The sim screening lasts around 2 hrs, the first part is around 1h15' and you'll be flying raw data IFR, the second part (after a 10' break) is an MCC exercise that lasts 20-30'.
Part 1: IFR departure, general handling to get used to the aircraft (turns, climbs descents), then you'll be told to join the hold somewhere. After you enter the hold you'll be performing an ILS approach to go around followed by radar vectors for a non precision approach to land.
Everything is flown a/p off, a/thr off and f/d off, with rose NAV/ILS.
There will be no failure, but if you are B737 rated you'll be doing a non precision followed by an ILS with circle to land instead.
LHI will give you LIDO approach plates and sim profiles before the sim screening (including pitch/power settings), however the plates are only to get used to them, they might not reflect the actual airport used in the sim detail. (In my case it was HAM).
The sim partner (a LH trainer) will seat on the other seat and will act as a robot, he will only do what you tell him to (example: atc tells you to change freq, he will reply but not change freq unless you tell him to).
The brefing will explain how everything works, and they will be playing no tricks.
Part 2: it will be a LOFT scenarios, the sim partner will become human and you'll be using all the automations you want (they don't expect you to be proficient flying the a/c, it is all about decision making and crew co-operation).
You'll find yourself crusing at FL 300-340 over nothern Italy, something will happen (non tech, most likely a medical emergency) that requires you to divert. Wx at en-route diversions is not the best, some airfield will have CB, others will require a circle to land...
They want you to enter a decision making process with the sim partner, go through a briefing and descend towards the airfield (the sim will stop before you get there, once the decision to divert is made).
In my case the captain was trying to test my decision making, for example:
once we were told by a cabin crew that the SCCM collapsed in the front galley, he told me that it was likely to be nothing serious, just too many drinks the night before (my reply: yes, most likely, but let's ask if there is a doctor onboard,and let's get some wx for diversion....just in case!)..doctor found and diversion needed.
Then we planned for a circle to land, he said he hasn't done one in ages and felt most confident landing with tailwind....with 15 kts tailwind! Obviously can't do it and I tried to reassure him that I was more than happy to fly a circling since I am used to them.
This second part of the sim, as I said, is all about making a decision together about the best course of action... but expect to be questioned by your sim partner if you still think that's a good idea.... it's test after all!
Best of luck
Ricky