In just about any military organization a recruit is exactly that, and it is not a rank, it is a pay grade, or could be described as a rate. Because there are no pay grades in Star Trek, it would constitute a rate at the same credit grade as a crewman. You don't actually have a legitimate rank until you pass this level.
Crewman - After training is complete, crewmen are assigned to a department, and being on-the-job training under supervision.
Senior Crewman - Promoted once a supervisor is satisfied with the level of training a crewman has received.
Master Crewman - Promoted once a supervisor is satisfied with the level of training a crewman has received.
This is where the 'rule of three' starts. A "Crewmen" usually do a basic school followed by a trade school (or technical proficiency).
Petty Officer 3rd Class - After time in service is satisfied, competent crewmen may be promoted to Petty Officer (PO)
Petty Officer 2nd Class - Rate/Rank assigned for duty/service requirements, and/or time in service.
Petty Officer 1st Class - Rate/Rank assigned for duty/service requirements, and/or time in service.
Again, 'rule of three' but now we are getting into higher levels of experience and training. Isn't there a DS9 book that references an Engineering specialty schools in San Francisco attended by O'Brien, or I am remembering incorrectly? You would have to imagine that in the way Star Trek seems to have ships that keeps crews together over long periods of time, at least half the enlisted crew on any Federation starship over 10 years old would be a Petty Officer.
Taking bits and pieces of dialogue from various sources (Crewman First Class Tarses, Yeoman 3rd Class Tina Lawton, Yeoman (Crewman) and one reference to an Engineer Grade 4 (which under the WWII Specialist System would be roughly equivalent a navy PO3, US Army Specialist or RN Able Seaman), make me favor a six-rank "rule of three" following roughly the RN model, rather than a USN/CG-esque 9-rank model:
Crewman (Specialist Grade 4) - US Army "Specialist" or USN/CG "striker". First substantive rank. Recruits and uniformed advisors would wear no insignia.
Crewman 1st Class/Petty Officer 2nd Class (Specialist Grade 3) - roughly PO3-PO2 (know as Leading Crewman/Hand in RN language), like US Army Specialist v Corporal, which rank is used may depend on rating, for example Yeoman or Mess Specialists might be PO2s, whereas Medics and Engineers (who require more advanced training), would still be regarding as "advanced trainees" and would therefore be "Crewman 1st Class"?
Petty Officer [1st Class] (Specialist Grade 2) - Equivalent to Petty Officer 1st Class (USN) or Petty Officer (RN).
Assuming you meant that the
ship or mission was "ten years old" rather than the crewmen in question, I agree that most enlisted personnel would rank with modern Petty Officers within ten years of enlisting (though in the scheme above this would also be dictated by the "promotion slot" availablity in all likelihood)
Chief Petty Officer - POs who have served xxx years advance to Chief and are able to work alone. By this time, Chiefs are expected to know most, if not all jobs and duties specific to their department.
Senior Chief Petty Officer - Rate/Rank assigned for duty/service requirements, and/or time in service.
Master Chief Petty Officer - Chiefs serving in senior positions or jobs that require them to oversee their respective departments.
These are ranks. On a starship it is easy to see how each Department might have 1 Chief Petty Officer, and each Section might have one Senior Chief Petty Officer.
An example might be how a ship has multiple Engineering Departments responsible for different Engineering requirements on a starship (the IT guy, the Warp Core guy, the Transporter guy, etc.); and each distinct Engineering Department would have a Chief Petty Officer led by a Department head being a LT. In that context, the primary role of the Chief Petty Officer would basically be to teach the Ensigns and help the LT lead the enlisted men in the Department. The entire Engineering Section of the ship would like be led by a Senior Chief, with the Chief Engineer represented as a LCDR or CDR, depending up on the vessel size/type. Just as there is one Captain per ship, there is only one Master Chief per ship - basically the senior enlisted officer."
I mostly agree with this, other than to suggest that the
Section Leading Specialist would be the Chief (Specialist Grade 1), with the
Department Leading Specialist would be the Senior Chief or even Master Chief depending the size of the Department/Ship (no longer a Specialist
per se but with a decent understanding of all jobs within the Department). Department
Officers to my mind would be two to three ranks below the rank of the Commanding Officer, depending on whether they are also Bridge Officers (So LCDRs on Explorers, LTs on medium-sized Cruisers/Frigates, LTJGs or even
experienced ENSs on Escorts/Science Vessels/Auxiliaries)
Command Master Chief (of the Ship/Station) - The most senior serving Chief onboard a Starship or Spacestation.
This is where I would deviate from Levi. "Command Master Chief" is usually associated with a command element, and that command element would be a Flag Officer (Admiral rank). A "Command Master Chief" would be more likely found in a squadron command associated with a Commodore (a title, not a rank), or within the organization of a command structure rather than as part of a ship or bases command structure. Logistics Command for a Sector Block or Starfleet Security for a Sector, if either was led by an Admiral, would have a Command Master Chief, but the general idea is you would have a Command Master Chief as the enlisted counterpart to a Flag Officer (Admiral) or Commodore (Senior, post-Command Captain), not a station or ship command (Captain, CDR).
According to USN policy a "Command Master Chief" should be assigned to any command of 250 personnel or more. Which would include all the
Enterprises (apart from NX-01), but not
Voyager or
Defiant (which would rather have a Command Senior Chief or even a Command Chief). O'Brien's title of "Chief of Operations" might be the Starfleet equivalent via the Submarine Service's "Chief of the Boat" title. The Senior Enlisted Advisor to an Admiral (rather an temporary Commodore/Taskforce Commander) would be an Area CMC, Force CMC or even Fleet CMC depending on assignment, with the 'CMC of the Starfleet' as the terminal title (though somewhat in line with current policy in the DoD (US) and MoD (UK), additional personnel with the same
rank might be held by the SEA to the Head of Starfleet Operations, Starfleet Intelligence, Starfleet Corps of Engineers et al.