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18 Cards in this Set
- Front
- Back
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5 Factors Affecting Lift
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1. Surface Area
2. Angle Of Attack 3. Velocity Of Airflow 4. Air Density 5. Blade Stall |
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Coriolis Effect
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- 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 |
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Bernoulli's Principle
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- 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 |
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Drag
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- The Force That Resists Movement Of Objects Thru The Air
- Byproduct Of Lift - Always Parallel To Relative Wind (RW) |
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Coning
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- 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 |
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Translating Tendency (Drift)
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- The Tendency For The Helicopter To Drift In The Direction Of Tail Rotor Thrust
Counteraction: 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 |
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Dissymmetry Of Lift
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- 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 Note: Blowback: - Max Flap Up Over The Nose - Max Flap Down Over The Tail - Tip Path Tilts Rearward |
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Translational Lift
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- Any Horizontal Airflow Across The Rotor System
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Parasite Drag
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- Caused By the Movement Of Any "Non-Lifting" Component Thru the Air
Example: - Cabin - Tail Boom - Landing Gear - ETC... |
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Induced Drag
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- Created By Airflow Circulation Around The Rotor Blades
- As They Create Lift - High Pressure Meets Low Pressure @ Blade Tips - More AA = More Induced Drag |
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Effective Transaltional Lift
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- 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 |
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Pendular Action
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- Since The Helicopter Is Suspended By A Single Point
- It Is Free To Osillate - Either Longitudinally Or Laterally Note: - Keep Control Movements To A Minimum |
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Profile Drag
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- 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 |
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Induced Flow
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- Large Amounts Of Air Being Sucked Down Thru The Rotor System
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Gyroscopic Procession
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- 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 Note: Pitch Horns: - Compensate For G.P. By Applying The Control Input 90 Degrees Prior To The Desired Output |
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Transverse Flow
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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 Note: - 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 Note: - As The Helicopter Accelerates To Apporx: 20 KTs Or A 20 KT Headwind Is Felt |
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In-Ground Effect
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- 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 Note: - Best In A NO Wind Condition Over A Hard Surface |
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Out-Of-Ground Effect
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- 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 |
