Aircraft Flight instruments

Pitot/Static Pressure Flight instruments


If you ever visited in pilot's cockpit you will see lots of indicators. And you will get amazed how pilot take care of all the readings of flight instruments at a time.

Before learning about instruments let's take a look at some terms

Atmospheric pressure:- Atmospheric pressure is air pressure at the sea level.

Static pressure:- Static pressure is the air pressure outside the aircraft. In aircraft there are some static ports which measures air pressure outside aircraft. Static ports are located at such a place where there is no pressure difference because of motion of aircraft. E.g. at the sides of aircraft.

Pitot tube pressure:- Pitot tube is tube located at place such that there is maximum pressure difference due to motion of aircraft. E.g. at the nose of aircraft. As due to aircraft motion air will enter in pitot tube & pressure difference between pitot pressure & static pressure is maximum.

Here all the flight instruments which uses pitot or static pressure to take readings are listed & also their short description is given.

1.Altimeter:- Altimeter is a flight instrument used in aircraft to measure the altitude of aircraft. Altitude of aircraft is not a height of aircraft from the ground but altitude is height of aircraft above sea level. Altimeter actually measures pressure difference between atmospheric pressure at the sea level & static pressure. As air pressure decreases with height. Altimeter scales are calibrated with air pressure difference & altitude.
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2.Air Speed Indicator (ASI) :- Air Speed indicator is a flight instrument which is used to measure the speed of the aircraft. Air Speed Indicator actually measures the difference between pitot tube pressure & air pressure at sea level. Air Speed Indicators is calibrated with pressure difference & speed of aircraft. Air Speed Indicator is a colourful instrument with each colour some meaning. To know more about Air Speed Indicators Click Here
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3.Vertical Speed Indicator (VSI) :- It is also known as Variometer. It measures climbing or descending speed of aircraft. Variometer consists of aneroid capsule connected to static port and also surrounded by calibrated leak of static pressure( Just for understanding:- Consider aneroid capsule as balloon inside box, & surrounding pressure is pressure inside box). As altitude of aircraft increases outside atmospheric air pressure decreases so pressure inside aneroid capsule decreases immediately, but it decreases slowly due to calibrated leak. Actually VSI measures difference between static port pressure & surrounding calibrated leak of static pressure. Scale of VSI is calibrated with pressure difference & verticle speed of aircraft.
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I know that these things are quite complex to understand but I tried my best to explain it in simple words. Even if you have doubt comment below or mail me!

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