Emirates Team New Zealand capsized their AC75 Te Aihe when sailing in strong winds yesterday morning, damaging their steering pedestal.
Sail-world reported the boat was quickly righted and towed back to Auckland following the incident in Tamaki Strait, off the southern coast of Waiheke around 9.30am.
The capsize occured in an early morning test session during a high-speed run when the AC75 loaded up at high speed and sailed under, in what Sail-world described as a "high-speed plough".
Conditions were beyond the wind limits for racing at the America's Cup.
Team NZ CEO Grant Dalton told Sail-World that they wanted to test what was possible in terms of top-end speed and to find out if there were any edges in extreme conditions for the AC75, ahead of the launch of their second AC75 and race boat.
The AC75 suffered damage to a steering pedestal in the incident - and returned to shore. Otherwise, Te Aihe would have continued training - as happened in their first capsize pre-Christmas when they trained for a further three hours after the incident.
Emirates Team NZ is the first team to have admitted to a double-capsize. They have previously reported a high-speed nosedive at around 50kts, after which the team again kept training.
US Challenger American Magic capsized in the same location a month ago. The other two challengers have been recorded in "near-miss" capsize incidents.
The Challengers are expected to begin launching their second AC75's later in October, with Team New Zealand expected to launch in November.
"The days are really counting down fast now, and every hour we can get on the water just helps us learn more and more," Team NZ's Glenn Ashby told Sailingscuttlebutt.
"And we are basically stepping into what is the most exciting time of the whole campaign as we start to see each of the teams second AC75's which will be their race boats. While there is still a lot of time for development, a big chunk of the AC36 puzzle is about to be put in place."
The first serious hit-out for all teams will occur in mid-December with the three day Christmas Cup. Racing in the Prada Cup begins a month later in mid-January.