On Friday, September 28, 2018 at 10:42:00 AM UTC-5, wrote:
I've been mulling this over for years now. We have had 3 similar accidents, Ivens/Egon, Naddler/cadet, Sergio/Jim......all high speed dive, wings bent up into a U shape followed by one or more wing separation!............all in the same basic fuselage (SH 2 place), all with motors. The motors were not in use, so we can eliminate the actual motor, but all fuselages had a large opening in the aft fuselage to allow for the engine. The fuselages were strengthened around the hole, but maybe not enough for a high speed pullout? Let's say these ships got into a high speed dive for whatever reason, maybe as simple as both pilots thought the other guy was flying! Anyway, they realized the problem and pulled hard to get the nose up. Let's say they pulled about 5 G's. What is the aft boom going to do under a 5 G load? It's going to try and bow up a little, but the designed strength prevents any noticeable movement except around the engine hole. What might be going on there? The lower skin is holding in tension, but the upper skin is trying to fail under compression load. Where is it likely to fail? Around the engine hole that buckles slightly inward. This buckling allows the boom to bow upwards, slightly. Now let's look at what this buckling does to the horizontal stabilizer, it digs is slightly and therefore increasing the G load, which increases the bowing in of the engine hole............more G's, more buckling.......you get the picture! I could see this resulting in a 2 second loop
Something to think about,
JJ

Fuselage will bend down both in front of and behind the wing during high g loading. Tail pushes down to make the nose go up. Top of fuselage should be in tension during high positive g maneuvers. So, I don't think fuselage flexure is a contributor. Could be wrong, but I think that is the wrong tree to bark up.

Steve Leonard