America's Cup Race 13: USA Beats NZL
Photos from Gilles Martin-Raget and John Eric Mangino

A pivotal moment in Race 13 was this downwind cross by Emirates Team New Zealand, which drew a penalty for not keeping clear of Oracle Team USA.

 Oracle Team USA is heeling downwind on starboard gybe.  ETNZ is to the left, just out of from on port.
Photo:©2013 Isailmedia Images/John Eric Mangino

ENTZ doesn't gybe away, and Oracle is coming faster than they expected.  ETNZ on port is required to keep clear of Oracle.  If ETNZ can cross their track without Oracle needing to alter course, they will be okay.
Photo:©2013 Isailmedia Images/John Eric Mangino
 

 ETNZ is committed, they can't gybe now, either, without fouling.
 Photo:©2013 Isailmedia Images/John Eric Mangino
 

Collision course.  USA is going 25 knots according to telemetry.  Oracle has right-of-way, but needs to avoid contact.
Image:©2013 ACEA/Photo: Gilles Martin-Raget
 

 Oracle starts to alter course, heading up to get behind ETNZ.
Photo:©2013 Isailmedia Images/John Eric Mangino
 

Oracle is turning to starboard.  Note angle of windward rudder. Image:©2013 ACEA/Photo: Gilles Martin-Raget
 

Still turning. Image:©2013 ACEA/Photo: Gilles Martin-Raget

Oracle clear behind ETNZ waves the electronic "Yankee" flag, protesting ETNZ for not keep clear.  The umpires take time, but penalize ETNZ.  NZL has already lost distance on their gybe, but with the penalty on top of it, they come in late to the downwind gate and Oracle ahead of them switches sides at the last second, leveraging the gains from the penalty into even more margin as they start the upwind leg.  Photo:©2013 Isailmedia Images/John Eric Mangino
 

Also:  View the animated tracking of the incident as seen by the America's Cup Umpires (mp4)

The Racing Rule applicable in the incident above is Rule 10, one of the most basic right-of-way requirements:

"Rule 10. ON OPPOSITE TACKS. When yachts are on opposite tacks, a port-tack yacht shall keep clear of a starboard-tack yacht." -- Racing Rules of Sailing for the America's Cup (RRSAC)

"Keep Clear" has a specific definition in the RRSAC:

"Keep Clear: One yacht keeps clear of another if the other can sail her course with no need to take avoiding action...."  -- RRSAC Definitions
 

Links of Interest:
See CupInfo's America's Cup 2013 Main Page Race 13 Report