Reverse Vacuum Damging to Instruments?

Depends on the vacuum system in your a/c. I'd expect a pressure relief
or check valve of some sort would be there to prevent this kind of
thing. Anything in the POH?



"O. Sami Saydjari" wrote in message ...
Recently, I had an A&P put the wrong vacuum pump into my Piper Turbo
Arrow 3 (the work was done about 3 weeks ago). When I started the
engine, the wrror was obvious because none of the vacuum instruments
functioned. The D.G. was spinning wildly. The A&P was there when I
started my engine and saw this. The engine was running for only about 2
minutes. We shut it down and he replaced the vacuum pump with one that
turned in the correct direction.

When I asked if running the vacuum backwards could have damaged any of
my instruments, he said that he did not know for sure, but that I should
bring it back if I had problems.

I have not noticed anything really significant...but then again, I have
only hhad the plane a few weeks...so I am not sure what the average
precession is on the D.G. Also, I do not know what subtle damage might
have been done that will reduce the life of my instruments in the long
term. Can someone please tell if they know for sure one way or another
if the event was potentially damaging to my instruments?

-Sami

Putting the wrong direction pump on would not cause the any significant
problem. The engine still turns the same way. It is just a factor of pump
longevity. The other post speculating that the lines were hooked up backwards
is more serious if that occured. The suction regulator is not designed to let
out air, it lets it in to regulate suction. Reversing the lines could seriously
"over-boost" the gyros. I agree if this is the case, talk to an instrument
shop. The key question is what did the suction gauge say. If it read zero
during the run, bad problem, hoses were reversed. If it read normal 5.0-6.0
inhg then no damage done. But you probably have a worn out DG. (I have had DGs
spin around when they start to fail.)
Good luck,
John A&P, IA

Unfortunately, I did not think to look over at the vacuum gauge
immediately. When I saw the DG spinning wildly, I shut it down
immediately. -Sami

RV6John wrote:

Putting the wrong direction pump on would not cause the any significant
problem. The engine still turns the same way. It is just a factor of pump
longevity. The other post speculating that the lines were hooked up backwards
is more serious if that occured. The suction regulator is not designed to let
out air, it lets it in to regulate suction. Reversing the lines could seriously
"over-boost" the gyros. I agree if this is the case, talk to an instrument
shop. The key question is what did the suction gauge say. If it read zero
during the run, bad problem, hoses were reversed. If it read normal 5.0-6.0
inhg then no damage done. But you probably have a worn out DG. (I have had DGs
spin around when they start to fail.)
Good luck,
John A&P, IA