Oscar

DJP - perhaps I should PM you on this one? And of course you are correct that the Gazelle is basically safe if operated within limits - but as that wing separation a couple of years ago showed, it's possible to get it outside limits quite inadvertently with disastrous results. I don't think anyone has ever suggested that the pilot was doing anything wrong, or even close to wrong, but a gust basically took the wing off due to lift reversal that collapsed the forward (I think) lift strut and the wing was gone. As far as I understand, it's a feature of the airfoil, and an airfoil that can generate a load from a change in conditions that is not wildly unexpectable, I reckon is a fundamentally dangerous problem. If the pilot had been pushing VNE, well, obviously it's not the airframe's fault, but certainly the witness reports did not suggest he was doing something silly - just got caught in a hard gust in a medium turn.

 

 

Mick, you might be somewhat pleasantly surprised; remember the lch mod means more than just the cost of the heads, to do it properly you'll need to not only add the extra cooling function (radiator plus cowling mods), but have cooling performance tests done, probably re-do the W&B. The CAMit modified engine has just about every major part renewed - not re-used - and offers a few extra things that the lch heads won't bring to the engine. Whether those represent desirable value, obviously is something every prospective CAMit / vs. lch heads engine owner will need to research and decide for themselves.

 

All of that said - if the CAMit mods weren't on the near horizon, I too would be looking at the Rotec heads very seriously (and did so not too long ago) - and if I were using the Jab. engine in a STOL aircraft that operates in the low-airspeed 'lugging' area, I think they're still a very viable option to 'Rotax-ise' a Jab basic engine. However, I suggest that if you can pick up a 230 at a bit of a 'discount' price because it has a fairly high-time engine in it, you may find on doing the sums that what you end up with for not much more money than doing the lch conversion work is basically a 230 with a pretty much brand-new and better than standard engine. All those figures should be available to you before you have to splash the cash..

 

 

thanks jetjr. training isn't an issue as we have a 230 at our school, so I'll have plenty of hours in that by the time i buy one. i don't rekon ill be doing any maintenance myself. im way more dangerous than any jab engine is. will keep an eye on the Camit engine over the next 6 months or so. would be good to hear how people are going with them...

Mick, CAMit have been making good progress with both their in-house final development work and flying experience in a number of aircraft and are (I understand) heading towards a higher-level of acceptance for their modified engine in the relatively near future. I don't think - though I have no particular information - that the Rotec heads are in any way a bad thing, but they do make changes necessary (obviously, providing a cooling system for the heads, for a start) that will be at the very least a lot simpler for owners substituting a CAMit engine for a standard Jab. engine in their aircraft. If you are looking six months away from making a purchase decision, I strongly suspect there will be a considerable improvement in the level of information available to you to make that decision.

 

 

Actually, we're having a huge amount of fun doing all of this stuff, and we'll know every damn bit of what's in and on our aircraft. But on a more serious (and thread-relevant) note, thanks to the patience of everybody who has been 'mentoring' us along the way with both the airframe and engine to take the time to explain the what, how and why of things, we've gained a hell of a lot of understanding about just what goes into the design for efficient manufacture of an aircraft. We do have to ask the engineers to explain things in layman's terms but they generally sigh and comply, and we're better off (we think) for knowing this stuff.

 

 

Yes they did, you just missed the context.

No they didn't; there are quite a few ots components in Jabiru engines - Holden pistons, just for a start. OTS bearing shells, OTS shaft seals, OTS coils...

 

 

DJP - we didn't use a point load, we set up a whiffletree arrangement with a main load beam with the load centre at 46% span (sorry, not 43%, I've been preparing the damn test report and I have figures floating around my head like snowflakes in a globe..), an intermediate pair beam with the inner load pad centred at 20.5% span, middle pad centred at 43% span and an outer load pad centred at 73% span - so, as you say, a distributed load. That replicated the certification set-up for the fin we are using (a UL fin on an LSA55). That original test load arrangement was justified (if that is the correct word) in the certification report by comparison of 3-pad BM, Schrenk BM, 3-pad Shear and Schrenk shear plots (or maybe it's curves??) - and I don't have the foggiest idea what all of those mean, I'm not an engineer, but I can do what I'm told and pass it back to the engineers to play with their computers.

 

Why only Limit Load? - because that's what the engineer preparing the EO - the same one who did the UL certification tests - asked for. If the Limit Load test had raised any questions, I'm sure he'd have required more; but he knows the structures of LSA55's through to J160's at least, better than just about anybody.

 

In fact, we actually went 20.1% over limit load because I don't have access to calibrated scales, just commercial ones (though we did double-weighing of each major load component and both scales agreed within .1 of a kg) and we felt a decent margin for measuring error was wise. FWIW, the deflection under a test load of (what we calculated as) 83.56 kgs, was 70mm at the fin tip (to within 0.5mm, allowing for parallax error on a visual sighting on the deflection pointer), and after a test load application of 129 seconds, the fin returned to within 0.5mm of its pre-test unloaded position which is (probably) to have been just from settling of the test rig frame. We don't have sophisticated gear here, but we believe that test was decently performed; mind you, the video soundtrack of it is a bit like the two grumpy old muppets exchanging unpleasantries, but if the old-fart owners of an aircraft can't send each other up a bit, life just is TOO serious.

 

 

Well, I think we have to put this one down as another Jab engine failure - it completely failed to not get him all the way to the accident site.. I reckon that's as good a 'Bugger' moment as one is likely to walk away from..

 

 

I'll take that as a no, shall I? BCAR S doesn't mention skinny blokes OR ladies not suffering body-image paranoia anywhere...

 

 

"Shortcuts" have been outlaid in the engine thread, e.g. production 'off the shelf' crankshafts and cylinder heads whereas Jabiru developed everything themselves from scratch - that was my meaning.

No, they didn't. They produced their first aircraft using a KFM engine. Then KFM pulled the rug from engine production and Jabiru were forced to either completely redesign their aircraft for a different engine or build an engine that could fit their aircraft. They decided to go the 'produce something that will fit' route; in the light of the success of the airframes, just possibly they were justified in making that particular decision - though quite obviously the engine has been far more troublesome than the airframe.

 

Can you name me a manufacturer that produces both their airframes and their own engines that has had the sales success of Jabiru in this class? Textron couldn't - despite its massive presence in other classes. Bombadier don't, yet they have a hugely successful engine sitting on their corporate shelf. Savannah have announced their intention to produce their own engines - this is a road to be traveled.

 

Bex, if you can provide an airframe and engine package that gets people in the air for low cost, safely and reliably, more power to you. In my opinion, the two best aircraft designers of high-performing, excellent small aircraft for low cost have been/are Walt Wittman and John Monnet (Sonex). If you can manage something similar, you will indeed be in line for 'legend' status - go for it. However - and I say this with respect for what you are seeking to do - the allowable by regulations gap between a Homebuilt-spec. aircraft (basically, 19-reg here) and something eligible for 24-reg, is very, very considerable, and you can't just blindly state that a 24-reg aircraft should be cheaper because a 19-reg aircraft can be produced for so much less.

 

To get the necessary ticks in the boxes for different levels of regulatory acceptance is not at all trivial. Just to do a few modifications to a 55-reg aircraft and have it still eligible for 55-reg requires a complete engineering justification to the original standard - in our case, BCAR S. Every damn para. of BCAR S. I just spent a weekend doing a Limit Load test on a new fin on our Jabiru - recorded deflection of the fin with a load of 69 kgs at 43% fin span. Would you like to have a guess at how much engineering time went into determining that 69 kgs @ 43% span is what is required by the BCAR S standard for that particular aircraft? And how much time was required to develop a test regime to demonstrate that that could be achieved? Then, multiply that by ALL of the requirements for BCAR S for the entire airframe.

 

Bex, anyone can build a billycart. Some of those are really rather clever machines. But to build a car that meets the various standards is a whole different ballgame. Same applies in the aviation world.

 

 

Matty, I'm not knocking Vans, obviously they produce many very good aircraft. And the Vans site is extremely informative, Vans obviously takes pride in what it does and provides great support to its customers - absolutely no argument. However, I don't think it's accurate to call the ATSB report 'suspect'; it's not my opinion, it's the ATSB opinion. However, to keep this thread on track, let me reiterate my earlier comment: draw your own conclusions / do your own research. You obviously have and are satisfied, that's fair enough. I assume you've seen this article: http://rvbuildershotline.com/articles/accidentrate.html. It makes a very good case for the safety record of Vans aircraft, it also provides some reasonable analysis of the actual fatal rate for the various models.

 

 

Hey! Go easy on Volkswagens! Next you'll be saying that that the Road safety feds will be taking action behind the scenes.......

I go easy IN Volkswagens (well, I did in the early Beetles, that's why I'm still alive.That and cussedness, really.)

 

 

Matty, too many points for me to make any clear answer, and I have no idea of the qualifications of the guy who wrote the USA report. However I certainly know the guy who did the cabin strengthening mod for the RV6 and prepared the expert opinion on the crash for the Coroner's report. He happens to be an aeronautical engineer with a number of type certifications to his credit, an ex-DCA/DoT crash inspector for part of his career, and a (still) CASA-endorsed test pilot.

 

Vans certainly did NOT admit any fault (would you expect them to?) but DID make similar changes to the Australian mod.

 

Care to provide a link to the Service Bulliten for this apparent RV-6 cockpit strengthening mod?That link you provide is interesting too... How much experience did the pilot have in RV's? Its all well and good to provide a story, but a story is just that without context; as Mat says above, who is the author and what makes him an expert?

The RV6 is an Experimental - therefore no SB. However, you ought to read (read all tabs): http://www.atsb.gov.au/publications/investigation_reports/2000/aair/aair200005572.aspx

 

I have NO idea about the US pilot. I can only suggest that you draw your own conclusions/ do your own research if you are thinking of owning / flying in an RV6 - I have no interest there. I don't like /dislike them, I'm just not very interested in them. I do know that the failure described in the ATSB report happened and the pilot's head was smashed as a result.

 

 

Merv - that's really, really bizarre - wish we could see the view from the other side. I don't mean to be combative here - but the 'break' line on the port wing is so extremely clean, and noticeably at the level of the water surface - and that water is very, very opaque. The glass used (certainly in the solid wings) is a biaxial 90-90 glass laminate laid at 45 degrees to the spar, so a spanwise tear would be jagged. Did you have a report that the wing had torn spanwise? - (that appears to be well behind the spar line). The starboard wing appears to be fairly normal in that piccy; the later failure MAY not have been a result of the earlier one - though any wing that is repaired is suspect unless you have explicit details of the damage and the repair scheme. That said - repair of a 'glass laminate is documented to be 100% 'as good as new' - PROVIDED that the proper techniques are used. Same goes for any material, really, it's just a case of how much 'repair' is needed.

 

 

A little early for that just yet.

Bex, you can't be serious. You cannot design a plane and then shop around for a standard that it fits. You HAVE to design to a standard. Go ask the Australian owners of Ibis aircraft what happens if you buy an aircraft that isn't demonstrably compliant with an acceptable standard.

 

The 'web is full of 'breakthrough' aircraft with fancy CAD drawings and splashy sites, that promise a revolution in aircraft design. They are the aeronautical equivalent of Nigerian princes offering untold wealth because you are a good mate...

 

Bex, give us something to hang your bona fides on.

 

 

Work smarter.... it's possible. You don't need to be paid less to produce the same if you can be paid the same to produce more... just takes management savvy.

 

 

The biggest light aircraft company in the WORLD sells 188 aircraft manufactured in China - with all its competitive advantage - into the LSA market. A small establishment in Bundaberg using people in their garages to produce their bits, sells more than 10 times that number, worldwide. What a damn shame we are crippled with such terrible union-led high wages, wildly uncompetitive costs of production, the tyranny of distance from component suppliers, a venal government/public service that stifles enterprise etc. etc.

 

Hell, without all those disadvantages, we could have been a competitor...

 

 

I would add RV3s to that equation too...http://www.atsb.gov.au/publications/investigation_reports/2000/aair/aair200000885.aspx

Yes, it's the same fundamental engineering problem. In a low-wing aircraft, there is an entirely obvious 'hinge-point' for forces at impact: the wheels attach to (or close to) the mainspar, the engine mount has to be reacted out to the mainspar, draw the lines and see how they interconnect. In a high-wing aircraft, there is a triangle formed by the mainspar, the engine mount and the main wheels. In the latter type, the pax's ( in a twin rather than a tandem), anyway) sit inside that triangle.) To get an equivalent level of secondary safety in a low-wing aircraft, you have to make the structure strong enough to resist the 'out-of-triangle' forces. The smaller the aircraft, the bigger the hole you have to provide in the 'cylinder' that is the fuselage, for pax. access. There's a damn good reason that the 'hole' for the pax(s) on fighter aircraft is really, really small compared to the size of the fuselage, and it's strength, not that the designers were sadists..

 

 

There's a case for planes (or cars or especially boats) being so expensive that people justify going to further expense to maintain an equal level of fitment throughout and that if the base price is cheap then the fitout will also be cheaper, win win.It's called China - if it can be done properly.

 

No, I have never previously indicated my plane plans in public anywhere, hope that helps.

Well, you certainly have our attention! To what standard will your machine be certified?

 

 

No, it's also the available options. In the Jab. ( or Lightwing, Pipistrel, Tecnam etc) you have a radius of options available because of the 'here to there' flight profile that is considerably more than the RV6 even at 3,000. What the author has said is that at 3,000 in an RV6, you have bugger-all options, just pick a spot that is possible and go for it at 80 kts. - and NO LESS than 80 kts. And that means that you have to have a field that is big enough to get over the fence at 80 kts and wash off your speed before the other fence comes up - in a slippery aircraft. Paddocks like that are dime-a-dozen out west of say Narromine, or Dalby, or Tocumwal; try to find them on the coastal route from Sydney north or south..

 

For the USA, Ohio maybe has those sort of fields; I suspect they are pretty sparse in Colorado or Utah or Oregon or Washington State...

 

 

The Gazelle is a fundamentally dangerous aircraft both from an aerodynamic and a structural POV. However, it is a major improvement on its progenitor - the Kitfox. It is one of those devices that is delightfully benign until pushed, when it turns into a killer. A bit like an early Volkswagen Beetle: fine until it all goes wrong, when it spins out and wraps you around a light-pole and catches fire and incinerates your mangled body.

 

The Gazelle would NOT be certified under today's rules. Do you really WANT to fly in something that, if it hits a decent gust in a turn, may well throw a wing away? The engineering work that went into getting the original Gazelle to actually meet the regs, at the time was very considerable; amongst the problems of the Kitfox was aileron binding and aileron flutter. The engineers who managed to get the damn thing to pass the regs. minimum requirements were pushed (how would YOU like to experience 10 seconds of aileron flutter in a test flight?)

 

 

That reads somewhat scary. The RV story .Steer with rudder?? Sounds like it flys like a brick, with the engine silent . Nev

Just think about that report: the author is saying that if you are lower than 3,000 AGL, your landing options are bugger-all, or in RAA terms, about what you should adopt as a strategy from 1,000 AGL or less. Pick the softest spot... In gliders, it used to be the 'rule' that you committed to landing if in no lift at 1,000 AGL . I have done climb-outs on weak thermals from less than that, but I could see the damn lift from the dust etc. Ingo Renner used to consider 300 AGL to be a decision point - and I don't believe he ever bent an aircraft. But Ingo was a god, a thermal-whisperer. The rest of us aren't.

 

Things like the RV6, or (and I think possibly the most dangerous aircraft ever foisted on the market) the Lancair 3x series, get across the countryside in a splendid fashion until the noise goes out. The Mitsubishi MU-2 is another. These are aircraft that basically if the prop(s) stop turning, you are praying..sometimes the gods wink in your favour; often they don't.

 

 

Oscar I will see if I can dig the pics up from the original accident. Not that much can be seen, but i cant recall if the rear spar connection failed or not. I dont think it did.

Merv, from the description, I doubt it did; to tear along the spar you'd have to have a major shear load in the wing skin as you said, so if the rear attachment had failed then that would release the shear load. Once the shear strength has gone, then the load on the rear attachment reduces dramatically, so it's one or the other goes first... Your surmise that the tear started from a high stress point introduced by an interruption to the skin sounds entirely likely, though obviously the skin/mainspar attachment produces a line of high stress that could act a bit like the fold in an envelope..

 

The solid wings are as tough as hell, basically; they'll withstand a crash that cuts them open from the l/e back to the spar ( e.g. hitting a fence post or the like) and be entirely repairable. They're only a write-off if the spar is damaged. I don't know much at all about the later wings so can't comment, but I guess it's the old story: more technology, less forgiveness. There just is no free lunch; the reason a J120 can be put out Jab's door for such a low cost for what you get is a factor of the cost of production: those solid wings are cheap to make (and repair) but you trade that off for losing the room behind the seats to a fuel tank and a lower useful load.

 

It all comes back to the rather complicated equation of 'what do you want from your aircraft'? If I were flying mostly one-up and wanted a minimum-maintenance, reasonably-performing, safe if it all goes pear-shaped device (which I do!) that I can head out to most anywhere in this country, a J120 with a full CAMit-modified engine would be damn hard to beat for the money - possibly impossible to beat. Pack 200 mls of LC3600 and a sandwich-bag full of appropriate 'glass and you can repair it pretty much anywhere en-route that you have a mid-level oopsy, if you have the basic knowledge of 'glass repair techniques... and your chances of being in a physical condition to DO a repair is pretty damn good.

 

 

Merv, we're being VERY careful with those wings (are using both) because both our and the WA starboard wing tore out the rear attachment just from the kinetic energy of the stop. We've replaced the rear attachment points in both those wings with a replica of the front attachment point stub-spar arrangement (all done to the specification of the aero-engineer who did all the original structural justification work on the early Jabs, btw.) The solid wing rear attachment points don't fail in normal service BUT - as with any aircraft - an abnormal loading requires very detailed consideration of how those abnormal loads were reacted out. When I had a CofA inspector's ticket for Gliders, the first place we went to look if a tip had hit anything even slightly hard, was the root fittings.

 

That's certainly a very weird form of failure and I agree with your surmise that there was pre-existing undetected damage. With a low-tech thin-glass structure, that's usually reasonably easy to see; with carbon fibre components in high-strength areas, it requires laboratory-class equipment and inspection techniques to be sure. Metal is generally pretty good for inspection PROVIDED you can get to see the bits you need to see...

 

 

Not so sure about the RV6 opinion ,it was based on one crash in Australia where the pilot held the stick hard back and ploughed into the ground, there has never been any mention of a problem in the USA ,and there's hundreds flying there(thousands actually) , but the jabs certainly have a tough fuselage,Matty

Vans quietly adopted (well, put out a similar) cockpit strengthening mod as the Australian one and I believe made it standard on all kits many years ago. But the aerodynamic problem that leads to the hard hit is very real: suggest you read para 6 of this: http://www.sdsefi.com/air44.htm

 

 

Very similar occurrence to an ST1 in WA - noseleg went into a deep rut beside a tree stump, took the firewall with it. Pilot completely undamaged. Jabiru was happy to repair it; eventually the owner decided not to repair it as he'd seen an SP6 for good money; we got the wings for our ST1 out of that crash. The firewall will tear away from the bottom of the window pillars down and leave the pax. sitting windy but unharmed.

 

By comparison, I've seen a demolished Sting where the complete cabin just basically exploded into small bits of c/f back to the mainspar, you couldn't do more damage by dropping hand-grenades into it. Harnesses tore their shoulder-straps out of the totally useless fixings. Two dead, didn't stand a chance. That was a forced landing that wasn't a stall/spin, just hit the ground hard and basically exploded. RV 6's lose elevator power in a dead-stick landing and if trying to flare at normal landing speed just fly into the ground, and if they haven't had the fuselage strengthening mod, will fold up and smash the pax's heads. If there were an ANCAP rating for crash-worthiness, Jabs. would sit right up at the top for pax. security. Lightwings are pretty good, too.