Piper Arrow Gear in Transit Remains Illuminated

Discussion in 'Maintenance Bay' started by Deelee, Jul 26, 2020.

  1. Deelee

    Deelee Cleared for Takeoff

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    Hi folks. Probably going to be posting in this section quite often since we are in the process of finding all those year-one issues on an old airplane, so let me say in advance thanks for the help and for bearing with me.

    We have a new-to-us 1969 Piper Arrow PA-28R-200. While flying in the pattern the past two times, we noticed that the gear in transit light doesn't always extinguish. I'd say about 50% of the time it won't go out. Gear down indicators do go out when the gear lever is moved to up position. Gear down indicators come back on when gear lever is moved to down position (thank God).

    When the gear up lever is moved to up position, you can hear the gear going up... you can sort of feel it going up, too... that feeling that the aircraft has when gear is stowed. Now I can't say for sure that it is full up since I can't see it. But it feels like it is up. Like I said, 50% of the time, the light goes out and no problem. We didn't have this problem during the test flights and during the flight from FL to the DC area. Aircraft has a current annual and the prebuy was just done where they did swing the gear and check it. Also I swear I saw my airplane partner tap on the light itself on the panel and got it to come on, so maybe it is the light itself? (I could be imagining this).

    Some light googling turns up some possibilities - up-limit switches, power pack problems, actuators that need to be replaced. We have the aircraft in for some unrelated service, so I'm going to ask the shop to take a quick look to see if it is something simple.

    Anybody have any thoughts on what the issue could be? Better yet, anybody ever encounter this issue? If so, what was the problem/resolution?

    Thanks!
     
  2. hindsight2020

    hindsight2020 Final Approach

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    TL;DR version: It's a microswitch misalignment issue on the up cycle, likely the nose gear up cycle microswitch. Not a gear operation or powerpack problem at all. Mostly a nuisance, not a safety or performance degrading indication.


    If you're still reading:

    Yes, I own one. Yes I have and continue to encounter the issue. It's a nothing burger.

    The yellow gear in transit light has no relationship to the pressure switches that actually serve to stop the pump from operating in either the up or down cycle. This yellow light comes on whenever the struts are not all making contact with the up-microswitches in the up cycle, or the down micro-switches in the down cycle. The down microswitches happen to give you the three green, which people consider important for the obvious reasons. The up microswitches otoh do nothing in the arrow system, beyond give you that annoying light when not depressed fully. Since there are no mechanical uplocks in the arrow system, only the pressure switch (and the squat safety switch) have any interaction with the pump and the gear selector. The rest merely deals with simpleton indicator light.

    At any rate, to your issue. During the up cycle, that light will remain on until all three up-limit microswitches are depressed. Again, they don't do anything to the pump operation; the pressure switch does that. They only indicate the wheels are *presumably all the way in their respective wells.

    Why do I say presumably? Because well, they don't do that particularly well. They displace in their bolted position, and/or settle with the cycles, so they don't make the proper contact with the strut(s) which are otherwise effectively tucked into their wells. In other instances, one of the three switches is bad, which gives the same indication. In any event, it's not a cycle problem, it's just an indication problem.

    In my experience, it's always the nose one. Doesn't make the right contact, gets dirty with gunk from the engine et al. Sometimes you can unload aggressively and the nose strut vomit-comets up and makes contact with the stupid thing, and the light goes out. Conversely, you can be flying around and hit a large turbulence and pull up with Gs, the light comes and stays on until the nose doors settle under the windstream.

    It's a very common thing with these older models; the newer samples removed the stupid thing and only left the gear unsafe (red light), which is the one that indicates mismatch between gear selector and three green illuminated (aka gear up handle, with three green illuminated, or auto-extender operating with the gear handle up, obviously).

    This will result in pearl-clutching from the pride in ownership crowd, but I've been going for 7 years with the light on seasonally. I could go chase the gremlin constantly, but it's largely not worth it to me. The reason they won't be able to replicate on the ground is that if it is indeed the nose gear up-limit switch, the airstream is missing from the diagnosis and you won't get the nose doors to sag the strut away from the misaligned or gunked up microswitch. If the misalignment is bad enough, or either three of the switches are legitimately open circuited at zero airspeed, then sure you will see it and able to replace.

    How do I know it's an indication and not a retraction failure in flight? The aircraft suffers no speed penalty at the known power setting. It's not rocket science, but it does require one understand the yellow light has nothing to do with the components that extend and retract the gear in the Vero beach retracts. I've also had to overhaul/replace a powerpack after I had a legitimate failure to retract (pump slowly failed), so I know what the indications are like for that (pressure switch kills the powerpack halfway through the cycle, partial green lights or all green lights remain or eventually come on as the gear gravity falls fully, aircraft never attains cruise speed). It's one of those "you know it when you see it" type diagnostics in flight.

    Good luck chasing the gremlin. Don't be surprised if it recurs years later, as a function of use. Which is why I don't bother much with it. Nothing's wrong with the gear pump or actuators. You can also have the AP check the alignment of doors. Mine sagged a bit and with the faster airspeeds it would pull the strut ever so lightly away from that microswitch to cause the light to come on. Slowing down would prove it to be the case. Of course I won't slow down, so I just accept it. I haven't had the need to replace a single microswitch in 7 years, so I don't know how much they go for these days. Hope this helps.
     
  3. Morgan3820

    Morgan3820 En-Route

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    I had the same git issue. Mine was not the micro switches. I had a $0.30 O ring in the hoof valve come apart. The leaking oil allowed the system to depressurize, drooping the gear. Replaced the O-ring. The effort took several months to chase down and three weekends to actually fix. PIA. PM me if you want more info. Piper forum has a lot on this issue as well.

    or it could be your micro switches.
     
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  4. Deelee

    Deelee Cleared for Takeoff

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    Thanks guys. That is all great info. From reading this, I am thinking it might be the up limit microswitch in the nose gear well. We just started seeing this issue after getting some work done on the engine ( fuel hose replacement) and they had to take the oil filter off which caused a bit of a mess. It was cleaned up but I wonder if oil got splashed under there and is causing issues with the switch contact. It’s just a real coincidence that we saw the issue for the first time after getting the plane back from the engine work. And hindsight’s description of how these things work leads me to think that the switch is either dirty or maybe even got knocked out of position.

    Good new is we have the plane back in the shop to have them tighten a loose adel clamp they left loose. So I will ask then to check out at least the nose up limit switch while they have the plane.

    Thanks again for the great write up.
     
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  5. bflynn

    bflynn Final Approach

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    Would it be inappropriate to point out that this is not an issue with the manual gear Mooneys? The gear is either or or down and you have a great big thick Johnson bar to tell you which.

    :D:D :devil::devil:
     
  6. Ghery

    Ghery Touchdown! Greaser!

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    In the years I flew the club's Arrow (also a 1969 model) I never had this problem. Good luck to you in checking it out and fixing it.
     
  7. Morgan3820

    Morgan3820 En-Route

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    :nono:
     
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  8. Deelee

    Deelee Cleared for Takeoff

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    :) Totally appropriate! It would also be appropriate to say if we had a high-wing Cessna RG of some sort, we could SEE the gear up or down (the mains anyway). :)
     
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  9. Deelee

    Deelee Cleared for Takeoff

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    Update - shop jacked the aircraft and adjusted the right main up limit switch for proper indication. 190 bucks and I don’t have to look at that yellow light anymore.
     
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  10. pburger

    pburger Pre-takeoff checklist

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    Glad you got it corrected. And thanks for following up with the solution.
     
  11. Deelee

    Deelee Cleared for Takeoff

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    Thanks to everyone here for posting. Probably saved me a few hundred since y’all helped focus the possible problem areas.