![]() |
If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
|
#1
|
|||
|
|||
![]()
I bought a G-103 that had been in a hangar fire in Georgia, Peach State Club. We needed a left wing and the photos showed what looked like a useable left wing on a fuselage with canopies that had been hot enough to melt the canopies. Both canopied draped down like a tarp, but it was the new shape of the plexiglass! The outer skin of the left wing top was blistered and had to be replaced, but the spar caps were undamaged. I figured the wing hadn’t been in 350 degree environment long enough to affect the more dense spar cap. We proof-loaded the wing and it took 5.3 G’s with flying colors! That was some 25 years ago and that ship is still flying today!
Just a little data point about how much heat a fiberglass structure can take, JJ |
#2
|
|||
|
|||
![]()
On Friday, April 19, 2019 at 7:10:14 AM UTC-7, wrote:
I bought a G-103 that had been in a hangar fire in Georgia, Peach State Club. We needed a left wing and the photos showed what looked like a useable left wing on a fuselage with canopies that had been hot enough to melt the canopies. Both canopied draped down like a tarp, but it was the new shape of the plexiglass! The outer skin of the left wing top was blistered and had to be replaced, but the spar caps were undamaged. I figured the wing hadn’t been in 350 degree environment long enough to affect the more dense spar cap. We proof-loaded the wing and it took 5.3 G’s with flying colors! That was some 25 years ago and that ship is still flying today! Just a little data point about how much heat a fiberglass structure can take, JJ I remember seeing those Peach State gliders tied down at Williamson after the fire. Have also flown an ASH25Mi that was previously an ASH25M and involved in an engine compartment fire. The factory replaced the fuselage, worked on the wings, got it flying as good as ever. Jim |
#4
|
|||
|
|||
![]()
On Friday, April 19, 2019 at 7:10:14 AM UTC-7, wrote:
I bought a G-103 that had been in a hangar fire in Georgia, Peach State Club. We needed a left wing and the photos showed what looked like a useable left wing on a fuselage with canopies that had been hot enough to melt the canopies. Both canopied draped down like a tarp, but it was the new shape of the plexiglass! The outer skin of the left wing top was blistered and had to be replaced, but the spar caps were undamaged. I figured the wing hadn’t been in 350 degree environment long enough to affect the more dense spar cap. We proof-loaded the wing and it took 5.3 G’s with flying colors! That was some 25 years ago and that ship is still flying today! Just a little data point about how much heat a fiberglass structure can take, JJ There is a reason why fiberglass gliders are painted white: they can't withstand high temperatures. There is a critical temperature called the "glass transition temperature" which is where the plastic starts transitioning from a solid into a liquid. A typical glass transition temp for fiberglass is 100C, well below the temps seen in that hanger fire. The fact that they canopy melted demonstrates that the temp was that high for some period of time.. https://en.wikipedia.org/wiki/Glass_transition |
#5
|
|||
|
|||
![]()
On Saturday, April 20, 2019 at 11:07:40 PM UTC-7, 2G wrote:
There is a reason why fiberglass gliders are painted white: they can't withstand high temperatures... It's a bit more complicated than that. We could have blue or black or red composite gliders if we really wanted. Unsurprisingly it comes down to economics. There are epoxy resin systems that can be used to achieve a Tg well above those achieved by darkly colored surfaces exposed to direct sunlight. We're using one such system right now on some aircraft parts that for a variety of reasons must be painted black. However, compared to the MGS285 system that has become the de facto standard for European sailplane manufacture, those high-temperature systems are generally some or all of: * More expensive * Harder to mix and use * More toxic * More sensitizing Furthermore, for some such systems, the parts must be subjected to elevated post-cure just to make them tough enough to demold. And then they must get an even hotter post-cure after all the parts are assembled. All of these reasons that high-temperature systems are a pain to use make them more expensive to use, and for no easily justified reason. There is a critical temperature called the "glass transition temperature" which is where the plastic starts transitioning from a solid into a liquid.. A typical glass transition temp for fiberglass is 100C, well below the temps seen in that hanger fire. The fact that they canopy melted demonstrates that the temp was that high for some period of time. https://en.wikipedia.org/wiki/Glass_transition Our tests have shown that exceeding Tg does not necessarily weaken a composite structure; depending on a variety of factors it will quite likely regain all its former strength and stiffness once it cools down. Furthermore, the melting of the canopy is not necessarily an accurate indicator of the temperatures reached by the rest of the structure; clear acrylic plastic absorbs a lot of wavelengths that reflect off of a white painted surface. --Bob K. |
#6
|
|||
|
|||
![]()
On Sunday, April 21, 2019 at 8:04:21 AM UTC-7, Bob Kuykendall wrote:
On Saturday, April 20, 2019 at 11:07:40 PM UTC-7, 2G wrote: There is a reason why fiberglass gliders are painted white: they can't withstand high temperatures... It's a bit more complicated than that. We could have blue or black or red composite gliders if we really wanted. Unsurprisingly it comes down to economics. There are epoxy resin systems that can be used to achieve a Tg well above those achieved by darkly colored surfaces exposed to direct sunlight. We're using one such system right now on some aircraft parts that for a variety of reasons must be painted black. However, compared to the MGS285 system that has become the de facto standard for European sailplane manufacture, those high-temperature systems are generally some or all of: * More expensive * Harder to mix and use * More toxic * More sensitizing Furthermore, for some such systems, the parts must be subjected to elevated post-cure just to make them tough enough to demold. And then they must get an even hotter post-cure after all the parts are assembled. All of these reasons that high-temperature systems are a pain to use make them more expensive to use, and for no easily justified reason. There is a critical temperature called the "glass transition temperature" which is where the plastic starts transitioning from a solid into a liquid. A typical glass transition temp for fiberglass is 100C, well below the temps seen in that hanger fire. The fact that they canopy melted demonstrates that the temp was that high for some period of time. https://en.wikipedia.org/wiki/Glass_transition Our tests have shown that exceeding Tg does not necessarily weaken a composite structure; depending on a variety of factors it will quite likely regain all its former strength and stiffness once it cools down. Furthermore, the melting of the canopy is not necessarily an accurate indicator of the temperatures reached by the rest of the structure; clear acrylic plastic absorbs a lot of wavelengths that reflect off of a white painted surface. --Bob K. Yes, it is always more complicated than what most people are interested in reading. But in the case of this glider, the manufacturer clearly considered it to be unairworthy, period. Further, without having the glider fully instrumented with thermocouples, no one can say how hot, and for how long, each part of the glider got. Absent such data, the only safe course of action is to declare it unairworthy unless the manufacturer details an inspection and test regimen that can assure the glider's safety and continued airworthiness. Additionally, changing the serial number is a blatant effort to disguise the damage history of the glider and constitutes fraud, in my opinion. Tom |
#7
|
|||
|
|||
![]()
Speaking of complicated, I have direct knowledge of this one, and it's a lot more complicated than you realize. Just know that the manufacturer declaring it's unairworthy has nothing to do with anything, other than them not getting their way. I'll leave it at that.
|
#8
|
|||
|
|||
![]()
On Sunday, April 21, 2019 at 9:26:20 PM UTC-5, Echo wrote:
Speaking of complicated, I have direct knowledge of this one, and it's a lot more complicated than you realize. Just know that the manufacturer declaring it's unairworthy has nothing to do with anything, other than them not getting their way. I'll leave it at that. On Sunday, April 21, 2019 at 9:26:20 PM UTC-5, Echo wrote: Speaking of complicated, I have direct knowledge of this one, and it's a lot more complicated than you realize. Just know that the manufacturer declaring it's unairworthy has nothing to do with anything, other than them not getting their way. I'll leave it at that. I must admit, It's not my glider, nor is it my $60K, But, How does the type certificate holders specific determination Not have anything to do with it? That information would surely matter to an insurance company, and should concern any potential buyer. I have no doubt any future incident with this particular airframe would draw the lawyers like Buzzards to a carcass. Makes me wonder if the last inspector to sign it off is comfortable, and did he know? and will the next one be made aware? I'd bet Five bucks the owner was the last A&P to sign off this glider. I apologize if my skepticism is showing. P.S. respond here if anyone was the last inspector and I owe you five bucks.. |
#9
|
|||
|
|||
![]()
On Sunday, April 21, 2019 at 7:26:20 PM UTC-7, Echo wrote:
Speaking of complicated, I have direct knowledge of this one, and it's a lot more complicated than you realize. Just know that the manufacturer declaring it's unairworthy has nothing to do with anything, other than them not getting their way. I'll leave it at that. As I said before, things are ALWAYS more complicated than they seem. But your assertion that the manufacturer's opinion on airworthiness is completely irrelevant is, simply, bizarre. Do you realize that the FAA could declare the glider unairworthy based on that opinion alone? This is not hypothetical - it happened to the Blanik L13. Unless you are willing to provide more information I will stick with my origin assessment. Tom |
#10
|
|||
|
|||
![]()
Sure. Ok. The manufacturer tried to buy it from the insurance company, but failed to come up with the money. Therefore, it went to the next bidder. It was only THEN that they decided to deem it unairworthy. Also of note is who the OP works for. The circumstances of the fire itself are also pretty interesting, considering what was conveniently removed beforehand, but I'll choose not to speculate on things I don't know to be factual.
I've flown the airplane in question. I've also witnessed it being tested to G loading spec, and seen in during refurbishment. I have zero issue with its structural integrity. If ANY of you have a mechanical engineering background and know more then the typical know-it-all soaring pilot, with firsthand knowledge of the airframe, I'm all ears. |
|
Thread Tools | |
Display Modes | |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Pipistrel Taurus: Club Glider? | Phil Chidekel | Soaring | 3 | February 29th 16 04:05 AM |
Glider equipment for sale | Roger Fowler[_3_] | Soaring | 0 | August 2nd 14 06:05 PM |
GLIDER 4 SALE | BobD | Soaring | 0 | March 16th 14 08:45 PM |
Glider for Sale | 5 ugly | Soaring | 1 | December 8th 13 12:57 AM |
Taurus Glider Ready for Flight Tests | Michael Coates | Soaring | 5 | April 5th 04 04:05 AM |