Wren 44 TurboProp Users Manual. Copyright Wren Turbines Ltd February 2008 Page 8
exceeding 2:1! With a static thrust exceeding 16kg (35lb) the unit should be quite adequate in
power to enable an acceptable flight performance in a plane of 25kg (60lb) or more.
What about flying in noise sensitive areas?
Fliers with noise sensitive flying fields will enjoy the almost silent operation of the unit comparable
to electric flying. Such users are encouraged to make good use of the current crop of quiet
propellors and resist the temptation to zoom around the field like a pylon racer! Sports fliers can
make full use of the highly tractable response and enjoy quelling the myth that turbo-props cannot
prop-hang.
What about smoke?
The engine itself is a clean burning gas turbine that does not produce any smoke in normal
operation. However the gearbox bearings are lubricated with a very small amount of fuel which at
low rpms or throttling down can sometimes be seen as a small puff of smoke, but this is normal.
The minimal oil percentage used in the fuel helps to minimize pollution from unburnt fuel,
although operation of the gas turbine does produce an very distinguishable smell which for many
is the "
raison detre
" of this type of model flying.
What propellers do you recommend?
An important question.
In all cases, we recommend only
wooden props
as in the even of a nose-
over in a taildragger aircraft, the prop will break and not damage the engine. Similarly, in the
event of an undercarriage failure where the u/c will not extend and a belly landing is required, a
prop strike is inevitable and a strong carbon prop will not bend enough to protect the engine and
can cause serious damage to the propshaft. Wooden props are available in sufficient styles and
shapes to cover most needs although users should satisfy themselves in the case of three or
more blade props, that the hub fixing is adequate enough for the power of this engine.
