Wren 44 TurboProp Users Manual. Copyright Wren Turbines Ltd February 2008 Page 10
The Mounting
The gearbox housing incorporates a Wren Turbines’ innovation – a fully integral mounting
system. This specially designed housing answers two of the criticisms of turbo-props – that of
their generally awkward mounting arrangement for gearbox and engine, and the amount of heat
they generate within the airframe.
Our unique new system is machined from solid aircraft
grade aluminium and carefully anodised to retain its
corrosion resistant qualities and durability of finish. It
provides a secure and rigid connection between the
firewall and gearbox and provides full support to the gas
generator at its C of G. This eliminates the danger of
distorting the hot section between the engine and
gearbox when individually clamping engine and
gearbox to different sections of the airframe. The Wren
system also allows a very simple mounting for the
engine – just align the supplied template (at the back of
this manual), and cut out the shape, drill the six mount
holes and bolt onto a firewall like a 2-cycle engine. This
also allows for the simple offsetting of the thrust line by
simply building it into the firewall at the point of construction, as recommended or included for the
I/C installation.
The mounting has a further advantage – it envelopes the hot section and exhaust sections and
holds in the heat which would normally be released to the interior of the aircraft. Such heat
release can cause heat damage to paint finishes cowl materials, or make it difficult for the engine
to get an adequate supply of essential cool air for the engine to run on. We think the system is so
good that some day all turbo-props will look like this.
Ancillaries
ECU (Engine Control Unit)
Data display terminal
RPM pickup (mounted in engine)
Temperature Probe (mounted on engine)
Fuel pump
Propane valve and flow restrictor
Fuel valve
Ecu battery
Propane tank
ECU (Engine Control Unit)
The ECU and ancillaries are identical to the thrust engine
variant and use similar programmed settings. It is
important however, that users do not change settings
from those set without refering back to Wren Turbines.
The ECU is the well proven Digitech type supplied by
Gaspar Espiell and which the engine, fuel pump and ecu
battery plugs into. It controls the engine through its
starting, running and cooling down phases. A signal lead from your receiver connects to the ecu and
provides the throttle commands to the engine from the receiver throttle channel and next to it is the larger
socket for plugging in the Data terminal (see below). The ECU unit has a printed label which shows where all
the engine accessories are plugged in; “RPM” - rpm pickup (the servo-type lead coming out of the cowl of
the engine), “EGT” - temp’ probe, “Fuel” - fuel valve, “Prop” - propane valve. To orientate these servo-type
leads, the “-“ refers to the brown wire. There are various timers that are used to keep track of running hours
– see the detail section on setting the ecu.
