America's Cup challengers American Magic have warned that faults in onboard data systems threaten the credibility of racing on Auckland's Waitematā Harbour and Hauraki Gulf.
Starting Friday, three teams will contest the Prada Cup series, with the winners earning the right to challenge Emirates Team NZ for the 'Auld Mug'.
This week, the combatants are putting their AC75 foiling monohulls through their paces, before on-water hostilities begin.
But the Americans have told an America's Cup arbitration panel that challengers have little confidence in the electronic race management system that provides vital information to crews on their boats.
The system has been provided to competitors by event organisers, but every team encountered problems during the world series, reducing some races to uncompetitive affairs.
"The race management system is a complex electronic system supplied and provided by the organisers, and it includes the media system on board each AC75," American Magic has told the arbitration panel.
"For the crew to see the onboard instrument data while racing, such data must first pass through the media system, and from there to the displays and screens of the AC75.
"Furthermore, all racecourse information and all umpire calls are managed and received by a competing AC75 in the race management system. In short, with the failure of the race management system, no fair racing is possible.
"All competitors have experienced serious failures, which fundamentally curtailed their ability to race and foil the boat safely. New York Yacht Club American Magic have serious concerns that failures will occur during racing."
After the opening day of world series racing, Ineos Team UK complained that their foiling system - also provided by Team NZ - had malfunctioned, affecting their ability to compete. The claim earned a swift rebuke from the defenders.
Racing was also delayed on day three, when management made a late change to the course and took more than an hour to clear spectator craft.
But race director Iain Murray has assured teams that the problems encountered during the world series will be ironed out before racing begins.
"Having America's Cup boats racing amongst the crowd is not acceptable," he says. "It can't happen and it won't happen.
"In general, the whole race management, getting the marks out there... we've had some things which need an upgrade and maintenance.
"There's always going to be software upgrades and debugging. Getting out today and tomorrow, and testing all of that is important before race day."
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