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Flashcards in Flight Instruments Deck (64)
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Explain the different in pressure between static air and air in motion

Air in motion exerts dynamic pressure. Static air exerts static pressure all around


What is the purpose of the pitot tube?

To measure ram air pressure (dynamic pressure due to forward motion)


What is the purpose of the static port?

To measure static or ambient air pressure through ports placed parallel to the relative airflow


How does the static port affect air pressure?

It allows air pressure inside the instruments to become equal with the air pressure outside the cases


What should be done in an emergency for an aircraft not equipped with an alternate static source?

Break the face glass of the VSI to provide static pressure from the cabin


Describe the set up of the pilot static system


Describe the VSI, ASI, and ALT readings when a pitot or static blockage occurs


When is pitot heat used?

Anytime ice is suspected in the pitot tube. The ice could create erroneous or no readings on the ASI


An aircraft is not in motion. What is the ASI reading?



In what unit does the ASI display airspeed?

knots or miles per hour


How does the ASI measure airspeed?

By measuring the difference between dynamic and static pressure. The larger the difference, the higher the reading


Describe the different ASI markings

Red line: VNE (never exceed)

Yellow arc: VNO - VNE (caution range)

Green arc: VS1 - VNO (normal operating range)

White arc: VSO - VFE (flap operating range)


List the causes of ASI errors

Position error (angle of attack)

Compressibility error (250kts+)

Density error (temperature, pressure)


What kind of instrument is the VSI? What does it display?

A trend instrument that displays the rate of climb or descent


Describe the set up of an aneroid barometer


List three things to do doing a VSI serviceability check

Check if VSI reads 0 on the ground

Check static port clean

Check alternate static source (VSI should jump)


What is the standard international atmosphere?

- Perfectly dry gas

- 15°C

- Surface pressure of 29.92" Hg

- Lapse rate of 2°C/1000' within troposphere

- Weight of column of air is 14.7lbs


Describe the purpose of the altimeter. When does it work properly?

Indicates correct altitude above sea level when conditions of temperature and pressure are those of the ISA


Describe what happens to the altimeter readins when pressure varies along the route


What happens to the altimeter reading if temperature is standard? Why is this dangerous?

Error in reading. This is dangerous because extreme variations in temperature may cause a 2500' difference in indicated altitude


Describe the affect of nonstandard temperature and pressure on actual and indicated altitude


Where does a mountain wave form?

Where wind faster than 50 knots blows within 30 degrees of the perpendicular to the main axis of the mountain range


How far can the effect of a mountain wave extend?

As far as 100 miles downward of the moutains to altitudes many times higher than the mountain elevation


Describe the pre flight altimeter serviceability check

Must read within +/- 50' of the field elevation

Static source checked clean and clear

Alternative static source checked (ALT should jump)


How often should the pilot static system and altimeter be calibrated for IFR flight?

Every 24 months


What should you do if you have no altimeter setting available at the aerodrome?

Adjust the altimeter setting knob to the known field elevation until the altimeter indicates that same elevation


What is an advantage of the encoding altimeter?

Aircraft can be 3D identified by ATC


Define the magnetic meridian and magnetic variation

Magnetic meridian - magnetic line in which in the compass needle lies in

Magnetic variation - angle between the true meridian and magnetic meridian


List sources of compass error

Magnetic dip, deviation, turning error, acceleration error


What is a cause of compass deviation? How can deviation from the magnetic meridian be determined?

The compass can be influenced by the aircraft's metal frame, the engine, or electrical devices. Deviation can be determined by swinging the compass