Pre-buy after Annual

Quite a few mechanics and quite a few shops tend to shy away from the
"pre-buy" inspection for one main reason. There are a gazillion items that
can be inspected to a fare-thee-well and wind up being unairworthy next
week. Then you come back to me and ask me why I didn't find this glaring
problem on the pre-buy and expect me to fix it for free.

Example -- on July 20th last year I did an annual on a 182. I found a
couple of minor things wrong, fixed them, and signed off the annual. Two
weeks later that aircraft split a cylinder in two in flight and had to make
a forced landing in a cow pasture. Now the question becomes -- how could I
have detected this fault by inspection? Perhaps if I had removed all the
cylinders and taken them down to be nondestructively tested (mag particle,
zyglo, etc.) we might have spotted that incipient crack. We might not have.
But that's not reality. Pulling the jugs on every annual (and removing the
wings to inspect for corrosion, taking out all the radios to run a bench
specifications test, and all that stuff) just isn't the real world.

I won't take a pre-buy job except for a good friend and even at that we have
to have the understanding that (s)he is going to be standing right at my
side during the entire process and watch everything that I look at. Six
months later when the veeblefeltzer snaps a rittit both (s)he and I looked
at the damned thing and agreed that it looked normal. That and I charge
double for a prebuy what I charge for an annual.


Jim



" My specific question is ... Since the plane was just annualled, what
should
I look for in my (free, amatuer) pre-buy and ask the mechanic too look for
in the professional inspection, that would indicate a "don't buy"
decision,
even if the annual is fresh.

Well, thank you for a mechanic's perspective on this.

Seeing as every piece of "how to buy a used airplane" literature recommends
a mechanic's pre-buy, what do consider a real-world way for the amatuer to
avoid the big money pits like wing spar problems?


"RST Engineering" wrote in message
...
Quite a few mechanics and quite a few shops tend to shy away from the
"pre-buy" inspection for one main reason. There are a gazillion items
that
can be inspected to a fare-thee-well and wind up being unairworthy next
week. Then you come back to me and ask me why I didn't find this glaring
problem on the pre-buy and expect me to fix it for free.

I won't take a pre-buy job except for a good friend and even at that we
have
to have the understanding that (s)he is going to be standing right at my
side during the entire process and watch everything that I look at. Six
months later when the veeblefeltzer snaps a rittit both (s)he and I looked
at the damned thing and agreed that it looked normal. That and I charge
double for a prebuy what I charge for an annual.

Wing spars are fairly accessable and moderately easy to inspect thoroughly.
It is the stuff that you can't get inside to see without ripping the
airplane completely apart that generally rise up and bite you. How do you
detect that an oil pump gear has a hairline fracture and is about to
self-destruct without pulling the back end of the engine apart? How do you
tell that a bladder cell is about to start leaking from an invisible
internal split in the cell wall? The stuff you can see is generally not the
problem ... but in the case of an invisible crack in a cylinder wall it was.

The answer is that there is no good answer except for a record of preventive
maintenance.

Jim


"Douglas Olson" wrote in message
ink.net...
Well, thank you for a mechanic's perspective on this.

Seeing as every piece of "how to buy a used airplane" literature
recommends
a mechanic's pre-buy, what do consider a real-world way for the amatuer to
avoid the big money pits like wing spar problems?

Jim,

Is there an easier way to check a Cherokee wing spar than pulling the tanks?

I mine inspected (SB-1006?) when I bought my PA28-140 in 2000. Did it again
last year when my tanks were sent to New Hampshire for overhaul.

"RST Engineering" wrote in message
...
Wing spars are fairly accessable and moderately easy to inspect
thoroughly.