Facts of Airspeed Indicator Calibration

Airspeed Indicators (ASI) are flight instruments used to measure the airspeed of an aircraft. They function either electronically or via a pitot-static system and are crucial to the safe operation of an aircraft. Because of this, pilots must be able to ensure their ASI is accurate and functioning properly. Electronic ASIs provide the peace of mind that readings will be accurate, but typically only newer, more sophisticated aircraft will feature an electronic ASI. For all other aircraft, a pitot-static system will be in use. In this case, to ensure reliability, the ASI must be calibrated and maintained regularly.

In addition to calculating pressure plate, the ASI provides measurement uncertainty - essentially the margin of error. Because of the different types of airspeed such as indicated airspeed, calibrated airspeed, true airspeed, and ground airspeed, pilots and technicians must know what is an acceptable margin of error and what is not. More frequently calibrated ASIs will provide a calculated and therefore more reliable uncertainty measurement.

It is important to realize what a delicate piece of machinery an ASI is. Seeing as it is a highly sensitive pressure gauge assy, the best option is to allow a professional to calibrate it for you. Improper calibration can cause serious damage to your ASI and result in a heavy financial blow. Should you choose to calibrate it yourself, follow these six steps:

Obtain a manometer, it will be used to measure the pressure in the ASI.
Ensure that the ASI is disconnected from the pitot-static system.
Connect the manometer to the ASI’s pitot line.
Apply a controlled amount of pressure to the manometer.
Calibrate the ASI by checking accuracy through comparison with standardized pressure numbers.
Re-connect the ASI carefully to ensure that all hoses are hooked in tightly, correctly, and in the same position as prior to removal.

Once again, calibration of your ASI is not a job that should be taken lightly, and sending the instrument to lab professionals is the best way to ensure your product will be properly calibrated.