FDR Time Sources?

[Badmachine]

Do FDRs:

- contain their own independent clock?
- base time on the FMC clock?
- base time as provided by GPS?

[chuzwuza]

fdr time ref

Any particular type?? Airbus use both the captains clock ( signalled primarily by gps) and a dedicated clock built into the fdimu. Either can provide the signal to the fdr in the event of failure however it is usually a very reliable system in my experience.

[lomapaseo]

The only time I can think of a problem to sort out is to sync the times to CVR and ATC time bases in the event of an accident.