WATERS SURROUNDING THE KOREAN PENINSULA (NNS) -- USS John C. Stennis and Republic of Korea navy destroyer Gang Gam-chan, worked together to land aircraft during exercise Foal Eagle, March 23. 

The landing signal officer has mere seconds to determine how low or high an aircraft is coming in and whether to signal the aircraft to land or to wave it off. 

On especially dark nights, when the LSO can't see the horizon line, a ship called the horizon reference unit is used to signify the horizon.

"When there is no horizon, a destroyer or cruiser will be brought about a mile-and-a-half off of the starboard stern of the carrier," said Lt. Bobby Richards, a tactical action officer for John C. Stennis, from Fredericksburg, Va. "The lights from the ship let the LSO determine an aircraft's positioning."

The HRU ship turns off all their lights except a mast light which indicates the horizon.

"Imagine you are in a dark gym and someone points a laser pointer at the wall and asks how high it is," said Lt. Cmdr. David Wrigley, an LSO from Carrier Air Wing 9, from Olive Branch, Miss. "You just don't know, especially when it's a few hundred yards away. It's the same for us when an aircraft is coming in. The HRU provides us a reference instead of just guessing." 

Moon brightness, fog and the sea roughness play a role in how critical it is to have an HRU and make clear communication a key factor.

"Communicating with another nation's navy isn't always easy," said Richards. "It all depends on the captain's experience being an HRU. If the unit hasn't done [it] before we will station them a little farther back and see how they operate. If it goes well we will pull them closer so the LSO has a better reference."

Training another navy's ship to be an HRU builds the interoperability between the nations, one of exercise Foal Eagle's goals.

"It's awesome that we can use another nation's navy as an HRU," said Richards. "Just because we are from a different country and serve different navies, we still do the same job."

Foal Eagle is a series of joint and combined field training exercises conducted by U.S. and ROK Combined Forces Command and United States Forces Korea (USFK) component commands (ground, air, naval, and special operations) taking place on the Korean peninsula and surrounding waters. The John C. Stennis Strike Group participated in the Maritime Counter Special Operations Force portion of the exercise, which wrapped up March 24.

Providing a ready force supporting security and stability in the Indo-Asia-Pacific, John C. Stennis is operating as part of the Great Green Fleet on a regularly scheduled 7th Fleet deployment.