REFLECTOR: Hydraulic Fluid

Terry Miles terrence_miles at hotmail.com
Mon May 25 12:11:20 CDT 2009


Chuck

The dump valve is pretty goof proof.  Larry makes a good point about
possible internal bypass in the pump.  You can go to Harbor Frgt or the like
and get one of those stethoscope things and see if you can hear anything odd
at the pump or on a fluid supply line.  If you can eliminate fluid loss as
an issue, that helps determine what it is not.  (Parker makes some stuff
called O-lube that helps with seeps out the nose cyl shaft (but that is
likely not your issue) .but be sure to check in the keel area for leaks.

 

 I would toss in to check for a single failed electrical control signal
somewhere that tells the pump what to do.  Make sure your cannon plugs are
all on good, and you have no cable insulation that's chaffed.  On mine,
regards the retract function:   it is common to see the nose move first to
say 80% travel, then the mains move in one motion from full down to full up,
and then the nose moves the last 20%.  Wayne Lanza designed the gear control
box (gold box in the nose) and the gear sw on the panel and all the squat
switches for main/nose and up/down.   I am not sure that the detailed gear
control handout with all the drawings always makes it into the construction
manual.  Mine is pretty beat up and the zerox of a zerox but it is readable.
The factory can send you one.  Lanza doesn't work for them anymore, but he
would be a further resource if you get good a stuck.  They probably have a
way to find him.

 

How about your nose gear overcenter spring?  Make sure it is not inhibiting
full normal motion.  

 

Terry

 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Michael Watson
Sent: Monday, May 25, 2009 09:46
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Hydraulic Fluid

 

Are you positively sure that the dump valve isn't leaking?
even a small leak will cause the pump to run continuously.

On Sun, May 24, 2009 at 1:17 PM, Laurence Coen <lwcoen at hotmail.com> wrote:

Chuck,

 

I have used ATF exclusively and have never had a leak or malfunction of any
kind with several hundred cycles.  I can leave the gear up for 48 hours
without the pump cycling.  I haven't taken the pump apart but there must be
some sort of a shuttle valve in there to allow the inlet and outlet to
reverse roles when the pump reverses.  I'll bet that's where your problem
lies.

 

Larry Coen

N136LC

SE/RG Franklin /IVO

 

From: Chuck <mailto:cjensen at dts9000.com>  Jensen 

Sent: Sunday, May 24, 2009 10:44 AM

To: Velocity Aircraft Owners and <mailto:reflector at tvbf.org>  Builders list 

Subject: Re: REFLECTOR: Hydraulic Fluid

 

Al,

 

Thanks for the comments, but now I have additional information, since I
topped off the hydraulic reservoir with fluid, but the situation remains.  

 

When I toggle the gear switch to the up position, the pump runs constantly
(appearing, by sound, to be free wheeling, in that it runs with no
resistance).  Joggling the master on/off, eventually the nose hear rose
slowly to it's 3/4 up position, as usual, but the pump continued to run with
no movement of the mains, which would normally follows.

 

By chance, I pushed down on the nose gear...and the mains moved up a small
amount and the nose wheel moved back up to its 3/4 position when I released
it.  I did this again, and it was quite amusing, pushing down the nose gear
several inches would cause the mains to more up a few inches.  Repeating the
process, it was like I was jacking up the mains by using the nose gear as a
jack handle, all the while, the hydraulic pump was merrily making noise, but
apparently not much pressure.

 

Until, that is, the mains were about 1' from being nested, when the pump
took over and raised the mains up into their pockets and did that finally
'chinch movement' that says they are snugged away.  I did this a number of
times, with same behavior each time.  After being nested for a couple
minutes, there was that short blip on by the pump to 'snug' the mains tight
again, all as usual, and then the pump shutoff and stayed off.

 

But moving the switch to 'down', the pump would start running, but nothing.
However, if I opened the dump valve for about a second and then closed it,
the hydraulic would start moving the gear down.  Once in the down position,
the red 'unsafe' light did not extinguish and the pump continued to run,
even though the main and nose appeared locked in place.

 

The pump acts like it is cavitating and not creating pressure.  However,
once there is some back pressure on the pump, such as when the mains are
close to being nested, then the pump will 'engage' the hydraulic fluid,
creating pressure to snug the mains.  The dump valve must be opening and,
most importantly, closing properly or the pump would keep running when the
mains are snugged away.  Nonetheless, the pump runs as though it is free
wheeling, just like the dump valve was open.

 

So, there's obviously some things I don't understand about the pump, or
what's going on.  Any guesses?


Chuck Jensen 

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Al Gietzen
Sent: Sunday, May 24, 2009 11:32 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Hydraulic Fluid

Chuck;

 

There are significant differences (primarily in the additives); the most
notable is the change is viscosity with temperature. At very low temps; like
-20F, ATF becomes quite viscous while the 5606 does not.  This is important
for aircraft flying at the flight levels, or in cold climates.  If you do
neither, ATF will work fine.

 

When I first filled my system, I put in ATF - which is what the pumps we use
are designed for.  Later I thought at some point I may be flying high and
into colder climes; and changed it out for 5606.  I was surprised, and
disappointed, at how much noisier the pump was.

 

I was concerned about mixing of the two, so developed a method for changing
the fluid that gets most of the old out before putting in the new.  I wrote
up that procedure, and probably still have it somewhere, and could share it
with you it you like.  I don't know that mixing is an issue, but I would
hesitate to do it.

 

Al

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Chuck Jensen
Sent: Saturday, May 23, 2009 4:39 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Hydraulic Fluid

 

Okay, I need to add hydraulic fluid and the FBO is shut tight for the
weekend...no 5606 available.  It was speculated that the automatic
transmission fluid (ATF) is just a rebranded/repackaged 5606.  Has people
used ATF in their gear retract system?


Chuck Jensen 

 

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-- 
Mike W.
1997 Velocity Elite RG
Franklin /IVO Electric CS
Dual GRT EFIS Synthetic Vision

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