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Aerodynamics 1
Rotary WingAERODYNAMICS
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Aerodynamics 2
Airfoil Force Vectors
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Aerodynamics 3
Aerodynamic Terms
Rotational Relative Wind
Opposes Direction of Blade Rotation in Tip Path Plane
Induced Flow
Vertical Component of Airflow Drawn Through theRotor System
Resultant Relative Wind
Actual ind that Acts on the Airfoil(Vector Sum of Rotational Relative Wind & Induced Flow)
Angle of Incidence
Angle Between Chord !ine " Rotational Relati#e ind$Tip Path Plane%
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Aerodynamics 4
Aerodynamic Terms (Cont)
Angle of Attack
Angle Between Chord !ine " Resultant Relati#e ind
Lift
Acts Perpendicular to Resultant Relati#e ind
Drag
Acts Parallel " Opposite to Resultant Relati#e ind
otal Aerodynamic Force
Vector Sum of Airfoil !ift " Drag
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Aerodynamics !
Lift
"ressure Differential
Between &pper " !ower Airfoil Surfaces Creates !ift
Lift #$uation
%am&ered Airfoil in "ositive Lift
L V SCL
1
2
2
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Aerodynamics '
Drag
y(es of Drag
' Induced) Caused (y the Production of !ift
' "arasite) All Drag )ot Caused (y !ift
* "rofile) Parasitic Drag of Rotor Blades PassingThrough the Air
Drag #$uation
Largest %ontri&utor to otal Drag' Low *(eed) +nduced Drag
' +ig, *(eed) Parasite,Profile Drag
D V SCD
1
2
2
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Aerodynamics -
Helicopter Drag vs. Airspeed
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Aerodynamics .
Airflow At A Hover - OGE
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Aerodynamics /
Airflow At A Hover - IGE
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Aerodynamics 10
Translating Tendency
endency of Aircraft to Drift In t,e Direction ofail Rotor ,rust at a +over
%om(ensated for &y iing nit "ilot In(ut
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Aerodynamics 11
Dissymmetry of Lift
Difference in Lift Associated wit, t,e Advancing Retreating *ides of t,e Rotor *ystem
%om(ensated for &y 5lade Fla((ing %yclicFeat,ering
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Aerodynamics 12
Blade Flapping
(6Down ovement of t,e Rotor 5lade A&out AFla((ing +inge
%auses 5low&ack 7Rearward ilt of Rotor Disk8
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Aerodynamics 13
Blade Lead & Lag (Hunting)
Fore Aft ovement of t,e 5lade in i( "at,"lane Due to %,anges in 5lade *(eed
%oriolis #ffectAngular Velocity Changes with Blade C-
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Aerodynamics 14
Retreating Blade Stall
9ut&oard *ection of Retreating 5lade *talls at+ig, Forward Airs(eed
%ausesBlade .lapping " Cyclic .eathering that /0ceed Critical Angle
Aircraft "itc,es ( Rolls Left
%onditions %onducive to Retreating 5lade *tall1 2igh -T 1 !ow Rotor RP3
1 2igh DA 1 2igh 4-5 3aneu#ers
1 Tur(ulent Air
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Aerodynamics 1!
Retreating Blade Stall
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Aerodynamics 1'
Compressibility
9ut&oard *ection of Advancing 5lade #ceedst,e *(eed of *ound at +ig, Airs(eed
Aerodynamic %enter oves Aft!arge Down Pitching 3oment at Out(oard Tip ill Cause
Structural .ailure of Blade
Aircraft "itc,es Down
%onditions %onducive to %om(ressi&ility
1 2igh Airspeed 1 2igh Rotor RP3
1 2igh -T 1 2igh DA
1 !ow Temperature 1 Tur(ulent Air
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Aerodynamics 1-
Settling with Power(Vortex Ring State)
Formation of an Inner :orte on t,e 5lade%auses *u&stantial Loss of Lift
Increased %ollective Results in Larger :orteRings +ig,er Rates of Descent
%onditions %onducive to *ettling wit, "ower
' Very !ow .orward Airspeed' 6718779 of A#aila(le Power Applied
' :77 ft,min Rate of Descent or -reater
Recover &y #sta&lis,ing Directional Flig,t
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Aerodynamics 1.
Vortex Ring State
Induced Flow 5efore :orte Ring *tate
:orte Ring *tate
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Aerodynamics 1/
Offset Hinges
ends to Align t,e +elico(ter wit, t,e Rotor
i( "at, "lane
9ffset %reates a +u& oment
!arger the Offset; 2igher the 2u( 3oment
Results in ;reater aneuvera&ility FasterAircraft Res(onse
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Aerodynamics 20
Dynamic Rollover
Aircraft #ceeds %ritical Rollover Anglewit, a Rolling oment
Dynamic Rollover %riteria' Pi#ot Point
' Rolling 3oment
' !ift Component and,or 2u( 3oment
ail Rotor %ontri&ution
%ollective is ost #ffective %ontrol
Cyclic is also /ffecti#e Due to Offset 2inges
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Aerodynamics21
Fuselage Hovering Attitude