Chief engineering officer
The chief engineering officer, also known as the chief engineer or the engineering officer, was the officer in charge of all engineers and engineering-related duties aboard a vessel.

The chief engineer's duties ranged from making the duty shift roster for engineering personnel to advising the captain on possible solutions for certain technical problems. 

In general, the chief engineer was an officer with enough experience in his or her own field of expertise and with seniority over the rest of the engineers. A chief engineer was also a member of the senior staff and was accountable for the overall performance of the vessel.

In the context of engineering, the chief engineer could be seen giving orders to persons who would ordinarily outrank him, such as the second officer. For example, Data regularly took orders from Geordi La Forge in engineering contexts, even though as the second officer Data outranked La Forge in absolute terms. ( )

The captain of a Starfleet starship had the prerogative to appoint someone to the post of chief engineer even if he or she did not have the seniority which normally would apply to this function. Persons with vast experience and engineering knowledge but no appropriate Starfleet rank could be appointed as chief engineer in this manner. ()

Some noted chief engineers in Starfleet history were:

 Commander Charles Tucker III of 
 Commander and Captain Montgomery Scott of the  and 
 Lieutenant Commander Geordi La Forge of the  and the 
 Senior Chief Petty Officer Miles O'Brien of the , also chief of operations of Deep Space 9
 Lieutenant junior grade B'Elanna Torres of the 

The Starfleet of the alternate reality established in 2233 by the temporal incursion of the Romulan Nero had one note worthy chief engineer:
 Lieutenant Commander  of the  (NCC-1701)

List of chief engineers 
Named
Argyle
 (2364)
Bjorn Bensen
 Velara Base (2364)

 (2259)
Joseph 
 (2360)
Donald Kaplan
 (2370)
Kelby
 (2154)
Joshua Kelly
 (2369)
Geordi La Forge
 (2365-2371)
 (2372~2380)

 (2364)
Louvier
 (2257)
Leland T. Lynch
 (2364)
MacDougal
 (2364)
Nog
 (2374)
Miles O'Brien
 (2371-2375)
 (2375)
Olson
 (2258)
Reginod
Mondor (2365)
Jett Reno
 (2257)
Jacques Romaine
Starfleet, retired (2269)
Montgomery Scott
 (2265-2285)
 (2285, Captain of engineering)
 (2286-2293)
Montgomery Scott (alternate reality)
 (2258-2263)
 (ca. 2260s)
Solin
Seleya (2153)
Tavana
  (2373)
B'Elanna Torres
Val Jean (2371)
 (2371-2378)
Charles Tucker III
 (2151-2161)
 (2154)
Vanderberg
 Janus VI colony (2267)
Unnamed
 Hera chief engineer
  (2370)
 Ki'tang chief engineer
  (2375)
 Pegasus chief engineer
  (2358)
 Voyager chief engineer
  (2371)

Appendices

Background information 
Argyle appeared to have replaced MacDougal as chief engineer and was apparently replaced himself by Lieutenant  prior to , who was in turn seemingly replaced by Leland Lynch by . However, Commander William T. Riker's line in  that engineering matters were overseen by "one of our chief engineers, in this case, [Mr.] Argyle" seems to imply that the ship had more than one chief engineering officer at the time. Therefore, it is possible that MacDougal and Argyle both served as chief engineer simultaneously. This practice of having more than one chief engineer seems to have come to an end by 2365, when Geordi La Forge became the sole chief engineer of the Enterprise. It is also however possible that the term chief engineers actually applied to the most senior engineers (possibly the three most senior, as typically three shifts would be run in a day so there would have to be at least three engineers who would run the department during their own shifts), however, chief engineer was still an individual position in its own regard. This multiple application of titles has been seen before with regard to the title of commanding officer, which could be used to apply to the single position of the highest-ranking officer in command of a starship or starbase or also to the person whom one directly reported to in the chain of command or in a department.

Apocryphal chief engineers 

 (Vulcan's Glory; The Rift; Desperate Hours)

 (Star Trek: Titan)

 (Voyager relaunch)

USS Enterprise-F (Star Trek Online)

External link 
 

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Occupations
Mining