Lieutenant Logan is the Enterprise-D chief engineer who tries to take command from Geordi La Forge while the ship is under attack above Minos.
Logan appears in The Arsenal of Freedom. With Picard, Riker and the rest of the senior staff stranded on Minos, the junior La Forge is left in charge of the Enterprise-D when an automated weapon begins attacking it from orbit.
Logan comes to the bridge to argue that the ship should leave, and then that he should take over because he outranks the acting captain. La Forge refuses, pointing out that Picard gave him the bridge and only Picard or Riker can relieve him.
La Forge later separates the ship, giving Logan command of the saucer section with orders to take it to safety at Starbase 103, while he returns in the stardrive section and destroys the weapon in the planet's atmosphere.