FWIW I am also aware of the four -- on flights 1, 2, 4 and 19.

Mine was on flight 19 back in December. The manufacturer was responsive etc., and given it was flight 19 I ultimately took it on the chin and hoped (for all of us) I had just been unlucky. It didn't have the rear former. IMHO I had built it solidly, well, and to instructions, and it had had no 'incidents' in flight (or ground contact!!) -- I would regard myself as a competent Expert level competitor and this was F3A plane number 5 I have built. One of my colleagues had flown most of the F schedule with it the flight before, and there were no signs of damage. But given it was flight 19 you never know -- the manufacturer (especially their local rep) were very professional and responsive, and there are so many different things outside the manufacturer's control through building, equipping and flying that I erred on the side of not taking it broadly public at the time. I have a number of colleagues who are flying them with no issues at all (and flying them hard!).

The failure was more severe than the first two in the that the whole tail section broke off in front of the fin/stab while pushing into the outside loop section at the start of the triangle rolling loop. The view is it had to have been flutter to cause such extensive and sudden damage. What caused it is unclear -- is it fin/rudder aerodynamics, the bottom hinge (which had worked very slightly loose -- not in glue failing, but in the balsa around it softening and allowing some minor movement under force)?

One thing I will note (and I am not an expert in composites) is that the Impact construction is more like an egg shell than other models I have -- in that when in its normal shape it is very rigid/strong, but when compromised it fails easily. The outer and inner 'layers' that sandwich the core are very light and somewhat brittle -- and are very easy to both pull off and tear by hand with little force. This is quite different to the very 'tough' combination of Kevlar/Poly foam/glass cloth of my Hydeaway -- which survived a mid air that removed a wing and put it nose first into a dry swamp. There was some compression failure in the foam centre of the sandwich on one side of the rear where the tail had clearly swung round on impact -- but the inner and outer cloth were intact and it was quite fixable. Unfortunately the same could not be said of the Impact -- but it did go close to straight into hard ground from 400 foot (bent crankshaft, stripped servo gears etc.).

I have since become aware of one that failed in almost the same way -- except it had the former and had been built by a very talented and experienced builder in full knowledge of the warnings around rudder hinges etc. While I remain happy to take mine on the chin given its larger number of flights, I will aim to eliminate all possible risk areas on the second one I am building (so replace rudder, traditional hinges, ladder in fuz), and would suggest others do similarly until there is a clear explanation for these incidents. I won't take the risk again. I am also glad I was flying at an isolated field and no where near a populated area.

Tough and light are achieveable in F3A building!!

David