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AVAT11001: Course Outline Aircraft and Terminology
Radio Communications Structure, Propulsion, Fuel Systems Electrical, Hydraulic Systems and Instruments Air Law Aerodynamics: Basics Aerodynamics: Performance Human Factors Meteorology Loading Take-off and Landing Performance Navigation
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Stuff to read Required Reading: BAK Chapter 6, pp
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Questions from the Reading
How does a pilot enter a climb? What causes stall? Why must the pilot not use the ailerons during the stall recovery? What is a steep turn? Why is it generally unwise to close the throttle before commencing the landing flare?
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Climbing If you wish to gain altitude, you should: Increase power
A climb at a given airspeed requires more thrust than level flight at the same airspeed Increase attitude When thrust is increased it can have 2 effects: it will increase airspeed and/or it will increase altitude. You can use the pitch attitude to hold a given airspeed and let the thrust increase altitude Trim Once you are established at the airspeed and climb rate you desire, you can use the trim controls to relieve the amount of force you need to apply to the control yoke
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The Physics of Climbs Forces Power See Figure 6-61 page 197
During a steady climb, the forces are balanced (they sum to zero) Velocity is constant, it just contains an upward component Potential energy is increasing, this requires power Power See Figure 6-65 page 199 Power is thrust multiplied by velocity Power can be used to change the energy of the vehicle It can be used to increase the kinetic energy (= ½mv2) by increasing velocity It can be used to increase the potential energy (= mgh) by increasing altitude
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Airspeed There are different airspeeds used for climbing
See Figure 6-60 page 196 and Figure 6-65 page 199 Vx, the best climb angle speed This speed occurs when you have the most excess thrust. You get the most altitude gain for the least horizontal distance covered If thrust is much greater than weight, you can climb vertically (no horizontal distanced covered) Vy, the best climb rate speed This speed occurs when you have the most excess power You get the most altitude gain in the least amount of time
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Descent If you wish to lose altitude, you should: Decrease power
A descent at a given airspeed requires less thrust than level flight at the same airspeed Decrease attitude When thrust is decreased it can have 2 effects: it will decrease airspeed and/or it will decrease altitude. You can use the pitch attitude to hold a given airspeed and let the thrust decrease altitude Trim Once you are established at the airspeed and descent rate you desire, you can use the trim controls to relieve the amount of force you need to apply to the control yoke
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The Physics of Descents
Forces See Figure 6-69 page 201 During a steady descent, the forces are balanced (they sum to zero) Velocity is constant, it just contains a downward component Potential energy is decreasing Power The power required for a descent is less than the power required for level flight This is not shown on the power required figure, but you can understand that it takes no power for a rock to fall from the sky. As you descend, you must be careful to not let your speed become too great The potential energy lost by descending will be converted into kinetic energy unless you take action to balance the forces
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Turns velocity desired path To cause an object to turn, a force must be applied perpendicular to the velocity of the object Think of a ball on a string To swing the ball in a circle, the string needs to apply a force in towards the centre of the circle For aircraft, this force is supplied by banking the wings and using a horizontal component of the lift force See Figure 6-76 page 205 force required to turn velocity force required to turn
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Steep Turns Turns are classified by the amount of bank angle used
Medium level turn: level flight with a 20° to 30° bank angle Climbing turn: during a steady climb, keep the bank angle 15° or less to maintain the climb rate Descending turn: keep the bank angle 30° or less to avoid high descent rates Gliding turn: keep the bank angle less than about 30° Steep turn: a turn of 45° or more Maximum rate turn: a turn which will change your heading as quickly as possible. Only used in emergency situations, like collision avoidance The greater the bank angle, the more difficult it is to maintain level flight in a turn See Figure 6-88 page 215
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Stalls Stalls occur when the angle of attack exceeds the critical stall angle See Figure 6-21 page 179 Most aerofoils have the property that the lift coefficient, CL, increases as the angle of attack increases. Eventually, the airflow over the top of the aerofoil will separate and lift will be lost. This will occur at a specific angle of attack that is a function of the shape of the aerofoil
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Stall Speed The speed at which a stall will occur is a function of many variables Weight Load Factor Bank Angle Power Flap Setting When stall speeds are calculated for aircraft operating manuals they often assume the worst case to produce conservative numbers Often you can fly below the listed stall speed without stalling. Especially if you have power on and are below the maximum weight You may still manage to stall the aircraft above the listed stall speeds. Especially if you have a high load factor (i.e. during a steep level turn)
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Spins Spins are complex aircraft motions in which all of the following occur: Rolling Yawing Pitching Slipping Rapid descent They are usually caused when one wing stalls before the other To recover from a spin: Centre the controls Close the throttle Apply full rudder opposite to the direction of the yaw Apply forward pressure until the rotation stops Recover from the dive (gentle aft pressure on the control yoke)
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Spiral Dives Spiral dives occur when the aircraft begins to bank. If you bank the aircraft and make no power or pitch changes, you will begin to descend. As the descent begins, the aircraft speeds up and the turn tightens. Spiral dives are very different from spins Spiral dives begin slowly, usually starting from high speeds Spins begin suddenly, usually starting from slow speeds To recover from a spiral dive, roll the wings level The danger of the spiral dive comes from a pilot noting a high descent rate and pulling back on the controls. This only tightens the dive and makes things worse if you do not level your wings first.
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For next week… Required Reading: BAK Chapter 8, pp
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