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Are you aware that the pump has a pressure relief's that vent to
the reservoir at about 1500 psi to prevent excess pressure in the lines? Build
your system to handle 3000 psi like it should be and you're good. I have
attached the spec sheet of the Oildyne 108 pump for your inspection.
I say again, I don't like the idea of relying on the friction of an O-ring
for the proper operation of the landing gear.
Did you ever figure out why you had a pump failure causing your gear-up
landing ? Would my module have prevented that ?
Wolfgang
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Wolfgang,
I know that this was discussed a while back, but it
occurs to me that this module could induce catastrophic failure if it
activates a few times in flight, e.g. if the pressure for some ungodly
reason is NOT relieved the pump could build up so much pressure that it
blows a seal or worse.
Bypassing the pressure switches
AUTOMATICALLY is not, IMHO, an actual solution but rather a work-around
that could unintentionally cause unexpected consequences. While
fixing the pump with the latest mods and installing the three-way dump
valve is probably the best actual solution (fix the problem, not the
symptoms), if you want to do a work-around it's probably safer to use the
momentary push-button solution (e.g. manually bypassing the pressure
switch by intentional pilot command) than to have an automatic system
repeatedly exercising a workaround without the pilot's
knowledge.
Everyone,
By now some of you know that I
experienced engine loss a few months ago and ended up attempting to land
on a highway. Unfortunately an SUV pulled onto the highway at the
last moment, and the energy spent waiting to get past the SUV was simply
too much to leave enough for a flare. The result was a hard
touchdown, breaking off the left main and slamming the left wingtip onto
the highway. The plane pulled hard left, leaving me concerned that
the plane would cross the grass median into oncoming traffic. There
was just enough energy left to momentarily re-raise the left wing, apply
the right brake and rudder to straighten out, and make a split second
decision as to whether I could land on two wheels safely or whether
attempting that would result in either resuming course towards oncoming
traffic or result in flipping in the median. Given the choice, I
chose to raise the remaining gear and slide rather than risk flipping and
being trapped in a scenario that might possibly have involved gasoline
leaking on a hot engine with us trapped inside. Google N351E for
photos of the result.
Why is that pertinent to this
discussion?
Prior to that I had had a gear-up landing from pump
failure and other factors involving a potential partner. I spent 3
yrs of weekends rebuilding and a year flying before this incident.
In the mean time, I became VERY familiar with my systems. And, I
just don't want to see any more of our community end up busting their ass
if it is avoidable or spending your time fixing what might have remained a
perfectly good airplane.
SOooooooo....
Chris has made
an EXTREMELY generous offer to all of you. If you don't KNOW that
your pump has the latest mods, take him up on it. He is sharp and an
obsessively careful individual.
Install the 3-way valve if you
have the time and inclination. Install the push-button override,
too.
But do NOT install automated work-arounds that may be
disguising or exacerbating real problems.
Please.
Blue
skies,
Bill Reister
From: Wolfgang <Wolfgang@MiCom.net>
To:
lml@lancaironline.net
Sent:
Sun, April 17, 2011 10:13:18 AM
Subject: [LML]
Gear operation fix for the LNC2
Here are some details on the Gear Fix
Module - - - - -
There is a potential for the landing gear
to fail to operate in the LNC2.
The spool in the hydraulic pump can come
off it's end position and seal the fluid volume in the lines. When the
system incurs a large temperature rise, the trapped fluid expands
raising the pressure in the lines, tripping both pressure switches
open and making the hydraulic pump inoperable.
A module to fix this gear operation
failure in the LNC2 using the standard hydraulic system is now
available. It is installed across the pressure switches and monitors
their operation. If both switches are tripped open by high
pressure, the pump is made to run in the direction set by the gear
switch re-seating the spool in it's end position restoring normal
pump operation and relieving pressure in the offending side. This
happens automatically without pilot intervention.
The module is 2.5" x 1.5" x .75",
weighs 2.3 oz. and has two pairs of leads that connect directly to
each pressure switch with 1/4" spade terminals. No other wiring is
necessary. Price is $250.00 each. Simple installation instructions
included.
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