I also would like to know what "recent accident" means as stated in the SB. Was this SB prompted by the original accident in the upper midwest two to three years ago, another more recent mishap or additional testing (either analytical testing or actual destructive testing) as performed by Van's Engineering? Please?
All of the above Marty.
Re-evaluation was prompted by a more recent accident. Do an NTSB search using "RV" as the model and you should find it (If I remember right, the make/model info was inputted incorrectly).
A huge amount of resources were dedicated to this project, including, but not limited to, materials and part testing to destruction, along with a full blow dynamic test failing the gear out of an actual fuselage.
One thing I hope people will keep in mind is that there are an infinite number of overload scenarios. The failure mode is effected by impact angle of attack (relative to the ground), fwd velocity, etc. This all translates into some specific vector angle of impact.
Examples - the most horizontal vector would be clipping a brick wall with the main gear in level flight. The most vertical vector angle would be the airplane dropping straight down on to the gear (nearly impossible if the airplane was in flight before hitting the ground). The normal reality will be some where in between. In this accident, it appears the vector was much closer to horizontal than vertical.
In the end, it doesn't really matter. If a situation
could occur, it needs to be designed for.
I am not going to go into any more detail than that, but I will say that because it is sometimes hard to design for loads and situations that are not fully known (Ask Boeing about that regarding their development of the 787), there is a high level of confidence (proven by physical testing) that this fuel tank mod. should have a broad margin of safety beyond the loads that have been physically tested and verified.
I understand peoples frustration, which is why everything that could be done to ease the pain, has been (designing a modification that would be as easy of a retrofit as possible, supplying the parts for free, allowing it to wait until a condition inspection is being preformed, etc.).
The RV-12 has definitely been evolving since its introduction. That has caused some frustrations along the way, but I believe most would agree that it is now reaching full maturity and stands at or near the top (depending on the criteria you are judging by) when ranked against all others in this class of airplane.