Don’t worry about moving the thread…
I think the FL040 minimum is a consequence of the Biggin EGKB issue. I am personally not keen on it being that low because it is a trap for all fresh victims of the FTO IR sausage machine who were taught to plan routes straight off the airway chart and who quite reasonably think they can fly at any level which Eurocontrol validates 
No-oxygen is interesting, but human physiology varies, and one person will be fine at FL120 while another will have bad headaches at FL100, especially after some hours. I suppose one could implement the EASA oxygen regulations.
no oxygen required
You can either choose your default maximum altitude in the aircraft settings or override it under the advance route settings for each route. There are people that would not go above FL100 without oxygen, others are fine up to FL130. I found that kids sleep better the higher the flight level
I found that kids sleep better the higher the flight level
Silent cockpit
You flew at 4000ft? I know that’s no problem under IFR in Northern Germany where the only terrain features are windmills, I’ve done it myself several times. Don’t know about low level IFR in Holland.
I flew EHLE-EDAZ last saturday and was fighting 40+ kts headwinds.
Asked Langen Radar what the lowest level was they could provide..
I was cleared to fly at 3500ft. Bremen Radar asked me to climb to 3700ft because of radar minima.
In the Netherlands you can plan and fly IFR at 2000ft.
For example, Lelystad-Maastricht:
EHLE DCT LLS/N0140A020 IFR DCT NYKER DCT TOTNA DCT OSGOS EHBK
validates perfectly. Flight schools use this all the time for winter non-FIKI IFR training…
What would be really interesting would be whether you can file a Eurocontrol flight plan, partly at say 3000ft, partly at FL150, and make that transition smoothly. For that to work, the system would need to be organised in a very seamless way.
In the Netherlands you can plan and fly IFR at 2000ft.
Do you validate such a route via Eurocontrol?
You can file and fly such routes in Germany, too. However, only where Germany looks like Holland, i.e. in the north. Germany has CAS from very low, between 1000ft and 2500ft AGL, throughout the country.
Do you validate such a route via Eurocontrol?
Yes
You can file and fly such routes in Germany, too
The bit I am trying to get my head around is what exactly happens in the ATC machine when somebody does that.
Let’s say you file this, as “I” AT 3000FT
EGKA SFD EGMD
The CAS base there is 5500ft.
Hilariously, that route validates ok at 3000ft. (It also validates at FL100, etc, but let’s not go there 
)
Eurocontrol will validate it and distribute it to (maybe via some UK message distribution centre)
Out of Shoreham, you will be asked to call up Farnborough LARS East, probably. You are not “in the IFR system” in any way. You cannot – now taking a longer route, say 200nm – climb up into CAS, because there is no Eurocontrol flight plan for you in the system.
Try it!
If it validates surely they must accept it?
They may throw you around some. But they must accept it and cannot throw your plan out as you suggest.. At least that would really amaze me.
Peter our example is only a “UK” Problem. The rest of Europ knows only IFR or no IFR traffik. Every filed IFR FLP is in the seystem, only in UK you can fly uncontrolled IFR ;-) Battelt to get into the CAS on Saturday after depature from Goodwood, its not easy ;-) also battelt the headwind with 30-40 Knots for 4h :-(
