78 Piper Turbo Arrow Gear Not Properly Retracting

Discussion in 'Maintenance Bay' started by ItsACardinalRG, Jul 23, 2020.

  1. ItsACardinalRG

    ItsACardinalRG Filing Flight Plan

    Joined:
    Apr 4, 2019
    Messages:
    11

    Display name:
    DigThatTurboArrow
    I have a 78 Turbo Arrow. A couple months ago, the gear started acting up. Sometimes I would flip the gear switch and the gear would not even attempt to raise. Sometimes I would flip the switch and it would raise part of the way and then stop in mid-retraction with the warning light on. The shop lifted it this week and cycled the gear several times without a load and the gear worked fine. However, when they put load on the gear simulating wind pressure, they found that the gear pump stopped while retracting.

    Two key details. The gear was supposed to have been overhauled about two years ago (before I bought the plane). During the overhaul, the low-speed switch that would automatically extend the landing gear was removed via Piper STC. That's the switch that could cause the gear to extend unexpectedly.

    The shop is thinking the pump needs to be overhauled or replaced and it is quite an expensive proposition. The service manual indicates the pressure switch may be out of adjustment or an obstruction in the hydraulic system. Any other thoughts on this?
     
  2. Doc Holliday

    Doc Holliday Pattern Altitude

    Joined:
    Dec 9, 2016
    Messages:
    2,442
    Location:
    Tombstone

    Display name:
    Doc Holliday
    Until further trouble shooting occurs, it's hard to say.

    Could be one or more of those items you mentioned, or could be the pump is weak. Who did the previous pump overhaul? The pump should be able to be removed and bench checked, that will tell quickly if it's a pump problem.
     
  3. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    9,879

    Display name:
    Dan Thomas
    Can't help you from here. A good mechanic, with the service manual (system test section), a pressure gauge and a multimeter, will figure it out a lot sooner and more cheaply than someone that starts throwing parts at it. Once you mix hydraulics with electrics there are just too many possibilities for SGOTI to identify it at first glance.
     
    Doc Holliday and RyanB like this.
  4. hindsight2020

    hindsight2020 Final Approach

    Joined:
    Apr 3, 2010
    Messages:
    6,144

    Display name:
    hindsight2020
    I went through it on ye 'ol Arrow II. Powerpack overhaul fixed it. Yes, they mention that the pressure switch being whacked out might create similar effect because it triggers the electrical circuit to stop the pump based on a false high pressure perception. That one is a bit unobtanium for what it is. The powerpack otoh is probably one of the most common trinkets out there, and overhauls are readily available.

    Expensive? Well, for EAB and automotive standards, yes this is all of an absolute rip off, but that's fac-built land writ large. For a guy flying a TSIO-360 powered sample of this thing, the characterization strikes me as ironic. One of the features of flying an arrow is ease of support; that pump is just a mercury marine trim pack, it's found everywhere.

    At any rate, n=1 and fwiw it was 2.2Amus in 2017 or so for me. That's for everything, labor to R/R, flush system and gear swing labor. I can't remember what the portion of the bill was the 3rd party overhaul. Mine lasted like 7 years before that, 3 of which was with the previous owner in a more frigid climate, admitted to at least a couple nosegear jams due to nose doors freezing with ice (iow that guy wasn't nice to that pack in the winters). Point being, 2 years life cycle, if true, is a very below average lifespan for that powerpack. I still have my auto-extender in place, but the behavior you describe in flight, both modes, is exactly what my symptoms were.

    As to @Dan Thomas post, 100% agreed on this being easiest to diagnose in person. It's not that complicated to diagnose, all vero beach samples share this system, even single commanders. To the legitimate concern of throwing parts at a problem, which I raised, that prior AP of mine even told me he would eat the overhaul if it wasn't the problem. It fixed it so he looked 100% vindicated on his assessment, typical behavior as it may have sounded at the time. These things are not that complicated, and shops have seen these vero piper gear systems for a while now.

    ETA: Just found the invoice. $1,440 was the portion for an overhaul/exchange of the powerpack, 2017. Good luck!
     
    Last edited: Jul 23, 2020