Preflight - Flight Instruments

Question 1

What instruments operate from the pitot/static system?

Answer 1

Altimeter

Airspeed Indicator (ASI)

Vertical Speed Indicator (VSI)

Question 2

How does an altimeter operate?

Answer 2

An aneroid wafer expands and contracts as atmospheric pressure changes, and through a shaft and gear linkage, rotate the pointer on the dial of the instrument

Pressure sensitive altimeters adjust for the set pressure setting by moving the needs higher or lower

Question 3

What types of errors is the altimeter subject to?

Answer 3

Mechanical errors: Differences between ambient temperature and/or pressure can cause an erroneous indication on the altimeter

Inherent errors: Non-standard temperature or pressure

Warmer than standard air - True altitude will be higher than indicated when the temperature is warmer than ISA

Colder than standard air - True altitude will be lower than indicated when the temperature is colder than ISA

Extreme cold altimeter errors - When operating in extreme cold temperature (+10 Celsius to -50 Celsius), pilots may have to compensate for the reduction in terrain clearance by adding a cold temperature correction

High pressure to low pressure - If not corrected, true altitude will be lower than indicated

Low pressure to high pressure - If not corrected, true altitude will be higher than indicated

Note: High to Low or Hot to Cold - LOOK OUT BELOW!

Question 4

For IFR flight, what is the maximum allowable error for an altimeter?

Answer 4

If the altimeter is off-field elevation by more than 75 feet, with the correct pressure in the Kollsman window, it is considered to be unreliable

Question 5

List and define the 5 different types of altitudes.

Answer 5

I.T.A.P.D.

Indicated altitude - read directly from the altimeter when it is set to current altimeter setting

True altitude - the height above sea level (MSL)

Absolute altitude - the height above the ground (AGL)

Pressure altitude - the indicated altitude when the altimeter is set to 29.92 in. Hg.

Density altitude - Pressure altitude corrected for non-standard temperature

Question 6

Does adjusting the altimeter’s Kollsman window have any effect on the altitude that is displayed to an ATC controller? Why?

Answer 6

No, the controller sees your pressure altitude sent from the transponder, changing what is displayed in the Kollsman window has no effect on this

ATC equipment adjusts the displayed altitudes to compensate for local pressure differences allowing display of targets at corrected altitudes

Question 7

How does the airspeed indicator operate?

Answer 7

The airspeed indicator measures the difference between the ram pressure from the pitot tube head and atmospheric (static) pressure from the static source