I asked a large avionics/instrument shop where I got the failed gyro
replaced, so it was one (experienced) guys observation, not a scientific
study. There isn't a lot of difference between different vacuum gyros that
is going to affect their lifespan. Even with a good filter, there is dust
and grit constantly being sucked through the unit and the bearing grease
eventually dries out as well. There are larger differences between electric
gyros and I asked about the ones installed in my airplane which use a AC and
DC power. Look in your logbooks and see how long yours lasted. I'm sure
that there are a lot of variables too. If your plane sits outside in
Pheonix, the bearing grease will probably dry our faster and if it sits
outside in Barrow, it is going to have a lot of very cold starts.

Mike
MU-2


"O. Sami Saydjari" wrote in message
...
Mike, Who did you ask? Tha manufactuerer? Seems like these stats would
be specific to the make and model of the instruments. -Sami

Mike Rapoport wrote:

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