This Q&A is now closed and replaced with a new Q&A based on the latest upgrade drawings at

To all 601XL and 650 builders and aircraft owners. If you have a specific question regarding the upgrade, post it here and I will consult with Chris Heintz so that we can give you the best possible answer. Please be specific about your questions.

When posting a question or replying to an existing comment, PLEASE add it to end of the last page.

Zenith Aircraft is upgrading its 601 XL, so a lot of questions are answered on the step-by-step Blog Posts on this main page.

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Replies to This Discussion

Well Said! .I was also thinking of "checking out" a recess to solve this cosmetic problem.As it happens my nose skin has ended up with a 12.5mm overlap of rivet line(was not worth trimming back to 10mm ,the important bit was ok ie rivet line bang in centre of spar cap angle).Therefore as the hinge is butted against this ,with a very small extra gap to allow it to rotate it looks like I only have 2.5 mm to "check out" of the new extrusion.
I spent a long time getting the locker doors to fit perfectly and dont want to end up with this unsightly gap that several of us have noticed .
Hi Mathieu,
I have noticed that there is some flex in the top of Rear Frame Channel part No 6B5-2.
Do you think it might be a good idea to strengthen this Channel and perhaps tie the two rear wing attach points, part No 6B5-4, into it as well. Thank you for helping us, I'm sure we will end up with an even more beautiful aircraft.
Kind regards,
Rick Morris
We did not reinforce the rear spar channel 6B5-2 for the ultimate load test and there was no signs of deformation. 6B5-4 is now significantly thicker and ties into the 6B5-6. It is important that 6B5-6 is well riveted to the side skin with "L" angle on the back side etc. If you notice that the top of 6B5-2 is buckled, add an "L" angle to the top. Also, when replacing 6B5-4 and drilling out the rivets, make sure that the holes are not oversized. If they are, add an extra rivet beside each oversized hole, or go up to the next size hole etc.
Hi Mathieu,

Thank you for your very prompt reply. Could the rear attach bracket, 6B5-4, be one piece and also act as a doubler to stop any flexing of the Rear Frame Channel part No 6B5-2.
Kind regards,
Rick Morris
Yes, you can do as much as you like but we do not see the need for it. I have not seen any issues with 6B5-4 getting ripped out of the fuselage.
I would think that the rivets are too long for a hand squeezer. I strongly recommend a pneumatic riveter or bolts.
Mathieu is right they really should be bucked or bolted. Having been a sheetmetal mechanic on larger aircraft I can tell you that more than likely when you try to squeeze that long of a rivet you will find that the rivet will bend to the side and it will also throw your spar web and caps out of alignment. Squeezes generally for the type you would need for the spar work do not close the jaws in a straight line.
Ther was no reply to this Q..

I have a 601XL. Is it possible during the upgrade to set the angle of incidence of the main wing so as to match
the 650? This would resut in a lower deck angle and improved forward visibility.

Since we are pulling the center section appart, I am also interested in doing this as well if it can be done during the upgrade??


waiting, watching and learning till the final plans are released..

► Reply to This

Mathieu responded to this already. His answer is below.

Reply by Mathieu Heintz 12 hours ago
Yes, you can do this but you are adding a lot of extra work as you will have to change the fuselage side skins, your seats and arm rest area etc. We really did not see much change in performance or visibility with the new angle. Big reason for changing was to make the European and USA 601XL more the same as it makes it a lot easier for us to build and ship similar items. If you want to do this, you will need to purchase the 650 drawings.
Thenks ken

I could not find it in the answers....

Mathieu dont worrry about it my Q is answered.
Yes, you can do this but you are adding a huge amount of work. You will need the 650 drawings and you will have to change your fuselage side skins as the spar uprights rivet holes in the skins are at a different location. Seat area and arm rest etc. will have to be changed. I just do not see a real advantage with the little extra visibility etc.
Yes, I think that Zenith will be releasing the upgrade video's and procedures through the Zenair news letter.


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