So when it's dropped from the array, do you lose the contents if that drive?
Not if the array is a parity type like RAID 5 or 6 -- the RAID controller will just check the drive and then start rebuilding the array. Of course, if it's RAID 0, and a drive drops out the array is broken and probably unrecoverable without recovery software (that might work if you are lucky).
On most of my RAID 5 arrays I have a hot spare so that one drive going out will allow the array to rebuild using the hot spare and I can replace the drive.
Also understand that a RAID 5 or 6 array will continue to work with the loss of one drive (or 2 drives for RAID 6), it's just that the array is at much greater risk when there are no drives that are left to fail without data loss and the performance is degraded substantially.