Hi all,

A mate of mine in South Africa who owns an HDS has recently heard of another guy out in SA who has, apparently with appropriate engineering (aeronautical) and local civil aviation authority, put extensions essentially to the existing wing design and is allegedly in flight testing. From what I understand the individual is experiencing significant increases in performance specifically cruise and climb.

I have never heard of anyone doing this before and was frankly a bit sceptical. Has anyone else ever heard of this being done? With the higher fleet numbers in the US if it has been done I would expected it to be done first in the US.



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I own an HDS and have not heard of anyone in the US making extensions for an HDS.  I have heard of folks changing the wings out for a set of HD wings to get the stall speed lower.


Thanks Jerry. I had also heard of people swopping out for HD wings but this is apparently an extension to the existing HDS wings. I will try and get a picture as this is news to me.

I have been thinking about this for sometime but just not sure where to start but apparently Zenith was thinking along these same lines before producing the XL, here's part of an email exchange with a guy who has a set of 25' HDS wings instead of the standard 23'. I would love to add 12" or 18" to each wing I wish Zenith would create a factory approved kit for us, Id buy one.

To make a long story shorter, I accidentally learned about the factory built prototype wings that sat in storage at the Zenith factory for many years.  There were no drawings for them and they were long forgotten, but to me, they were beautiful and exactly what would make my beloved Zodiac perfect.

I couldn't have been happier - they were lively and responsive in flight and I couldn't stop looking at them, they were beautiful  and I couldn't believe what a huge difference that extra two feet of span  made.  I even liked them much better than the looks of the HDS wings that originally wanted.

Rich Whittington

Zenith 601HDS

3L Corvair

MGL Enigma

Thanks for that Rich. I wonder if this guy in SA will publish the designs that he has had success with. My friend Leon saw the new wings and also said that they looked way better that the original HDS wings.

Sounds like Zenith should have gone with the prototype wings. Do you have any photos?


I found this on Matronics:

This for sale Zodiac, N601ML, received it's airworthiness certificate in 2004, as a plans-built, 601 HD. It is unique in that in 2007, I learned of and purchased a second set of prototype Zenith factory built, interchangeable outer wings for it. These beautiful wings, tapered in both chord and thickness, similar but longer than the HDS wings were a one-of-a-kind, (pre XL) design that was never marketed. Zenith decided to pursue the speedier XL design instead and put these in storage were they were forgotten about for years, until I learned of them.

It is powered by a 115 HP, Lycoming O-235-C1 with 240 hrs TT SMOH. It meets all LSA specs, with either set of wings, for present or future Sport Pilots.

The price is $42,500 and it is hangared at Hobby Field (77S) Creswell, OR about 10 miles south of Eugene, Oregon along I-5.

Additional details, as well as photos and video can be seen at the Zenith Aircraft Builders and Flyers website at www.zenith.aero/profile/JamesCMahaney .

Please contact me directly, if interested, at mahaneyj(at)msn.com or through the zenith.aero website.


Jim Mahaney
Eugene, OR
601, Lycoming, 601ML

- The Matronics Zenith-List Email Forum -

I've been in contact with the guy referenced in my October 21st email and have some additional information. He provided a picture and dimensions which I have used to create a sketch which are in the attached file. It would be great if we could get Zenith to help us develop a modification to the HDS wing.


Rich Whittington

Zenith 601HDS

3L Corvair

MGL Enigma


Hey Rich,

Thank you for posting that information.

It looks like he extended the wing out by not cutting the lower skin and beveling to make the wing tip.  Maybe the top and lower skin are a little longer.  It is hard to know much more from the photograph.  I was hoping that it was some kind of retro-fit to an existing wing; guess not.


Mark Napier

The thing to keep in mind with this extended wing is it's not a user modification, this was built by Zenith as a design concept prior to the XL design. Unfortunately per Zenith they have no drawings, etc to help us with this endeavor, my wish is someone at Zenith will read this and offer us some help.

I agree that it would be nice to get Zenith involved with developing a modification to the HDS wing. I suspect that Zenith is looking forward with their 650 and 750. It might be hard for us to get them to look back at modifications for the HDS wing. Perhaps I will shoot them an email and see what they say. I will report back any response.
Damien Graham
601 HDS with Rotax 912
Watertown, NY
I contacted Zenith about offering an improved wing for the guys who have the HD and HDS models. The responder thought that it was a great idea and he said that he would keep it in mind but that the were working on other things right now.
Damien Graham

Hello James,

Did you ever get any pictures of the wing extensions?


Mark Napier


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