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Re: Lancair IVP Outflow Valve
Problem
In case this initial reply from Duke's helps anyone (now or in
the future)
HI DOC
I THINK I MAY BE ABLE TO HELP. FIRST, THE PIN 3 AND 4 ANRR NOT
EVEN REQUIRED IF YOU ARE NOT USING VACUUM TO THE OUTFLOW VALVE.
AS I REMEMBER , YOU ARE NOT. IF YOU DO USE VACUUM, THE CIRCUIT
SHOULD BE CLOSED ON THE GROUND AND OPEN IN THE AIR. NORMALLY BY
THE SAME SWITCH (AIRSPEED OR LANDING GEAR SWITCH) AS THE DUMP SWITCH
TO ASSURE THE AIRCRAFT IS NOT PRESSURIZED ON THE GROUND.. AN OVERRIDE
SWITCH IS USUALLY PROVEDED TO ALLOW THE CIRCUIT TO OPEN ON THE GROUND
TO CLOSE THE SOLENOIDS FOR GROOUND TESTS. PINS 12 AND 13 SHOULD ALWAYS
BE CONNECTED IN THIS WAY . POWER SHOULD BE ON THE SOLENOIDS ON
THE GROUND AND NOT ON IN THE AIR . ALL OTHER POWER TO THE OUTFLOW
VALVE IS FROM THE CONTROLLER TO RUN THE MOTOR TO POSITION THE
ANEROID THAT CONTROLS THE CABIN ALTITUDE. YOU SHOULD BE ABLE TO
HEAR THE MOTOR RUN ON THE GROUND WHEN A DIFFERENT ALTITUDE IS SELECTED
ON THE CONTROLLER.
PLEASD CALL ME IF YOU HAVE FURTHER QUESTIONS.
PAT PATRICK
V.P. ENGINEERING / MARKETING
(818) 998-9811 X219
Members
I recently wondered if my Duke's valve
was working correctly. I found the outflow dirty (from
construction debris), and sent both components for service; they
cleaned it, upgraded it, and fixed some things ($660). Still, it
didn't seem to be very responsive with the panel control changes.
The cabin would pressurize to 3 psi quickly, and then I see this
increase to 5 psi with altitude and remain fairly stable. Rate
changes on the controller had no real effect.
So I disconnnected the harness to the
Duke's valve and went flying...the cabin behaved the same.
That's right, completely disconnected, the cabin pressurized inn the
same manner.
The harness has wiring labels that are
easily confused, so I wondered if this was the case.
I went through all the connections on
both components and confirmed every pin is correct except the
uncertainty of Pin 4 on the outflow valve...this is the ground switch
that closes the 12V circuit to power the valve. This is, on the
ground, checking continuity, an open wire...not connected to ground.
I can not tell if it closes with airspeed and gear up. Without
power, the Duke's valve is not participating at all in cabin
pressurization.
Recall the actual valve is to open when
gear goes down or airspeed gets low (to avoid cabin retaining pressure
on the ground). But if Pin 4 removes GROUND as the action, then
apparently the solenoid drive outflow valve is fairly closed already,
and does not actively open (N.O.) in the absence of
power.
For the valve to come alive, it needs the
12V circuit to close (pin 4 to ground) to activate the device. I
must assume this is not happening, since all other connections are
confirmed.
Again, all wiring, power, dump switch,
connections with controller...all are correct. But apparently,
there is a persistent problem with Pin 4 giving ground to the outflow
valve, since the valve seems to be completely uninterested in
manipulating cabin pressure.
I plan to fly with the outflow valve
disconnected again, and place a circuit test on Pin 4 opposite 12V to
see if I can get confirmation that the circuit closes with airspeed &
gear up.
Any other ideas how to diagnose the
problem? Can you help with a specific set of checks to determine
if the valve (behind me) is working?
I want to avoid on the ground gear swing
while a friend blows into the pitot tube...what a scene that would
be.
Jeff Liegner
The "Dump Switch" is a simple
throw switch on the panel, closing ground for the valve.
The "Vacuum Switch" is the key
circuit. 12V on Pin 3, and Pin 4 is the questionable ground
connect that is currently open.
http://www.dukesinc.com/contact.html
9060 Winnetka Ave.
Northridge, CA. 91324
(818) 998-9811
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