Transcript Flight Instrument Systems

Flight Instrument Systems
Gyroscopic Flight Instruments
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Attitude Indicator
Heading Indicator
Turn Coordinator
Gyros are mounted on gimbals which
allow the plane to move about the gyro
which remains fixed in space
Fundamental Concepts
• Rigidity in Space - a wheel with a
heavily weighted rim spun rapidly tends
to remain fixed in the plane in which it is
spinning
• Precession - when an outside force is
applied the gyro responds as if the force
had been applied at a point 900 further
around in the direction of rotation
Pendulous Vanes
• Open and close to help keep the gyro
parallel to the ground
• Act on the attitude indicator in an
undesirable way during turns do to
centrifugal force
• Errors are at a maximum in a 1800
turn, no more than 50 of bank
Tumbling
• Old attitude indicators would precess
rapidly or tumble if you exceeded 1000
or 600 of pitch
• Often these attitude indicators had a
caging device to right them
Heading Indicators
• Must be aligned with the magnetic
compass to make it work (Free Gyro)
• Must be checked approximately every
15 minutes
• A heading indicator with a north
seeking system is called a slaved gyro.
Turn Indicators
• Standard rate turn is 30
• A 3600 turn takes 2 minutes
• To determine the angle of bank
required to make a standard rate turn
take the (true airspeed in Knots divided
by 10) + 5
• At 100 Knots it is approximately 150
Turn Instruments
• Turn coordinator
– Rate of roll
– Rate of turn
• Turn and slip indicator
– Rate of turn only
• Inclinometer
Slip and Skid
• Slip - rate of turn is too slow for the
bank and the ball moves to the inside
of the turn
• Skid - rate of turn is too great for the
angle of bank and the ball moves to the
outside of the turn
Slip
Skid
Instrument Checks
• With the power off, warning flags
display OFF indications
• Inclinometer full of fluid and ball at
lowest point
• Turn on master and listen for grinding
noise in electric gyros
• After starting check ammeter
Instrument Checks
• Listen for noise from vacuum gyros
• If you think you hear noise, shut off the
engine and listen to the gyros spin
down
• It can take 5 minutes for the gyros to
reach full operating speed
Instrument Checks
• While taxing out, the turn coordinator
and heading indicator should indicate a
turn in the correct direction
• The ball should swing to the outside in
turns
• Align the heading indicator with the
magnetic compass during runup and
check again before takeoff
Magnetic Compass
• Errors
– Variation - the angular difference between
the true and magnetic pole
– Deviation - errors due to magnetic
interference with the metal components
of the aircraft
– Magnetic dip - the compass tries to point
down deep inside the earth
Variation
Deviation
Magnetic Dip
Northerly Turning Error
Acceleration Error
Pitot Static Instruments
• Airspeed Indicator
• Vertical Speed Indicator
• Altimeter
Airspeed Indicator
Airspeed Indicator
VSO
VNE
VNO
VFE
Colored Arcs
• Yellow - operate in the caution area
only in smooth air
• Green - normal operating range
• White - full flap operating range
Types of Airspeeds
• Indicated - displays the speed of your
plane. It is the basis for determining your
aircraft performance
• Calibrated is indicated corrected for
installation and instrument error
• Equivalent airspeed is calibrated airspeed
corrected for adiabatic compressible flow
at a particular altitude
Types of Airspeeds
• True Airspeed is the actual speed your
airplane moves through the air. The
calibrated airspeed corrected for
density altitude
• Mach is the ratio of the aircraft’s true
speed to the speed of sound
Altimeter
Types of Altitude
• Indicated - is what you read on the
altimeter
• Pressure - is displayed when you have
the altimeter set to 29.92. It is the vertical
distance above the standard datum plane
• Density - pressure corrected for
nonstandard temperature
Types of Altitude
• True - is the actual height of an object
above mean sea level.
• Absolute - is the actual height of the
aircraft above the earth’s surface
ISA
• International Standard Atmospheric
Sea Level - 150 C - 29.92 in HG
• Before IFR flight the altimeter set to
the current altimeter setting should be
within 75 feet of the actual elevation
Vertical Speed Indicator
Vertical Speed Indicator
• Displays rate and trend information
• 6-9 second delay
• Gives erratic readings during turbulence
or when applying abrupt control inputs
• Not setting before starting engines and
use that setting for zero
• Not legally required for IFR flight
Pitot Static System
Ram air
inlet
Drain hole
System Errors
• Can be caused by blockage of the pitot
tube, static port or both
• Blockages can be caused by moisture,
ice, dirt or even insects
• Use pitot tube cover when parked
• Use pitot heat when flying in visible
moisture
Pitot Blockage
• Ram air inlet clogged, drain hole open
pressure in line to airspeed indicator
drops to zero, airspeed indicator
indicates 0
• Ram air inlet clogged, drain hole
clogged, air trapped in line, airspeed
indicator does not react to changes in
speed but altitude like an altimeter
Static Blockage
• Airspeed indicator will continue to
react to changes in airspeed but they
will not be accurate
• Altimeter will freeze in place
• VSI will freeze at zero
• Use alternate static source or break
glass in VSI