A few people have mentioned to me that a maintenance approval is required to update the GPS databases and sign off the maintenance release to this effect
When I first read this thread I assumed it referred to updating the internal software of the unit - which would seem to be a maintainance issue. However, on further reading I get the feeling that the question relates to changing the data card of a TSO'd GPS unit.
I am a regular user of GPS RNAV as my primary means of navigation in the IFR environment, using the TSO 145 Garmin 430W in the Bo. I have done all of the approved training required to use this unit enroute, for arrivals and approaches - and at no time has anyone told me that changing the data card required endorsement of the Maintainance Release.
If this is the case, can anyone point me to the appropriate Reg?
In my opinion, refueling the aircraft or checking the tyre pressures are more complex maintainance/airworthiness issues than updating/changing data cards. For the G430/530 type units, for example, the whole process is automated once you put the card reader/writer into a computer and fire up the appropriate software. The integrity of the updated card is automatically verified by the software. Changing the card in the GPS unit is simply a matter of pulling the old card out and pushing the updated card in !!
The validity/integrity of the database is checked by the unit on start-up and the user has to acknowledge this as part of the start-up process.
I have now changed data cards on at least 50 occassions without writing anything anywhere.
What's the deal here?
Dr 
PS: Make that 51 - just updated the card again!