Aerodynamics Class 1

8/13/2019 Aerodynamics Class 1

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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


5/21

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


6/21

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


7/21

Aerodynamics -

Helicopter Drag vs. Airspeed


8/21

Aerodynamics .

Airflow At A Hover - OGE


9/21

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


15/21

Aerodynamics 1!

Retreating Blade Stall


16/21

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


17/21

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


18/21

Aerodynamics 1.

Vortex Ring State

Induced Flow 5efore :orte Ring *tate

:orte Ring *tate


19/21

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

Documents

Aerodynamics Class 1