Re: [c-a] VE/LE rollover structure


Mike Tooze
 





As there seems to be a bit of a pause in group correspondence I thought I'd raise an idea sparked by a comment in March 2018 from David Frobe re. a possibly of a structure able to provide protection in the case of an inversion accident. - As an alternative to those 'roll-over steel bars'.


What I am asking is did anyone follow-up on this approach or have any subsequent comment?


I have added/attached a Word sketch that I did following the original emails.


Sincerely,


Mike Tooze

O-235 VE




------ Original Message ------
From: "Mike Tooze miketooze@... [canard-aviators]" <canard-aviators@...>
To: "canard-aviators@..." <canard-aviators@...>
Sent: Wednesday, 21 Mar, 18 At 16:11
Subject: Re: [c-a] Long EZ roll over structure



All this talk of inversions made me nervous such that I engaged brain....

I think that Dave Froble gave the clue.

>> 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.
>>

Well, there is such a belt - but it is internal and does, Dave, lend itself to a retrofit solution.
The pilot’s seat bulkhead is bonded to the fuselage by the floor and both fuselage sides so forming such a belt – of a kind. It is a sandwich (i.e.tension/sheer/compression) structure and I include with it the plans headrest.

By reinforcing both sides of this bulkhead with two or so plies of carbon on each of the front and rear extending up to and overlapping the headrest, also extending the lap onto the fuselage sides by 9 to 12 inches, we can form a strong cocoon/seat structure. Further lapping up to under the top longerons for a few inches will add linkage to the outer skin of the fuselage. . (The number of plies of carbon/Kevlar depends on personal preference, the weight of material used, etc. - This is given as an approach not a detailed design.)

In the even of an accident involving an inversion.
Forward sliding forces acting on the headrest are reacted by the front laminates in tension and the rear laminates in compression.
Rearwards sliding forces similarly are reacted by the rear and front laminates.
Sideways sliding forces are reacted by front and rear laminates in shear aiding the side laminates of the headrest lapping around and transferring load into the main front and rear laminates.
Loads directed down onto the seat are distributed via the laminates into the fuselage sides.

I have referenced the plans headrest here but the headrest could be any shape you please that fits the canopy and is able to transmit the side and vertical loads. i.e. ideally no concave surface

I estimate that this reinforcement procedure, with normal economy of lay-up, will weigh less than the bolted steel rollover bars seen thus far. Due to the load distribution characteristics of this composite solution, I believe that longeron/point secured solutions are more likely to fail at the attachment points than for my distributed load solution.
In support of my approach I have seen in the accounts/pictures of survivable Eze accidents/inversions and here in the UK, none involving displacement or a detachment of the pilot’s seat bulkhead from the fuselage sides.

Just a thought, OMV,

Sincerely,

Mike Tooze
O-235 VE G-EMMY
Rochester, England



Bill Allen billallensworld@... [canard-aviators] wrote:
>
>
> 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'
> marc_zeitlin@... <mailto:marc_zeitlin@...>
> [canard-aviators] <canard-aviators@...
> <mailto:canard-aviators@...>> wrote:
>
>
>
> Burrall Sanders wrote:
>
>
> We’re not the jet guys, but have built steel many rollover
> structures for Long-Ez’s
>
> Freeflightcomposdites.com
> <http://www.freeflightcomposites.com>. Can custom build one for
> you.
>
>
> 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/>
> marc_zeitlin@... <mailto:marc_zeitlin@...>

> http://www.cozybuilders.org/
> Copyright © 2018 Burnside Aerospace

> <http://www.burnsideaerospace.com/>

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
it does.

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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Posted by: Mike Tooze <miketooze@...>



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