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

I have hingeless aileronse on my 601xl and am wondering how these will be handled in the upgrade.
All the CZAW built 601 XL's have the hinged ailerons so this was not addressed in the UK LAA mandated upgrade. However, even though there is possibly less chance of vibrations and or flutter with hingeless ailerons, we cannot say for sure so we want all aircraft to upgrade. The German flutter report clearly states that there are no flutter issues with the aircraft when properly rigged. However, in the name of safety, it is important that everyone upgrade.
So if this is the case and I now have to remove my hingless ailerons and install hinged ones is there a Zenith approved Plan and Photoguide now on how this is to be done. I may not use the correct strength hinge or L anges or , rivets?
Your hingeless ailerons are fine. You just need to install the aileron counterbalance weights and the rest of the upgrade.
Of course it is important for everyone to upgrade. That is understood. What is now becoming unclear is exactly what the upgrade is. It is my understanding that the structural upgrade is what is required in the 3 drawings provided by Zenith. I have 4 questions:
1. Does the upgrade require(by the FAA) replacement of hingeless ailerons with hinged ones?
2. If so, do the hinged ailerons need to be mass balanced
3. Does the upgrade reqiure any modification to the 601xl elevator trim system.
I want to upgrade my 601xl, NOT turn it into a 650.
4. Additionally, Zenith and the FAA have issued an instruction. Is this, or is it not, independant from the British LAA insruction


John Partridge.
If you have the hingeless ailerons, you do not need to convert them to the hinged ailerons. Just add the counterweights and rest of the upgrade. The upgrade has nothing to do with making a 601 XL into a 650. This upgrade is for the 601 XL and the 650. For the installation of the aileron counterbalance weights, we are using the UK LAA drawing and instructions but extending that the the hingeless ailerons. Zenith is not changing that. However, we are not following the rest of the UK LAA modifications. For the elevator trim tab, we are not changing that. However we are adding "L" angle stiffeners to the trim servo area as the elevator skin flexes easily.
I am in work on a 650 Horizontal tail and elevator. Are there drawings and work instructions for the added L stiffeners?

Glenn Morris
OK. Given that flex ailerons are the standard setup and that we have to install mass balance weights. is it possible to modify the flex ailerons to accept a piano hinge? For example if a standard "L" is installed on the under aft side of the flexing skin to accept the piano hinge this would we don't have to make another aileron!
Yes, that would make sense.
Ian -- Clyde Barcus posted a message with photos on the ZBAG forum dated 11/10/09 describing this modification to his 601XL. In an earlier post he mentioned discussing the mod with CH prior to doing the work. He added an L-angle between the bottom of the hinge and the front of the aileron.
I am about to start on the 650 horizontal tail, and just want to make sure there are no issues with that area and that I can proceed according the plans I have.

Also, it would be nice to get a ballpark estimate of when revised drawing sheets incorporating the wing mods (as opposed to upgrade drawings) will be available.

The upgrade may include stiffening of the elevator trim motor. Other than that, I do not foresee other changes in the tail area.
We hope to have the upgrade drawings 100% finished next week. AMD and Zenith are presently upgrading an aircraft right now where we are verifying everything. You can view the Zenith upgrade in the blog section of this site. Once this is all done, we hope to update the 650 drawings within the next 2 to 3 months or sooner.


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