Flashcards in Lift Production And Drag 2-2 Deck (44):
Explain the Aerodynamic relationship of 4 Forces in Equilibrium Flight.
Lift, Weight, Thrust, Drag.
Equilibrium flight when sum of all forces and moments are =Zero.
Lift acts against Weight and Drag acts against Thrust.
Describe how the primary Aerodynamic Forces affect each other.
AF- is the net force that results from Pressure and Shear Stress distribution over an Airfoil. And broken down int Lift and Drag.
*Pressure acts perpendicular to the body and Sheer Stress acts tangential to the surface.
**Lift=Pressure - Perpendicular to relative wind
**Drag= acting parallel to & same direction as relative wind.
State Pressure Distribution around an Airfoil, Given changes in AOA and Camber.
Increasing AOA results a continued reduction of the cross-sectional area of the stream tube flowing over the top surface resulting in more lift being created.
The component of the Aerodynamic Force acting Perpendicular to the Relative Wind.
Describe how factors in the Lift equation affect Lift Production.
*Density(p), Velocity(V), Surface Area(S), Compressibility, Aspect Ratio(AR), Viscosity(u), AOA, Camber
*Shape of the Airfoil and AOA are Pilots Control for more Lift.
*Increase p or V or S will increase Lift.
**u, Compressibility, AR will be ignored for Lift.
List the Factors affecting the Coefficient of Lift that a Pilot can Directly Control.
Velocity, AOA, and The Shape of the Airfoil(limited)
**AOA is the most important factor in CofL
***Increase AOA until CLmax- the most effective AOA
The Aerodynamic Force that is parallel to the relative wind, and acts in the same Direction.
Define Parasite Drag and its Components.
(Dp) Drag not associated with the production of Lift.
Form Drag- airflow separation from a surface and Low Press Wake
Friction Drag- Air Viscosity, air interacts with the surface of an object
Interference Drag- generated by the mixing of streamlines b/w Form and Friction.
Describe the measures that can reduce each of the components of Parasite Drag.
Form- reduce by streamlining-reduce High Ps near Leading Edges
Friction- smoothing exposed surfaces-paint,clean,wax,polish.
Interference-minimize by proper Fairing and Filleting.
State the effects of Upwash and Downwash on a Infinite Wing.
Upwash exactly balances the Downwash resulting in no net change in Lift.
*exist any time an airfoil produces lift.
State the effects of Upwash and Downwash on a Finite Wing.
Upwash and Downwash are not equal, and some air flows up and around the wingtips producing more downwash. Thus Doubles due to Spanwise airflow resulting in Wingtip Vortices.
Define Induced Drag.
Portion of Total Drag associated with the production of Lift.
*the parallel component of Total Lift, since it acts in the same direction as drag and tends to retard forward motion.
State the cause of Induced Drag on a Finite Wing.
Twice as much DW as UW near Wingtips, the Avg Relative Wind has a Downward slant compared to the free airstream Relative Wind = Total lift vector to now be inclined aft = Effective Lift will be less than Total Lift = Di.
Describe factors affecting Induced Drag. Given the Di Equation.
Di = (kL(^2)) / (pV^2b^2) = (kW(^2)) / (pV^2b^2)
Weigh = Lift.
*Increase WT = Increase Di
**Inverse with Velocity and Direct with AOA.
State when a plane will enter Ground Effect.
Significantly reduces Di and Increases Effective Lift when the Airplane is Within 1 wingspan of the ground.
State the effects of Ground Effect on Lift, Effective Lift and Induced Drag.
Downwash at the Trailing Edge of the Wing is unable to flow Downward. Decreasing DW allows the Total Lift vector to rotate FWD, Increasing Effective lift and Decreasing Di.
Describe the effects of AOA changes on Coefficient of Lift and Coefficient of Drag.
Most important component and determines L/D ratio.
As AOA increase the CofL and CofD Increase up to CLmax.
Explain the Lift to Drag Ratio, using L/D Ratio Equation.
Is used to determine the efficiency of an airfoil. A high ratio indicates a more efficient airfoil.
*(CofL / CofD)
Explain the importance of L/D MAX.
The Maximum L/D ratio.
Located at the bottom of the total drag curve, any movement away from L/D max will increase Drag.
*High L/D ratio indicates a more efficient Airfoil.
Define Total Drag.
Dp and Di can be added together to create a Dt.
Describe the effects of changes in Velocity on Total Drag.
As Velocity Increases Dt Increases.
Define Thrust Components; Tr and Ta.
Thrust Required: Thrust required to overcome Drag and expressed in LBS.
Thrust Available: amount of thrust the airplanes engines actually produce at a given Throttle Setting, Velocity, Density.
Define Power Components; Pr & Pa.
Power Required: The amount of Power Required to produce Tr
Pr is the product of Tr x V.
Power Available: The amount of Power the the airplanes engines actually produce at a given Throttle Setting, Velocity, and Density.
Describe the effects of Throttle Setting, Velocity, and Density, on Ta & Pa.
Ta: Max Eng. Output at FullThrottle(Pa), Density Decreases Ta Decreases, Prop-can only Accel air to Max V thus as Air Accel Ta Deacreases. Jet doesn’t bc of Ram-effect.
Pa: Pilot Reduces Throttle Pa decreases, Jet- V increases Pa Increases Linerarly, Prop-V Increases Pa initially increase until Ta Decreases, Decrease in Density Pa decreases.
Define Thrust Horsepower and components; Shaft HP and Propeller Efficiency.
Thrust Horsepower- (THP) The Output from the Propeller.
Shaft Horsepower- (SHP) The output from the engine.
Propeller efficiency (PE)- the ability of the Propeller to convert SHP & THP (PE=THP/SHP)
State the Maximum rated Shaft HP in the T6B.
Explain how PE affects Thrust HP.
Due to Friction in the gearbox and drag on the Propeller, PE is never 100%.
2 ways to minimize loss of Thrust:Fixed Pitch or Variable Pitch Propellers.
Describe Pr in terms of Tr.
Pr is the product of Tr and V.
Pr is the amount of Power Required to produce Thrust Required.
State the location of L/D MAX on the Tr and Pr curves.
Tr: L/D Max AOA is the point of minimum Tr, bottom of the Curve.
PR: L/D Max AOA not at the bottom but slightly to the right of the curve.
*V and AOA for L/DMax are the same on Pr & Tr Curves.
Describe how Tr and Pr vary with Velocity.
Flight at greater V require a reduction in AOA and Increase in Thrust to match the increased Parasite Drag.
Flight at lower V require an increase in AOA and Increase in Thrust to match the increased Induced Drag.
Define Excess Thrust and Excess Power.
Thrust Excess (Te): Ta is greater than Tr at a particular V.
Power Excess (Pe): Pa is greater than Pr at a particular V.
Describe the effects of Excess Thrust and Excess Power.
Positive Excess produce a climb, Acceleration
Negative or Deficit: result in a descent or a deceleration.
Describe the effects of change in WT on Thrust and Power components; Tr, Pr, Te, Pe.
Increase in weight requires an increase in Tr and Pr
Pr is a function of Tr.
Tr and Pr curve shifts up and to the right - higher velocity = higher Dt.
Describe the effects of changes in Altitude on Thrust and Power components. Tr, Pr, Ta, Pa, Te, Pe.
*Tr and Pr curve shift to the right- Altitude Increases(density decreases) V increases.
**Ta and Pa decrease at higher altitudes
**Te decrease with an increase in altitude due to decrease in Ta.
**Pe decrease with an increase in alt due to Pa decrease and Pr increase.
Describe the effects of changes in configuration on Thrust and Power Components; Tr, Pr, Te, Pe.
Tr and Pr increase when Landing gear is lowered. Curve shift up.
**Ta and Pa are not affected
**Te and Pe decrease due to Tr and Pr increase.
Describe the Aerodynamic effects of Raising or Lowering the Flaps.
Lowering Flaps increase CofL, increase Dt and Tr.
*Tr curve shifts left.
Shift both Tr and Pr curves up and to the left - more thrust and power are required to maintain alt for a given V.
Describe the aerodynamic effects of Raising and Lowering the Landing Gear.
Ta and Pa not affected.
Te and Pe will decrease with Tr and Pr increasing.
Explain the aerodynamic effects of each Primary Flight Control.
Elevator - pitching moment around the lateral axis
Ailerons - rolling moment
Rudder - yawing moment.
Describe how the Trim Tab System holds an Airplane in Trimmed Flight.
Attached to the trailing edge of each control surface.
Trim tab move in opposite direction as the Control surface and creates a small force that exactly opposes the moment created by Control surface.
Define Aerodynamic Balancing and Mass Balancing.
Aerodynamic Balancing - balancing forces that act at the Aerodynamic center.
**keep control pressures associated with higher velocities within reasonable limits.
Mass Balancing - balancing the forces that act at the center of gravity and relocate them to the hinge line through weights in ctrl surfaces.
State the methods for Aerodynamic and Mass Balancing employed on the T6B.
Aerodynamic Balance - Shielded horns on the elevator and rudder.
Mass Balancing - weights in the overhang of ailerons.
State the Characteristics of the 3 basic types of Control Systems.
Conventional - direct control - push pul tubes, pulleys, cables and levers
Power-Boosted - mechanical linkages, hydraulic, pneumatic, electrical assists.
Full Power - fly by wire, no direct connection with Control surface, computer commands.
State how Trim Tabs can be used to generate Artificial Feel on a Control Surface.
Anti-Servo - move in the same direction, requiring more force to hold the control surface.
Neutral- maintains a constant angle to the control surface (elevator)