" . . . you can only
override one pressure switch at a time or overload the system.
You need one
switch each for the up and down. In the event of a problem you have to make
sure you push the right switch"...
Overload what
exactly? The gear selector determines which pressure switch is
powered. If you jumper across an unpowered switch, nothing happens.
While I do not
advocate putting in switches to mask a pump problem that should really be
investigated and fixed at the source, momentary switches have other
benefits.
1. Checking the
relief valve settings in the pump. By holding down the switch, one can
see the relief valve setting of the pump.
2. Back-up for a failed pressure
switch. This was more common with the VEP switches, but current version
is not immune.
3. Recharging the
system on demand - The hysteresis loop on the pressure switches is quite
large. The gear can start to sag before the pressure switch recharges the system.
This is more of an issue for the Outback Gear due to the higher
aerodynamic loads pulling on the gear.
With automation and
complexity come new failure modes. Give the pilot enough
information about the state of the aircraft systems to figure out what
happened and enough controls to solve the problem.
Last summer when the
high pressure switch went out, the pump shut off before the gear was all
the way up. Higher than normal air noise was the first clue. A
quick look at the pressure gauges revealed the high side at only 800
psi. The momentary switch pulled the gear the rest
of the way up. Examination of the pressure switch uncovered
intermittent electrical contact within the switch when
pressurized.
Chris Zavatson
N91CZ
360std
From: Wolfgang
<Wolfgang@MiCom.net>
To: lml@lancaironline.net
Sent: Monday, February 20, 2012 4:58
AM
Subject: [LML] Re: 320/360
Hydraulic Pressure Switch
Yes, that would be easy . . .
except . . . you can only override one pressure switch at a time or overload
the system.
You need one switch each for the up and down. In the event of a
problem you have to make sure you push the right switch.
If you come up
with some more complicated wiring, you could make it work with only one switch
for both up and down but you still have to push the button if something isn't
working as required.
. . . or . . . you could put in a completely automatic
system . . .
Wolfgang
----- Original Message ----- From:
"Greenbacks, UnLtd." <
N4ZQ@VERIZON.NET>
To: <
lml@lancaironline.net>
Sent:
Friday, February 17, 2012 1:07 PM
Subject: Re:320/360 Hydraulic Pressure
Switch
Seems to me the simplest and least expensive option would be
to install a momentary on switch in the cockpit to override and close the open
pressure switches.
Just my 2 cents.
Angier Ames
N3ZQ
--
For archives and unsub
http://mail.lancaironline.net:81/lists/lml/List.html