MAULE AEROSPACE TECHNOLOGY, INC.
MAINTENANCE MANUAL
FOR
MT-7-420
9/02
28
trol.
Two (2) auxiliary wing tip fuel tanks, twenty-one (21) gallon capacity, are mounted in the
second from the outboard wing bay. They are fuel transfer tanks and simply supply fuel to the
main tank through a small vibrator pump.
The fuel lines should be checked for cracks and chafing every 100 hours or annually and
the external fuel filter should be cleaned at the same time. The auxiliary tank transfer pump
strainers should be cleaned at the same interval. This is done by removing the pump bottom
with a 5/8” wrench. The pump is on the rear spar, inboard of the auxiliary tank, and the bottom
is exposed.
ELECTRICAL SYSTEM
The electrical system is a 28 volt, 100 amp, direct current, single wire circuit using the air-
plane structure as a ground return to the battery. All wiring in the airplane is fabricated into
harnesses which are groups of related wires tied together. Most of the harnesses originate at
circuit breakers on the main bus (center of instrument panel) and terminate at the load (light,
pump motor, etc.) A wiring diagram is shown at the end of this manual.
CAUTION: Addition(s) of electrical equipment must not cause the total load to exceed 100 am-
peres.
BATTERY:
A lead plate type storage battery rated at 24 volts is installed in the battery box on right side
of firewall. The battery supplies current for the airplane electrical system when the master
switch is in the “ON” position only.
The battery is the sealed type or the manifold vented type, with the base being integrally
vented. Tubes attached to the case vent the battery to the fuselage bottom. Battery caps
should be kept tight to prevent electrolyte spillage. If spillage does occur, the affected area
should be cleaned with a liberal application of an acid neutralizing solution such as baking so-
da and water. The vent tube must be properly routed through the fuselage bottom as battery
acid will destroy the fabric.
This battery is considered fully charged at a hydrometer specific gravity reading of 1.265.
A low charge would be 1.225 or lower. Operating with a low charge will shorten the life of bat-
tery and can be prevented by recharging are operating with electrical equipment turned off until
the battery has been sufficiently recharged.
Some batteries are sealed recombinant design which do not require the external vent tube.
