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Thread: How to check landing gear alignment?

  1. #1
    McDaver63's Avatar
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    Default How to check landing gear alignment?

    I'm in the process of getting my 52' PA22/20-135 ready for annual after my rebuild. I read some of the post about the handling of the Pacer and how much the gear alignment effects that. I wanted to find out how is the best way to check your gear alignment. I tried doing a search on the forum for this and found some related threads but not really anything that explains the procedure. Any information would be awesome. Thanks DC

  2. #2
    Administrator Steve Pierce's Avatar
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    Default Re: How to check landing gear alignment?

    Level the airplane and put two straight edges on each wheel going fore and aft. Measure between the two straight edges at the front and at the rear to see if you have toe in or toe out. Another way is to push and pull the airplane and see which way spreads the bungees out.

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    walt.buskey's Avatar
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    Default Re: How to check landing gear alignment?

    DC, there's also a pretty good article, originally published by McFarlane Aviation, in this month's (Jan 2014) issue of Light Plane Maintenance. It mainly discusses nose wheel shimmy, but also describes the same procedure Steve mentioned as far as checking the toe angle. Walt

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    SuperPacer's Avatar
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    Default Re: How to check landing gear alignment?

    Gear Alignment Fixture.jpgGear Fixture.jpgHere is a fixture that I built to help align a PA22-20 conversion. In this photo, we used it to "Check" alignment of converted Pacer from Bolder NV. It was most helpful when welding the front gear attach points to the Fuselage. As you can see, the bungee / Hydo-Sorbes were disconnected. When in the fixture, severail measurements can be made to verify the alignment, or not! of the gear. This fixture is available to anyone for loan, however is is heavy, so probably would be best to come pick it up!! It is probably over kill for just checking alignment, it is very good for a T/W conversion work.
    Enjoy the day,

    john
    Utah Pacer

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    Stephen's Avatar
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    Default Re: How to check landing gear alignment?

    John,

    Great looking tool!

    What angle is your alignment tool set?
    "You can only tie the record for flying low."

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    Default Re: How to check landing gear alignment?

    Nice fixture - How much toe in does it establish? - and also it would allow to also make the very important measurement from the end of each axle to the tail for triangulation.

  7. #7
    SuperPacer's Avatar
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    Default Re: How to check landing gear alignment?

    HI Stephen,
    We built the fixture to hold the gear when aligning the forwward gear attach "mounts" and so didn't put any "angle" into the tool. It holds the axel level and square to the centerline of the fuselage, so in this slightly "compressed" position (note the lower Hydro-Sorbe mounts are about an inch or so beloe the belly) the gear has "0" degrees toe in / out, and "0" camber. This would represent a "right after landing gear compression, assuming the bungees werent really stiff!! The original idea was not to replace the proper measuring of the postions for the attach bracket, but to simply hold the gear relatively square while making minor adjustments prior to welding (with the over all reference being the original forward Tri-Pacer mounts, now the rear Pacer mounts). As it turns out, the three PA22-20 conversions we have completed using the tool, all track srtaight down the runway and are well behaved Pacers. In the end, there is some "geometry" at work, because when its back on wheels, with bungees re-attached & "sucked up", we typically see an 1/16' or so toe in, as well as a bit of camber as the gear swings into the "home position". Your mileage may vary.
    Enjoy the day,

    john
    Utah Pacer

  8. #8
    McDaver63's Avatar
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    Default Re: How to check landing gear alignment?

    Thanks for the replies. John, That's sure a nice fixture you made. Wish I had the resources and skills to make something like that. I ended up taking measurements after leveling out the plane by finding the centerline of the firewall between the engine mount to firewall attach bolts, dropping a plumb bob to the ground and marking a line. I then hung a plumb bob from the tailwheel springs and centered below the tail post tube and marked that on the ground. I stretched a string nice and tight from the firewall mark to the tail post mark and duct taped it tight to the ground. I dropped a straight edge vertical down to the ground from the forward and aft inside surface of the brake disk and made marks on the ground. I took measurements from the forward and aft disk marks to the centerline string on the ground. Both wheels are almost dead on equal measurements between for and aft marks. I think the alignment is very close. When I get back out to the airplane I will check the measurements between the axle ends and the tail post like Pacer24c suggested. Also I'll do Steve's measurement between the left and right wheels. Do you think it is OK to measure at the disk inside surface?
    Thanks for your help.

  9. #9
    rocket's Avatar
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    Default Re: How to check landing gear alignment?

    I use a plumb bob and chalk lines on the floor. I have a couple sets of wheels with no tires on them that I can attach to lay my straight edge on. It's not rocket science to check but it is an art to correct!

    Rocket

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    Default Re: How to check landing gear alignment?

    Quote Originally Posted by Steve Pierce View Post
    Level the airplane and put two straight edges on each wheel going fore and aft. Measure between the two straight edges at the front and at the rear to see if you have toe in or toe out. Another way is to push and pull the airplane and see which way spreads the bungees out.
    I dont quite understand what you are saying here.. can someone explain a little better exactly where the strait edges are placed.. im not understanding how to measure the toe in/out

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