Level 4 PC Assessment Review – Aviation

Theory of Flight

  • Boundary Layer
      * Very thin layer of air lying over the surface of the wing
      * Includes laminar and turbulent flow, which are separated by the transition point
  • Laminar flow
      * Smooth airflow over the wing
      * Initial portion until the boundary layer is tripped at the transition point
      * Laminar flow airfoils reduce the drag by maintaining the laminar flow throughout a greater percentage of the chord
  • Conventional Airfoils
      * Thickest airfoils are generally thickest at 25% of the chord
  • Aspect ratio
      * Dividing span by the average chord
  • Wash in vs wash out
      * Wash in: increasing the angle of incidence at the wing tip relative to the wing root
      * Wash out: decreasing the angle of incidence at the wing tip
  • Wing tip modifications designed to increase lift or reduce drag
      * Wing tip fuel tanks
      * Winglets
      * Drooping wing tips
  • Slots and slats
      * Slots: auxiliary airfoils that remain fixed on the leading edge
      * Slats: auxiliary airfoils that move out in front of the leading edge at high angles of attack
  • Camber
      * Curvature of the airfoil

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Instruments

  • Pitot static system
      * Pitot static system
        * Connected to the airspeed indicator, altimeter and vertical speed indicator
        * Includes a pitot pressure source and static pressure source
          * Pitot tube measures ram air pressure, or dynamic pressure, by the air rushing in due to the forward movement of the aircraft
          * Static port measures the differences in atmospheric pressure, and are not affected by ram air pressure
        * All instruments are connected to the static pressure source, where only the airspeed indicator is attached to the pitot tube
  • Airspeed Indicator errors
      * Density Error
        * Density of air depends on atmospheric pressure and temperature
        * These variables affect the air speed indicator reading as it changes the pressure differential between components within the airspeed indicator
      * Position Error
        * Depends on location of pitot tube on the aircraft
        * Farther back on the aircraft, it may receive more eddies and give a less accurate reading, where as at the front of the aircraft it is in more smooth, laminar flow
      * Lag Error
        * Mechanical error due to friction between working parts
      * Icing or Water Error
        * Blocks the pitot or static pressure sources
  • Airspeeds
      * Indicated
        * What is read off the airspeed dial
      * Calibrated
        * Indicated corrected for instrument error
      * Equivalent
        * Calibrated corrected for compressibility factor
      * True
        * Equivalent corrected for the airspeed indicator error due to density and the temperature
        * Actual speed of the airplane through the air mass
      * Mnemonic to remember airspeeds: ICE Tea is a Pretty Cool Drink
        * Moves in a zig zag pattern from I to P to C, and so on to show the different airspeeds (top row) and the factor (bottom row) that changes it to the next airspeed

I C E T

P       C       D

  • Density altitude
      * Pressure altitude corrected for temperature
  • Precession
      * Tendency of a rotating body, when a force is applied perpendicular to its plane of rotation, to turn in the direction of its rotation 90 degrees to its axis and take up a new plane of rotation parallel to the force applied.
  • Mach number
      * Mach number is calculated by dividing the airspeed by the speed of sound

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Engine

  • Fuel selector valve
      * Use to select desired fuel tank to draw fuel from
      * Use to shut off the flow of fuel from the tanks
  • Throttle
      * Forward movement opens the throttle valve, which increases the fuel to air mixture and increases the power being produced by the engine
  • Gauges
      * Oil Pressure Gauge
        * Indicates oil pressure supplied by the oil pump to lubricate the engine
      * Oil Temperature Gauge
        * Gives a reading of the temperature of the oil
      * Cylinder Head Temperature Gauge
        * Records the temperature of one or more of the engine cylinder heads
        * Gives a reasonably good indication of the effectiveness of the engine cooling system
      * Carburetor Air Temperature Gauge
        * Indicates temperature of the mixture entering the manifold
        * Or may record temperature of the intake air entering the carburetor
      * Tachometer
        * Shows the speed at which the engine crankshaft is turning in hundreds of revolutions per minute
        * Arcs:
          * Green – good
          * Yellow – caution range
          * Red – danger range
      * Manifold Pressure Gauge
        * Settings are controlled by the throttle
        * Indicates the pressure of the fuel to air mixture in the engine intake manifold between the cylinders and the carburetor
  • Pitch
      * Distance a propeller travels forward in one revolution
  • Thrust is maintained throughout most of the diameter of the propeller by means of the variation in airfoil sections and the angle of attack
  • Increase in Altitude
      * Air becomes less dense so power decreases without corrective action by the pilot

Meteorology

  • Surface friction on winds
      * Causes lower wind speeds than would be expected from the pressure gradient
      * Slows down the wind speed due to contact resistance with the ground
  • Define air mass
      * Large section of the troposphere with uniform properties of temperature, moisture within the horizontal.
  • Anabatic and katabatic winds
      * Anabatic: up slope winds flowing from valleys up the slopes to higher elevations
      * Katabatic: down slope winds flowing from high elevation down to the valleys below
      * Mnemonic: Ana ran up the hill and kicked the cat down
  • Gust
      * Rapid and irregular change of wind speed
  • Main factors determining weather in an airmass
      * Moisture content
      * Cooling process
      * Stability of the air
  • Stable air conditions
      * Stratus clouds
      * Poor visibility
      * Steady precipitation
  • Unstable air conditions
      * Cumuloform clouds
      * Good visibility
      * Showering precipitation
  • Cold Air Mass
      * More dense so sinks
      * Undercuts warmer air where will ascend over the colder air

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  • Great Circle
      * Shortest distance between two points on the surface of the earth
  • Rhumb Line
      * Lines that cuts all meridians at the same angle
      * Allows for constant direction so that the navigator may have a constant heading
  • TVMDC Headings
      * Variation is the angle between true and magnetic headings
      * Deviation is the angle between magnetic and compass headings
      * Moving from T -> M -> C add west and subtract east (east is least, west is best)
  • Isogonal Line
      * Lines drawn joining places having the same variation
  • Agonic Line
      * Joining places of zero variation
  • Compass Lead and Lag
      * ANDS – acceleration causes turns to the north, deceleration causes turns to the south
      * Occurs on east and west headings
  • Meridians of Longitude
      * Semi-great circles joining the geographical poles of the earth
      * Measured 0 to 180 degrees east and west
  • Parallels of Latitude
      * Circles in the Earth’s surface that lie parallel to the equator
      * Measured 0 to 90 degrees north and south of the equator