Fuel system

Question 1

What are the main elements of the fuel storage system?

Answer 1

2 vented, integral type tanks
Crossfeed valve

Question 2

What is the max fuel capacity of the E175?

Answer 2

4714kg + 34kg unusable per tank
9496kg total

Question 3

How are the fuel tanks divided?

Answer 3

• Collector bay (IB edge)
• Surge tank (OB edge)
• Main tank
• Dry bay (close to engine pylones)

Question 4

Max fuel imbalance?

Answer 4

360kg

Question 5

What is the main pump to supply fuel to the engines?

Answer 5

Ejector pumps, powered by motive flow from the engines

Either pump can supply sufficient fuel to one engine and APU at TO/GA setting

Question 6

What is the secondary fuel providing system?

Answer 6

2 AC pumps (aka Boost pumps)

Left one is powered by AC Bus 1, right one is powered by AC ESS Bus or RAT Gen

Question 7

When do these AC pumps provide fuel?

Answer 7

• During engine start
• During crossfeed
• To run the APU when engines are off
• In case of a failure of ejector pump

Question 8

What is the third mean of providing fuel to the engines?

Answer 8

DC pump in the right tank (powered by DC ESS Bus 2)

Centrifugal pump, works in flight or on the ground

Question 9

What powers the XFeed valve?

Answer 9

DC ESS Bus 3

Question 10

What triggers FUEL 1 (2) LO LEVEL?

Answer 10

Less than 300kg in the associated collector tank

Question 11

What is the limitation associated with Fuel XFeed?

Answer 11

You can’t T/O or Land with XFeed open

Question 12

When does the LO FUEL TEMP message appears?

Answer 12

When the fuel T is below -37C

Question 13

Describe the CF34-8E5 sections briefly

Answer 13

Low-pressure rotor : 4-stage low-pressure turbine that drives 28-blade fan (N1)
High-pressure rotor : 2-stage high-pressure turbine that drives a 10-stage compressor

The 10-stage compressor includes variable stator vanes to prevent compressor stall

Question 14

What is the bypass ratio of the CF34-8E5?

Answer 14

5:1

Question 15

Accessory gear box (AGB)

Answer 15

Powered by N2 through a radial drive shaft

Powers :
- Lube and scavenge oil pump
- Engine-driven hydraulic pump
- Engine fuel pump
- IDG
- PMA (Permanent magnet alternator)

Also includes the starter (pneumatic/bleed air) which drives the compressor through the radial drive shaft

Question 16

Combustion chamber

Answer 16

18 fuel injectors (spray atomized fuel in the chamber)
2 igniters

Question 17

Where is the ITT measured?

Answer 17

Between the high-pressure and the low-pressure turbines

Question 18

How are the FADECs powered?

Answer 18

N2 below approx. 50% : DC ESS Bus 1 (channel 1) and 2 (channel 2) of each FADEC
N2 above approx. 50% : associated engine PMA provides DC power

Question 19

What does the FADEC control in the engine?

Answer 19

• Fuel Metering Unit : fuel input into combustion chamber
• Stator vanes actuation
• Bleed air output
• Thrust reverser actuation
• Starter control valve (bleed air to starter)
• Igniters energizing

Question 20

Briefly describe the engine oil system

Answer 20

Lube and scavenge pump brings oil from oil tank to fuel/oil heat exchanger through an oil filter module

After the heat exchanger, the oil is sent to engine and AGB bearings

Question 21

What is the purpose of the differential pressure switch in the oil filter module?

Answer 21

It actuates the filter bypass valve in case the filter is clogged and oil doesn’t

Question 22

Where is oil pressure measured?

Answer 22

After the oil filter, before the fuel/oil heat exchanger