Second officer

From Memory Alpha, the free Star Trek reference.

A function aboard a starship, a second officer assumed command of the ship when both the captain and first officer were unavailable. It was common for a second officer on a Starfleet vessel to hold the rank of lieutenant commander. The second officer was a department head aboard the ship first, and a second officer second. He or she was rarely involved in the day to day command of the starship or starbase the way the captain or first officer was.

It was standard procedure for the second officer to accompany the away team. (TNG: "Time's Arrow")

[edit] List of second officers

• Lieutenant Commander Data
  • USS Enterprise-D
  • USS Enterprise-E
• Lieutenant/Lieutenant Commander Jadzia Dax
  • USS Defiant (NX-74205)
• Lieutenant Klag
  • IKS Pagh
• Lieutenant Commander Montgomery Scott
  • USS Enterprise
• Commander Charles Tucker III
  • Enterprise (NX-01)
• Lieutenant/Lieutenant Commander Tuvok
  • USS Voyager (NCC-74656)

Note: Spock seemed to be the second officer of the USS Enterprise in "The Cage", but this was not established in dialog.