AIRCRAFT FLIGHT
MANUAL
BRISTELL B23
Document No.: ADXC-73-001-AFM
Non-approved page
Revision: A2
7-22
Date of Issue: 15.04.2021
7.10
Fuel system
Fuel is stored in two fuel tanks. The fuel tanks are integrated part of the
wing. Their volume is 60 litres each. The tanks are located in the leading
edge of the first third of the outer wing span in front of the main spar. The
ribs and rear tank wall are structurally independent from the main spar
and wing ribs.
Each fuel tank has a filler neck with flush head filler cap, venting tube,
fuel strainer, floater type quantity sensor, low fuel sensor and a drain
valve. Fuel is filled into each tank through the filler neck, which is located
on the top skin. Fuel drain from the tank is through the drain valve
located in the rear corner of bottom skin close to the root fuel tank rib.
Fuel flows from the tank, through fuel strainers to the selector valve and
from there through the firewall. On the engine compartment side it flows
to the gascollator, electrical fuel pump and finally to the mechanical fuel
pump located on the engine. A bypass of the electric pump with a check
valve is installed.
From the mechanical pump the fuel is supplied through the fuel
distributor lines to the carburettors and to a return line which dumps into
the left tank.
The selector valve also serves for interruption of fuel supply in case of
engine fire or for airplane long
–time parking. The selector is located on
the middle console between the seats in the cockpit.
The gascollator is located on the firewall at the lowest point of the fuel
system. It features a drain valve to check for contamination and water.
The electrical fuel pump is located on the firewall above the gascollator.
The electric fuel pump not only serves as (emergency) back up for take-
off and landing but also to suppress fuel vapor formation in extreme hot
and high conditions. It should be switched on for take-off and landing, but
also at any time the fuel pressure drops unexpected. Unnecessary fuel
pump operation with engine off should be avoided to not overflow the
carburettors.
NOTE
Switching the electric fuel pump off causes a transient fuel pressure drop
caused by the changed operating point of the mechanical pump
–
sometimes below the minimum level. This can cause a low fuel pressure
warning. The acceptable time limit for this warning (according to engine
manufacturer) is 5sec.
The operation of the fuel pump upon start up when the strobe lights are
switched on is audible influenced by the power surge of the strobe lights.
