Wren 44 TurboProp Users Manual. Copyright Wren Turbines Ltd February 2008 Page 25
Propane System
The propane supply is either plugged in externally or contained in a
small canister on-board the aircraft – see later. For either installation the
control side is the same.
The propane supply feeds into the inlet of the propane valve, note the
direction arrow. The output of the propane valve feeds into the bottom of
an adjustable flow control and the output of this feeds the green
propane pipe to the engine. It is important the flow should be in this
direction as the flow control only works in this direction.
The flow control is preset at the point of engine test so should not need
any, or at least only minor adjusting for first trials.
The lower part of the flow control has a brass bulkhead fitting screwed
on. This enables you to fit it to a mounting point in the aircraft where it is
externally accessible in case of required adjustment. The fitting can then
be refitted after mounting the brass adapter. Do be careful to eliminate any leakage from the
threads.
On-Board Propane Supply
If you plan to feed the propane from an on-board tank, mount this vertically with the connector at
the top. This is to prevent the possibility of liquid propane finding its way into the system which
can cause aggressive and uncontrolled surging starts and local freezing of the flow control
components. The filling side of the tank has a one-way valve in it. The outlet is plain and should
be fitted with a suitable length of tube to the propane valve.
The tank only requires to be partially filled and needs to be liquid. Use the self-sealing quick-
release connector to connect the supply to the aircraft. The main body part of the quick release is
fitted with a short tube and then connected to the one-way valve. This valve protects against
leakage in case the quick release connector does not seal properly.
With most canisters liquid propane can be obtained by first connecting up, then inverting the can
and then turning on the supply tap. Before doing this always ensure it is safe to do so – no naked
flames, no smoking in the vicinity and never do this indoors. After filling the connector can be
released and propane will remain sealed in the tank.
Once the tap is opened flow can then be seen to move along the pipe to the tank. Always wait a
few minutes for the liquid to settle and clear the supply pipes before try for an engine start.
Off-Board Propane
If you plan to use off-board or external propane, then simply plug the external canister into the
aircraft, using the quick release connector supplied.
The supply in this case must be gaseous only – no liquid propane. The gaseous supply is then
fed directly to the propane valve and the outlet of the propane valve feeds the flow control as
before.
To Engine
From Gas
Supply
Adjustable
flow
control
Brass connectors
together- propane flows
Brass connectors apart-
propane is sealed in
