Flight Instruments Flashcards
PRINCIPLES OF A GYROSCOPE
Rigidity in space - a gyroscope remains in a fixed position in the plane in which it is spinning.
Precession - the tilting or turning of a gyro in response to a deflective force; occurs 90* later in the direction of rotation.
Describe the ATTITUDE INDICATOR
bank and pitch information
rigidity in space
normally vacuum-driven in GA aircraft but may electrically powered in others
Describe the HEADING INDICATOR
Rigidity in space
Normally powered by vacuum system in GA aircraft
What instrument is this
Turn coordinator
What does a turn coordinator show?
Rate of turn
and
Rate of roll
What instrument is this?
Turn-and-slip indicator
What does a turn-and-slip indicator show?
Rate of turn only
What are the 3 gyroscopic instruments?
Attitude indicator
Heading indicator
Turn indicators
What are the 3 pitot-static instruments?
Altimeter
Vertical speed indicator
Airspeed indicator
How does the ALTIMETER work?
Stack of aneroid wafers expand and contract with pressure from the static source
Mechanical linkage between aneroid and display translates pressure to an altitude indication
Above 18,000’ MSL the altimeter should be set to
29.92” Hg and operate in Flight Levels
INDICATED ALTITUDE is…
uncorrected altitude on the altimeter when set to local pressure setting
PRESSURE ALTITUDE is…
altitude above 29.92” Hg plane
Used when flying above transition altitude (18,000’)
DENSITY ALTITUDE is…
It is used for…
pressure altitude corrected for nonstandard temperature
performance calculations.
TRUE ALTITUDE is…
altitude above Mean Sea Level
ABSOLUTE ALTITUDE is…
height above airport elevation
Describe the VERTICAL SPEED INDICATOR
Diaphragm inside is connected to the static source
Area outside the diaphragm gets static pressure from a calibrated leak
Diaphragm expands or contracts and mechanical linkage moves the needle
Instantaneous VSI (IVSI) solves lag issue
Describe the AIRSPEED INDICATOR
Diaphragm receives ram air from pitot tube
Outside of diaphragm receives static pressure
Diaphragm expands and contracts and mechanical linkage displays airspeed
The ATTITUDE INDICATOR should show the correct attitude within…
5 minutes of starting the engine
What errors is the ATTITUDE INDICATOR susceptible to?
Acceleration (pitch up)
Deceleration (pitch down)
Rollout (after rollout shows slight turn in opposite direction)
What does the HEADING INDICATOR show?
Shows heading changes, doesn’t measure heading itself
What must you do to the HEADING INDICATOR for it to display the correct heading?
Calibrate it to magnetic compass to show correct heading
Some can be slaved to magnetic heading source, allowing it to sync automatically
Older ATTITUDE INDICATORS may be susceptible to what?
Tumble limit
DYNAMIC PRESSURE in regard to airspeed is the result of what?
Impact pressure minus static pressure
What is INDICATED AIRSPEED (IAS)?
Airspeed shown on the Airspeed Indicator
What is CALIBRATED AIRSPEED (CAS)?
IAS corrected for instrument and position errors
What is EQUIVALENT AIRSPEED (EAS)?
CAS corrected for compressibility error
What is TRUE AIRSPEED (TAS)?
Actual speed through the air
EAS corrected for nonstandard temperature and pressure
What is MACH NUMBER?
Ratio of TAS to the local speed of sound
What is GROUND SPEED (GS)?
Actual speed over the ground
TAS corrected for winds
What is the WHITE ARC on the ASI?
Flap operating range
Starts at Vs0, ends at Vfe
What is the GREEN ARC on the ASI?
Normal operating range
Starts at Vs1, ends at Vno
What is the YELLOW ARC on the ASI?
Caution range
Fly only in smooth air and with caution
What is the RED LINE on the ASI?
Vne
How will static port blockage affect the Airspeed Indicator?
Shows correct airspeed ONLY at blockage altitude
Climb - indicates lower speed than it should
Descend - indicates higher speed than it should
How will static port blockage effect the Altimeter?
Will freeze on the altitude where it was blocked
How will static port blockage affect the Vertical Speed Indicator?
It will freeze on zero
After verifying a static port blockage what should you do?
Use the alternate static source
or
Break the VSI window and expect reverse VSI information
When using the alternate static source a _______ static pressure is measured.
The ASI will…
The Altimeter will…
The VSI will…
lower
show a faster speed than it should
show a higher altitude than it should
momentarily show a climb
What is the only instrument affected by pitot tube blockage?
Airspeed Indicator
The ram air inlet of the pitot tube is blocked but the drain hole is open. What will happen the your IAS?
Drop to zero
The ram air inlet and the drain hole on the pitot tube are both clogged. How will your airspeed indicator respond?
It will act like an altimeter
No longer reliable
You suspect pitot tube blockage. What should you consider using?
Pitot heat
Ice might have formed in the tube
GENERIC INSTRUMENT TAXI CHECK
Airspeed - 0 KIAS
Turn Coordinator
- wings level, ball centered
- turns, correct direction, ball opposite turn
Attitude - pitch/ bank +-5* w/in 5 mins
Heading Indicator - set and correct
Altimeter - set, field elevation +-75’
VSI - 0 FPM
Mag Compass
- swings freely, full of fluid
- deviation card installed
- marker beacons, tested
NAV & Comms - set
GPS - checked and set
EFIS Cockpits
- PFD/MFD/EICAS
- check for X’s, messages, warnings, removed symbols
What are the Magnetic Compass errors and limitations?
Deviation - magnetic interference with compass (radios, magnetized parts, etc)
Variation - diff. between true (geographic) north and magnetic north
Magnetic Dip - compass dips along magnetic field toward magnetic pole. Unreliable close to poles
Accel/decel errors - E/W heading, accel shows temp N turn, decel shows temp S turn
North/south turn errors - compass leads to north, lags to south
Oscillation error - combo of mag dip, accel/decel and N/S turn errors
What is AHRS?
Attitude and Heading Reference System
Measures and sends attitude and heading information to the PFD for display
More accurate and reliable than traditional gyro systems
What is an ADC?
Air Data Computer
Replaces the mechanical pitot-static instruments
Takes inputs from pitot, static and temperature ports and computes airspeed, true airspeed, vertical speed and altitude
What computes and displays command bars on the attitude indicator to help you fly a selected heading, course or vertical speed?
Flight Director
What does the Flight Management System (FMS) do?
- Gives guidance to the autopilot and flight director
- Monitors and selects the best navigation source for accurate positioning
Describe the EFIS
Electronic Flight Instrument System
AKA “glass cockpit”
What is a PFD?
Primary Flight Display
Shows flight data such as attitude, altitude, airspeed, VSI, heading and rate tapes
What shows a variety of info like moving maps, systems status, weather and traffic?
Multi-Function Display (MFD)
In the US, when operating below 18,000’ MSL…
Regularly set the altimeter to a station within 100 NM
Nemonic for when you’re flying from an area of high pressure to low pressure
or
from an area of hot temps to low temps
High to low - Look out below
This error occurs at altitudes above 10,000’ and airspeeds faster than 200 knots as air begins to “compress” in the pitot tube causing CAS to indicate higher that it should
Compressibility Error
