West Point Aviation Club Private Pilot Ground Instruction Aerodynamics of Maneuvering Flight

Left-Turning Tendencies Torque Gyroscopic Precession Asymmetrical Thrust Spiraling Slipstream

Left-Turning Tendencies Torque Torque Effect is greatest at low airspeeds, high power settings, and high angles of attack Newton’s Third Law: “For every action, there is an equal and opposite reaction” prop rotates clockwise, fuselage reacts counterclockwise

Left-Turning Tendencies Gyroscopic Precession Turning prop exhibits rigidity in space and gyroscopic precession, like a gyroscope Gyroscopic precession is the resultant reaction when a force is applied to the rim of a rotating disc Reaction to a force occurs 90º later in the plane of rotation; only experienced when there is a change of aircraft attitude

Left-Turning Tendencies Gyroscopic Precession

Left-Turning Tendencies Asymmetrical Thrust P-Factor causes an airplane to yaw to the left when it is at high angles of attack. P-Factor results from the descending prop blade on the right producing more thrust than the ascending blade on the left

Left-Turning Tendencies Spiraling Slipstream As prop rotates, it creates a backward flow of air, or slipstream, which wraps around the airplane The slipstream can cause a change in airflow around the vertical stabilizer; it strikes the lower left side of the vertical fin, resulting in a yaw to the left

Questions Under what speed and power circumstances are the left turning tendencies most pronounced? In what phases of flight do you encounter these speed and power circumstances?

Left-Turning Tendencies Aircraft Design Considerations Some manufacturers include design elements to help counteract left-turning tendencies In small aircraft, often a metal tab on the trailing edge of the rudder that is bent to the left so pressure from the passing airflow will push on the tab and force the rudder slightly to the right This slight right-hand rudder displacement creates a yawing moment that opposes the left-turning tendency caused by spiraling slipstream

Climbing Flight Transition from level to climbing flight: normally change in pitch attitude and increase in power Excess thrust, not excess lift, needed for a climb

Descending Flight In stabilized descending flight, aerodynamic forces are in equilibrium with the force of weight comprised of two components One component of weight acts perpendicular to the flight path The other component of weight acts along the flight path

Descending Flight In stabilized powered descent, four aerodynamic forces are in equilibrium (top figure) In stabilized descent with power at idle, three aerodynamic forces are in equilibrium with the forward component of weight equal and opposite to drag

Lift-to-Drag Ratio Lift-to-drag ratio (L/D) can be used to measure the gliding efficiency of your airplane The angle of attack resulting in the least drag on your airplane will give you the maximum lift-to-drag ratio (L/Dmax), the best glide angle, and the maximum gliding distance

Glide Speed At a given weight, L/Dmax will correspond to a certain airspeed This speed correlates to your best glide speed (maximum horizontal distance for altitude lost) If power failure occurs after takeoff, immediately establish the proper gliding attitude and airspeed

Glide Ratio and Angle Glide Ratio represents the distance an airplane will travel forward, without power, in relation to altitude loss Example, 10:1 means aircraft will travel 10,000 feet of horizontal distance for every 1,000 feet loss of altitude Glide Angle is the angle between the actual glide path of your airplane and the horizontal; glide angle increases as drag increases

Factors Affecting the Glide Weight Configuration Wind

Factors Affecting the Glide Weight Variations in weight do not affect the glide ratio, however there is a specific airspeed that is optimum for a given weight Two aerodynamically identical aircraft with different weights can glide the same distance from the same altitude; can only be done if the heavier aircraft flies at a higher airspeed than the lighter The heavier aircraft will sink faster and will reach the ground sooner, it will travel the same distance as the lighter one

Factors Affecting the Glide Configuration If you increase drag, the maximum lift-to-drag ratio and glide ratio are both reduced To maintain the airspeed you had before your lowered gear, you’d have to lower the nose

Factors Affecting the Glide Wind A headwind will always reduce your glide range while a tailwind will always increase your glide range In a strong headwind or tailwind (winds > 25% of glide speed), best glide may not be found at L/Dmax, and you may have to make adjustments to maximize your travel over the ground

Turning Flight For an airplane to turn, must overcome inertia, or tendency to continue in a straight line We create the necessary force by using the ailerons to bank the airplane so that the direction of total lift is inclined The horizontal component of lift causes an airplane to turn

Turning Flight To maintain altitude in a turn, you will need to apply backpressure, and therefore, angle of attack until vertical component of lift = weight Horizontal component of lift creates force toward center of rotation; centripetal force Opposite force, centrifugal force; not a true force; apparent force resulting from effect of inertia during turn

Turning Flight Adverse Yaw Adverse yaw is the yawing tendency toward the outside of a turn It is caused by higher induced drag on the outside wing, which is producing more lift Need to apply rudder into the turn to control adverse yaw Adverse yaw is greatest at high angles of attack and with large aileron deflection

Turning Flight Overbanking Tendency As you enter a turn and increase the angle of bank, you may notice the tendency of the airplane to continue rolling into a steeper bank Overbanking tendency is caused by the additional lift on the outside, or raised wing Counteract overbanking tendency with small amount of opposite aileron

Turning Flight Rate and Radius of Turn Rate of turn refers to the amount of time it takes for an airplane to turn a specific number of degrees If airspeed increases and angle of bank remains same, rate of turn decreases Radius of turn refers to the amount of horizontal distance an aircraft uses to complete a turn

Load Factor Load factor is the ratio of the load supported by the airplane’s wings to the actual weight of the aircraft and its contents Aircraft in cruising flight, while not accelerating in any direction, has a load factor of one. The wings only supporting its own weight and contents If wings are supporting twice as much weight as the weight of the airplane and its contents, the load factor is two “G Force” same name; “pulling G’s”

Load Factor in Turns During constant altitude turns, the relationship between load factor, or G’s, and bank angle is the same for all airplanes In a 60º bank, 2 G’s are required to maintain level flight

Load Factor and Stall Speed Additional load factor incurred during constant altitude turns will also increase stall speed Stall speed increases in proportion to the square root of the load factor Stalls that occur with G forces are called accelerated stalls

Limit Load Factor Limit load factor is the amount of stress or load factor that an airplane can withstand before structural damage or failure occurs Usually expressed in terms of G’s

Maneuvering Speed Design Maneuvering Speed, or VA, represents the max speed at which you can use full, abrupt control movement without overstressing the airframe