LFLN (St-Yan) : IFR possible at weekends ? Answer : No
To land or to take-off IFR without any ATCO on duty, the airfield must be equipped with a "STAP" and (by night) a PCL.
A "STAP" is a "Système de Transmission Automatique de Paramètres".
A pilot, clicking quickly five times on the PTT on the frequency get instant and current information (synthetic voice) on ceiling, visibility, wind (direction and force), QNH ....etc and a runway lighting too.
STAP and PCL are paid for by the local airfield operator. St-Yan is in the middle of nowhere, and the operator doesn't bother to buy such equipment.
By daylight (ie from SR-30 to SS+30), when ATCO are not in duty (on weekend days), relevant airspaces become class G.
As usual in France, St-Yan is available to any VFR traffic, no PPR, just turn up and land.
Minimum VFR met conditions (by daylight) on French class G airfields are : no cloud under 500 ft (agl or aal), viz 1500 m.
You transmit blind on the tower frequency in French (if not in Frenglish).
With ATCO (Clermont) approval you could do a let-down at St-Yan (by daylight), and must able to see the surface at 500' aal.
You transmit blind on TWR 122.300 (LFLN) :
" November Alpha Charlie en percée ILS sur piste 33, 800 pieds Fox Echo"
a "percée" is literally a breakthrough (a let-down in French). Percer is in English to pierce.
percée ILS: say pair-say ee-L-S
800 pieds FE or 1600 pieds at LFLN (with no pressure reference, it means always QNH).
Again : " NAC en percée ILS piste 33, 600 pieds Fox Echo "
" NAC en vue du sol, finale 33 "
Now, tell me if you could land IFR at Caen (Normandy) LFRK at night without any ATCO, FISO ... ? Please look at the VAC chart.
At some airfields, STAP and PCL are not available anytime, anynight, but only on request (PPR) : ie Colmar LFGA : the LFGA operator switch on STAP and PCL for a requested arrival or departure.
Usually STAP and PCL are not permitted for IFR circuit training at night.
Hope that helps you.