Maintenance Manual STEMME S10-VT
Date of Issue: Jan. 01, 1998
Page 3-35
Amendment Nr. 0
Date: --
A4011121_B23.doc
Doc. No. A40-11-121
3.7 Electrical System
(Fig. 3.7.a - l)
3.7.1 General
The STEMME S10-VT is equipped with a 12 VDC system. Electrical power sources are the main battery,
capacity 26 Ah, an optional additional battery, 7.2 Ah, and a 600 Watt - generator (Nippon Denso). This
generator (the
„external generator“)
is driven by a V-belt. The V-belt pulley is mounted at the engine propeller
shaft. A second generator, integrated in the engine (the
„internal generator“)
supplies only essential electric
engine systems (main fuel pumps, ignition and TCU). The internal generator and the essential electric engine
systems make up a separate electric system, connected to the a/c system at common ground.
3.7.2 Wiring
The layout of the a/c wiring is with a central cable harness and several tappings. The installed cable harness
is routed from the main battery to the right side of the instrument panel frame (RH electric plate) in the foot
area of the RH cockpit. The main battery is installed behind the engine compartment. Beginning at the main
battery, the wires are routed as follows:
from the battery to the junction box (E-box), installed in the upper area of the steel-tube frame,
from the junction box (E-box) along the upper left chord tube to the upper frontal cross tube of the frame,
from the upper frontal cross tube along the top of the drive shaft tunnel to the lower area of the instrument
panel frame,
from the lower area of the instrument panel frame to the RH electric plate.
The cable harness is protected against mechanical damage by a spiral-winding-tape and is fastened at
adequate distance from hot areas.
The components for voltage distribution and propeller-blade control are installed close to the main battery in
the junction box (E-box) in the upper area of the steel-tube frame outside of the fire-wall. To protect the
battery connectors mechanically, a distributor plate is installed on the RH side of the front tail-boom frame.
Via this distributor plate, the battery is connected with the junction box, the starter relays and the engine
housing.
3.7.3 Bus-Structure of the Electrical System
Soaring and powered flight mean different requirements to the electrical system. Taking this into account, the
electrical system is split up into 5 busses:
Battery Bus 1VV (1VV-1 and 1VV-2)
Bus 1VV is always connected to the main battery. The engine starter is connected to bus 1VV-1. The
rest of the electrical system is connected to bus 1VV-2. A shunt in between bus 1VV-1 and 1VV-2
allows to monitor the battery load. Engine starter power is not measured because of the high current.
Main Bus 2VV (2VV-1 and 2VV-2)
Bus 2VV is powered via the main relay from bus 1VV when electric master switch is ON.
Engine Bus 3VV (3VV-1 and 3VV-2)
Engine Bus 3VV is supplied via relay by bus 2VV in powered configuration. This relay is closed, when
the propeller-dome is open and locked.
Main Avionic Bus 4VV-1
Main Avionic Bus 4VV-1 can either be supplied by the Main Bus 2VV or by the additional battery,
selected by the "battery selector switch".
Secondary Avionic Bus 4VV-2
Secondary Avionic Bus 4VV-2 can either be supplied by the Main Bus 2VV or is de-energised,
selected by the "battery selector switch".
Generator Bus 5VV
When the generator is operating, Generator Bus 5VV is powered by the generator.
