Airplane Flight Manual
Van’s Aircraft RV-7A
HB-YMT
7 Aeroplane and system description – Page 9
Edition 01.11.2017
Each tank has a mechanical “float type” fuel sender installed. Although
they are carefully calibrated, a visual check of fuel quantity / dipstick is
recommended before flight.
Each tank is vented via a line that enters the fuselage and terminates near
the firewall on the belly. The vent lines are protected by a screen from
insects etc… They should be verified unobstructed during the walk-around
inspection.
Each tank has one drain valve at the bottom, mainly to remove any water
that could have entered the tank. They also work well as a grounding
point during refuelling.
Due to the construction of various chambers in the tanks, fuel will take a
while to balance from the chamber with the nozzle to the rest of the tank.
When intending to “top it off”, it has to be done in several steps and with
a bit of patience.
The Fuel Selector is a Andair duplex fuel selector. It simultaneously selects
/ shuts off both the feed and return lines from each tank.
There are 3 positions, “LEFT”, “RIGHT” and “OFF”. To select off, the safety
latch has to be lifted while turning the handle simultaneously.
The Fuel Pump is the standard Van’s Fuel Injection pump kit, produced by
“Airflow Performance”.
First the fuel is filtered through a serviceable fuel filter, then it enters the
fuel pump package.
The package offers three flow paths. One is low-resistance unpowered
through a check valve and only based on suction by the engine. A second
flows through the electrical boost pump to the engine. And the third is a
pressure relief circuit within the package in the event that the pump is
running but no fuel is flowing downstream. Also, there is a tiny orifice in
the check valve, whose function is to relief pressure when the whole
system is unpowered/airplane parked.
Due to the characteristic of the fuel system, the electric boost pump is only
needed for engine start. Thereafter it only serves as a backup in case of
mechanical pump failure. If the boost pump is turned on during normal
operation, the engine will run over-rich. Barely noticeable at high power
settings but rich enough to kill/flood it at low power.
The fuel system features a fuel return line to each tank, providing a
constant flow and with it Mogas compatibility.
Unusable fuel has been designated 2l/tank. Tests however have shown
that the actual value is quite a bit lower, but the 2l is ample to cover for
piping loss and various flight attitudes.
