I work as an ATC and came to few impressions and ideas about the game. I hope devs can read this thread and maybe think about these matters for their next version.
There are some minor things that probbably everyone is aware of (for example possibility to backtrack, cross runway instruction etc.) but here I want to discuss the technology of ATC work. I think this game gives quite nice balance between realism and playability. While learning the correct prhaseology and the airline names may take few hours but after that everyone should be able to control the traffic pretty effectively. This is where realism kicks in. I'd really like to see something like an expert setting.
Probbably most people play the game mainly watching the ground movement radar screen sometimes with the help of air radar. Tower3D is designed to be played this way. On the radar screen we see all aircraft, their callsigns and paths. But this is not how a real ATC works.
Ok there are some advanced ASMGCS systems which work in similar fashion but they are designed mostly for low visibility conditions and are still quite rare. Most controllers work with their windows and outside view which in Tower3D seems to be only a feature to make the game prettier.
What I would like to see is an expert mode in which I can turn of the ground movement radar and still work effectively. Actually we can do it on TIST even in current state but other aerodromes seem out of reach.
What we need?
1) We need to rework flight strips. In current state they are completely unrealistic. And I don't really mean lack of proper aircraft type, wake turbulence, SID etc. I don't care about it that much (SIDs actually could be helpful because they tell us how to seperate the departures but oh well). The basic idea of flight strips is that we can move them all around the bay. Because they have to represent current traffic situation. So we have different colours for departing strips and arrival strips and we should have at least two parts of the bay. The upper part represent runway+airborne. The lower part represents taxiways. When we push back an aircraft we put it in the lower part of the bay. When aircraft taxies it moves up. When we have several aircraft taxing we move the strips to represent the order in which we build the queue. In other words when there are several aircraft at the holding point - the first one would be represented by the top strip, second one by the strip below it etc. This way all the time I know which aircraft is which without even analysing their liveries (which in reality can be misleading). Onces an aircraft lineups the runway it goes up, to the bottom of the top part and when it goes airborn it's moved to the top.
Arrivals start at the top, when they land they are moved to the bottom of the top section, when they vacate they move to the top of the bottom section and then travel down.
Whenever arrival strip touches departing strip just below it, there is a potential conflict. If there is no conflict it is moved further down. For example when arrival vacates runway I would check every single strip below it - if it's in potential conflict and put it below those strips that are not in conflict (for example they are already in holding point) and above those strips that still might be in conflict (for example those which just started to push back). This way my strips represent traffic situation and help to detect conflicts. Of course we would also need a tutorial how to use the strips.
2) We need to know exactly where is the plane going to and from where it is pushing back. Therefore on bigger airports the push-back bays need to have names or numbers and when pushes are made directly to a taxiway (on smaller airpots) we need stand numbers. They have to be put on the strips. What controller do the first time aircraft calls is to identify where exactly he is and realise where he would be pushed back. The same moment the controller looks at arrivals strips to check where they are going. This is a basic thing every tower controller does all the time. I know we can now check where the arrival is going on the ground movement screen but first of all it's not realistic and second the information is not precises (it shows only apron but not exact stand). We could also use a pdf map for each airport to be printed. Once we issue a taxi instruction it could be written on the strip (in current state only runway is written). The push back time is also not reallistic, it should take about 3-4 minutes for an aircraft to be ready to taxi.
3) In expert mode clicking on a strip or radar echo (or talking to it) should never point a camera at the airplane. It's the job of the ATC to point his eyes at the airplane he wants to see. It really breaks the immersion for me.
4) In expert mode ground movement radar should show only echos without any identification. It's the job of the controller to identify the airplane by his strips and remember where he was instructed to go. Again - some real life GMC radars can identify aicraft but it's not always accurate and often doesn't work for aprons (they might be hidden from the antena) so it shouldn't be the main tool used for that purpose.
Of course there are a lot more of things that could be adressed in future versions like introduction of vehicles (thy are very important part of every airport), snowploughs in the winter, deicing process, VFR etc. but I don't really find it that important. What is important at least to me is to make the experience more realistic mainly by changing how the strips and ground radar work.
I hope this help the devs in improving their game.