PAI 700 VC Compass Failing

[Mike Spera]

My PAI 700 has performed quite well for the past 4 years or so until
now. I bought the "official" mounting bracket after seeing others that
were mounted without the bracket failing badly. Lately, even after
recalibration, I have noticed it seemed to be off 5 degrees or so
between 350 and 10 degrees. As slight tap on the side and it would get
back to where it should be. The other day with the nose pitched up into
a climb while turning, I noticed the thing sticking at North and
suddenly roll 100 degrees (to where it should have been) somewhere in
the turn. I just chalked it up to the very nose-high attitude the
student pilot friend had the plane into and the normal compass lead/lag
behavior.

The last straw was on the ground. While pointed at 150 degrees after the
runup, I reached over to set the DG to the compass and it was stuck at
North. A little tap to the side did nothing. A little bigger tap also
did nothing. Not until we rolled onto the runway and turned 30 degrees
did it finally catch up. These things do have a wee bit of sticking that
is usually not noticed if the engine is running and supplying its usual
copious vibrations. But this time it was sticking after a runup. This is
quite a bit of vibration.

So, a new one was ordered last night. I really cannot tolerate a balky
compass. But I had always praised this model over others because the
folks who I talked to all said this model would last the longest. Others
have had poor luck with the cheaper models.

Anyone else have or had a prematurely failed PAI 700? I figured one of
these units should last 7-10 years before the gearing wore out and began
sticking. Is my expectation unrealistic or was this one just a fluke?

Thanks,
Mike

[Mike Granby]

There's an article somewhere out there about them failing due to some
bit or another coming off a mount as a result of ferous metal being too
close...

http://www.avionicswest.com/articles.htm

[Denny]

I have yet to see this mechanical style compass survive... Someone
always lays something up on the glare shield that is steel, while
either working on the aircraft, or simply loading/unloading and that is
all it takes... The compass continues working after a fashion, but is
unreliable... If you don't want to go back to a traditional compass,
perhaps a SIRS Navigator might suffice...

denny

[Paul kgyy]

Because of the gearing, these units are more likely to wear than a
simpler compass. I'd guess that the amount of wear is more related to
the number of hours of use, and the level of vibration experienced,
than the number of years you have owned it.

I just installed one and like it a lot but I'm sure that "stickiness"
will ultimately cause a replacement.

[NW_PILOT]

Had my cessna wet compas seal go out then the light fixture broke upon
removal was a simple $100.00 bill to get it rebuilt aka re sealed, should
work for another 30 years.

"Mike Spera" > wrote in message
et...
> My PAI 700 has performed quite well for the past 4 years or so until
> now. I bought the "official" mounting bracket after seeing others that
> were mounted without the bracket failing badly. Lately, even after
> recalibration, I have noticed it seemed to be off 5 degrees or so
> between 350 and 10 degrees. As slight tap on the side and it would get
> back to where it should be. The other day with the nose pitched up into
> a climb while turning, I noticed the thing sticking at North and
> suddenly roll 100 degrees (to where it should have been) somewhere in
> the turn. I just chalked it up to the very nose-high attitude the
> student pilot friend had the plane into and the normal compass lead/lag
> behavior.
>
> The last straw was on the ground. While pointed at 150 degrees after the
> runup, I reached over to set the DG to the compass and it was stuck at
> North. A little tap to the side did nothing. A little bigger tap also
> did nothing. Not until we rolled onto the runway and turned 30 degrees
> did it finally catch up. These things do have a wee bit of sticking that
> is usually not noticed if the engine is running and supplying its usual
> copious vibrations. But this time it was sticking after a runup. This is
> quite a bit of vibration.
>
> So, a new one was ordered last night. I really cannot tolerate a balky
> compass. But I had always praised this model over others because the
> folks who I talked to all said this model would last the longest. Others
> have had poor luck with the cheaper models.
>
> Anyone else have or had a prematurely failed PAI 700? I figured one of
> these units should last 7-10 years before the gearing wore out and began
> sticking. Is my expectation unrealistic or was this one just a fluke?
>
> Thanks,
> Mike