalent to span extension w/o increased wingspan�Reduces wingtip vortices�Reduces drag
�Equivalent to span extension w/o increased wingspan�Reduces wingtip vortices�Reduces drag
NASA B-727 Wingtip Vortex Test Flight
http://www.airspacemag.com/ASM/Mag/Index/2001/AS/htww.html
Learn more about winglets:
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Drag – Ground EffectDrag Drag –– Ground EffectGround Effect
TIP:
On a soft-field
runway, you can
takeoff at a lower
speed and then
accelerate while in
“Ground Effect.”
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Drag vs Angle of AttackDrag Drag vsvs Angle of AttackAngle of Attack
Relationship between drag and angle of attack
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Torque / P-factor (Left-Turning Tendencies)Torque / PTorque / P--factor (Leftfactor (Left--Turning Tendencies)Turning Tendencies)
�Newton’s 3rd law: “For every action there is an equal and opposite reaction.”♣ Propeller rotates CW
when viewed from pilot’s seat.
♣ Torque reaction rotates the airplane CCW about longitudinal axis
�P-factor (asymmetrical thrust) caused by descending blade taking a greater “bite” of air than ascending blade at high angle of attack
�Newton’s 3rd law: “For every action there is an equal and opposite reaction.”♣ Propeller rotates CW
when viewed from pilot’s seat.
♣ Torque reaction rotates the airplane CCW about longitudinal axis
�P-factor (asymmetrical thrust) caused by descending blade taking a greater “bite” of air than ascending blade at high angle of attack
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Stability & ControlStability & ControlStability & Control
� Center of Gravity concerns:
♣ Unable to compensate with elevator in pitch axis
♣ Weight and Balance becomes critical – taught in a coming lecture
� Center of Gravity concerns:
♣ Unable to compensate with elevator in pitch axis
♣ Weight and Balance becomes critical – taught in a coming lecture
� Inherently stable airplane returns to its original condition after being disturbed. Requires less effort to control
� Inherently stable airplane returns to its original condition after being disturbed. Requires less effort to control
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Stability & ControlStability & ControlStability & Control
yaw
roll
pitch
� The 3 axes of motion: roll, pitch, yaw
� The 3 axes of motion: roll, pitch, yaw
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Tail PlacementsTail PlacementsTail Placements
Looks like the A-10Also called “H-Tail”
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CanardsCanardsCanards
�Stabilizer located in front of the main wings
�Used on the Wright Flyer
�More aerodynamically efficient than an elevator b/c canards provide positive lift
�Stabilizer located in front of the main wings
�Used on the Wright Flyer
�More aerodynamically efficient than an elevator b/c canards provide positive lift
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Accident Report – Loss of ElevatorAccident Report Accident Report –– Loss of ElevatorLoss of Elevator
AIRCRAFT FINAL REPORTTHE AIRCRAFT HAD JUST BEEN REPAIRED AFTER RECEIVING TORNADO DAMAGE. THIS REPAIR INCLUDED REMOVAL AND REPLACEMENT OF THE ELEVATOR CONTROL TUBE. THE PILOT TAXIED TO THE RUNWAY FOR THE PURPOSE OF A TEST FLIGHT. ALL FLIGHT CONTROL CHECKS APPEARED NORMAL. AFTER LIFT-OFF, THE PILOT INTENDED TO LEVEL OFF AT 5 TO 10 FEET, THEN TOUCH DOWN AGAIN. HOWEVER, AFTER THE AIRPLANE BECAME AIRBORNE, HE LOST ELEVATOR CONTROL, AND THE AIRCRAFT CLIMBED STEEPLY TO 50 TO 75 FEET. THE PILOT THEN REDUCED POWER, THE AIRCRAFT'S NOSE DROPPED, AND THE AIRCRAFT DESCENDED. WITH NO ELEVATOR CONTROL, THE PILOT WAS UNABLE TO ARREST THE DESCENT, AND THE AIRCRAFT IMPACTED THE GROUND. A POST-CRASH EXAMINATION REVEALED THAT A BOLT AND NUT WERE MISSING FROM THE ELEVATOR CONTROL LINKAGE, WHICH ALLOWED THE LINKAGE TO BECOME DISCONNECTED.
AIRCRAFT 1 CAUSE REPORTFAILURE OF MAINTENANCE PERSONNEL TO PROPERLY REINSTALL A BOLT AND NUT IN THE ELEVATOR CONTROL LINKAGE, WHICH RESULTED IN A DISCONNECT OF THE LINKAGE AND LOSS OF ELEVATOR CONTROL.
AIRCRAFT FINAL REPORTTHE AIRCRAFT HAD JUST BEEN REPAIRED AFTER RECEIVING TORNADO DAMAGE. THIS REPAIR INCLUDED REMOVAL AND REPLACEMENT OF THE ELEVATOR CONTROL TUBE. THE PILOT TAXIED TO THE RUNWAY FOR THE PURPOSE OF A TEST FLIGHT. ALL FLIGHT CONTROL CHECKS APPEARED NORMAL. AFTER LIFT-OFF, THE PILOT INTENDED TO LEVEL OFF AT 5 TO 10 FEET, THEN TOUCH DOWN AGAIN. HOWEVER, AFTER THE AIRPLANE BECAME AIRBORNE, HE LOST ELEVATOR CONTROL, AND THE AIRCRAFT CLIMBED STEEPLY TO 50 TO 75 FEET. THE PILOT THEN REDUCED POWER, THE AIRCRAFT'S NOSE DROPPED, AND THE AIRCRAFT DESCENDED. WITH NO ELEVATOR CONTROL, THE PILOT WAS UNABLE TO ARREST THE DESCENT, AND THE AIRCRAFT IMPACTED THE GROUND. A POST-CRASH EXAMINATION REVEALED THAT A BOLT AND NUT WERE MISSING FROM THE ELEVATOR CONTROL LINKAGE, WHICH ALLOWED THE LINKAGE TO BECOME DISCONNECTED.
AIRCRAFT 1 CAUSE REPORTFAILURE OF MAINTENANCE PERSONNEL TO PROPERLY REINSTALL A BOLT AND NUT IN THE ELEVATOR CONTROL LINKAGE, WHICH RESULTED IN A DISCONNECT OF THE LINKAGE AND LOSS OF ELEVATOR CONTROL.