Flight Instruments Flashcards
How does the altimeter work?
Android wafers expand & contract as atmospheric pressure changes.
Shaft & gear linkage rotate the pointers on the dial of altimeter.
What instruments operate from Pitot/static system?
Altimeter
Vertical Speed Indicator
Airspeed Indicator
What limitations does a pressure altimeter have?
Temperature variations: expand/contract atmosphere and raises/lowers pressure levels.
Changes in surface pressure also affect pressure levels at altitude
Rule of thumb for limitations of a pressure altimeter:
Hi to low or hot to cold look out below!
For IFR flight, what is the maximum allowable error for an altimeter?
75 feet off field elevation
anything more considered unreliable
Define indicated altitude:
Read off the face of the altimeter
Define pressure altitude:
Indicated altitude with 29.92” Hg set in Kollsman window.
Define true altitude:
Height above sea level
Define absolute altitude:
Height above ground.
Subtract the terrain elevation from true altitude.
Define density altitude:
Pressure altitude corrected for nonstandard temperature
How does airspeed indicator work?
It measures the difference between RAM pressure from the Pitot and atmospheric pressure from the static source
What limitations does an airspeed indicator have?
It must have proper flow of air through the pitot/static system
What errors does an airspeed indicator have?
Position error: slip stream flow
Density error: changes in altitude and temperature not compensated for by the instrument
Compressibility error: packing the air into pitot tube at high airspeed
Define indicated airspeed:
Speed read off the airspeed indicator
Defined calibrated airspeed:
Airspeed after corrected for position, installation and instrument errors
Defined equivalent airspeed:
Airspeed corrected for position, instrument error and for adiabatic compressible flow
Defined true airspeed:
Speed in relation to air mass in which it is flying
Function airspeed indicator: white Arc
Flat operating range
Function airspeed indicator: bottom of white arc
Flaps down stall speed
Function airspeed indicator: top of white arc
Maximum airspeed for flaps down flight
Function airspeed indicator: green arc
Normal operating range
Function airspeed indicator: bottom of green arc
Flaps up stall speed
Function airspeed indicator: top of green arc
Maximum airspeed for rough air
Function airspeed indicator: yellow arc
Structural warning area
Function airspeed indicator: bottom of yellow arc
Maximum airspeed for rough air
Function airspeed indicator: top of yellow arc
Never exceed airspeed
Function airspeed indicator: red radial line
Never exceed airspeed
How does the vertical speed indicator work?
Change of pressure expands/contract a diaphragm.
It is connected to the indicating needle through gears and levers.
VSI is connected to a static pressure line through a calibrated leak.
What are the limitations of the vertical speed indicator?
Not accurate until stabilized.
Sudden or abrupt changes will cause Arronia’s instrument readings.
Not reflected immediately due to calibrated leak.
Is Pitot ram air inlet & drain hole freezes, what instruments are affected?
Only airspeed indicator.
Acts like the altimeter.
What instruments are affected if static port freezes?
Airspeed indicator: descent will read high, climb will read low. (Very dangerous)
Altimeter: will indicate sustained altitude
Vertical speed: will indicate level flight
What is the corrective action if the Pitot tube freezes?
Turn pitot heat on
What is the corrective action if the static port freezes?
Use alternate air if available
or break the face of the static instrument
When using alternate air, altimeter will indicate:
Higher than actual altitude
When using alternate air, airspeed will indicate:
Greater than actual airspeed
When using alternate air, vertical speed will indicate:
A climb while in level flight
