10/11/2023 0 Comments Fuel quantity indicating systemFor example, if the fuel tank maximum capacity is 10,000 KG, then the tolerance of the gauging is 0.03 (airplane with analog indicators) * 10000 = 300 KG. The total tolerance for the FQIS system is based on a full tank. The 737 fuel quantity indication system has the following accuracy tolerances:įQIS accuracy with digital indicators: +/- 2.5 %įQIS accuracy with analog indicators: +/- 3.0% Power to shut off the fuel in an emergency.ĭigital Sunburst Fuel Gauges - Simmonds 4 Tank NG/MAX: The engine spar valves and APU are normally powered by the hotīattery bus but have a dedicated battery to ensure that there is always They were solenoid held andĪutomatically moved back to OFF after one minute. The 1/200's had heater switches these used bleed air to heat theįuel and de-ice the fuel filter. The -1/200 panel also hasīlue VALVE OPEN lights similar to that on the crossfeed valve. The NG/MAX's have separate ENG VALVE CLOSED & SPAR VALVE CLOSED lights in The fuel panels for the various series have not changed much over ![]() The AFM limits are higher, but not normally Upon how many tanks the customer has specified (max 12). įAA source: FAA-H-8083-31A, Aviation Maintenance Technician Handbook-Airframe Volume 2 (via faa.Maximum declarable fuel capacity for tech log, nav log, etc is 16,200kgs forģ-Tank Classics, 20,800kgs for NG/MAX's and up to 37,712kgs for BBJ's depending The use of tank unit capacitors, a reference capacitor, and a microchip bridge circuit in the fuel quantity indicators is complicated by the fact that temperature affects the dielectric constant of the fuel. The tank units are located throughout the tanks so an accurate reading is provided whatever the attitude of the airplane.Īnd indeed this sensor would be affected by temperature as Ralph has noticed, but it has nothing to do with directly sensing the mass or weight: The inner tube is profiled to correspond to the irregular shape of the inside of the fuel tank. Tank Units are hollow coaxial cylindrical capacitors mounted vertically to ribs inside each fuel tank. The 737 is the same as the A320 in principle (sensing filled volume then converting to kg or lbs for the crew). ![]() The information provided to pilots in the form of the low level alert results from a physical measure (sensors dry or wet) rather than from a calculation.Do not provide pilots with a continuous indication of the fuel quantity in the wing tanks, but only the signal that the fuel level has reached below 750 kg (threshold crossed).The low level sensors are fully independent from the Fuel Quantity Indication, and are different in that they: If two sensors in the same tank remain dry for more than 30 seconds, a low level alert triggers in the cockpit (fig.2). These sensors are located in such a way that they become dry when the remaining fuel in the tank is approximately 750 kg. In addition to the sensors and probes feeding the FQI system, each wing tank is equipped with three independent dedicated low level sensors. The ECAM can then display fuel temperature and mass as calculated by the FQIC.Īdditionally, there is an independent system sensing low fuel level, which would alert the pilots even if something goes wrong with the normal FQIS: Using the densitometer (or the backup CIC), the conversion from volume to mass is performed by the FQIC. (Airbus A320 FCOM - Fuel Description - Fuel Quantity Indication and Level Sensing) one Capacitance Index Compensator (CIC) in each inner tank giving the dielectric constant of the fuel in case of cadensicon failure.one densitometer (cadensicon) sensor in each wing inner tank permitting the calculation of the fuel quantity.A set of capacitance probes in each tank to measure fuel level and temperature.The FCOM lists the sensors involved in this measurement: ( Airbus Safety First - Fuel monitoring on A320 Family aircraft) The translation of fuel volume into fuel weight is performed by the FQIC using the fuel density measured by specific devices in each wing tank Yet the information that is needed by pilots is the quantity of fuel on board expressed as a weight. ![]() This allows the determination of the fuel volume in the tank. ![]() The probes measure the level of the fuel in the tank, as a consequence of changing capacitance due to the amount the probe is immersed. The FQI system calculates the fuel quantity based on values taken from probes in the tanks. On the Airbus A320 family, the fuel volume is measured via capacitance probes and then converted to mass by also measuring the fuel density:
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