An easy explanation of the terms frequently used here.
- Dynamic Pressure
The dynamic pressure is the difference between the total pressure and the static pressure. Dynamic Pressure (p dyn )= Total Pressure (p total) - Static Pressure (p stat).
- Mounting Adaptor
Esa systems offers different types of mounting adaptors (sockets) for the various probe types. Probes with the ending /ST fit into adapter ST1 8mm. Probes with the ending /ST2 fit into the adaptor ST2. Probes with the ending /UN fit into the adaptors SUN and UN, and probes with the ending /UNG fit into the adaptor UNG. Details are explained under the menu item --> Products/Mounting Adaptors.
- Mounting Adaptor Seal
The mounting adaptors in the tail unit should be closed off with a seal after the probe has been removed in order to prevent dust and insects from entering it. The plug's venting is very important and prevents damage caused by excessive pressure when inserting it. If you buy a replica please make sure that it has vents! There are two different diameters, for 6mm and 8mm mounting adaptors. Alternatively, of course, good old adhesive tape works too.
- Pitot Tube
A Pressure Probe (according to Henri Pitot) is a probe for measuring the Total Pressure. A simple Pressure Probes is often combined with a Static Pressure Probe in order to be able to measure velocities. Its most famous representative is the Prandtl Probe.
- a) the simple Pressure Probe (pitot tube or tailpipe) measures only the Total Pressure
- b) the Static Probe measures exclusively the Static Pressure,
- c) the Prandtl Probe measures both Static and Total Pressure.
- Prandtl Tube
The Prandtl probe (according to Ludwig Prandtl) represents a combination of pitot tube and static pressure probe, with which the pressure is determined. The impingement probe has an opening in the flow direction for measuring the total pressure and annularly at a well-calculated distance from the tip on the shaft lateral openings for the static pressure. The difference between these two pressures corresponds to the dynamic pressure used for the speed indication. In the English language, Prandtl probes are often referred as pitot tubes, which in some cases can lead to misunderstandings.
- Static Pressure
The Static Pressure corresponds to the air pressure of the stationary ambient air in which an object is located. It can be measured directly. In the stationary medium, the Static Pressure is equal to the Total Pressure, since the dynamic pressure is then 0. Important for a clean signal is a precise Static Pressure over the entire speed range.
- Tightness Test
Crucial for the correct display is the tightness of the pressure system. This should be regularly checked in the annual maintenance for leaks. Even the smallest leaks lead to false displays. A 'How To' can be found in the Support section under Instructions.
- Total Energy Compensation
Simplified: An old vario signals any climb, even if the pilot, e.g. only 'pulls' out the speed. In order to suppress this 'stick thermal' largely from the vario signal, current variometers have the possibility to connect a so-called total energy compensation probe / nozzle (TEC probe / nozzle).
Mechanical variometers are therefore not connected to the Static Pressure pick-up in gliders, but to the (TE) compensating (under) pressure of the TEC probe. Electronic variometers can be compensated either by a TEC probe, or electronically. However, a clean static pressure pick-up with a probe is strongly recommended. Electronic compensation is in general lightly less precise.
- Total Energy Probe
A Total Energy Probe is essential to get a compensated variometer signal, see also Total Energy Compensation. In general with a Total Energy (TE) Probe (more precise a Total Energy Compensation (TEC) Probe), a variometer can be precisely compensated. There different designs available.The quality of a Total Energy Probe can be measured by generated coefficient. It is very important for the accurate vario signal that the coefficient remains as constant as possible over a wide speed, pitch and angle range. Ideally the coefficient is -1.
- Total Pressure
The total pressure is the pressure acting in a pressure point and can be measured directly. The total pressure is the sum of static pressure (simplified: the air pressure of the direct environment) and the dynamic pressure (simplified: pressure generated by a forward movement in the atmosphere). Total pressure = static pressure + dynamic pressure.