19 WWW.GOFLY.ONLINE Y ONLI NE FLI GHT SCHOOL PRINCIPLES OF FLIGHT also creates an opposite force which acts horizontally to the lift force in the opposite direction of the centripetal force. This force is called the centrifugal force. The force of gravity versus the amount of lift that is required is also known as load factor or G loading. Forces acting on the aircraft in turns The effect of power application on a level turn During a turn, more drag is created by the extra lift required to maintain the turn. Because drag has increased, if we do not increase our thrust (the opposite force), the aircraft will start to slow down. Therefore, more power is often required in a turn to ensure the thrust equals the drag and to maintain the same airspeed. However, for gentle and medium turns, the loss of airspeed is insignificant and normally power is not applied. During a balanced turn, adding power will create more thrust than drag and the aircraft will accelerate. As the aircraft accelerates, this creates more airflow over the wings and more lift and therefore the aircraft may start to climb. The overbanking tendencies present in level and climbing turns When turning the plane, the outer wing travels slightly faster than the inner wing. This creates more lift and a tendency for the outer wing to continue to roll or ‘overbank’. The pilot may need to input some aileron control to stop this tendency from occurring. This can also happen in a climbing turn. ‘Underbanking’ can occur in a turning descent due to the inner wing having a slightly higher angle of attack and therefore producing more lift than the outer wing. This causes the aircraft to underbank in a descending turn and may require the pilot to input some aileron control to stop this tendency from occurring. The effect of aileron drag on turn performance The effect of aileron drag on turn performance in a light aircraft primarily influences the aircraft’s roll rate and the amount of adverse yaw experienced during a turn. Adverse yaw is the tendency of the aircraft to yaw in the opposite direction of the intended turn when the ailerons are deflected. Aileron drag exacerbates adverse yaw by creating more drag on the wing that is producing most lift (the wing on the outside of the turn). This additional drag causes the nose of the aircraft to yaw away from the direction of the turn. The extra drag can also affect roll rate and increase the total drag of the aircraft. However, in a level balanced turn the ailerons should be close to the neutral position and therefore the effect on turn performance should be minimal. Factors affecting climb performance Rate of climb Rate of climb is altitude gained over time, for example 500 feet per minute.The best rate of climb (Vy) is the airspeed at which an aircraft achieves the maximum altitude gain per minute. Angle of climb Angle of climb is altitude gained over horizontal distance. It may be expressed as an angle, or a percentage. The best angle of climb (Vx) is the airspeed at which an aircraft achieves the maximum altitude gain per unit of horizontal distance travelled. Generally Vx results in a steeper, slower climb while Vy gives a faster, shallower climb. It’s important to remember that both the best rate of climb and best angle of climb are generally expressed as airspeeds in an aircraft’s Pilot Operating Handbook. Holding these airspeeds in a climb results in the required climb rate and angle. Factors that affect rate and angle of climb Weight Heavier aircraft require more lift to climb, which can reduce the rate and angle of climb. Conversely, lighter aircraft can climb more rapidly, and achieve a steeper climb angle because they require less lift.
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