DOC AIRBUS | AMM A320FINDICATING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The fuel system is monitored from:
** ON A/C NOT FOR ALL The fuel system is monitored from:
Indicating - Location- The fuel flow indication on the upper ECAM display unit permanently displayed in green and under numerical form.
- The fuel filter clogging caution (amber) on the lower ECAM display unit.
2. Fuel Flow Indication
A. Fuel Flow Indication
The fuel flow transmitter signal is fed to the FADEC which processes it and transmits the information to the ECAM system for display
through the digital FADEC data bus
The fuel flow transmitter signal is fed to the FADEC which processes it and transmits the information to the ECAM system for display
through the digital FADEC data bus
(1) Description
The fuel flow transmitter is installed in the fuel line between the fuel metering unit and the fuel distribution valve. It is mounted on the lower left-hand side of the fan case, rearward of the LP/HP fuel pump.
The fuel flow transmitter is made of these primary assemblies:
The fuel flow transmitter is installed in the fuel line between the fuel metering unit and the fuel distribution valve. It is mounted on the lower left-hand side of the fan case, rearward of the LP/HP fuel pump.
The fuel flow transmitter is made of these primary assemblies:
- the transmitter body,
- the inlet fitting and clamps
- the turbine assembly,
- the measurement assembly.
(a) Transmitter body
The transmitter body is an aluminium alloy casting that has a central bore into which the other assemblies are installed. An inlet adapter is clamped to the end of the transmitter body. Attached to the side of the transmitter body are two pick-off coils and an electrical connector.
The transmitter body is an aluminium alloy casting that has a central bore into which the other assemblies are installed. An inlet adapter is clamped to the end of the transmitter body. Attached to the side of the transmitter body are two pick-off coils and an electrical connector.
(b) Turbine and valve assembly
The turbine assembly is connected to the inlet end of the shaft. It is used to drive the measurement assembly connected to the opposite end of the shaft.
The turbine assembly is connected to the inlet end of the shaft. It is used to drive the measurement assembly connected to the opposite end of the shaft.
(c) Bypass valve assembly
The bypass valve opens increasingly with flow and thus maintains a constant turbine assembly rotational velocity.
The bypass valve opens increasingly with flow and thus maintains a constant turbine assembly rotational velocity.
(d) Measurement assembly
The measurement assembly has a multi-vane impeller installed in a drum. These are connected by a linear spring attached radially between them.
Two pairs of magnets are attached to the measurement assembly, one pair to the drum, the other pair to the impeller. Each pair of magnets are set 180 degrees apart.
The measurement assembly has a multi-vane impeller installed in a drum. These are connected by a linear spring attached radially between them.
Two pairs of magnets are attached to the measurement assembly, one pair to the drum, the other pair to the impeller. Each pair of magnets are set 180 degrees apart.
(2) Operation
Fuel goes into the transmitter and drives the turbine. At low fuel flow rates all the fuel goes through the turbine. As the fuel flow increase, the bypass valve starts to open to let some of the fuel go through the large holes in the turbine. This prevents the turbine from turning too quickly.
The fuel leaves the turbine and the bypass valve and then all of it flows through the straightening vanes. These vanes straighten the fuel flow before it goes into the measurement assembly.
When the fuel flow transmitter is stopped, the magnets on the impeller align axially with the magnets on the drum. As the measurement assembly is turned, a pulse is generated each time a magnet passes its related pick-off coil. When the fuel goes into the measurement assembly its flow, through the impeller vanes, resists the movement of the impeller.
The spring permits the impeller to move in relation to the drum. The magnets are then not aligned and there will be a time difference between the pulses generated in the drum and impeller pick-off coils. This time difference is directly proportional to the fuel mass flow rate and is used to calculate the fuel flow.
Fuel goes into the transmitter and drives the turbine. At low fuel flow rates all the fuel goes through the turbine. As the fuel flow increase, the bypass valve starts to open to let some of the fuel go through the large holes in the turbine. This prevents the turbine from turning too quickly.
The fuel leaves the turbine and the bypass valve and then all of it flows through the straightening vanes. These vanes straighten the fuel flow before it goes into the measurement assembly.
When the fuel flow transmitter is stopped, the magnets on the impeller align axially with the magnets on the drum. As the measurement assembly is turned, a pulse is generated each time a magnet passes its related pick-off coil. When the fuel goes into the measurement assembly its flow, through the impeller vanes, resists the movement of the impeller.
The spring permits the impeller to move in relation to the drum. The magnets are then not aligned and there will be a time difference between the pulses generated in the drum and impeller pick-off coils. This time difference is directly proportional to the fuel mass flow rate and is used to calculate the fuel flow.
3. Fuel Filter Clogging Indication
A. Fuel Filter Clogging Indication
The fuel filter clog indication is provided on the lower ECAM display unit. When the pressure loss in the fuel filter exceeds 5 plus or minus 2 psid, the pressure switch is energized. This causes:
The differential pressure switch signal is fed directly to the SDAC through the hardware
The fuel filter clog indication is provided on the lower ECAM display unit. When the pressure loss in the fuel filter exceeds 5 plus or minus 2 psid, the pressure switch is energized. This causes:
- The engine page to come on the lower ECAM DU with the caution signal FUEL CLOG.
- The associated caution message to come on the upper ECAM DU.
The differential pressure switch signal is fed directly to the SDAC through the hardware
B. Fuel Filter Differential Pressure Switch
(1) Description
The pressure switch is bolted to the fuel filter housing and connects to ports in it.
The switch is in two housing held together with screws. One housing contains a bellows and the other a switch.
The bellows housing is connected to the fuel supply with two ports.
The bellows is connected to the filter inlet side and the housing (vent side) is connected to the filter outlet side. A lever connects the bellows to the switch.
The switch housing contains the switch and an electrical connector.
The switch is lever operated by the bellows lever.
The pressure switch is bolted to the fuel filter housing and connects to ports in it.
The switch is in two housing held together with screws. One housing contains a bellows and the other a switch.
The bellows housing is connected to the fuel supply with two ports.
The bellows is connected to the filter inlet side and the housing (vent side) is connected to the filter outlet side. A lever connects the bellows to the switch.
The switch housing contains the switch and an electrical connector.
The switch is lever operated by the bellows lever.
(2) Operation
The bellows and bellows housing are each filled with fuel at the pressure of the system. The pressure in the bellows and bellows housing is thus the same so the bellows do not move. If the filter element gets clogged or not fully clogged, the filter inlet pressure will increase. This will cause the bellows to extend. At the pressure set point the bellows will extend sufficiently far to push the lever and close the switch contacts. The switch will then transmit a message signal of a clogged filter to the cockpit.
The bellows and bellows housing are each filled with fuel at the pressure of the system. The pressure in the bellows and bellows housing is thus the same so the bellows do not move. If the filter element gets clogged or not fully clogged, the filter inlet pressure will increase. This will cause the bellows to extend. At the pressure set point the bellows will extend sufficiently far to push the lever and close the switch contacts. The switch will then transmit a message signal of a clogged filter to the cockpit.