Bill Allen billallensworld@...
> This subject has come up before, and I understand how Marc is a “rollbar
> sceptic” but there is at lease one documented rollbar “save” written up
> in an old CSA news with pics of a bent and twisted rollbar (instead of a
> bent and twisted neck)
> This is one of those areas where objectivity and data are balanced
> against probability and risk acceptance level.
> Are our engines reliable? Yes, in general.
> Do we have engine failures? Yes, it happens.
> How do our aircraft behave in off field, rough surface landings? Badly.
> Usually the noseleg breaks/collapses, the nose digs in and it flips. But
> it might not.
> What happens if it flips inverted? Well, with the pilots head being the
> high point (and Burt stating that the “rollover” structure is really a
> “headrest”) you may be lucky, or not.
> If your engine failure is over flat farmland or wide roads without dense
> traffic etc (or near a handy airfield) you could luck out, but that’s
> the Gold Standard of engine failures. I like to plan for the worst case,
> so have a 6 point harness, energy absorbing seat material and a rollbar.
> I’d wear a helmet too if I could (I do on a bicycle)
> It’s not just our aircraft that can be neck-breakers in an off field
> landing (Ken Brock died in his Thorpe this way) it’s just that any
> top-heavy wheelbarrow doing 70mph over a moonscape would need the divine
> intervention of Chtuhulu to make it work out well. I just prefer,
> subjectively, to stack the odds in my favour with a rollbar and other
> passive safety devices.
> I have made and sold several of them since Burt “approved” my design,
> but I no longer sell them because with the good ‘ole USA being
> lawyer-ridden it isn’t worth the risk - a rollbar won’t make one
> death-proof but I’m sure a case could be made that I said it would.
> There are lots of other folk out there quietly making a few here and
> there; I noticed many more installed at Rough River last year - my
> advice would be to copy one. They also make great hand-holds for ground
> handling, seatbelt attach points, antennae attach and canopy stay mounts.
> Roll-on summer!
> Bill Allen
> CZ4 G-BYLZ EGBJ
> LE160 N99BA FD51
> LE-Diesel G-LEZE EGBJ
> VE N2CR KMTH
> On Mon, 19 Mar 2018 at 19:20, 'Marc J. Zeitlin'
> [canard-aviators] <canard-aviators@...
> Burrall Sanders wrote:
> We’re not the jet guys, but have built steel many rollover
> structures for Long-Ez’s
>. Can custom build one for
> I'm not the jet guys or Burrall (hell, I'm not even always sure that
> I'm me), but I'd like to see any evidence that these rollover
> structures have worked in a rollover. Certainly the idea is
> reasonable and rational - I'm just wondering if anyone's ever
> actually tested them in a rollover event (obviously not on purpose).
> I've seen some really good ones, from a structural design
> standpoint, which tend to make access to the rear seat difficult,
> and I've seen some that were useless from a structural standpoint
> (although they looked good) and didn't restrict access. There's a
> wide range of techniques...
> Just looking for evidence of efficacy, and obviously any evidence at
> this point will be anecdotal at best.
> Marc J. Zeitlin <http://www.mdzeitlin.com/Marc/
It's things like this that are a serious problem for home builders.
As an example, Boeing needed to seriously test the wings on the 777 Dreamliner.
Not as simple as one might think. It;s my impression that they built that
special purpose building to test the wings, pulling them into a rather good
imitation of a "U".
That wasn't cheap. But, they are building many aircraft, and they had to know
that the design was sound.
Home builders are a much tougher spot. If some entity with the resources and
desire to test something doesn't step forward, we have to do the best we can.
Now, that "should" avoid "that looks about right" engineering. Somehow I doubt
Sometimes one must "do the best one can" and accept that "this is as good as it
gets". Lot of that in experimental aircraft.
My concerns with a roll over structure is, what to attach it to so it doesn't
just rip out? Similar issues with whole aircraft parachutes. Just what is
strong enough in the aircraft to take a rather violent point load and remain
sort of intact.
After considering the roll over structure that Mike Melville designed, I thought
it had some good points, until the whole canopy got ripped off. Thinking a bit
further, I asked myself if a hoop type structure, going totally around the
fuselage and tied in tightly to the "tub" might provide some protection for the
"tub", which is where all the important stuff is. Possibly carbon. Not sure
what else might work. Of course, I doubt such would lend itself very well to
retrofit. Easier in a new build.
Since I'm rather partial to the Berkut style canopys, such a structure would
work well with such.
Just thinking ...
David Froble Tel: 724-529-0450
Dave Froble Enterprises, Inc. E-Mail: davef@...
DFE Ultralights, Inc.
170 Grimplin Road
Vanderbilt, PA 15486
Posted by: David Froble <davef@...
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