Header Tank with 2 Fuel Transfer Pumps, 2 EFI Pumps - no engine driven pump
Folks,
I thought I provide some information about the fuel system we have on the Subaru driven Robin - just food for thought.
The plane:
The aircraft is fitted with two fuel tanks: a main tank underneath the rear bench and one header tank behind the rear bench. The main tank contains 110 litres (29 gals) of fuel, the header tank 28 litres (7.4 gals). As fuel is transferred by two fuel transfer pumps from the main tank to the header tank all fuel of the main tank is usable in level flight.
The engine always runs off the header tank. Two manually operated low pressure fuel transfer pumps are used to transfer fuel from the Main Tank to the Header Tank via two filters. An overflow tube between the Header Tank and the Main Tank prevents fuel spilling. The overflow tube doubles as a vent line for the Header Tank. The Main Tank is vented to the outside by means of a vent tube behind the main landing gear but on the underside of the fuselage.
From the Header Tank fuel is gravity-fed (no vapour lock) into two high pressure Engine Fuel pumps (as well called Electric Fuel Injection or EFI pumps) which feed via two fuel filters (situated underneath the Header Tank aft the rear bench) fuel to the engine using a single fuel line at a 2 Bar pressure and pass by all six injectors via a common rail system. Via a pressure regulator, the excessive fuel is returned to the header fuel tank to be cycled through the system again.
Both automotive fuel (98 or more octane; Europe standard) and AVGAS may be used. In order to avoid the build-up of lead deposits, unleaded (automotive) fuel is preferred. All seals and fuel lines are suited for the use of automotive fuel. If using AVGAS ca. 0,5 once (30 ml) of Decalin RunUp should be used per 10 gals (ca. 38 ltrs) to avoid the build-up of lead deposits.
Use of the tank system
? Make sure that at least one Fuel Transfer Pump keeps the fuel level in the header tank at an appropriate level.
? Cycle the fuel transfer pumps (Fuel Transfer Pump A or Fuel Transfer Pump B) from time to time to check both are operational, check one fuel transfer pump is ON all the time.
? Two panel warning lights indicate fuel state and inform about the operation of the fuel transfer pumps
? Green light: the main tank contains ca. 18-20 litres of fuel only. If so switch OFF both Fuel Transfer Pumps after ca. 30-45 minutes depending on fuel consumption to prevent the Fuel Transfer Pumps running dry, be aware that than some 28 litres are left in header tank only.
? Red light: header tank is at a fuel level of 18-20 litres. The exact behaviour of this light is this: Flight testing with both transfer pumps OFF at 30 Ltrs. Fuel Flow per hour proved that this light starts flickering after ca. 8 minutes (so at ca. 23 Ltrs reserve) and becomes continuously lit after ca. 16 minutes (so at ca. 20 Ltrs reserve).
? If the main tank is empty or both Fuel Transfer Pumps do not transfer fuel to make the red light go off land within the next 30 minutes on an appropriate airfield or execute emergency landing if necessary if no appropriate airfield can be reached with the fuel remaining.
? If fuel is still in the main tank and ie. just the transfer pump selected failed or no transfer pump was ON it takes 6 minutes to fully refill the header tank at 30 Ltrs. Fuel Flow from 20 Ltrs. reserve remaining (the fuel transfer pump pumps ca. 8 Ltrs in 6 minutes or ca. 80 Ltrs. in one hour).
310+ hrs without a hick up and no vapour lock whe using Mogas.
Best, Heinz
P.S. I AM NOT TEACHING SOMETHING TO ANYONE AND I AM NOT SUGGESTING THIS WORKS IN OTHER APPLICATIONS TOO.