Downloaded from https://www.everyspec.com ADS-79D-HDBK with engine speed sensor signals. Great care should be taken to prevent these signals from being corrupted by the EMS/EMHS devices. In cases where it is not feasible to directly monitor a required parameter, it may be easier to derive the parameter from other measured data using a suitable model algorithm. This approach would not be suitable, however, if the existing instrumentation does not cover the operating envelope of the monitoring system with sufficient accuracy. Typical requirements for instrumentation accuracy and resolution are provided in Table G-IX.
For fluids monitoring, multiple COTS sensors are available for monitoring oil, lubrication, hydraulic, and fuel systems. These systems have been lumped together as the sensors used are nearly identical. Temperature sensors for oil are pervasive, but a necessary system for monitoring the performance of engines or APUs. A rapid rise in oil temperature is usually an indicator of a component failure and typically leads to an emergency shutdown. Day to day monitoring which indicates a shift in oil temperature for a steady state operating condition may indicate impending trouble and thus is an important part of a CBM system. Equally as pervasive are oil pressure sensors.
Oil pressure sensors may be used as an indicator of a loss in oil pressure which can indicate a hose failure or some other source of leakage or blockage. when used as part of a CBM system, the pressure sensor can also provide day-to-day indications of changes in steady state oil pressure. Based on the system and types of changes observed, the pressure fluctuations can indicate impending pump failure or existing partial blockage in the system. Oil quality condition and debris sensors are also available. For specific descriptions and guidance on aircraft engine oil condition, oil debris, and oil filter sensors, refer to Appendix M of this document.
37 RTO TR 28, ―Recommended Practices for Monitoring Gas Turbine Engine Life Consumption‖, North Atlantic Treaty Organization, Research and Technology Organization, April 2000, pg. 8-8. 124 TABLE G-X Typical sensor requirements37 Signal Accuracy Resolution Spool speed 0.1% 0.05% Temperature 1.8 °F 0.9 °F Engine intake 7.2 °F 3.6 °F Compressor exit 7.2 °F 3.6 °F Stator outlet 7.2 °F 3.6 °F Exhaust gas 3.6 °F 1.8 °F Turbine blade 7.2 °F 3.6 °F Engine intake pressure 0.290 psi 0.145 psi Compressor exit pressure 1.45 psi 0.435 psi Indicated airspeed 2 kts 1 kts Pressure altitude 100 ft 50 ft G-load 0.01 g 0.005 g