Hi
My airplane project requires a fuel system manager, or AFC (Auto Fuel Computer).
The System consists of 2 wing tanks and a center main tank. The engine feeds
from the main tank only. It is a 28VDC system
The electrical components of the system are a High Pressure solenoid, 2 low pressure
solenoids (1 for each wing tank), a high level sensor and a low level sensor.
2 3 position switches (Off,Manual,Auto) and a low level or "bingo" light.
There is also a jet pump (non electrical) that uses high pressure fuel from
the engine to "siphon" fuel from the wing tanks to the main tank.
All the solenoid valves are Normally Open and require power to close. The fuel
level sensors are NC or Normally closed. The planned sensors FU-ll25-03 from
SMD Fluid Controls. I have attached a copy of the data sheet.
LPFS is Low Pressure Fuel Solenoid
HPFS is High Pressure Fuel Solenoid
Auto Mode Single-
When the pilot selects the Auto mode on either transfer switch the fuel computer
reads the level inputs from the fuel level sensors. If the fuel is below the
low sensor the AFC will remove power from that selected LPFS, allowing it to
feed fuel into center tank. It will continue this until the high sensor tells
the AFC that the center tank is filled to its location. At that point, the
AFC will apply power to the selected LPFS to close it.
Auto Mode Double-
When the pilot selects Auto mode for both transfers, both LPFSs are controlled
as above.
Manual Mode Single-
When the pilot selects either transfer in Manual mode then the selected LPFS will
have no power and therefore be open. The HPFS has no power any time that either
LPFS has no power.
Manual Mode Double-
When the pilot selects both transfers in Manual mode then both LPFSs and the HPFS
will have no power and therefore will be open.
Off Mode Single-
When the pilot selects one transfer switch into the Off position the selected LPFS
will be powered closed. No fuel will transfer from that wing.
Off Mode Double-
When the pilot selects both transfer switches into the Off position then both LPFSs
and the HPFS will be powered closed. This is the position for start up of
the engine
Finally if there is an 20 second uninterrupted signal from the low level sensor
the low level light is activated.
Originally this was operation was controlled by the use of a PLC (Programmable
Logic Computer) system. I can't get anyone to provide me with it. Can a system
like this be implemented using other means?
Any help would be appreciated
Pete
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