International flights and Mode S

[Mark A]

I've obtained clarification of the German situation post 31/3/2008.

In general most trips should be possible with mode A/C or even with no transponder.
Mode S is required for the following cases for VFR flights:

(5) For the following VFR flights, aircraft shall be
equipped with an SSR transponder:
1. flights in Class C Airspace or Class D Airspace
(non-control zone);
2. flights in transponder mandatory zones
(TMZ);
3. flights at night in controlled airspace;
4. flights with power-driven aircraft, except for
gliders, above 5000 ft MSL or above a height
of 3500 ft GND, whichever is higher.

TMZs exist at Friedrichshafen, Paderborn, Karlsruhe and
Nürnberg.
I have copies of all the relevant AIP and AIC extracts and can forward them if you PM the contact details.