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Re: [Lancair] Hydraulic system failure (?) Lancair 360

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  • Chris Zavatson
    Dave, I used pressure gauges from McMaster http://www.mcmaster.com/#atmospheric-pressure-gauges/=o7c3z5 With gauges installed you can actually observe the
    Message 1 of 16 , Aug 24, 2013
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      Dave,
      I used pressure gauges from McMaster
      http://www.mcmaster.com/#atmospheric-pressure-gauges/=o7c3z5
      With gauges installed you can actually observe the pressure spike I described in the write-up.  In fact, after observing many extensions, I could predict the magnitude of the spike based on conditions just prior to selecting gear down.  Once the low side pressure was increased to about 800psi, the spike was no longer able to affect gear extension.
      My first set of pressure switches were VEP (95 kit).  These are essentially a small plunger pushing on a microswitch.  These switches have two adjusting screws that need to be adjusted equally.  You can easily removed the 'can' that covers the inner workings to see why. 
      VEP switches were phased out and Suco switches were introduced.  These are much more robust.  They have a single adjusting screw in between the blade terminals.  Lancair carries these.  The upper end of the adjustment range if the 550psi switch is right around 800 psi.
       
      Chris Zavatson
      N91CZ
      360std
      www.N91CZ.net

       

      ________________________________
      From: Douwe de Boer <dbotop@...>
      To: lancair@yahoogroups.com
      Sent: Saturday, August 24, 2013 1:00 AM
      Subject: Re: [Lancair] Hydraulic system failure (?) Lancair 360

       

      Hello Chris and Sam,

      Thank you for your comments. The description of the hydraulic system as given by Chris and especiaaly the remarks on page 10 (failure to extend), make me think that I must have encountered such a rare coïncidence. I will check the LP pressure switch and see if this type (supplied around 1990) is adjustable. Nonetheless I will also check al contacts and connectors of the electrical system, although it is hard to imagine that I will find something wrong here. Until now it was a “one time occurence”. Chris I also saw a set of nice pressure meters for the gear in your aircraft. Could you mention me the type and source. Do you also know a source for the pressure switches in case I have to replace them?

      Regards,
      Dave
      Lancair 360 MK1, PH-DBO

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    • Douwe de Boer
      Hello Chris and Randy, Thnak you for the details regarding meters and pressure switches. I found Suco to be a German manufacturer with a good representatation
      Message 2 of 16 , Aug 25, 2013
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        Hello Chris and Randy,

        Thnak you for the details regarding meters and pressure switches. I found Suco to be a German manufacturer with a good representatation in the Netherlands. It must be possible to obtain the pressure switches directly from them.
        Randy thanks for the schematic. However I need a bit help in understanding how it works. Could you give a brief description about the functioning?

        Kind regards,
        Dave
        Lancair 360 MK1, PH-DBO

        [Non-text portions of this message have been removed]
      • Chris Zavatston
        Dave, If you find a local source for Suco pressure switches, you should be able to get one nominally set for 800 psi for the low side instead of 550 as Lancair
        Message 3 of 16 , Aug 25, 2013
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          Dave,
          If you find a local source for Suco pressure switches, you should be able to get one nominally set for 800 psi for the low side instead of 550 as Lancair sells.
          Chris

          Sent from my spiffy iPhone

          On Aug 25, 2013, at 1:56 AM, "Douwe de Boer" <dbotop@...> wrote:

          > Hello Chris and Randy,
          >
          > Thnak you for the details regarding meters and pressure switches. I found Suco to be a German manufacturer with a good representatation in the Netherlands. It must be possible to obtain the pressure switches directly from them.
          > Randy thanks for the schematic. However I need a bit help in understanding how it works. Could you give a brief description about the functioning?
          >
          > Kind regards,
          > Dave
          > Lancair 360 MK1, PH-DBO
          >
          > [Non-text portions of this message have been removed]
          >
          >


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        • Randy
          Hi Dave, It’s quite simple, as soon as the low side sensor sees a pressure build up the sensor activates the pump relay for a brief second to open the spool
          Message 4 of 16 , Aug 25, 2013
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            Hi Dave,
            It’s quite simple, as soon as the low side sensor sees a pressure build up the sensor activates the pump relay for a brief second to open the spool valve and let the fluid back into the reservoir. The switch configuration prevents the pump from getting a hi and lo voltage at the same time, the diodes are for isolation. These new sensors from McMaster Carr are much more beefy and precision then the Lancair sensors. This fix prevents pressure build up on the low side for any reason, heat, leaking seals, lazy spool valve. Your down switch will always work. I came up with this after getting tired of opening the dump valve almost every landing to let the pressure out. Two different pumps same thing. I’ve been running this about 7 years without a hitch. It’s completely automatic, install it and forget it.

            Hope this helps.

            Randy


            From: Douwe de Boer
            Sent: Sunday, August 25, 2013 1:56 AM
            To: lancair@yahoogroups.com
            Subject: Re: [Lancair] Hydraulic system failure (?) Lancair 360


            Hello Chris and Randy,

            Thnak you for the details regarding meters and pressure switches. I found Suco to be a German manufacturer with a good representatation in the Netherlands. It must be possible to obtain the pressure switches directly from them.
            Randy thanks for the schematic. However I need a bit help in understanding how it works. Could you give a brief description about the functioning?

            Kind regards,
            Dave
            Lancair 360 MK1, PH-DBO

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          • Douwe de Boer
            Randy and Chris, Thank you both for your additional information. As summer is over and I have more time to make modifications I will decide what to do. For the
            Message 5 of 16 , Aug 26, 2013
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              Randy and Chris,

              Thank you both for your additional information. As summer is over and I have more time to make modifications I will decide what to do. For the time being everything works fine now, probably to the lower temperature in the Netherlands.

              Regards,
              Dave
              Lancair 360 MK1, PH-DBO

              PS. On the schematic of Randy (comming form the Lancair manual) I also saw the old remark about “cutting off” the small black wire comming out of the pumpmotor. I remember this turned out to be a faulty advice. The black wire had to do with some sort of overload protection and I remember that it had to be connected to ground. Does anyone remember this story?

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