| Aircraft instruments are driven by aerospace sensors. | | | | pressure-sensitive switches and, in the case of fuel, |
| Aero engine temperature sensors | | | | flowmeters which indicate the actual flow. All transmit |
| The thrust indicator measures jetpipe pressure, | | | | to the cockpit in the form of electrical signals. |
| sensing pressures at inlet and exhaust, pressure | | | | Vibration transmitters are transducers of the |
| sensors. Temperature sensors have a sensing | | | | magnetostrictive or piezoelectric crystal type, which |
| element, a thermocouple, a heat-resistant tube | | | | send out signals to a sensitive milliammeter with a dial |
| containing two wires of different materials, such as | | | | calibrated in terms of vibration amplitude, the |
| one of nickel-aluminium and one of nickel-chromium. | | | | unacceptable region being red. Often signal filters are |
| They are joined at the end of the protective tube, | | | | inserted so that the pilot can check on vibration in |
| which projects into a suitable point in the hot gas. | | | | particular bands of frequency corresponding to an |
| Usually there will be from two to ten thermocouples | | | | rpm value. |
| arranged round the turbine section, plus others to | | | | Thermocouples can give warning of excessive |
| sense the inlet air temperature. Each pair of wires is | | | | temperatures, and avoid costly damage to the |
| joined again inside a cool box, and it is the difference | | | | turbine and other hot parts of the engine. Warnings |
| in temperature between the hot and cold junctions | | | | can also be given by thermally triggered switches in |
| which generates a small voltage which drives cockpit | | | | strategic locations such as overboard air vents. The |
| instruments and their indicators. | | | | entire installed aircraft powerplant must be protected |
| Both fuel and lubricating-oil systems incorporate | | | | against fire. |
| various temperature sensors and pressure sensors, | | | | |