I received these from the chief scientist at the NTSB responsible for investigating recent 601XL crashes and flutter incidents.

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Thanks Doug - I have enjoyed it so far and fully intend to keep flying it until told otherwise. It will be great flying weather this weekend in Northern VA.
The NTSB mentions in a footnote that there are two aileron types : Hinged, and Hingeless, but I didn't see any reference to which type ailerons the accident aircraft had. Does anybody know? By the way, there is a drawing on "MACSMACHINE.Com of a home-made cable tensiometer .
I too would like to know which type of aileron is involved. I don't know all the history, but circumstantially, it seems all of these accidents occurred after Zenith (apparently due to customer requests) added the piano hinge option? Just throwing that out, would be happy to be corrected!

One of my first decisions was to install a BRS in my plane. A few thousand dollars extra, along with weight & likely performance hits, but I never want to experience that helpless spin to the ground after a structural failure, midair, bird strike or whatever.
Hi guys
I also am one who believes that there is a control problem with the xl. I hope that this is the only problem and that nothing remains hidden like the canopy latch issue which did not exist but with the 650 comes a new more simple latching system. Here in Australia it is mandatory to fit a secondary latching system for the canopy on the zodiac range. I have some pics from Dave Nixon's pushrod system that I requested from him some weeks back as it is my intention to convert my plane. On the Vans RV8, they are using 6061-T6 1.25 x .035 tubing or 32 x .9 mm aluminium tubing with machined ends riveted in.
Everything is out in the open this time on Zenith's home turf and I think it's time for them to face the music and take responsibility for THEIR design that we have paid dearly for. It's time to be in the business of saving lives not money. I spent my lifetime saving money to buy a plane and I gave it all to you Zenith, give us some answers. I flew in the Ausie demo plane about 3 weeks before it went down apparently to bird strike. When pieces of the canopy were recovered from the surf club's roof that same sunny day, there was no bird guts to be seen on the shards of canopy. I've got the pics. RIP Garry.

I love my plane and my life and I don't wish myself, my Wife or my 4yr old Son to lose either.

Come on Zenith, please respond.

Regards
Phill Barnes

This was the Aussie demo plane that I flew in. Not a good outcome for anyone.

I agree and expect that answers are all that any of us want. Until we get some, here are some links to videos from Airfox Ultraleves in Brazil that uses mass balances on their ailerons and a full wing tip housing the balance and incorporating a winglet which disgards of the wing tip vortices away from the aileron. Funny thing is that Zenith know of their mods and appears that's also where the the original design for the 650 canopy latch came from.

These are some pics that Dave Nixon sent me of his pushrod system for those who are interested. I hope you don't mind me posting them Dave.

Anyway, that's my two cents worth for tonight.

Regards
Phill Barnes












http://www.youtube.com/watch?v=2eo51hMIQV8

http://www.youtube.com/watch?v=q_D4bt0guvM
Sorry for your loss. However, did you notice the placards on the a/c before you got in? When you get in an experimental you do it at your own risk. If you trust the builder, if you trust the pilot and if you trust the maintainer, get in. But if you have any doubt do not get in and do not buy in. Why should big government do your thinking for you. Your logic would have never allowed the Wright Brothers off the ground. Your thinking would have stopped Lindbergh from flying across the Atlantic.
Maybe your family would have been better served by putting your money in a trust fund, educational fund or a boat. Playing the blame game is just wrong. There are too many varibles and too many unkowns to blame Zenith. I make a point to read everything written one the 601XL; NTSB, FAA Zenith, youtube, all the ADs, etc. Pilots bragging about 180 mph dives and stand the a/c on it's tail. One guy in a new 650 on youtub made a T/O which clearly shows him dragging the tail on the concrete runway. Is that Chris Heinz's fault, too? Do you really think his family is out to hurt you? Thank God the FAA is not buying into your witch hunt.
Meanwhile, your gossip is misleading others. I have read every accident report on the 601XL. The Word flutter never came up on one of them. You are just impowering the airlines, TSA, and the FBOers to get us out of the skies, out of the market and out of the industry. In addition, you blogging drives the distrust in our a/c with the result of driving the value down, too.
OK. Address, adjust and fix the problem, but do not create bad guys where there are none. Grounding this model is over kill. Your killing the livilyhood of thousand of people w/ your over kill. Go to Oshkosh and tell all those people their grounded. Kill the venders, merchants and aviation related producers because .001 % of experimental crash. You are right to want a answer but you are wrong to hang us all for your loss.
I did not build my 601 hds . I wonder what the difference in structure between my plane and a 601 xl. I hope there aren't the same issues hiding as i'm getting ready for airworthiness insp,and I hope the dar does not say no go. thanks Dennis
I'm curious to see if the accidents occured with models that have the skin as the hinge point? I understand a little about stresses and fatigue of metals. Although normal deflection would probably not cause any harm to the integrity of the aluminum. Enough flutter at 130 mph could rip that aileron right off and subsequently create a tearing affect of the wing skin. Alot of you guys are right; Zenith needs to jump on this ASAP. When NTSB issues a statement it doesn't matter how many you have successfully flying.
The HD(S) and the XL differ exactly in the area where this problem seems to exist: The wing.
While the HD (and HDS) have a "fat" wing, composed of three panels, the XL has a much thinner wing, build in 2 pannels (the centre spar being the same width as the fuselage).

Here you can see how the HD wing is built:
http://www.zenithair.com/cad/601.html

I couldn't find equivalent for the XL, but on this page you might get the idea (note that the picture at the pottom of the page, a Zodie taking off, shows and HD, not an XL)
http://www.zenithair.com/zodiac/xl/features1.html

The problem does not involve HD or HDS.

Carlos
CH601-HD, plans
wings and tail done
I owned a Grumman Tiger for five years. A wonderful factory built airplane with delightful control harmony. The flight controls were all mass balanced. The aileron balance weight was on the end of a bar on the outboard end of the aileron, hidden in the wingtip. The really clever part is that when the aileron deflected upwards, the balance weight deflected downwards and poked out a slot in the bottom of the wintip and acted as an aileron spade. The weight was shaped so that it could act as a spade. This gave the Tiger a very nice, light, delicate feel in the roll axis.

Maybe Zenith (or some other party) could come up with a similar arrangement. I am still building my plane so I do not have much 601XL time yet. However, I remember my few flights in the 601XL as having a nice responsive elevator but a kind of heavy aileron. Maybe we could fix two things at once, get mass balancing and get lighter aileron feel.

Pushrod tubes in place of cables and pulleys would help the loose control cable tension issue, and would give smoother operating ailerons (I would like them for that reason alone) but only mass balancing will eliminate the possibility of flutter.
Has anyone out there ever heard of flutter on the 701 either the ailerons or the elevator?
I have not heard of any flutter on my or any 701/801 series. There are a number of reasons that it should not be as susceptible

Aileron (flaperon) controls are pushrod
Ailerons neutral set is effectively down droop meaning preload of the surfaces during flight
Aileron hinge point is aft of leading edge
Wing is twin strut braced
The plane doesnt go very fast - even in a dive

There are some areas that might be more susceptible
Elevator rigging does not have positive cable tension in all control quadrants
No rigging tensions given in the plans, construction manual or operating manual

Ralph

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