Geekyflyer - what an interesting bit of research you've done there.
Couple of qualifiers one might add:
- Plenty of flying goes on after 1700 local in summertime, although admittedly less training.
- Instructors may be happy to fly in worse conditions than those formal criteria you mention, depending on the exercise they are working with you on.
If it helps, from a personal point of view, up until this year, I always worked on the basis that I would get a dispatch rate for a given booked day's flying of about 75% in summer and 50% in winter.
This was based on C152/172-type flying in VFR as a PPL with a couple hundred hours. With experience, I would fly to slightly different criteria to those you mention, now I have the experience (e.g. 2000' en route cloudbase and stronger winds).
This year however it has worked out about 40-50% during the summer and 25% or less during the autumn/winter. I now mainly fly tailwheels, which restricts my criteria back more towards those you mention, but it doesn't get away from the fact that 2012 has been a truly diabolical year for VFR flying.
Until it returns to a more agreeable pattern, it may be worth scanning the long-range weather forecast and simply taking a day off when you see a potentially good day appearing on the horizon.
