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#11
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it looks a bit suspicious that the latest incidents
concerned gliders out of Schemp Hirth's Chechia licence fabrication only. CH ----- Original Message ----- From: "Chris OCallaghan" Newsgroups: rec.aviation.soaring Sent: Wednesday, September 10, 2003 12:29 AM Subject: Discus CS grounded in France Per the French Airworthiness Directive, "separation of the wing during normal operating conditions, possibly the result of a manufacturing defect." |
#12
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Eric,
Concrete and steel bonded together consitute a 'composite' structure. Steel girders used for bridges have steel studs welded on top flanges of the girders. The concrete deck is poured and bonds to the girders with the help of the numerous studs. The Portland cement in the concrete is the glue which makes the bonding possible. So, in a way, the concrete and the steel are 'glued' to each other. Calculating the strength of the structure takes the 'composite' structure into account. Ray Lovinggood Carrboro, North Carolina, USA At 02:42 10 September 2003, Eric Greenwell wrote: In article , says... Same happens as with a wooden glider....... JJ knows that...after all, wood and fiberglass are both composite aircraft;-) Not really. Wood is a material used 'as is', while composite aircraft mix at least two materials together; e.g., epoxy and fiberglass. Gluing or bolting materials together doesn't qualify as 'composite'. You probably knew that... -- !Replace DECIMAL.POINT in my e-mail address with just a . to reply directly Eric Greenwell Richland, WA (USA) |
#13
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Discussed this years ago in the UK, we concluded WRT
overloading/overstressing that 1. metal bends and fatigues and shows signs of cracking. Fatigue life can be estimated. 2. wood fails progressively with audible and visible cracking, though glue joints are something else (there's an English pub discussion about why the lengthwise cracked beams in the old pubs are stronger than solid beams. Turns out that cracks indicated that the wood was seasoned, therefore stronger in a load bearing sense. Wood without cracks was green, though more resilient to impact, was more flexible and resulted in more bending under load which apparently had resulted in some pub collapses, or at least the story goes. This was all discussed in a pub in East Anglia where it was said to actually have been built on a large raft in a boggy area a few hundred years earlier.) Wood has theoretically infinite life, or at least that was assumed. 3. composites (in the common sense) fail catastrophically (ever seen what happens when a fiberglass pole vault goes bad?, similar to twisting a wing section off I'd imagine, whether through overstress or defect.) BTW, your 2c is probably not one of the earlier heavies mentioned. I think most were 2b's. 1000 hours was 1/3 of the initial service life of the first generations of glass ships, based on 1/6 of a design life of 18,000 hours as a conservative estimate. Subsequent studies have shown long composite life, though some of the metal bits may need periodic crack testing and replacement. 2c is not really first generation glass, but still in the early carbon fiber period. Not sure what the initial service life SH might have assigned, but expect it would have been at least 3000 hours. Frank Whiteley "George William Peter Reinhart" wrote in message ... Oops!!! Should have been _forty two thousand_ hours on the Mooney sister ship. At 7200 hrs, mine had used up four engines. No telling how many on the sister ship. Cheers! George William Peter Reinhart wrote in article ... Ian, I've got a copy of the same articles. I used to think my Mooney was a pretty high time at 7200 hours until I parked it next to the sister ship with 4200+ hours. There is still the "turbulence" though, so I'm wondering if I should fly only on days when there is no lift. Cheers! (and still trolling) tango4 wrote in article ... I have a copy of Technical Soaring, the July 2002 vol 26 number 2 that discusses lifetime predictions of compostie aircraft. The general conclusions seem to be that "lifetimes far in excess of the current 12000 hours" and "a lifespan of 50000 ( yes fifty thousand ) hours with a high level of safety" so your 1000 hour Nimbus is hardly out of the running in period! Ian "George William Peter Reinhart" wrote in message ... Yep, Makes you wonder doesn't it? Where are the cut offs for High Time and "severe " turbulence that would make it not OK to fly? Currently flying a well aged Nimbus with over 1000 hours on it. Should I be worried about my personal safety because of the airframe hours? Are there some days I just shouldn't fly because the "turbulence" might be "too high"? All advice carefully considered. Cheers! Guy Byars wrote in article ... I heard it was a high time glider in severe turbulence. And that makes it ok? |
#14
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#15
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#16
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test
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#17
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![]() "Roy" wrote in message ... When getting antsy about composite life it's worth remembering helicopter rotors are similar in construction to our ships and have service life on the main rotor of 15 years + (I suspect life of the aircraft but 1 I know in particular had 15+ years and 000's of hours on) this is in a particularly harsh environment, Failures, I suspect have more to do with poor initial construction and or abuse rather than "lifeing" the items. my $0.02 (and belive me, I do have the flameshields UP) Reminds me of the rotor blades I saw that had been wrapped around a tree in about 1970. Steel strap inside balsa laminates with fiberglass cover and shielded leading edge. Pretty amazing. I have no doubts about the integrity of properly constructed composite structures. There have been some suggestions that at least one company may have been a bit heavy handed with the squeegees a few years ago on one model, as the airfoil was losing shape after three years. Current pre-pregs have improved lay-up quality in many areas, but sloppy joinery, well....... Frank Whiteley |
#19
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Earlier Reic wrote
Is plywood defined somewhere as a composite? To me, it's not a composite because it's just one material, glued together in distinct layers, not in a matrix like fiberglass and epoxy. One of the most common *Composite* examples is the cardboard box. Same material, although the center core is shaped to form the required seperation, then add the glue and we have a very cheap composite structure. JJ Sinclair |
#20
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My "suspicion" is that quality control broke down at the Chechia
factory. The quesiton on my mind is, "For how long and to what degree?" Two gliders from the same factory breaking up in flight in a single season deserves an explantion from the factory. Since we bet our lives on these products, that's the least Schempp-Hirth can do. Even a "We're looking into it" would be appreciated. "CH" wrote in message ... it looks a bit suspicious that the latest incidents concerned gliders out of Schemp Hirth's Chechia licence fabrication only. CH ----- Original Message ----- From: "Chris OCallaghan" Newsgroups: rec.aviation.soaring Sent: Wednesday, September 10, 2003 12:29 AM Subject: Discus CS grounded in France Per the French Airworthiness Directive, "separation of the wing during normal operating conditions, possibly the result of a manufacturing defect." |
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