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18 Cards in this Set

  • Front
  • Back
5 Factors Affecting Lift
1. Surface Area
2. Angle Of Attack
3. Velocity Of Airflow
4. Air Density
5. Blade Stall
Coriolis Effect
- Blade Acceleration & Deceleration
- As CenterMass (CM) Moves Closer To The Axis Of Rotation There Is An Increase In Velocity & ViseVersa
- Figure Skater Analogy
- Fixed By Underslinging
Bernoulli's Principle
- If We Increase Velocity, We Decrease Pressure
- The Venturi Effect
- Air Must Move Faster Accross The Top Of The Airfoil To Rejoin Air On The Bottom Of The Airfoil
- The Force That Resists Movement Of Objects Thru The Air
- Byproduct Of Lift
- Always Parallel To Relative Wind (RW)
- The Upward Sweep Of The Rotor Blades In Their Plane Of Rotation
- Caused By Centrifugal Force (CF) & Lift

Coning Hinge:
- Causes Less Stress On The Rotor Blades
Translating Tendency (Drift)
- The Tendency For The Helicopter To Drift In The Direction Of Tail Rotor Thrust

1. Transmission Rigging
- Main Rotor Mast Has A Built-In Tilt Opposite Tail Rotor Thrust

2. Cyclic Centering
- When The Cyclis Is Centered, The Disc Is Actually Slightly Tilted The Opposite Of TR Thrust

3. Pilot Correction (R22)
- Pilot Holds Slight Lt Cyclic To Maintain Positon
- Cause Lt Skid To Hang Low
Dissymmetry Of Lift
- Unequal Lift Accross The Rotor System
- As Heli Moves Thru The Air The Advancing & Retreating Sides Of The Rotor Disc Feel Different Amounts Of Lift
- If This Were Allowed To Persist, The Helicopter Would Roll Left
- In Reality The Blades Are Allowed To Flap
- Via The Teetering Hindge
- As A Unit
- To Equality

- Max Flap Up Over The Nose
- Max Flap Down Over The Tail
- Tip Path Tilts Rearward
Translational Lift
- Any Horizontal Airflow Across The Rotor System
Parasite Drag
- Caused By the Movement Of Any "Non-Lifting" Component Thru the Air

- Cabin
- Tail Boom
- Landing Gear
- ETC...
Induced Drag
- Created By Airflow Circulation Around The Rotor Blades
- As They Create Lift
- High Pressure Meets Low Pressure @ Blade Tips
- More AA = More Induced Drag
Effective Transaltional Lift
- When Translational Lift Becomes Effective
- Occures @ Airspeeds of 16 - 20 Kias
- At This Speed Rotor Blades Move Out Of Their Vortices And Are In Undisturbed Air

- Reduced Induced Flow
- Reduced Induced Drag
- Increased Angle Of Attack (AA)
- More Lift Is Felt

- Nose Pitch Up
- Lt Yaw B/C Tail Rotor Becomes More Efficiant
- Requires FWD Cyclic & RT Pedal
Pendular Action
- Since The Helicopter Is Suspended By A Single Point
- It Is Free To Osillate
- Either Longitudinally Or Laterally

- Keep Control Movements To A Minimum
Profile Drag
- Drag Developed By Friction Of Airfoil Traveling Thru The Air

2 Types:
1. Form Drag
- Turbulent Wake
- Caused By The Seperation Of Airflow From A Stucture
- Caused By Size & Shape (Form)
2. Skin Friction
- Surface Roughness
Induced Flow
- Large Amounts Of Air Being Sucked Down Thru The Rotor System
Gyroscopic Procession
- The Resultant Action Or Deflection Of A Spinning Object
- When A Force Is Applied To It
- Will Register That Force 90 Degrees After It Has Been Applied
- In It's Plane Of Rotation

Pitch Horns:
- Compensate For G.P. By Applying The Control Input 90 Degrees Prior To The Desired Output
Transverse Flow
As The Helicopter Accelerates In FWD Flight:

- Induced Flow (IF) @ The Front Of The Disc
- Is Reduced To Near Zero

- Induced Flow (IF) @ The Rear Of The Disc
- Remains The Same

- This Aerodynamic Increase In AA @ The Front Of The Disc
- Causes The Blades To Flap Up, Trying To Reduce AA
- The Opposite Takes Place At The Rear Of The Disc

- B/C Of G.P. The Max Displacement (Flap) Of The Rotor Blads
- Will Occur 90 Degrees Later In The Plane Of Rotation
- Max Flap Up @ LT Side Of Disc
- Max Flap Down @ RT Side Of Disc

- The Result Is A RT Rolling Tendency

- As The Helicopter Accelerates To Apporx: 20 KTs
Or A 20 KT Headwind Is Felt
In-Ground Effect
- Benificail Influence On Helicopter Performance
- When Within One Rotor Diameter Of The Surface
- 2 Ft Skid Clearence (R22)

- As Airflow Contacts The Airfoil It Is Deflected Downward
- In the Form Of Downwash
- As The Airflow Contacts The Surface It Is Impeded By Surface Friction
- The Downwash Stacks Up On Itself
- Catching Blade Tip Vortices And Pushing Them Outward

- Best In A NO Wind Condition Over A Hard Surface
Out-Of-Ground Effect
- As Helicopter Gains Altitude With No FWD Airspeed
- Induced Flow (IF) Is No Longer Restricted By Surface Friction
- There Is A Decrease In Outward Airflow
- Resulting In Blade Tip Vortex Increase
- Highter Pitch Angle Is Required For The Same Amount Of Lift