I may be in the need for an s-nav calibration. For the last few flights i've been wondering why the s-nav keeps showing 50+kt headwinds no matter which way I go. So I finally read the fine manual, and tried to adjust the airspeed offset in the box. Even at full -99 it till showed an airspeed of 50 knots. Is there something I can do, or does the box have to go to the shop to be adjusted?

Does Clear Nav now work on old cambrige prodicts?

Thanks

Peter