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#11
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Let's try posting that URL again, and see if I can make it not
line-break: http://babelfish.altavista.com/babel...p=de_en&tt=url Bob K. |
#12
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Stewart,
There is no such thing as "the manufacturer" for the ETA. Instead, a group of wealthy people financed the design and the building of the prototypes. Several different companys contributed by building parts of the plane. The web site www.eta-aircraft.de is run by the design bureau. Markus Stewart Kissel schrieb in Nachricht ... Okay, we can call any sort of "event" we choose. According to articles I= have read, the things cost more the $1 million US to build. Will the ma= nufacturer be able to absorb this sort of hit? |
#13
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Please explain, I do not understand.
If a 747 (just a little bit larger than the eta...) breaks up in flight due to overloading, killing 400 passengers, it is not a an accident. So what is it then? Robert Stefan wrote: Vaughn Simon wrote: information we have, it apparently broke up in flight, the occupants bailed out, and then gravity took its natural course until the failed airframe (crashed, fell, bumped, decellerated, sprinkled, oopsied) into/onto the surface of the earth. Help me with the finer points of English please; how is this not a crash? Ok. Technically (and linguisitcally), it *is* a crash. Nothing wrong. However, when I read the headline "aircraft crashed", I understand "accident", and I guess that's what the vast majority does. My mistake, agreed, as it wasn't written anywhere whether the plane broke up during normal flight, did a bad landing or was destroyed voluntarily. Anyway, "accident" ist what that headline implies. But it wasn't an accident. It was a test flight to explore the limit, and they found the limit, although a bit earlier than they wanted, I guess. That's exactly what test flights are for. So a better headline would be "eta fails spin test". Stefan |
#14
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Robert Danewid wrote:
Please explain, I do not understand. Then read my post more carefully. Stefan |
#15
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Earlier, Stefan wrote:
...But it wasn't an accident. It was a test flight to explore the limit, and they found the limit, although a bit earlier than they wanted, I guess. That's exactly what test flights are for... I'm not sure I completely agree with that assessment of the situation. The way I understand it, the limits they were expecting to explore were control and handling limits, not structural limits. The way I read the Babel Fish translated report, they placed the aircraft into a spin, executed a recovery, and were surprised by a structural failure of the aft fuselage during the recovery. I think that if they were really executing a structural test, they probably wouldn't have had two people on board. Going forward, it will be very interesting to follow the investigation of why the structure failed. Did the maneuvers performed apply loadings beyond the expected ultimate limit? Or did the structure fail to provide the expected strength and stiffness? And if the latter, were the stresses miscalculated or did the stucture not perform as expected? It's really far too early to speculate, but it will be interesting to see if perhaps bending loads applied by the elevator plus bending and torsional loads from the rudder combined to produce stresses in excess of the expected maximums. I hope that they were carrying a flight recorder, and that it (unlike too many dented Cambridge Model 20s) yields usable data. Anyhow, I'm glad the pilot and observer weren't injured badly. That's what's most important. Thanks, and best regards to all Bob K. |
#16
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18 posts on this subject line: a large portion of them debating the meaning
of the word "crash" -- yes, the season is over. What kind of wax shall we use this year? Jack |
#17
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"Howard Franks" wrote in message ... I have always assumed the recent (last 20 years) composite gliders to be very robust, i.e. no issues flying right up against placarded limitations at anytime (maybe once or twice nipping over?). Perhaps the Eta break-up is a sign that we are reaching the structural/design limitations of the current materials and the designers ability to optimise gliders for performance. Are we at the point of diminishing returns where the small increase in performance only comes at a far greater risk of structural failure (similar to the Americas Cup yachts). This coupled with the recent Schempp-Hirth issues (agreed manufacturing not design defects), and the AD restricting GROB 103s is leading me to rethink just how tough these things are. There seems to be a prevalent attitude that all gliders are much stronger than the POH says. At least, as a CFI-G, I have a hard time convincing pilots that those placards mean just what they say. This is particularly a problem when it comes to overloading 2-seaters. Exceed a placarded limit and you become a test pilot - maybe a dead one. I think gliders are just as strong as the manufacturer says, but no stronger - and only then if the design and manufacturing rules are followed to the letter. The problem with the Schempp-Hirth gliders seems to be that the manufacturer's own procedures were not followed. The issue with the G103's MAY be that errors in design occurred. None of this says that composite construction is the problem, just that the process needs to be carefully controlled and monitored. (It also says that reputable manufacturers sometimes make mistakes that aren't found until after the gliders are in the field.) As for the Eta, this may turn out to be an intriguing case. At 31 meters it is certainly pushing the limits. Bob K. perceptively speculated about bending and twisting loads on the tailboom. It could also be that the spin recovery has to be performed exactly right of the airspeeds get way, way out of hand. I would expect that the Eta will be placarded against intentional spins for this reason. Bill Daniels |
#18
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Bill Daniels wrote:
I think gliders are just as strong as the manufacturer says, but no stronger Most Gliders are built in JAR country and are certified by JAR rules. For the utility category, JAR requires an allowed load of 5.3g at Vne and 4.0g at Vm. JAR further requires that the break load be no lower than 1.5 times the allowed load. Since every extra strengh comes at a price in weight and money, the break load of most gliders acually *is* 1.5 times the allowed load. This is when the glider is new. Take some turbulence, and the safety cusion is rather small. As for the Eta, this may turn out to be an intriguing case. At 31 meters it is certainly pushing the limits. Actually this is the whole idea of the Eta project: pushing the limits. Remember that the first prototype was too heavy and extra work was required to bring the take off mass down to 850 kg! (The 850 kg limit is again required by JAR as well as by contest rules.) Stefan |
#19
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Never assume the glider is stronger than the placarded
limits. As quite rightly stated earlier, exceed them and you become a test pilot - especially so on excess speed where there is little margin. A friend of mine broke the boom on a SF34 (best thing to do to the beast, some might say;-) recovering from an intentional spin. He's a Chief Flying Instructor and engineer so one presumes he knows what he's doing but even he was caught out. These things are not unbreakable in flight. The loads on spin recovery can be quite unpredictable, especially if the recovery pull-up is done with some twisting moment still present on the tail - hence we are trained to stop the spin, unstall the wings, recover, not one 'pot-stirring', stress-inducing manoeuvre. Rob At 09:12 03 October 2003, Stefan wrote: Bill Daniels wrote: I think gliders are just as strong as the manufacturer says, but no stronger Most Gliders are built in JAR country and are certified by JAR rules. For the utility category, JAR requires an allowed load of 5.3g at Vne and 4.0g at Vm. JAR further requires that the break load be no lower than 1.5 times the allowed load. Since every extra strengh comes at a price in weight and money, the break load of most gliders acually *is* 1.5 times the allowed load. This is when the glider is new. Take some turbulence, and the safety cusion is rather small. As for the Eta, this may turn out to be an intriguing case. At 31 meters it is certainly pushing the limits. Actually this is the whole idea of the Eta project: pushing the limits. Remember that the first prototype was too heavy and extra work was required to bring the take off mass down to 850 kg! (The 850 kg limit is again required by JAR as well as by contest rules.) Stefan |
#20
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