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Theory of Flight

Theory of Flight. 6.09 Flight Instruments and Performance Factors References: FTGU pages 32-34, 39-45. 6.09 Flight Instruments and Performance Factors. Pitot Static System and Instruments Pitot Static Blockages Asymmetric Thrust Precession Slipstream Climbing Gliding.

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Theory of Flight

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  1. Theory of Flight 6.09 Flight Instruments and Performance Factors References: FTGU pages 32-34, 39-45

  2. 6.09 Flight Instruments and Performance Factors • Pitot Static System and Instruments • Pitot Static Blockages • Asymmetric Thrust • Precession • Slipstream • Climbing • Gliding

  3. Pitot Static Instruments • There are three pressure instruments • The Altimeter (Alt) • The Vertical Speed Indicator (VSI) • The Air Speed Indicator (ASI) • There are two pressure sources • Static Pressure • Pressure surrounding the aircraft • Pitot Pressure • Pressure created by forward motion of the aircraft • Also called dynamic pressure

  4. Pitot Static Instruments

  5. The Altimeter Altimeter • Operates on static pressure • Higher pressure equals lower altitude • Aneroid capsules or wafers expand and contract, mechanically moving the needles

  6. Altimeter Markings • Small hand reads tens of thousands of feet • Medium hand reads thousands of feet • Large hand reads hundreds of feet

  7. Altimeter Errors • Pressure Error • Different pressures exist in different locations • The altimeter setting compensates for changes in pressure • Temperature Error • There is seldom standard temperature with a standard lapse rate • Mountain Effect Error • Air is deflected around mountains • According to Bernoulli's Principle, the pressure in the airflow drops, which will affect the altimeter reading

  8. The Airspeed Indicator Airspeed • Reads airspeed (not ground speed) • Measures the difference between static and pitot pressures

  9. ASI Markings • Marked in Knots or MPH • Red: VNE • Yellow: Caution Range • Highest point VNE • Lowest point VNO • Green: Normal Range • Highest point VNO • Lowest point VS • White: Flaps Range • Highest point VFE • Lowest point VSO

  10. Some “V” Speeds • VNE: Never Exceed Speed • VNO: Maximum Structural Cruising Speed or Normal Operating Limit Speed • VS: Power Off Stalling Speed (clean configuration) • VFE: Maximum Flaps Extended Speed • VSO: Power Off Stalling Speed (flaps and gear down) • VA: Manoeuvring Speed • VB: Maximum Gust Intensity Speed

  11. ASI Errors • Density Error • Nonstandard pressure or alt other than 0’ASL • Position Error • Eddies or the angle the pitot tube meets relative airflow • Lag Error • Mechanical friction • Icing Error • Ice covering the intake of the pressure sources • Water Error • Water in the system

  12. Vertical Speed Indicator • Reads Vertical Speed • Measures the rate of change in static pressure

  13. VSI Markings • The VSI is marked in positive and negative feet per minute (fpm) of vertical speed • Could also indicate in knots of vertical speed

  14. VSI Errors • Lag • The change in altitude must occur before the VSI can register the change • If pitch changes are slow, the lag will be less intense than if the pitch changes are sudden • Can reverse in extreme manoeuvres

  15. Pitot Static Blockages • Pitot Tube Complete Blockage • Effects airspeed indicator ONLY • Airspeed will over read in a climb and the speed will under read in a decent • Static Port Complete Blockage • Altimeter will freeze at the altitude indicated • Vertical speed indicator, if showing a rate-of-climb or -decent will reduce to zero and freeze at zero, if was showing no rate-of-climb will freeze at zero • Airspeed will under read in a climb and will over read in a descent

  16. Asymmetric Thrust • Caused by the descending blade of the propeller having a greater angle of attack than the ascending blade • Most noticeable at high angles of attack and high power settings • Rudder is used to compensate (clockwise prop rotation needs right rudder)

  17. Precession • The propeller acts as a gyroscope • Rigidity in Space • A gyro will rotate in the same plane and resist change • Precession • If forced to change, there is a tendency to rotate 90° to the original axis and rotate parallel to the applied force • These tendencies are overcome using control inputs as required

  18. Slip Stream • Air pushed backwards by the propeller has a corkscrew pattern which applies force to one side of the vertical stabilizer • Offset fin and rudder input compensates • Clockwise rotation moves the nose to the left requiring right rudder

  19. Climbing • Climbing changes how forces are applied to the airplane

  20. Climbing • Best Angle of Climb, VX • Best gain for distance(by flying) • Best Rate of Climb, VY • Best gain for time(by flying) • Normal Climb • Better engine cooling, control, and visibility over the nose

  21. Gliding • Gliding also changes how forces act on the airplane

  22. Gliding • Gliding for Range • Best distance covered for altitude (by flying best L/D) • Gliding for Endurance • Best time airborne for altitude (by flying min-sink)

  23. Confirmation Check

  24. Confirmation Check • What are the pitot static instruments? • What is another name for pitot pressure? • Which instrument uses pitot pressure? • What is the difference between VX and VY? • How does a glider maintain airspeed? • The difference between static and pitot pressure gives?

  25. CF-18 with Pilot Visible

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