I asked the same question after my only (vacuum) AI failied on a flight
(turbo Lance) and was told 500 to 1000 hrs for vacuum gyros and 1000 to
2000hrs for electric. If you only have one vacuum AI overhauling it every
500hrs seems prudent.

Mike
MU-2


"O. Sami Saydjari" wrote in message
...
As I reading through my aircraft logs, I noticed several replacements of
the Directional Gyro and Turn Coordinator. The plane is a 1978 Piper
Turbo Arrow 3. Is is normal to need to replace these things every 4-5
years?

Does anyone keep statistics or even projections for the mean time
between failures on airplane parts? It sure would be useful to know.
One would think the manufacturers would publish such information.

-Sami