Flight Instruments FLT 110 H1

CONTENTS

  • Pitot Static Instruments
  • Vacuum System
  • Magnetic Compass

Atmospheric Conditions 

International Standard Atmosphere (ISA)

  • Pressure = 29.92 inches Hg at Sea Level or 1013.25 MB
  • Temperature = 15 Degree Celsius (50 Degrees F)

Standard Lapse Rate 

  • Temperature lapses 2 Degree per 1,000 feet
  • Pressure lapses at 1 inch Hg per 1,000 feet

The 6 Basic Flight Instruments 

  1. Airspeed Indicator
  2. Attitude Indicator
  3. Altimeter
  4. Turn Coordinator
  5. Heading Indicator
  6. Vertical Speed Indicator (VSI)

Pitot Static System

Airspeed Indicator 

Labeled Airspeed Indicator

Types of Airspeed

  • Indicated Airspeed - Speed shown on the airspeed indicator
  • Calibrated Airspeed- Indicated Airspeed corrected for calibration error
  • Equivalent Airspeed- Calibrated Airspeed for compressibility error
  • True Airspeed- Equivalent Airspeed correct for density error (altitude and nonstandard temperature)
  • Ground Speed (GS)- Speed over the ground

Altimeter 

How to Read an Altimeter

Types of Altitudes 

  • Indicated Altitude- is the altitude you read from the altimeter when it is set to the current altimeter setting. When operating below 18,000 feet MSL, you must set the altimeter to the local setting to indicate your approximate height above mean sea level (MSL).
  • Calibrated Altitude- is indicated altitude corrected to compensate for instrument error.
  • Pressure Altitude- is displayed on the altimeter when it is set to the standard sea level pressure of 29.92 in. Hg. It is the vertical distance above a theoretical plane, or standard datum plane, where atmospheric pressure is equal to 29.92 in. Hg. Regulations require that you set the altimeter to 29.92 when operating at or above 18,000 feet MSL.
  • Density Altitude- is pressure altitude corrected for nonstandard temperature. It is a theoretical value used to determine airplane performance. Example: When density altitude is high (temperatures are above standard), aircraft performance degrades.
  • True Altitude- actual height above mean sea level (MSL)
  • Absolute Altitude- Actual height above ground level (AGL)

Altimeter Errors 

  • Flying from high pressure to low pressure without changing altimeter setting (instrument thinks you’re higher). Indicated Altitude will be higher than actual altitude. 1 inch change in altimeter setting per 1,000 feet.
  • Temperature impact on true altitude. Warm days Actual altitude is higher than indicated
  • Cold days= Actual altitude is lower than indicated.

Altimeter Checks

On the ground, set altimeter to local altimeter setting. Once set, altimeter must shown within 75ft of field elevation.

Vertical Speed Indicator

Pitot Static System Blockages

Vacuum System

Turn Coordinator

Characteristics of Turn Coordinator

  • Miniature Airplane
  • Turn Index= 3 Degrees Per Second
  • Shows roll and yaw of airplane
  • Ball shows whether the angle of bank is coordinated with the rate of turn

Attitude Indicator

Characteristics of Attitude Indicator

  • Artificial Horizon (blue side up)
  • Miniature Airplane
  • Bank Scale
  • Adjustment knob

Heading Indicator (Directional Gyro)

Characteristics of Heading Indicator

  • typically "free gyros" not magnetically driven
  • Periodically needs to be manually aligned with the compass- error due to gryoscopic precession
  • Adjustment Knob

Magnetic Compass

Magnetic Compass Terms

  • Variation-angular difference between Magnetic North and True North. Shown on sectionals and will be taught in navigation lessons.
  • Deviation-compass error due to disturbance from metals and electrical accessories within the airplane. Correction card shows adjustments to magnetic heading.

Magnetic Compass Errors

  • When accelerating or decelerating on an easterly or westerly heading the compass will make a turn. Through inertia in the compass and because the acceleration/decelerating vector is more or less perpendicular to the earth magnetic lines this will result in a turning of the compass. On a northerly or southerly heading the compass will usually not turn but dip. Remember ANDS: Acceleration gives a turn to the North and a Deceleration to the South in the northern hemisphere. In the southern hemisphere it is exactly the opposite: an Acceleration gives a turn to the South and a Deceleration a turn to the North.
  • Turning Errors- Compass lags when turning from north.
  • Compass leads when turning south.
  • Use acronym UNOS (undershoot north overshoot south).

Credits:

Created with images by Dimitry B - "Cirrus clouds, El Calafate, Argentina"

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