Wren 44 TurboProp Users Manual. Copyright Wren Turbines Ltd February 2008 Page 12
Flow Restrictor
The “out” side of the propane valve has a short length of green tube attached by a quick
release connector to a small adjustable “Festo”- type flow valve. This valve controls the
volume of propane flowing to the engine for starting. It has been preset to the setting
required for starting as part of the engine test so should be approximately in the right place
already. There is a locknut just below the small blue control knob to help prevent it coming
undone and should be loosened before making adjustments. Do not adjust the valve until
you have tested it on an engine start and found you need to change the setting. It has a
soft seat and fine thread so it is not easy to tell if it it fully closed or not.
To confirm operation, unplug the outlet to the engine and connect a short length of 3mm tube to the valve
outlet. Fill your propane tank or connect up your usual supply, go for a start and after a click there should be
a hiss of flow coming out of the valve. If not open the valve gradually until it does. Note the ecu will only
allow about five attempts at a start on a single attempt before it shows “TimeOut”. If this happens simply put
the trim to off, then raise again to on and try again.
Fuel Valve
This is the same construction as the Propane valve with the same
direction arrow. Test by simply blowing through while plugging it into a
spare servo outlet on your receiver. There should be a click on powering.
Again if it fails there is little to be done but replace it. The quick release
connectors can be removed for re-use first though
.
ECU Battery
The ECU battery supplied is a 2-cell 7.4v Lithium Polymer (LiPo). The capacity of
this should be enough for at least three good flights but initially we recommend you
charge after each flight to keep tabs on how much is being taken out by the flight.
LiPo’s must be charged with a charger especially made for this type of cell and we
recommend those equipped with a balancer, or which charge through a balancer.
The battery has a balancing lead and it is best if you charge through this.
Warning. It is very important you disconnect the battery from the ecu while charging
or permanenet damage to the ecu can result. Such damage is checkable and ecu’s so damaged will not be
replaced under warranty. It is good practice anyway to remove the battery from the plane and charge in a
safe area.
Battery care - after flying.
It is most important that the battery is disconnected at the end of your flying
session. The ECU uses only a few milliamps when shut off but this can drain a LiPo down to nothing in a
couple of weeks. In this case the battery is deep discharged and permanently damaged – ie scrap. A LiPo
so discharged will not be covered by the warranty.
Propane Tank
This small tank is supplied for customers who wish to have an on-board propane system.
It is intended for mounting upright in the plane and to hold enough for four or five starts. It
is intended to be only filled to about 1/3
rd
to ½ full maximum. The connector on top
enables the feed supply from the outside to enter the tank and the outlet supply to exit the
tank to the propane valve separately. The advantage of this system is if it is a very cold
day you can simply leave your external propane supply plugged into the tank but not
supplying liquid, and make your start as normal, making use of the larger capacity of the
external supply.
It is good practice to vent the propane tank at the end of the flying session to ensure no
propane is left in the system that if seeped out could present a fire hazard.
