Flight Instruments Flashcards

1
Q

Static Pressure of Atmosphere

A
  • Pressure of atmosphere
  • Static Port
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2
Q

Total Pressure

A
  • Pressure created inside the pitot tube as the aircraft moves forward
  • Includes both static pressure and pressure increase due to forward motion of aircraft
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3
Q

Dynamic Pressure

A
  • Pressure difference between total pressure and static pressure
  • Direct indication of forward speed of aircraft
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4
Q

Density Altitude

A

Pressure Altitude corrected for non-standard temperature

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5
Q

True Altitude

A

Exact Altitude above sea level

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6
Q

Absolute Altitude

A

Exact Altitude above ground level

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7
Q

Altimeter Operation

A
  • When altitude increases, static pressure decreases, capsule expands, gears convert expansion to needle movement up
  • sub scale knob used to correct for high and low pressure air (28”Hg - 31”Hg)
  • Should not be more than +/- 50 feet of elevation when on ground
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8
Q

Altimeter Position Error

A

Static port senses dynamic pressure during slips, causing altimeter error

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9
Q

Altimeter Scale Error

A
  • Aneroids not assuming precise size of pressure difference
  • Increases with altitude
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10
Q

Altimeter Mechanical Error

A

Caused by misalignment or slippage in gears

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11
Q

Altimeter Density Error

A
  • Caused by variations in atmospheric pressures and temperatures
  • 1’’ Hg error = 1000’ ft error
  • High to low, lookout below (altimeter over-reading)
  • Low to high, clear blue sky (altimeter under-reading)
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12
Q

Altimeter Hysteresis Error

A

A lag in indications due to elastic properties of the materials used to construct aneroids

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13
Q

Altimeter Reversal Error

A
  • Caused by rapid or abrupt attitude changes
  • only momentary in duration
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14
Q

Vertical Speed Indicator (VSI) Operation

A
  • When altitude increases, static pressure decreases, capsule contracts, gears convert contraction to needle movement up
  • VSI returns to 0 when pressure in case matches pressure in diaphragm
  • Should be inspected if showing greater than 100 fpm on the ground
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15
Q

VSI Lag Error

A
  • VSI lags 6-9 seconds to settle on a rate due to calibrated leak which is connected to the static source
  • Shows trends immediately
  • smoother transitions produce less lag
  • Instantaneous VSI’s have accelerometers that move the pointer until diaphragm takes over
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16
Q

Calibrated Airspeed

A

Indicated airspeed corrected for instrument and position error

17
Q

Equivalent Airspeed

A

Calibrated Airspeed corrected for compressibility factor

18
Q

Airspeed Indicator Operation

A
  • Measures difference between total pressure (pitot tube) and static pressure (static port) to get dynamic pressure
  • Dynamic pressure is a direct indication of airspeed
19
Q

Airspeed Density Error

A
  • Since static pressure decreases with altitude, total pressure will also decrease
  • This means TAS will be higher than IAS
  • Increase IAS 2% for each 1000ft to obtain TAS
20
Q

Airspeed Instrument Error

A

Caused by mechanical errors present within the instrument

21
Q

Hysteresis Error

A

Lag in indications due to elastic properties of aneroids

22
Q

Airspeed Position Error

A
  • Airframe disturbing airflow around pitot tube or static port
  • Example is high angle of attack
  • CAS corrects this
23
Q

Pitot Source Blocked

A
  • Airspeed Indicator = increasing in climb / decreasing in descent
  • Altimeter = unaffected
  • VSI = unaffected
24
Q

One Static Source Blocked

A

All are inaccurate while slipping and very sensitive in turbulence

25
Q

Both Static Sources Blocked

A
  • Airspeed Indicator = decreasing in climb / increasing in descent
  • Altimeter = Freezes
  • VSI = Reads 0
26
Q

Both Static and Pitot Sources Blocked

A
  • Airspeed Indicator = Freezes
  • Altimeter = Freezes
  • VSI = Reads 0
27
Q

Pitot Source Partially Blocked

A
  • Airspeed Indicator =Reads 0
  • Altimeter and VSI unaffected
28
Q

Static Source Partially Blocked

A
  • All will under read in a climb and catch up after levelling off
  • All will over read in a descent and catch up after levelling off
29
Q

Attitude Indicator Operation

A
  • Gyro Mounted Horizontally and spins about a vertical axis
  • Usually Vacuum driven
  • Functions on principle of rigidity in space
  • Linkages transfer movements around gyro to artificial horizon face
  • Should be stable while taxiing
  • Limitations are 85 degrees of bank and pitch
30
Q

Heading Indicator Operation

A
  • Gyro Mounted Vertically and Spins Horizontally
  • Usually vacuum driven
  • Functions on principle of rigidity in space
  • Linkages transfer movements around gyro to heading indicator face
  • Excessive precession indicates that the gyro is worn
  • Limitations are 85 degrees of bank and pitch
31
Q

Mechanical Precession Heading Indicator Error

A
  • Frictional forces cause gyro to precess
  • Causes gyro instruments to drift 3º every 15 minutes
  • Reset heading indicator every 15 minutes
32
Q

Apparent Precession Heading Indicator Error

A
  • Earth rotates under the gyro
  • Heading appears to precess depending on latitude
  • zero at the equator, 15 degrees an hour at the poles
  • Corrected by resetting every 15 minutes
33
Q

Turn and Slip Operation

A
  • Provides direction and rate of turn, as well as coordination
  • Gyro Mounted Vertically and Spins Horizontally
  • Electrically Driven
  • Functions on principle of gyroscopic precession
  • Needle only sensitive to yaw, not roll
34
Q

Rate One Turn

A
  • On L or R in turn and slip or turn coordinator
  • 180º per minute
35
Q

Turn Coordinator Operation

A
  • Gyro Mounted Vertically and Spins Horizontally
  • Canted at 35 degree angle
  • Usually electrically driven
  • Functions on principle of gyroscopic precession
  • Sensitive to roll as well as yaw
36
Q

Magnetic Compass Operation

A
  • Mounted on a pivot and free to rotate within bowl of kerosene
  • Should be free and swinging during turns on the ground
  • Limited to 20º of pitch
  • Unreliable in NDA due to magnetic dip
37
Q

Variation

A
  • Difference between magnetic north and true north
  • Add westerly track / subtract easterly track to true track to get magnetic track
38
Q

Acceleration Compass Errors

A
  • Causes a turning error
  • ANDS (Accelerate North Decelerate South)
  • Error does not exist on north and south headings
39
Q

Turning Compass Errors

A
  • Causes an acceleration error
  • SAND (South Advance North Delay)
  • Error does not exist on east and west headings