I'd guess they are ground engineers who are trained and qualified as Flight Engineers. As there is no simulator, I'd guess training is done on the aircraft, same for the pilots. In reality, I imagine there are less that five flight engineers trained for the aircraft bearing in mind they fly quite sporadically. The majority of the flight engineer equipped aircraft most disapeared from airline fleets around 20 years ago so recruitment would be an issue otherwise.
Last edited by The Flying Stool; 21st Jan 2022 at 13:38.