Engineering
Modules
Drones
Engineering frigates passively construct drones, able to have a maximum of two out at a time. Drones will fire on enemies within 1700m and will repair the engineer's shields if they drop below 50%. In addition, drones can be activated to overload and restore a burst of shield to all allied ships (NOT including your own) in a small radius. The radius is 500m as of OBT version 0.9.9. After activation, the drone is destroyed and must be replaced through reconstruction.
Engineering Modules
Nanodrone Cloud and Mass Shield Generator
The Nanodrone Cloud and Mass Shield Generator slowly restore hull and shield respectively to ships around the engineer, including itself. Nanodrone clouds and mass shield generators do not stack from multiple engineering frigates.
Energy Emitter
The Energy Emitter passively restores capacitor energy to ships around the engineer, including itself.
Autonomous Repair Station and Autonomous Charging Station
The Autonomous stations are dropped and will repair the hull or shield respectively of the lowest ally in their range. Autonomous stations are destructible.
Warp Gate
The Warp Gate module deploys a warp gate structure that can be used by the engineer and allies to rapidly travel 5km directly ahead. Unlike the Recon's Microwarpdrive the distance travelled is fixed and uncontrollable, so make sure that rock in the distance is definitely more than 5km away before using it.
Static Barrier
The Static Barrier drops a solid shield directly in front of the Engineer. The shield will eventually fade or can be destroyed if it takes too much damage.
Factions
Engineering frigates are mainly manufactured by the Federation, but the Empire also have some on offer. Empire engineers are tougher, particularly their hull strength, while Federation engineers have balanced hull and shields, are faster and have better capacitors.
The Federation Vanguard produce most Mk 3 engineering modules, with the Empire Legion producing a few.
Role
Engineering frigates are very much support ships. The fact that they repair ships around them makes them priority targets for enemies, especially in big fights. Engineers must walk a line between being in a good position to give their buffs and being too exposed to attack. Engineers have the most varied choice of modules, having to choose between shield and hull repair modules or utility modules like the Warp Gate, meaning difficult fitting choices. While engineers are tough and have good self repair, they lack defensive abilities, so will likely die to attackers eventually without support, and will die quickly to focused fire that can overcome their regeneration.