Bob
>It is a bi-directional system, so where would you put the accumulator?   In
one direction it would be working against you.

No, in the same way as air in our lines would be working against us without
one.  That is, the shuttle valve allows for fluid return to the reservoir
when operating the opposite circuit.  I would put the accumulator vertically
off a T in a high pressure "up" line.

>In 815 hours, I have had one main gear actuator shaft seal fail.  Never
have rebuilt any of the others.  I get a pump chirp only every 30 minutes or
so, and I do not know why my system works so well.  I would like to drain it
and put in fresh fluid but I'm afraid that might do more harm than good.

Congratulations.  I too here an every 30 minute pump chirp.  I'd rather hear
an every 3 hour hum of motor run 5-10 seconds.  My electrics would be
happier too.  Regarding fear of fluid draining, I'm missing something.  Is
it the fluid on the hangar floor and in your face that is the problem?  The
removal of dirty fluid will extend seal life on the balance of your leak
free components.  Finally, by running the pump with the dump valve open for
a short while you'll remove the majority of your air.

Larry