Honda Aircraft Company
HA-420
SYSTEMS
POM
DESCRIPTION
HJ1-29000-005-001
October 30, 2016
1-98
fuel tanks decreases, the valves open and allow air to enter the fuel tanks
to replace consumed fuel.
The inboard wing tank and the C/T tank vent float valves incorporate an
integral pressure relief valve which opens to relieve positive pressure
build-up in the wing tank such as caused by thermal expansion of fuel.
Vent Surge Tank
The vent system incorporates a surge tank on the L and R wing vent lines
to allow air that may become trapped in the C/T tanks to vent to the
atmosphere during climb. If air becomes trapped in the C/T tank due to
the presence of fuel in the vent lines, then during climb the trapped air
pressure will push fuel through the lines and into the surge tank. The fuel
vent system includes a single float level switch installed in the L surge
tank to detect a dual failure of the L and R outboard wing vent valves.
Flame Arrestor
The vent system incorporates flame arrestors in the left and right fuel
vent lines leading from the fuel vent ram air inlets. A positive / negative
pressure relief valve is installed in the vent system. In the event both
flame arrestors become blocked, the positive / negative pressure relief
valve will open to relieve excessive pressure differentials between the
fuel tank and the atmosphere.
Expansion Space
Each left and right vent line connects the wing tank directly to the
respective vent outlet. A branch-off tee is incorporated into each vent
line to allow any fuel in the vent line to dump into the expansion space.
If the fuel expands enough such that the level of fuel in the vent line
reaches the level of the tee branch-off to the expansion space, fuel will
flow into the expansion space.
FOR TRAINING PURPOSES ONLY
