Login
Register
| Contents [show] |
Fuel System
Fuel is supplied to the engines from a collector tank in each of the integral wing tanks. The APU is supplied with fuel from the right collector tank. With the engines running, primary ejector pumps feed the engines and APU. With the engines not running, electric pumps feed the APU. The electric pumps also act as backups to the primary ejector pumps, and provide fuel under pressure to the engines and APU during ground and inflight start.
Each wing tank has a surge tank that collects fuel during uncoordinated flight. Fuel within the tanks flows inboard into each collector tank, and scavenge pumps ensure fuel does not flow out of the collector tanks. Each tank also has a vent line into the outboard surge tanks. Water collects in the collector tank and can be drained from there. There are 3 magnetic level indicators (dripsticks) per wing.
Fuel pumps
The ejector pumps are the primary fuel pumps. Electric pumps act as backups. The left AC electric fuel pump is powered by the AC Bus 1. The right AC electric fuel pump is powered by the AC ESS Bus. In an electrical emergency, the right AC fuel pump is powered by the RAT. A DC fuel pump in the right wing provides fuel for the APU, or engine start when the AC fuel pump is not available. Power is from DC ESS Bus 2.
Each pump has a pressure switch that monitors its output. MAU 1 monitors AC fuel pump 1 pressure switch, MAU 3 monitors AC fuel pump 2 pressure switch and the DC fuel pump pressure switch. The data is transferred on the ASCB for EICAS display.
Fuel quantity
The primary means is via an AC capacitance type electrical system. A backup mechanical system consisting of magnetic level indicators (dripsticks) can be used in case of a failure. The low level sensor is completely independent of the fuel quantity sensors. If the scavenge pumps in a tank are lost (for example after an engine failure), the level of the collector tank can drop as fuel flows out into the rest of the tank. This can result in a FUEL 1/2 LO LEVEL warning on the EICAS. Flameout is possible in attitudes greater than 15° or in uncoordinated flight.
Fuel temperature
A temperature probe is installed in the left tank only.
Crossfeed valve
Powered by DC ESS Bus 3.
Shutoff valves
The fuel shutoff valve opens when the corresponding fire handle is pulled.
Refuelling / defuelling
Pressure defuelling: the crossfeed valve must be open and the AC fuel pumps switched ON (requires AC power)
Suction defuelling: the crossfeed valve must be open (requires DC power)
Control panel
| OFF | pump is off |
| AUTO | SPDA determines when the pump should be powered (ejector pump failure) |
| ON | pump is on |
| LOW1 | tank 1 has a lower quantity than tank 2, so AC fuel pump 2 is activated (if it is in the AUTO position) and crossfeed valve is opened |
| Normal | refuel control solenoids and FCU powered by DC Bus 1 and 2 |
| Battery | refuel control solenoids and FCU powered by DC Hot Bus 2 (allows for refuelling with APU shutdown and no external power) |
| AUTO | FCU controls the refuel shutoff valve, automatically closing it when the preset amount is reached |
| MANUAL | bypasses the FCU |
Schematic
EICAS messages
FUEL 1/2 LO LEVEL - can occur while there is still 1800kg (E170) or 2800kg (E190) of fuel in the tank if the scavenge pumps fail
FUEL AC PUMP 1/2 FAIL
FUEL DC PUMP FAIL
FUEL IMBALANCE - greater than 360kg imbalance
FUEL EQUAL - XFEED OPEN - less than 45kg imbalance with crossfeed open
FUEL XFEED FAIL - indicates failure of the crossfeed valve or associated AC fuel pump