Hi, All;

As some of you know, I'm currently building a Cruzer, so aside from saying "it's a low-wing", I really have no knowledge on the 601 airframe.

One of our EAA Chapter members (I'm a Tech Counselor) asked if I knew any way to determine for sure if the "B" mods were done to an airframe or not. One came up for sale and he's interested. He doesn't want to rely on the logs.

Is there any VISIBLE checks I can do to tell if it's been modified? Properly?

Thanks for any guidance...

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Rivet patterns and added brace is obvious. You just need to know what to look for.

Obvious next question: so how do I find the rivet pattern for which I should look?  Is this in a plans update somewhere? I found the ?? notice on newplane.com that talks about doing the update, but it did not have any pics or plan pages.  I'm just trying to help a guy figure out if he should buy this plane or not.

View the YouTube video of Roger  doing the "B" mod on the factory 601, it shows  everything.

After viewing Roger's Youtube video the earlier answers will make sense. There is a heavy doubler added to distribute wing forces to the fuselage structure - it is vertical (flares wider at the top) and located between the top of the wing and the base of the canopy on both sides. Once you see the video you can easily look for it on the airplane in question.

The other easy thing to see would be the double line of rivits where the leading edge skin is attached to the top and bottom of the wing main spart - the inboard several feet of a B Mod wing have a double row of rivits while an unmodified wing has a single row.

Finally, you can look at the ailerons. The B Mod includes a balance arm that comes forward from the front of the aileron into the interior of the wing. On the forward end of the arm is weights to balance the aileron. The unmodified wing has no balance arm going forward from the aileron into the interior of the wing.

Have fun, Bob

The drawings for all modifications that are requried for the Mod-B can be found here:


Drawings 6-ZU-1, 6-ZU-2, 6-ZU-3 and 6-ZU-4, and LAA Aileron Balance

Thanks, Martin; helps a lot!


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