At 16:42 22 December 2018, Jonathan Walker wrote:
At 05:43 22 December 2018, Bob Gibbons wrote:
On Fri, 21 Dec 2018 16:02:33 -0800 (PST), Richard Frawley
wrote:

HI

Recently flew a 2008 Duo with the 5 bladed sustainer.

Started very fast and beautifully with very little height loss.

When it came to putting it away, it was, however, difficult to
get it to
stop rotating.

Yes, put it half way retracted and yes, used the
decompression to also
slow it down as advised. Only by reducing airspeed to close to
stall and
holding it there, did it finally stop.

The days was hot. OAT at 3,000' was 32C.

Of interest (as it seems counterintuitive), why does the
decompression
work to slow it down?

Regards

Richard

Richard, perhaps you skipped a few critical steps, or did them
but
neglected to mention this.

1. Either turn off the ignition, or shut off the fuel, or both.
2. Partially retract the engine, perhaps 30 degress tilt.
3. Open the decompression valve for a few seconds and then
CLOSE the
decompression valve. If you continue to hold the
decompression open
the prop will NOT stop.
4. When the decompression valve is then closed the prop
should stop
pretty quickly.
5. Complete retraction.

Hope this helps

Bob (19 years flying a Ventus C turbo)


I always find that pumping the decompression valve works best.

When the valve is closed the piston work like a bouncing spring,
as i
moves towards TDC it uses the energy of the prop to compress
the air in th
cylinder so slowing the props speed, as it goes over TDC the
compressed ai
is converted back into additional rotational movement of the
prop. When yo
pump the valve, depending on your timing, you keep removing
the compresse
air from the system. This means the system has to use more
energy t
re-compress the cylinder therefore slowing the prop faster than
jus
continually holding the valve open.

Works for me, Discus Bt and Ventus 2ct

I had the later Duo XLT with the later ilec control.It was fully
automatic so little to do.When you switch off it cuts the ignition
and about 1 second after the engine starts to retract, it stops just
about 1/2 way down NO USE OF DECOMPRESSOR and when
rotation stops ,about 3seconds it goes down the rest of the way.
Thats it nothing else just shut the fuel cock when you are done.
The turbo prop will fit into the engine box at any point in its
rotation so there is no need to stop at any particular spot unlike
the 2 bladed props.

I now have a ventus 2ct with the older ilec and the same system
works.
You don't want to turn the fuel off because you loose cylinder
lubrication.
Ignition off
When the engine stops firing retract until its as low as is safe(you
need to know that position by memorising it on the ground)
When rotation stops retract the rest of the way and shut the fuel.

The only problem we ever had with the duo was catching a door
on the final few inches of the retraction and this was because the
door spring had lost tension and was allowing the engine bay
doors to blow partially shut in the slipstream.A new spring fixed
it.