REFLECTOR: RG Problem

[Ronnie Brown]

I had a similar problem on my third flight - first flight to retract the
gear. The gear came up on the first two tries, after that it quit coming up.

After I got it back on the ground, I jacked the plane up and everything
worked - except I had to jump the squat switch - normal procedure.  So I
decided to jump the squat switch - actually an airspeed switch - everything
worked perfectly in the air.

So I removed the airspeed switch, took it home and checked its calibration.
It was pretty much where I had set it, 80 knots which is only about 4 inches
of water.  I did find a pinched pitot pressure nylon tube - tywrap too
tight.  I replaced the pitot pressure line.

Then I ran a short piece of tubing from the other connection on the air
speed switch to inside the cockpit.  If you look at the front of the nose
with the nose gear doors open, it is not hard to imagine that the pressure
in the nose section is close to pitot pressure since the nose wheel hole is
slanted upward.  This would reduce the differential pressure (pitot to
static) sensed by the airspeed switch.

After these two mods, I have never had problem retracting the gear - works
every time!!!

OTOH, I have had about three occasions where the pump motor didn't go down
when commanded - pressure built up on the low pressure side of the system.
Hitting the "reset" button (bypasses the low pressure switch) momentarily,
got the system running and extended the gear properly.

I would suggest trying putting a jumper in place of the squat/airspeed
switch and see if the problem goes away.

Ronnie


----- Original Message -----
From: "John Dibble" <aminetech at bluefrog.com>
To: <dvblack at comcast.net>; "Velocity Aircraft Owners and Builders list"
<reflector at tvbf.org>
Sent: Tuesday, August 03, 2004 8:51 AM
Subject: Re: REFLECTOR: RG Problem


| Thanks, Dave.  My engine monitor shows the voltage.  With the light off
(5-12 amp
| draw) it runs 14.1 v.  With the light on (12-20 amp draw) it is 13.9 v.  I
should add
| that my squat switch seems to be set a bit high.  On the ground (up on
blocks) it
| takes around 90 kias for the punp to go on and my speed is in that range
when I have
| the problem.  I can't find the switch and think I will have to remove the
canard to
| get to it.  I think adjusting the switch will solve the problem, but I
wonder why the
| light is affecting it.
|
| John
|
| Dave Black wrote:
|
| > John,
| >
| > > Lately, when I hit the gear up switch, nothing happens.  If I turn off
| > > the landing light, then the hydraulic pump comes on and the gear goes
| > > up.  If the landing light is not on to begin with, then I need to
| > > quickly switch it on and off to get the pump to come on.  Any ideas
what
| > > is going on?
| >
| > Nothing solid -- just brainstorming...
| >
| > Presumably there's no interconnection between the landing light and the
gear
| > pump. In which case, the only common point I can see is the main
electrical
| > supply. The landing light may be drawing so much current that the
voltage to
| > the gear pump drops below its operating level. Switching off the light
raises
| > the system voltage. If the light is off anyway, by this theory the pump
should
| > run OK. But maybe the voltage spike created by switching on and off the
light
| > is enough to give your pump that extra kick.
| >
| > Certainly this is not the way it should operate. I am assuming the pump
| > originally operated correctly and only recently began this behavior.
| >
| > The first thing I would do is put a voltmeter across the hydraulic pump
to see
| > when it's getting voltage and when it's not. Also check what the voltage
is. I
| > would expect 12v or more when the gear is operating. If it does not run
when
| > it's supplied 12v, this would point to a marginal gear pump motor.
Further
| > bench testing should confirm this. A variable DC power supply could come
in handy.
| >
| > If the hydraulic pump is receiving significantly less than 12v, I'd
check
| > voltages elsewhere in the electrical system. If voltages are low
generally,
| > that could point toward a defective alternator, regulator, or battery.
| >
| > If the hydraulic pump is not receiving voltage when it should, trace
back
| > through the wiring to find out where the circuit is broken. I'd be
especially
| > suspicious of any relays in that circuit.
| >
| > I suppose it's possible you may have an intermittent limit switch in
your
| > hydraulic system. I don't know how a voltage spike caused by cycling the
| > landing light could reset a limit switch, but stranger things have
happened.
| >
| > Sorry I can't immediately identify the source of your problem, but hope
these
| > tests can help lead you to a diagnosis.
| >
| > Dave Black
| > Shortwing RG
| > _______________________________________________
| > To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector
| >
| > Visit the gallery!  www.tvbf.org/gallery
| > user:pw = tvbf:jamaicangoose
| > Check new archives: www.tvbf.org/pipermail
| > Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
|
|
| _______________________________________________
| To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector
|
| Visit the gallery!  www.tvbf.org/gallery
| user:pw = tvbf:jamaicangoose
| Check new archives: www.tvbf.org/pipermail
| Check old archives: http://www.tvbf.org/archives/velocity/maillist.html