Contents
What are compressibility errors?
An error in the airspeed indicator, which presumes that the air is incompressible. However, air is compressible and the higher the speed, the higher pressure it will indicate.
What are the sources of error in a pitot tube?
Density errors affect instruments metering airspeed and altitude. This type of error is caused by variations of pressure and temperature in the atmosphere. A compressibility error can arise because the impact pressure will cause the air to compress in the pitot tube.
What are the application areas of pitot static tube?
It is widely used to determine the airspeed of an aircraft, water speed of a boat, and to measure liquid, air and gas flow velocities in certain industrial applications.
What causes a density error in a pitot tube?
Density errors affect instruments metering airspeed and altitude. This type of error is caused by variations of pressure and temperature in the atmosphere. A compressibility error can arise because the impact pressure will cause the air to compress in the pitot tube.
How are pitot static tubes insensitive to turbulence?
Pitot-Static tubes appear to be insensitive to isotropic turbulence, which is the most common type. Under some conditions of high intensity, large scale turbulence, could make the angle of attack at a probe vary over a wide range.
How big should impact holes be for pitot tubes?
This error is only noticeable in air under standard atmospheric conditions for velocities under 12 ft/sec with impact holes 0.010″ diameter or less. If the fluid stream is not parallel to the probe head, errors occur in both total and static readings.
What are the properties of a pitot tube?
The probe and boundary form a Venturi passage, which accelerates the flow and decreases the static pressure on one side. The curve shows that static readings should not be taken closer than 5 tube diameters from a boundary for 1% accuracy and 10 tube diameters is safer. Figure 3.