Fuel Systems Flashcards
How/when does an aft transfer of fuel to the trim tank occur?
It doesn’t! I.e. no more fuel gets sent to the trim tank after refueling. Fuel can only be transferred forward FROM the trim tank, not after to the trim tank.
The only form of aft fuel transfer that occurs is after liftoff when fuel is transferred (from where??) to the outer tanks for load alleviation purposes (ie counter the lifting force of the wing on the wing roots). Note: This normally results in the L and R outer tanks going from 4t to 8t.
Ref: FCOM / Aircraft Systems / 28-Fuel / System Description / Tanks
How much fuel is in the collector cell of each feed tank?
The collector cell in each feed tank has a fuel capacity of APPROXIMATELY 1,300kg.
Ref: FCOM / Aircraft Systems / 28-Fuel / System Description / Tanks /
What triggers a FUEL FEED TK LEVEL LO master caution?
Below what height is it inhibited?
What is the general ECAM process to deal with this caution?
A FUEL FEED TK LEVEL LO master caution is triggered when there is les than 1,375 kg of fuel in a feed tank.
(Note: If all 4 FEED TKS had only 1,375 then then total FOB would be 5.5t.). Don’t forget that some of the fuel in the FEED TKs in unusable.
This master caution is inhibited below 800’.
They general ECAM process to deal with this caution is to turn symmetrical crossfeeds and to try to send fuel from the trim tanks and transfer tanks forward.
Which feed tanks can contain more fuel: the inner feed tanks or the outer feed tanks?
The inner feed tanks.
The usable fuel in litres is as follows: (With average SG 0.785 kg/L)
- Inner feed tanks (tanks 2 and 3): 23.04t
- Outer feed tanks (tanks 1 and 4): 21.69t
In cold temps (SG up to 0.893 kg/L), in terms of weight, the fuel in the feed tanks is as high as:
- Inner feed tanks: 26.21t
- Outer feed tanks: 24.68t
Ref: FCOM / Aircraft Systems / 28-Fuel / System Description / Tanks
What is the normal sequence of the ‘main transfers’ (transfer of fuel from the non-feed tanks to the feed tanks) to ensure that fuel is keep in the feed tanks to compensate for engine fuel burn?
- Inner tanks to feed tanks
- Mid tanks to feed tanks (when the inner tanks are empty)
- Trim tank to feed tanks when the mid tanks are empty.
- Outer tanks to feed tanks when the trim tank is empty.
The FQMS employs a system logic whereby only one tank (or pair of symmetrical tanks) will provide fuel for main transfers.
Ref: FCOM / Aircraft Systems / 28-Fuel / System Description / Tanks
How is fuel gravity feed affected by altitude and time aloft?
The gravity feed properties of the fuel improve with time and altitude.
As a result the gravity feed ceiling is higher for more time aloft, as follows:
- FL300 if the flight time above FL300 is greater than 30 mins
- FL050 if the flight time above FL300 is less than 30 mins.
What are the important take home points from the Airbus WIN video about manual fuel balancing?
NEVER turn the crossfeeds on during manual fuel balancing (is this correct?)
Something about main or standby pump being turned on first?
Bear in mind that even if you don’t manual balance fuel and you are outside the FCOM ‘maximum allowed wing fuel imbalance limits (ie reciprocal-side Feed tanks 3.0t, inners 3.0t, miss 2.5t and outers 1,2t) then the aircraft is still safely flyable for landing. Yes, there will be some sort of out-of-balance flight control compensation, but the airplane should be perfectly flyable. The main issue when out of the fuel imbalance limits as listed above is that we will have a fuel penalty factor due to the spoilers working to keep the airplane flying straight and level. So, so long as we have plenty of fuel for landing, it may make workload much much easier if we accept the out-of-balance and land rather than get entangled in the fuel balancing procedure.
Ref: Airbus WIN App/ Videos
What is the difference between the FUEL LEAK DETECTED ECAM and the ENG FUEL LEAK ECAM?
ENG FUEL LEAK is an ECAM for a leak detected in the engine fuel system downstream of the fuel metering valve.
Note: The fuel metering value is downstream of the LP fuel valve and is upstream of the HP fuel valve.
FUEL LEAK DETECTED is am ECAM for a fuel leak detected in the fuel system upstream of the fuel metering value, ie in the tanks or transfer lines.
What triggers the ECAM: ENG FUEL LEAK?
A leak in the engine fuel system:
- Is detected by an abnormally high fuel flow of one engine
- Is detected by the FWS
- Triggers ECAM: ENG FUEL LEAK
What triggers the ECAM: FUEL LEAK DETECTED?
A leak in the fuel system:
- Is detected by an increasing difference between the BLOCK fuel and the sum of the Fuel On Board (FOB) + the Fuel Used (FU)
- Is detected by the FQMS
- Triggers the ECAM: FUEL LEAK DETECTED
