Aerodynamics Flashcards
Minimum speed for T/O is about ____ above power-off stall speed
20%
Bad for T/O performance:
High, hot, heavy, humid
Max rate of climb (Definition) (and T-6)
Gaining the most altitude in a given amount of time, 140 KIAS
Max angle of climb (Definition)
The most altitude for distance travelled
How does altitude affect cruise?
Decrease in temperature = turbine engine more efficient = higher range & endurance because of less fuel
Does wind affect maximum endurance?
No
How does head and tail wind affect max range?
Head = decreased, tail = increased
Best glide speed (Definition)
The maximum range in a power-off glide
Where does best glide speed occur?
At L/D MAX, T-6 clean ≈ 125 KIAS
What is P-factor?
The yawing moment caused by one propeller blade creating more thrust than its opposing blade, if the free airstream relative wind is above the thrust line
Where is P-factor noticeable?
High power setting, thrust axis displaced from the relative wind
What causes the aircraft to accelerate until thrust equals drag?
Excess thrust (Newton’s 2nd law)
Aerodynamic centre is also known as?
Center of lift
Maxium endurance occurs at ____
bottom of the power curve
Maxium range occurs at ____
L/D max
In a spin, which wing will have the higher AOA?
inside wing
What’s the difference between erect and inverted spin?
Positive og negative G
Post-stall gyration (Definition)
Aerodynamic forces during a stall that result in movement around the pitch, roll, and yaw axes
Autorotation (Definition)
Combination of roll and yaw that propagates itself and progressively gets worse due to asymmetrically stalled wings
Conservation of angular momentum
CG and centre of lift come closer together
How does anti-spin rudder aid in recovery?
Slows rotation and decreases AOA
Spin to which side has the lower pitch, slower with more oscillation, and increased rotation rate due to gyroscopic precession?
right side
What is progressive spin?
Caused by maintaining full up elevator while holding anti-spin rudder, until rotation stops and then turns the other way
On a graph, where does boundary layer separation start to occur?
Where the coefficient of lift starts to bend
Does a heavy aircraft have a higher or lower stall speed?
Higher
With IAS being the same, does stall speed increase or decrease with altitude?
Increase
When are the strongest vortices created?
Heavy + clean + slow
How does AOA affect vortices?
Higher AOA = bigger vortices, because greater lift
What are the four types that can cause yaw because of the propeller?
Gyroscopic processing, torque effect, p-factor, prop wash
Increasing performance wind shear
Lift and climb increases
Decreasing performance wind shear
Lift and climb decreases
Wind shear is caused by ______
low level jet streams, wind funneling, land-sea breezes, fonts, thunderstorms
What wind shear alert systems exists?
NEXRAD Doppler radars, Low-Level Wind Shear Alert Systems (LLWS), and PIREP
Wind shear T/O procedures
Longest suitable runway, T/O flaps but delay rotation by the amount of predicted shear (up to 10 knots), rotate to normal climb attitude and maintain
Wind shear landing procedures
Add up to 10 knots to speed (keeping in my the increased landing roll), resist temptation to make large power reductions, establish pitch, trim, and power settings by 1000’ AGL
Order of loss of conrols
- aileron 2. elevator 3. rudder
Boundary layer separation (Definition)
Point in the streamline where airflow no longer adheres to the airfoil
Moment (Definition)
Force applied at a distance from a pivot point (a lever)
Work (Definition)
Force * distance
Power (Definition)
Work / time or
Force * velocity
Total energy (Definition)
Full measure of a body’s capacity to do work
Potential energy (Definition)
Ability to do work based on position
Kinetic energy (Definition)
Ability to do work based on motion
Temperature (Definition)
Measure of the average kinetic energy of air particles
True altitude is also called ____
MSL
Pressure altitude is true altitude corrected for _______
atmospheric pressure
Density altitude is pressure altitude corrected for ____
temperature
Chordline (Definition)
an infinitely long line passing through the leading and trailing edges of an airfoil
Flight path (Definition)
Path of CG through the air mass. Always opposite to the relative wind
Relative wind (Definition)
always opposite to the flight path
Pitch attitude (Definition)
Angle between the longitudinal axis and the horizon
AOA (Definition)
Angle between the chord line and the relative wind
What does CG affect?
Pitch and stability
Aerodynamic center placement ____
normally aft of CG. (Relates the 4 forces)
Aerodynamic force (Definition)
Force that results from pressure and friction distribution over an airfoil
What has the greatest affect on lift?
velocity
How can the pilot change the cL?
AOA or flaps
Total drag decreases until _____ then increases
L/DMAX
Form drag (Definition)
Separation of airflow; function of size and shape of airfoil. Caused by a difference between leading edge Ps and trailing edge Ps
(kom endelig med en bedre forklaring)
Friction drag (Definition)
Turbulent airflow in the boundary layer
Interference drag (Definition)
mixing airstreams (fuselage and wing)
Minimum total drag occurs at _____
L/DMAX
Thrust required (Definition)
Equals total drag in equilibrium
Thrust available (Definition)
Thrust produced under a specific velocity, density and PCL setting
Thrust excess (Definition)
Difference between thrust available and thrust required. In a propeller aircraft, max thrust excess occurs below L/DMAX
Power required (Definition)
Power need to produce required thrust.
In a propeller aircraft, minimum power required occurs below L/DMAX
Power available (Definition)
Power actually produced by the airplane’s engine at a given PCL setting, velocity, and density
Power excess (Definition)
Difference between power available and power required.
When available a/c will either climb and/or accelerate.
Max excess occurs at L/DMAX
With an increase in altitude _____ is required to increase, but _____ remains constant
(which one is power and which is thrust)
1: Power, 2: thrust
Prop hp vs shaft hp
Prop = thrust hp
Shaft = engine output
Prop efficiency
Thrust hp divided by shaft hp
Critical Mach (Definition)
Mach number where first evidence of local supersonic flow occurs
Region of Reverse Command (Definition)
Area on the PR curve, left of min. power required, where a decrease in velocity requires an increase in power required
Slipstream Swirl (Definition)
Prop wash swirls clockwise around fuselage striking tail on the left side causeing left yaw
Torque factor (Definition)
Roll opposite the direction of propeller rotation
Gyroscopic precession (Definition)
Force progresses 90° in the direction of prop rotation. Affects variance in left and right spin
To maintain level flight during a 60° bank angle turn will require ____
2 G + thrust
Is a heavy/larger or a smaller/light plane hardest to meaneuvre, and why?
Heavy/larger, because it’s more stable
________ is the greatest positive contributor
Vertical stabilizer
Cross coupling
Roll causes adverse yaw and adverse yaw causes roll
Proverse roll (Definition)
Roll in the same direction as yaw
Geometric twist (Definition)
Reduction in angle of incidence from wing root to wing tip
Aerodynamic twist (Definition)
Reduction in camber from wing root to wing tip
Accelerated spin (Definition)
Spinning with the stick other than full aft
