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#91
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Winch Launch - Can it pull your wings off?
On Aug 22, 9:09*am, Chris Nicholas wrote:
We had a Foka 4 at my club in the 1970s, with this sort of expanding bolt. My recollection is that the owners used to count the number of turns to get the full expansion. If the number of turns was correct, and the top bolt was visible in the right place, then the invisible lower one must also have fully engaged with the lower lugs. Might be a useful check in the absence of a visible sign. (I'm not saying that this had anything to do with the recent accident - the latter may have been caused by something different.) It's an assumption that if the correct number of turns have been done and the top bolt is seen to be correctly expanded that the lower bolt has also correctly expanded. I gather that in the US Cobra accident there was some sort of fault in the bolt such that the top part expanded correctly but the bottom didn't, and it is very hard to see. Personally I am so glad I fly a relatively modern glass glider with two horizontal main pins where the only mechanism is me pushing them home and then crossing and latching their 'handles'. |
#92
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Winch Launch - Can it pull your wings off?
On Aug 23, 9:52*am, Cats wrote:
On Aug 22, 9:09*am, Chris Nicholas wrote: We had a Foka 4 at my club in the 1970s, with this sort of expanding bolt. My recollection is that the owners used to count the number of turns to get the full expansion. If the number of turns was correct, and the top bolt was visible in the right place, then the invisible lower one must also have fully engaged with the lower lugs. Might be a useful check in the absence of a visible sign. (I'm not saying that this had anything to do with the recent accident - the latter may have been caused by something different.) It's an assumption that if the correct number of turns have been done and the top bolt is seen to be correctly expanded that the lower bolt has also correctly expanded. *I gather that in the US Cobra accident there was some sort of fault in the bolt such that the top part expanded correctly but the bottom didn't, and it is very hard to see. Personally I am so glad I fly a relatively modern glass glider with two horizontal main pins where the only mechanism is me pushing them home and then crossing and latching their 'handles'. In the US Cobra accident the taper bolt mainpin expanded correctly, but wasn't centred due to wear in the central locating bush. Hence it didn't fully engage in the bottom wing root fitting. This failure could have been prevented by a visual inspection, but apparently it is difficult to see the bottom fitting in this type of glider. I will repeat that there is nothing intrinsically wrong with this rigging system, as long as it is properly maintained and a visual check is made after rigging. Derek C |
#93
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Winch Launch - Can it pull your wings off? - BGA safety alert
Following the recent break up of a Foka 4 glider during a winch
launch, the British Gliding Association has issued the following safety alert. Please note that it also applies to a number of other glider types fitting with expanding taper mainpins. http://www.gliding.co.uk/bgainfo/saf...lert020910.pdf Derek C On Aug 23, 10:19*am, Derek C wrote: On Aug 23, 9:52*am, Cats wrote: On Aug 22, 9:09*am, Chris Nicholas wrote: We had a Foka 4 at my club in the 1970s, with this sort of expanding bolt. My recollection is that the owners used to count the number of turns to get the full expansion. If the number of turns was correct, and the top bolt was visible in the right place, then the invisible lower one must also have fully engaged with the lower lugs. Might be a useful check in the absence of a visible sign. (I'm not saying that this had anything to do with the recent accident - the latter may have been caused by something different.) It's an assumption that if the correct number of turns have been done and the top bolt is seen to be correctly expanded that the lower bolt has also correctly expanded. *I gather that in the US Cobra accident there was some sort of fault in the bolt such that the top part expanded correctly but the bottom didn't, and it is very hard to see. Personally I am so glad I fly a relatively modern glass glider with two horizontal main pins where the only mechanism is me pushing them home and then crossing and latching their 'handles'. In the US Cobra accident the taper bolt mainpin expanded correctly, but wasn't centred due to wear in the central locating bush. Hence it didn't fully engage in the bottom wing root fitting. This failure could have been prevented by a visual inspection, but apparently it is difficult to see the bottom fitting in this type of glider. I will repeat that there is nothing intrinsically wrong with this rigging system, as long as it is properly maintained and a visual check is made after rigging. Derek C- Hide quoted text - - Show quoted text - |
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