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Flashcards in Flight INstruments Deck (29)

Pitot-static System

Air Sources?

•Vertical Speed Indicator
•Airspeed Indicator

Air Sources
•Pitot Tube
-Ram/Dynamic Pressure
•Static Port
=Static Air


Do Glass Aircraft do have pitot-static systems?
What lines are connected to the ADC and what does ADC mean?
What else is it connected along with?

•The pitot line and static line are connected to the Air Data Computer (ADC)
oAlong with the OAT



What is inside?
What are the markings?
What is the window called?

Aneroid wafer = sealed capsule of air. Shows indication or climb of altitude on face of the instrument.

•Ten Thousands
•Kollsman Window


Types of Altitude

Indicated Altitude – read right off the instrument

Absolute Altitude – height above ground (AGL)

True Altitude – height above sea level (MSL)

Pressure Altitude – height above standard datum plane of 29.92” Hg

Density Altitude – pressure altitude corrected for non-standard temperature (15°C)


91.121 Altimeter Settings

Below 18,000 MSL

•Current reported altimeter setting within 100 nm of the aircraft
•If no setting is available upon departure, the elevation of the departure airport may be set in to the altimeter

At and above 18,000 MSL
•All aircraft set altimeters to 29.92


Altimeter Malfunctions (1)

Blocked Static Port
•Solution – Alternate Static Source


Vertical Speed Indicator - Components

•Calibrated Leak
•Direct Static Pressure


Vertical Speed Indicator

As the altitude changes, pressure changes
Air in the diaphragm and case want to equalize with outside pressure

Diaphragm equalizes same rate as outside pressure

Case is restricted to equalizing by the

Calibrated Leak

This restriction allows the rate of climb or descent to be measured and is indicated on the face of the instrument


Vertical Speed Indicator Errors (1)

Static Blockage
•Solution – Alternate Static Source
Indication Lag
•Allow 6-9 seconds to stabalize
•Due to Calibrate Leak


Airspeed Indicator - System and Operation

•Only pitot-static instrument that uses both the static port and pitot tube

•Speed increases, ram air moves into pitot tube and expands diaphragm

•Static Port maintains ambient pressure in case


Airspeed Indicator Markings

White Arc?
Green Arc?
Yellow Arc?
Red Line?

White Arc – Flap Operating Range
•Vso to Vfe

Green Arc – Normal Operating Range
•Vs to Vno

Yellow Arc – Caution Range
•Vno to Vne

Red Line


Types of Airspeeds

Indicated Airspeed (IAS) – read directly off instrument

Calibrated Airspeed (CAS) – IAS corrected for installation and position errors

True Airspeed (TAS) – CAS corrected for non-standard pressure and temperature and pressure

Ground Speed


Airspeed Indicator Malfunctions


Blocked Pitot Tube
Blocked Static Port
Blocked Drain Hole (drain hole allows excess water out)

oPitot Heat
oAlternate Static Source


Gyroscopic Instruments

Instruments? (3)
Vacuum Systems? (2)

•Attitude Indicator
•Heading Indicator
•Turn Coordinator

Vacuum Systems
•Engine Driven
•Electrically Driven



Do glass aircraft have gyroscopic instruments?
What sensors replace conventional systems?
What reference system is included?
Does the c172 have a backup ?

Glass Aircraft do have gyroscopic instruments

•Accelerometers and Rate Sensors replace conventional systems

oAttitude and Heading Reference System (AHRS)

C172 does have a backup vacuum standby attitude indicator


Principles of Operation

What are the two principles and what do they mean?
What banks are available?

Rigidity in Space
•When rotating at a high rate the gyro will maintain its orientation in space

Gyroscopic Procession
•A force applied to the gyro will react 90 degrees ahead of the rotation

Attitude Indicator is based on rigidity in space, gyro connected to the face of the attitude indicator and the airplane moves. Gyro does not move however.

10-20-30-45-90 degree banks available.


Heading Indicator Information

When do you reset and why?

Is heading Indicator information connected to magnetic sources?

•Need to reset heading every 15 minutes
•Due to friction of moving parts

•55 degrees pitch and bank

*not connected to any magnetic source


Turn Coordinator - Components (2)

-Electrically Driven

Gimbal is canted (30 pitch up) to allow instrument to sense both rate of turn and rate of roll

•Depicts aircraft yaw (side to side movement)
•Step on the ball (brick) to correct

*works off of gyroscopic procession


Types of Turn Indications

What is a slip?
What is a skid?
What is a coordinated turn?

Slipping Turn - Inside of Turn
Horizontal component is greater than centrifugal component.

Skidding Turn - Outside of Turn
Centrifugal component is greater than Horizontal component.

Coordinated Turn - Inside of Balanced Turn Indication


Magnetic Dip (Magnetic Compass)

What causes magnetic dip and where is it's effect greatest?

Which direction does it dip to?

When is it more pronounced?

Areas of Magnetic Flux point toward the ground near the poles

As a result, Magnetic Compass magnets dip to the low side of the turn

More pronounced closer to the magnetic poles

*Dip is an error


Magnetic Compass Errors (DIP)

Acceleration Error (ANDS) -

Accelerate and the counter-weight falls back and shows a turn north on main screen.

Decelerate and weight falls forward and shows a turn to the south.


Northerly Turning Error (UNOS)

North Seeking Magnet shows accelerating turn, so you must undershoot. From South, we have to undershoot because it is lagging and must overshoot.


10 degrees tends to work.

Oscillation Error- Erratic movement of the compass due to turbulence


Magnetic Variation

Angular difference between True North and Magnetic North
•Agonic Line – Line where angular difference is zero (equal)
•Isogonic Line – Lines depicting angular difference

*comes into factors for cross-countries


Magnetic Deviation

Magnetic disturbance created by the aircraft and the operation of electronics.

Compass Card is required for flight


Technically Advanced Aircraft (4)

What is revisionary mode, where is it, and what does it do?

Primary Flight Display – PFD
Multi-Function Display - MFD

On Audio panel, it is called revisionary mode. if PFD Fails, the system automatically goes to MFD to provide essential information. *If system fails press revisionary and it moves all information to PFD


Attitude Heading and Reference System (AHRS) (3)

What does it provide information on?
What is connected to this system?
Where is it located?

•Provides pitch, bank, and yaw
•Magnetometer is connected to this system
•Located in the tail cone



What does it do, what information does it tell us, and where is it located.

•Senses the earth’s magnetic field information
•Determines aircraft magnetic heading
•Located in the left wing of the C172


Air Data Computer (ADC)

What does it provide, where is it located?

•Provides pitot-static information
oAirspeed, altitude, vertical speed
*also helps determine wind

Located up front*


Compass Errors - ALL TYPES

What does ANDS mean?
What does UNOS mean?

What other errors are there?

Magnetic Dip

Oscillation Error
Magnetic Variation
Magnetic Deviation


Oscillation Error

Erratic movement of the compass due to turbulence