REFLECTOR: Hydraulic Fluid

Mon May 25 09:46:10 CDT 2009

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 Jensen <cjensen at dts9000.com>
> *Sent:* Sunday, May 24, 2009 10:44 AM
> *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> *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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