One of our club members lost his GP cub yesterday. He, and other witnesses said that it was flying straight and level when "part of the tail flew off". The airplane then rolled inverted and went straight down into a field. I was fueling my plane so I didn't see it, but I heard a load pop just before it went down.

When we examined the wreckage, we found that both tips of the horizontal stabilizer were broken off at approximately the outboard joint. The elevators on both sides were gone. The rudder was intact, and the owner said that there had been no connection between the two elevator halves, yet they were both gone. Whatever happened, it effected both the left and the right hand side of the stabilizer/elevator equally and indepentently. My guess is that the failure was a result of elevator flutter.

Any thoughts?

I doubt it was flutter in the classic sense. Usually with flutter you'll hear a sort of buzzing or low frequency repetitive flopping sound before anything happens.

I gather the GP Cub is a giant model with separate elevator servos? The bit about no connection between the halves would bother me otherwise. From the description of the damage it sure sounds more like it's a speed related structural failure but that can happen without actual flutter. If the guy's glue joints were substandard or the tail bracing was not done right or the wood in the kit was substandard then anything can happen. Hard to say from here. Perhaps he didn't pin his hinges and THOSE popped out and resulted in the damage. He wouldn't be the first one that didn't do the hinges right and lost a model because of it.

Of course these are all just supposition based on what you wrote.

I could certainly be flutter. You are lucky if there is a warning buzz. It is sometimes sudden and catastrophic. Were the elevators in fact actuated by two servos, or a single servo with two pushrods?