What might happen if you departed at say 6am from an airport which opens 8am?
Assume it was daylight so, with no runway lights, there was no safety issue. So you broke the rules of the airport, plus maybe some national or EASA reg.
We do have a sort of benchmark from the UK for an un-cleared landing but that 8k fine was following a potentially dangerous situation.
This sort of topic is quite relevant to cases where an airport shuts because it has gone bust. This has happened lots of times in the UK (usually they re-open after some days or weeks). On one occassion I got my plane out in time but on another it was stuck for some days.
This EASA doc (local copy) lays down (page 11) an occurrence reporting obligation, but it doesn’t say what (if any) prosecution should follow.
Is there any known precedent for fines? Obviously it will be country and airport type dependent…
In the UK, I guess it will highly depend if the airport is under CAA licence or not?
- In a licensed airport/controlled airspace, even with no safety concern, you will be dealing with CAA, so expect roughly a 4000£ fine plus loosing licence, this was the benchmark for famous and serious airspace/airport busts 
- In non-licensed airport/farm-strip, you will be dealing with land owner/operator (e.g. operating hours = safe/legal to land + have land owner/operator permission), unless safety is compromised you will not hear anything from CAA, but the land owner could come after your or simply “waive opening hours”
If EGKA goes bust, I think 4000£ is worth paying to pull the TB20 out by air, alternatively you may get a cheaper ground transportation 
On extreme cases, rotary wings are famous for their unauthorized landings/takeoffs outside airports: city parks, parking lots, private/public lands…but I am not sure how far their fines/sanctions go?
I don’t actually think EGKA will go bust anytime soon, but the most common GA scenario is a licensed airport not in CAS. So no CAS bust.
Helicopters indeed tend to get out quick. In one such situation, a few years ago, the whole flying school got out, to a field not far away. But they heard about the airport closure in time, whereas the fixed wing based owners didn’t.
There were quite a few during a particular weekend during scheduled closures without any reprecussions. I suppose it must also depend on the circumstances, and the will power to pursue the parties concerned. I also suppose it is more diffcult to defend a departure, than an arrival. I have had a few nerve tingling events where it required a few corners to be cut and the ponies to not be spared to make it by the curfew.
Ultimately where an airport closes (goes bust) you would imagine an arrangement would be reached to remove the aircraft because a Reciever would not be interested in dealing with the resulting legal actions for one minute.
Departing outside operating hours without permit is not a good idea never mind what the fine may be.
In many cases in Europe, operating hours have been approved following severe battles with anti noise groups who are just waiting for someone to breach the rules to question the whole agreement. Also, on a private owned airstrip you are a guest and should obej to the house rules, despite the fact that you are paying to be there. In many cases, it is enough to ask and if they can, they will accomodate out of hours requests.
on licensed and/or controlled aerodromes, the staff will have to report any violation lest they become the target of prosecution themselfs. So therefore violating those rules also puts them in a bad situation.
Clearly, in situations where planes get blocked by closed airports which are unlikely to reopen, the situation is different. But what I understand is that most of these cases, the competent authority will try to find a solution to these ferry flights as quick as possible. Of course in an abandoned airfield going to another non controlled airfield you might get away with it, but it is always better not to get into this kind of situation.
This is highly depended on country and airport. In Sweden for example in many airports you may arrive/depart even when the airport is closed, it becomes just like any other uncontrolled farm strip, and the airspace above becomes uncontrolled. In Greece on the other hand it’s a big no no as you probably know. In Germany I think the tower/AFIS needs to be manned as well for A/C to be allowed to land/takeoff.
In some countries nothing will happen, as a runway is a runway no matter what time it is.
In GA haters countries you could loose you license on starting outside operating hours.
The key words in the OP are “broke the rules”.
If you have permission to use the licensed airfield out of hours, no problem. I’ve landed and taken-off under that situation many times in the UK. Inverness used to have “out-of-doors permits”. Most HIAL airfields still do. Notify ATC the previous day. I think circuit practice was forbidden.
I recall making blind calls, to a closed airfield, when ATC were having a statutory break. Another aircraft, not holding a permit, and not PPR’d, came on the frequency. ATC came on the air, and told him the airport was closed, and he could not land. I continued, making my blind taxi calls after landing.
Does anyone know of cases of a departure from an “officially not open” airport, OCAS i.e. no ATC clearance was required for the air above it?
