Zodiac HDS versus XL

Differences between the ZODIAC HD, HDS, and XL models

The HD and HDS were earlier Zodiac models with a very different wing structure than the problematic XL, - fatter, shorter (HDS), no flaps, and made up from 3 sections; a stout middle 7-foot “stub-wing” section that is integral to the fuselage, with 8-foot outer wing panels (10-foot for the HD) attached on the right and left with interlocking mounting plates and bolts. The later XL wing is in 2 sections (right and left), has no middle portion, is thinner, and also has flaps. There is a major problem with the XL design, as there have been 9 accidents with the XL that have involved in-flight breakups before 2010 – some here in the US, some in Europe. These accidents led to a call from the NTSB in May 09 to the FAA to consider grounding all Zodiac XLs pending investigations into possible flutter and overall wing structural strength. The FAA did not immediately take the NTSB’s recommendation to ground all XLs until a ninth XL broke up in flight in October 09. After that final XL crash, the FAA ordered all XL models to be immediately grounded until they could be retro-fitted with Zenith's XL new wing-bolstering kit. For more information on the Zodiac XL and this modification, see Zenith's statement on the XL at
www.zenithair.com .

The HD and HDS models have not been implicated in this problem, whatever may be causing it. There have been no accidents where an HD or an HDS has suffered in-flight breakup. There have been accidents, to be sure, but none that point to any hint of an underlying structural problem with the HD and HDS wings. Nor has the NTSB or FAA called for any action against the HD or HDS Zodiacs. This makes sense, as the HD and HDS wing design is so completely different from the XL. Unfortunately for us HD and HDS drivers, the Zodiac name that applies to all of these models has led to confusion in the pilot community, and many who do not know the different models assume all Zodiacs to be FAA-grounded, and dangerous until modified.

I was the test pilot for my HDS and have since put 105 hours on it, and have never felt it was anything but a very docile and easy flying airplane. Its short, fat wings are great for holding lots of stuff – including two 10-gallon gas tanks and two 40-lb capacity baggage lockers, and their thickness and short moment arm make them quite strong. Also, because of the relatively high wing loading, the HDS is a better aircraft for turbulence penetration. The HDS Zodiac is a very stable, simple and strong design, and has an excellent track record (which you can check online at the FAA).

For more information on the HD & HDS, go to Zenith's webpages for the HD and HDS at
http://www.zenithair.com/zodiac/601-hd.html
http://www.zenithair.com/zodiac/601-hds.html
(Note, by the way that Zenith shows a much faster cruise speed for both models than anyone really gets - most HDS drivers find 120 to 125 mph cruise speed, and most HD drivers report around 105 to 110 mph cruise.) 

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