Pitot static system is a complete system, which is used to calculate Airspeed, Mach no, Altitude, altitude trend. This system generally consist of a pitot tube, a static port and a pitot static instrument.
To understand the pitot static system we first need to understand pressure. In fluids there are 3 types of pressure- static, dynamic and total pressure or stagnation pressure. Static pressure is the pressure exerted perpendicular to a surface. dynamic pressure is the pressure of air in the direction of motion. Total pressure is the sum of dynamic and static pressure. The static pressure gives the altitude of the aircraft during fligh because as altitude increases the pressure decreases. The dynamic pressure is used to measure the airspeed as the airspeed increases with increase in pressure.
There are 2 outwardly visible ports on an aircraft related to pitot static system. One is pitot tube that is used to measure the total pressure and one is static port that is used to measure the static pressure. Dynamic pressure is calculated by differentiating those two. The use of diaphram is very important. The pitot static instruments include:
1.ASI air speed indicator uses the differential diaphram to find the difference between the pitot and static pressure which give dynamic pressure. This instument requires the dynamic pressure ie total-static. So this device receives both the static air and total ait outlet and the use of differential diaphrams help for the indication of the proper ASI.
2.VSI vertical speed indicator consist of a diaphragm that is filled with the static port outlet air. And is placed in a clossed volume where the static port outlet is leaked in a calibrated manner. when the aircraft decends or climbs then the pressure inside the diaphragm increases or decreases relative to the outside static pressure but the volume in which it is placed has a calibrated leak so the diaphragm expands or contracts in accordance to the leak calibration thus giving out the VSI.
3. Altimeter uses an aneroid barometer which is an advanced form of pressure measurement unlike mercury barometer. It doesnt use any liquid but makes use of a flexible alloy capsule that is depressurized. The capsule is put in a sealed volume which receives the air from the static port. Thus this causes the aneroid capsule to expand and contract in accordance to the outside temperature. The change in the physical size is recorded and indicated by a mechanical system. This is used by the pilot to gauge the proper altitude of an aircraft at any given time.
Thus pitot static system is a vital instrument system in a aircraft. There are various errors that can occur in this kind of system. They are:
1. Inherent error
density error, compressibility error, hysteresis error, reversal error
position error
lag error
2. System malfunction
Blocked pitot tube error
Blocked static port error
To understand the pitot static system we first need to understand pressure. In fluids there are 3 types of pressure- static, dynamic and total pressure or stagnation pressure. Static pressure is the pressure exerted perpendicular to a surface. dynamic pressure is the pressure of air in the direction of motion. Total pressure is the sum of dynamic and static pressure. The static pressure gives the altitude of the aircraft during fligh because as altitude increases the pressure decreases. The dynamic pressure is used to measure the airspeed as the airspeed increases with increase in pressure.
There are 2 outwardly visible ports on an aircraft related to pitot static system. One is pitot tube that is used to measure the total pressure and one is static port that is used to measure the static pressure. Dynamic pressure is calculated by differentiating those two. The use of diaphram is very important. The pitot static instruments include:
1.ASI air speed indicator uses the differential diaphram to find the difference between the pitot and static pressure which give dynamic pressure. This instument requires the dynamic pressure ie total-static. So this device receives both the static air and total ait outlet and the use of differential diaphrams help for the indication of the proper ASI.
2.VSI vertical speed indicator consist of a diaphragm that is filled with the static port outlet air. And is placed in a clossed volume where the static port outlet is leaked in a calibrated manner. when the aircraft decends or climbs then the pressure inside the diaphragm increases or decreases relative to the outside static pressure but the volume in which it is placed has a calibrated leak so the diaphragm expands or contracts in accordance to the leak calibration thus giving out the VSI.
3. Altimeter uses an aneroid barometer which is an advanced form of pressure measurement unlike mercury barometer. It doesnt use any liquid but makes use of a flexible alloy capsule that is depressurized. The capsule is put in a sealed volume which receives the air from the static port. Thus this causes the aneroid capsule to expand and contract in accordance to the outside temperature. The change in the physical size is recorded and indicated by a mechanical system. This is used by the pilot to gauge the proper altitude of an aircraft at any given time.
Thus pitot static system is a vital instrument system in a aircraft. There are various errors that can occur in this kind of system. They are:
1. Inherent error
density error, compressibility error, hysteresis error, reversal error
position error
lag error
2. System malfunction
Blocked pitot tube error
Blocked static port error
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