Airplanes usually have dozens of instruments that help the pilot to make informed decisions when piloting a plane. There are instruments that show the altitude of the plane at any given time, the air speed and the orientation of the plane. There are also instruments to show the state of the engine, cabin pressure and the likes. One of the most important instruments in a plane is the airspeed indicator. The instrument shows air speed in knots or miles per hour, depending on the manufacturer.
A faulty indicator will make it difficult for the pilot to navigate properly. Taking off and landing will also be an issue if the pilot does not see the correct speed on the airspeed indicator. Regular inspection and maintenance of this instrument is therefore recommended as a matter of airplane safety. In case it has been worn out, a replacement should be done.