Hi Gerard,

The new switches simply use a different mechanism to turn "on" and "off,"
and as I understand it "are just built that way."  I think they could almost
be considerd as "solid state transistors" in that they use piezo-electric
effects of crystal compression - they are reported to be good for up to
1,000,000 cycles so should NEVER need replacing.  The up switch is fixed at 1100psi.  If you are needing 1500 psi to hold the
gear doors up, I would investigate if there is a problem with your setup
which might require a different bracket (perhaps with a bit more leverage?).
The 235s typically didn't have this problem as much as the Legacys do - the
racers all use a modified setup to keep the gear tucked away.

The new switches are far more reliable, and I don't think they let the
pressure drop more than 100psi without kicking the motor back on.  My 235
pump used to cycle once or twice on a 3 hour flight for about a second -
Zzzzzzzt.  That doesn't mean the hydraulics are "leaking", it can be caused
because the check valve allows a tiny bit of the pressure to bleed back to
the pump.

Regards,

Bill


-----Original Message-----
From: gerardoconnell@optusnet.com.au [mailto:gerardoconnell@optusnet.com.au]

Sent: Wednesday, June 04, 2008 07:51
To: lml@lancaironline.net
Subject: new type hydraulic pressure switches for LNC2



Anyone know what the advantage offerred by the new "fixed" type hydraulic
pressure switch ?

Does it not give less control over things?

If you have  a small hydraulic  leak which allows the pressure to bleed off
ho long before the pump cuts in to restore pressure? Currently if you set the adjustable type to say 1500 psi and the pressure
slowly drops off to say1200 psi the doors will not open as there is
sufficient PSI to keep everthing shut tight.

How do the fixed pressure switches ehave in this instance and once gear is
up and doors closed how much PSI is actually required to keep eveythinn that
way?

I probably only have a limited understanding of the hydraulics and perhaps
this is where my quetsions arise...


What say y'all

Gerard