Date: Sunday, December 17 2006 01:09 pm From: To: europa-list@matronics.com Reply-To: europa-list@matronics.com Subject: Re: Europa-List: Vne Speed / Wing Load Test Attachments: Part 1: noname (TEXT/PLAIN 7bit 4347 bytes) Part 2: noname (TEXT/HTML quoted-printable 7230 bytes) Hi All,Casting my memory back some ten years ago.... to the testing we [Europa] did on the XS wings.... went something like this...First we built a steel jig to hold a single wing on, so that it was inverted, and tilted leading edge down , to simulate it flying normal way up / leading edge up [ worst case load is positive angle of attack, I forget the exact angle,] wing was fixed with the normal [ at that time] non pip pin spar pins, and the rigid drag pin sockets....... steel weights [10Kg & 5Kg] were then placed on the lower skin, with a carpet underlay to give a non slip surface, to a pre-determined plan to ultimately go past something like 12G.We supported the wing with a scafold tower arrangement whilst we were adding to the weights, going up in increments of ''G's'', taking away the support at each stage to measure deflection and twist, so rather than the required time [for the P.F.A.] unsupported of about 3 seconds, the wing was under load each time for probably a couple of minutes.......It got to something like 7G [at 1370 lbs AUW] the first try, before the tang of the spar ''walked off'' the spar pin and dumped the 3000 or so lbs of weight onto my workshop floor. [Hence my previous posting to the forum about leaving off the pip pin style spar pin in the port seatback bush?]Wing / spar undamaged, but rib/ lift & drag pin plates ripped.It was then decided to test wings in pairs, fitted to a fuselage, so a fuselage was set up on a pedestal, supported by the seat pan / seatback / baggage bay areas, in the same nose down / inverted stance. The height was set to allow spanwise deflection of the wings [ so the door sills were about 6' off the ground ] A strap was fitted to the port spar, in an attempt to contain the ''walking'' of the spars aft, and the swivel drag sockets and the ''tie bar'' were added. Loading [both wings together] went as planned, we were watching the spars through access holes cut in the fuselage, the wings passed the test[ forget the figure, something like 9.8] but it was obvious the spar strap was under stress. At this time, Francis Donaldson, and John Tempest [AKA Billy Bunter] of the P.F.A. wanted to see another test [I am still convinced for their own curiousity, rather than any truly technical reason] So we sourced and fitted the pip pins [as supplied in the XS kit nowadays] and did the test again. No problems, the pip pins were containing the aft movement of the spar tang. We kept going with the test, again, I can't recall the exact figure we went to, past 11G, I recall , when the wood core in the spar [between the two pin bushings] ruptured, and let the rovings in the spars twist over [ top cap to the bottom / bottom to the top] and something like 7000 lbs went on the floor this time. The spar cap rovings returned to their original positions, no visible damage, just the core was ruptured. So.... we picked up the weights, had a coffee or two, and started to reload the wings, and got to more than 3G before the spar cap rovings swapped place again.... so you can break the wing at + 12G, unload and it will return to position, and as long as you keep below 3G, fly yourself home. From memory, we did 3 sets of wings in during testing,[ P.F.A. kept moving the ''goal posts''.] All tests gave similar results. Years later, I managed to catch Francis off guard, asking what R.V. had to do to clear the RV10 to fly in the U.K ? His answer? Supply the paperwork to support the stress calculations... and have a couple of them flying....... when I enquired why Europa had to test 3 sets of XS wings, and dance through even more silly tests to get the MG wings cleared for over here [ when there were two allready flying in the U.S.A.] He went an embarrasing shade of red.... no answer then ? [The MG wings have been tested on the same single wing test rig [ beefed up, as we broke the rig itself the first time] to a much higher G load than the XS wings. You will not break either sets of wings. .re the VNE testing, Pete Clark did that, very carefully, increasing in small increments, at high altitude with a parachute..... well past the limit... but don't push YOUR luck in YOUR plane?Cheers, Nev.