Funny, McReady claimed that every Santana tandem ever made with a 1" steerer had a sleeve to protect against exactly that kind of failure:

http://tandem-fahren.de/Mitglieder/C...orkSleeve.html

One of my Cannondale tandems has a 1" steerer and one has a 1 1/8". The funny thing is that the head tube on both bikes measures the same outside diameter with calipers. The headset really steps down for the 1" fork.

I'm planning on upgrading the '92 to 1 1/8" very soon...

Scary pictures. Especially for a very heavy team (575lbs).

It does have a sleeve. Pretty short though, right above the crown. The break happened just above the sleeve.