On Friday, September 28, 2018 at 8:42:00 AM UTC-7, 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.

It's a bad thing anytime the tail feathers aren't pointing the way you like.. These accidents all ended the same way with the wings coming off from very high G-loads, but the evidence (such as it is) would seem to indicate mostly different starting points.

The Engen/Ivans Nimbus 4DM accident did not seem to involve any control circuit issue but, in the NTSB's judgement and according to witnesses, resulted from excessive Gs associated with recovery from a departure (spin or spiral dive) that started while thermalling.

The Nadler/cadet Arcus M incident apparently started with an uncommanded yaw (I believe flying straight) followed by an unrecoverable spiral dive. Maybe they will find the fuselage and get more information, but that sounds like a different root cause.

We may never know what happened with the Colacevich/Alto DuoDiscus accident, but a series of very high-G loops sounds more like a pitch control problem than a yaw control problem or a departure, though the chain of events up until these final maneuvers is unknown.

Sadly, there are a lot of different ways to end up with the wings coming off. It's important to learn from these tragedies, but for the moment I'd be hard-pressed to go down the path of some common root cause or a single design or construction defect with S-H two-seat gliders. These feel more like isolated incidents to me.

Andy Blackburn
9B