Preflight - Flight Instruments Flashcards
What instruments operate from the pitot/static system?
Altimeter
Vertical Speed Indicator
Airspeed Indicator
How does an altimeter work?
Aneroid wafers expand and contract as pressure changes in turn changing the pointer of the instrument
What type of errors are altimeter subject to?
Mechanical Errors: Differences between ambient temperature/pressure
Inherent Errors: Non standard temperature/pressure
-Warmer than standard: less dense air so true altitude is higher than indicated
-Colder than standard: more dense air so true altitude is lower than indicated
-Extreme cold: +10°C- -50°C pilots should add cold temperature correction
-High to low: True altitude is lower than indicated
-Low to high: True altitude is higher than indicated
*High to low/Hot to Cold look out below
For IFR flight, what is the maximum allowable error for an altimeter?
More than 75 feet with correct pressure setting should be considered unreliable
Define and state how to determine the following: Indicated altitude True altitude Absolute altitude Pressure altitude Density altitude
Indicated: what is read from the altimeter with correct setting
True: Vertical distance of MSL
Absolute: Vertical distance of AGL
Pressure: Indicated by 29.92” setting, used to compute density altitude
Density: pressure altitude corrected for non standard conditons
Does adjusting the altimeter’s Kollsman window setting have any effect on the altitude displayed to an ATC controller? Why?
No, encoding altimeter measured to 29.92”Hg on the transponder. The Kollsman window does not effect this information.
How does the airspeed indicator operate?
Measures the difference in ram pressure from the pitot tube and atmospheric pressure from the static port.
What are the limitations the airspeed indicator is subject to?
Must have proper air in the pitot and static system
What are the errors that the airspeed is subject to?
Position error- caused by sensing of erroneous static readings
Density error- changes in altitude and temperature are not compensated for by the instrument
Compressibility error- packing air in the pitot tube at high speeds (resulting in higher indications) above 180 KIAS
What are the different types of aircraft speeds?
Indicated: IAS shown on the instrument
Calibrated: CAS shows speed through the air, IAS corrected for instrument and position error
Equivalent: EAS, CAS corrected for compression in the air inside the pitot tube (CAS=EAS at STD pressure)
True: TAS, CAS corrected for non standard pressure/temperature (TAS=CAS as STD pressure)
What airspeed are indicated by various color codes found on the dial of an airspeed indicator?
White arc: Flap operating
Lower White arc: Vso Stall speed in landing configuration
Upper White arc: Vfe maximum speed with flaps extended
Green arc: normal operating range
Lower green arc: Vs1 stall speed clean
Upper green arc: Vno maximum structural cruise
Yellow arc: Caution range
Red line: Vne never exceed speed
How does the vertical speed indicator work?
VSI rate of pressure change instrument that gives a deviation from constant pressure. Uses an aneroid, static pressure and calibrated leak. Any change in static pressure cause the aneroid to compress or expand to move the needle.
What are the limitations of a vertical speed indicator?
Not accurate until stabilized, sudden or abrupt movements lead to inaccurate indications.
What instruments are affected when the pitot tube, ram, air inlet, and drain hole freeze?
Only airspeed affected, will behave similar to a altimeter
What instruments are affected when the static port freezes?
Airspeed: Will be accurate at the altitude port became frozen, otherwise it will be inverse of altitude
Altimeter: Indicates altitude is became blocked
Vertical speed: Will indicate level flight
If the air temperature is +6°C at an airport elevation of 1,200’ feet and a standard (average) temperature lapse rate exists, what will be the approximate freezing level?
4,200’
6°C / (average lapse rate 2°) = 3,000’ freezing level + 1,200’(field elevation)= 4,200’
What corrective action is needed if the pitot tube freezes? If the static port freezes?
Pitot tube: use pitot heat
Static system: Use alternate static or break the instrument face
What indications should you expect while using alternate air?
Altimeter: will indicated higher than normal altitude
Airspeed: will indicated greater airspeed
Vertical speed: Show a momentary climb
What instruments contain gyroscopes?
Attitude
Heading Indicator
Turn coordinator/indicator
Name several types of power sources commonly used to power the gyroscopic instruments in an aircraft?
Electrical Pneumatic Venturi tube Wet/dry vacuum systems Usually two different systems are used
How does the vacuum system operate?
Vacuum or pressures systems use air to spin the gyroscopic systems
*vacuum is usually 4.5”-5.5” Hg
What are two important characteristics of gyroscopes?
Rigidity: Gyro prevents the axis of rotation to tilt
-Attitude indicators
-Directional gyro
Precession: Force 90°from the direction of rotation.
-Turn coordinators
How does the turn coordinator operate?
Uses precession of the gyro to estimate bank and rate of turn
Inclinometer measures the force of gravity and the force of inertia caused by the turn
What information does the turn coordinator provide?
Miniature aircraft shows rate of turn, rate of roll, and direction of turn. Inclinometer shows quality of turn
- Slip: ball inside the turn - Skid: ball outside the turn
What is the source of power for the turn coordinator?
Driven by electricity or air
How does a heading indicator work?
Uses rigidity in space, rotor turns on the vertical plane. The airplane moves around the gyro to indicate heading information.
What are the limitations of a heading indicator?
≈55° bank
≈55° pitch
if limits are reach, instrument will tumble until caged
What type of error is the heading indicator subject to?
Due to precession HI will drift from set heading typically 15° per hour
How does the attitude indicator work?
Gyro mounted on the horizontal plane and used rigidity and space. Indicates the attitude relative to the true horizon
What are the limitations of an attitude indicator?
Bank limits are usually 100° to 110°
Pitch limits are usually 60° to 70°
If limits are reached, it will tumble until restablized
Is the attitude indicator subject to errors
Errors are uncommon
Can show nose high/low in acceleration/deceleration
Roll out of a 180° turn will show climb and opposite turn
How does a magnetic compass work?
Magnets mounted on the compass card align themselves with line of magnetic forces
What limitations does the magnetic compass have?
Jewel-and -pivot type mount allows for free movement up to 18° as steeper angles indications are unreliable
What are the various compass errors?
Variation: angular difference between true and magnetic north
Deviation: Electrical and magnetic interference
Magnetic Dip: Accelerate North Decelerate South
Oscillation: Erratic movement caused by turbulence
Northerly errors: Undershoot North Overshoot South (≈to the latitude of the location)
Describe the function of the following equipment acronyms: PFD, MFD, AHRS, ADC, FMS, FD, TAWS, TIS?
PFD: Primary flight display MFD: Multi function display AHRS: Attitude heading reference system ADC: Air data computer (sends information to PFD, AHRS, transponder) FMS: Flight management system FD: Flight director TAWS: Terrain awareness and warning system TIS: Traffic information service
What is the function of a magnetometer?
Measures the strength of earth’s magnetic fields, provides information to AHRS for PFD
Does an aircraft have to remain stationary during AHRS system initialization?
Some AHRS need to be initialized on the ground allowing proper attitude reference
If a failure of one of the displays (PFD or MFD) occurs in an aircraft with an electronic flight display, what will happen to the remaining operative display?
In the event of failure, some systems offers reversion capability to display necessary information
When a display failure occurs , what other system components will be affected?
Some systems, failure of a display will result in loss of nav, comms, and GPS
What display information will be affected when an ADC failure occurs?
Inoperative airspeed, altitude, and VSI by red Xs indicate ADC failure
What display information will be lost when an AHRS failure occurs?
An inoperative attitude by red X indicated AHRS failure
How will loss of a magnetometer affect the AHRS operation?
Heading information will be lost
