Pitot Static System Flashcards
What instruments are they?
altimeter, vertical speed, airspeed (only one for pitot)
how does an altimeter work?
measures pressure of the ambient air (static port) and displays it as feet above a selected pressure level
Limitations of a pressure altimeter?
nonstandard pressure and temp; temp variations expand or contract the atmosphere and raise or lower pressure levels that the altimeter senses.
on a warm day: pressure higher. Altimeter reads lower than actual
on a cold day: pressure lower. Altimeter reads higher than actual
Changes in surface pressure also affect it at altitude
higher than standard pressure: alt. indicates lower than actual
lower than standard: alt indicates higher than actual
Define the following and how you figure them out?
Absolute altitude: vertical distance of an aircraft above the terrain (AGL)
Indicated: read from altimeter afer it is set to current altimeter setting
PRessure: set to 29.92 and read altitude
true: MSL
Density altitude: pressure altitude corrected for nonstd temp.
How does the airspeed indicator work?
differential pressure gauge. measures the impact pressure or RAM air with pitot tube vs. static pressure from static port
Limitation of airspeed indicator?
subject to proper flow of air with the pitot static system
airspeed indicator errors?
position error: caused by static port(s) senseing erroneous static pressure from things like slipstreams
density error: changes in altitude and temp not compensated for
compressibility error: caused by the packing of air into the pitot tube at high speeds resulting in higher than normal indications. Not a problem at slow speeds like my little cessna
Different types of speeds?
indicated: read from airspeed indicator
calibrated: corrected for position or installation and instrument errors. It is = to TAS at sea level in standard atmosphere.
True: corrected for altitude and non-std temp. speed of airplane in relation to the air mass it is flying in
Color coded airspeed indications:
white arc: flaps range
Lower white arc: Vs0 (stall @ landing config)
upper white arc: VFE (max falp extension speed)
Green arc: normal operating range
lower green arc: Vs1 (clean stall speed)
Upper green arc: VNO: (normal ops speed or max structural cruise)
Yellow arc: caution range (smooth air only)
Red line: VNE (never exceed)
How does VSI work and what are limitations?
Also a differential pressure gauge. But it has a vent through a calibrated orifice that causes pressure inside the case to change more slowly than inside the aneroid.
Limitatiosn are that it lags behind the aircraft and only reads accurately when the aircraft is stablized. 6 to 9 second lag
