We know that planes have a fixed path and a fixed altitude, so how are these measured?
Although the pilot can estimate the distance to the ground with the naked eye, this conclusion is very inaccurate.
And when the light is bad or the plane is flying very high, visual altitude is impossible.
The aircraft altimeter has solved this problem by using the principle that atmospheric pressure changes are related to altitude.
Atmospheric pressure is caused by the accumulation of the weight of air. The higher you go, the thicker the air becomes, and the lower the air pressure.
As altitude increases, the air pressure decreases linearly.
If you can measure the air pressure outside the plane, of course, you can calculate the altitude of the plane at the moment.
Aircraft are now equipped with a barometer based on this principle, but the dial shows the calculated height, which is convenient for the pilot.
When an airplane is in the air, the pilot needs to know not only how fast the airplane is moving against the ground (ground speed), but also how fast the airplane is moving relative to the air (airspeed).
Here is an explanation of airspeed, which is important for aircraft.
The lift of a wing comes from the difference in the speed of the air flowing over the top and bottom surfaces of the wing, so airspeed determines the amount of lift.
The greater the airspeed, the greater the lift;
Without airspeed, lift disappears and planes fall out of the sky.
The faster the air moves, the more pressure it exerts on the plane. This pressure is called dynamic pressure.
The dynamic pressure is related to the airspeed, and when the dynamic pressure is measured, the airspeed can be converted.
The system for measuring airspeed consists of three parts.
The first part is called the full pressure tube.
It is a tube that protrudes forward in flight and is attached to the nose or wingtip of the aircraft.
When air is blown head-on into the tube, all the pressure of the incoming air is felt at the back of the tube.
This pressure consists of the dynamic pressure of the air flowing into the tube and the static pressure inside when the air is at rest.
The second part is static pressure hole.
Static pressure holes are small holes in the side of the fuselage that are not disturbed by airflow.
The air flows slowly into the hole from here, and the air pressure here is static pressure.
The third part is the pressure gauge, one end of the gauge is connected with the full pressure tube, the other end is connected with the static pressure hole.
The number measured by the pressure gauge is the difference between the total pressure and the static pressure, that is, the dynamic pressure.
According to the correlation between dynamic pressure and airspeed, airspeed can be converted.
Ground speed indicates the speed of an aircraft in flight with respect to the ground.
The ground velocity is the air velocity plus the velocity (wind speed) of the air itself.
Air speed, wind speed, and ground speed are vectors that can point in the direction of the mission.
When added together, these three vectors form a triangle, which is known as the velocity triangle.
Through this, the pilot can know what the plane’s ground speed is.
When flying at low speed, the pilot depends on signs on the ground to tell direction.
Once the plane is above the sea of clouds or flying over the ocean there are no ground markers.
This problem was solved with the help of one of our ancestors’ great inventions, the magnetic compass.
The magnetic compass on the plane is modified and called a course finder.
Because airplanes travel so fast, the curvature of the Earth is not felt by passengers as they travel along the surface, but the magnetic compass does.
If the magnetic compass couldn’t keep up with the plane’s changing attitude along the curvature of the earth’s surface, it was pointing in the wrong direction.
To this end, a gyroscope is attached to the magnetic compass, so that the magnetic compass can always stay parallel to the ground and point the plane in the right direction. This set of devices is called the channel compass.
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