I turned on the KLN94 today and it came up saying both the land and aero databases are corrupt:
The GPS works fine and drives the MFD etc with the right position.
I tried reloading the flash card but it says the land database is gone too.
Fortunately I have a spare KLN94 on the shelf 
so that will go in tomorrow, with a fresh flash card...
It might be the CMOS battery (Tadiran TL-5903) so I might get that changed also. Is the "land" database really stored in a CMOS battery backed up RAM??
I had exactly the same thing happen to me - not once but twice - in the course of my IR training. I know they fixed it very quickly, probably without opening up the unit. I can ask the guys next time I am at LKHK, but I suspect the culprit is the data card, not the GPS unit.
If both the land and the aero data live on the same flash card then that would sound right.
But the card content gets copied to some internal memory in the KLN94 when a new card is initially loaded. Maybe the KLN94 does a checksum on the flash card at powerup, and if it finds it duff it declares the whole lot duff?
It might be the CMOS battery (Tadiran TL-5903) so I might get that changed also
it should not be the battery because they got a special failure message for that, namely
Internal Battery Low: Service Required to Prevent Data Loss
Update: it was just a corrupted flash card. The card is totally dead - can't be read or written.
I had a total of 3 of them; will try to get a replacement because having extras is very convenient as one can just do a swap in the cockpit.
Hmmm. My KLN-94 said something similar right before departure from the Santa Monica airport a few months back, not the ideal place to lose your GPS (no DME in this aircraft). Funny thing was, it was right after I entered the first waypoint in the mini route, VPLSR, and it seemed to me that something about that specific identifier upset the software.
Anyway, it sort of worked intermittently on later flights, running for a few minutes before coming up with the same error and I had the FBO send out a replacement data card to meet me in Oregon. This fixed the problem for several days, but then Bingo! there it was back again.
So the symptoms were hardware-ish, but with the suspicious identifier behaviour. I don't believe these memory cards just 'corrupt' for no reason, although I accept it's possible. More likely the software does something to it, IMHO.
I've had flash memory failing where it started to intermittently read the wrong bit value out of one or two specific bits. So if these bits happen to be in the intersection index, which is probably used infrequently, that could explain your behaviour. I'd say it's not necessarily the software...
Or you could take your shaky steampunk GPSs and exchange your two KLNs for one 21st century tech GPS as in GTN ;)
Sorry couldn't resist - but the very idea of taking a spare KLN should get you off your fence..
A GTN is no less likely to pack up than a KLN (or any other box) but the cost of a spare one would be eye watering.
Actually I will most likely go for a GTN750, plus an MFD of some sort, and lose one of the radios.
